Ashly DPX-200 Stereo Equalizer User Manual
Contents
1. 1 2 3 4 5 6 7 8 Filter Filter Four Low Shelf High Shelf 6 m 007 4560 F1 OU 8 VR I 45 WV 90 C100 4 R76 cs 10K 2u VR X i Filter Two Filter Three Frequency Frequency ROS R112 A 10 4 Range Range R94 RIN 7 if iM T IM CIS 0015 0015 00154 0015 d 0015 001Su 00154 0015 ca C26 C30 006 006 0068u 0068u _4 SWIIB 4 SWHA _4 SW12B 159 12 NS 77 e CB 2 6 3 i 45 2600 245 2600 245 2600 24522600 O68u 068 RIIS 10K 2 gt 02 Riog gt UMA 82 4560 4560 gt gt 1 4 8 3K 4560 4560 gt 1 4 ois R87 886 IL R106 6105 IL m 17 UR 68K R84 RS 68K Rmo 100 15K 10K 15 10K DSS D59 4 IN4148 2 4148 Bandwidth EN Bandwidth gt VRISC Bus 2 VRIAC Peak Bus 2 R83 BIOK R102 BIOK 680 680 1 C40 6 ULB 6 R110 lt 2 274560 lt OUT 271560 33K ae ip mmi n p n R82 R92 R101 R109 Ashly Audio Inc 10K 1K 10K 1K 847 Holt Road Webster NY 14580 9103 ek he Phone 716 872 0010 Fax 716 872 07392. 11 TROUBLESHOOTING TIPS 12 WARRANTY INFORMATION SPECIFICATIONS 14 DIMENSIONS AND SCHEMATICS RIO Rh eee 2 ASHLY Operating Manual DPX 200 Parametric Equalizer Compressor Limiter 1 INTRODUCTION The Ashly DPX 200 combines a four band para metric equalizer and full function peak compressor lim iter in a single rack space product Both equalizer and compressor limiter can be used as stand alone processors or can be automatically chained together with a back panel switch Parametric EQ filters offer custom tailoring of equalization solutions Where a graphic EQ boosts or cuts fixed frequencies a parametric EQ boosts or cuts tunable frequencies The DPX 200 parametric equalizer uses two tunable shelving filters along with two fully ad justable 20Hz 20KHz parametric filters resulting in very precise control of frequency response The Ashly compressor limiter circuit was de signed in response to the need for universal peak sensi tive automatic gain control AGC devices with exceptional audio performance and rugged durability The result is a wide bandwidth ultra low distortion low noise VCA voltage controlled amplifier which is versa tile and highly listenable Premium components are used throughout the DPX 200 and computerized automatic assembly equip ment verifies
3. 1 2 s s D 10K T nm 15 dB to each filter REE Rp d gt AX9SWI3A gt 05 40Hz 400Hz 20Hz 20KHz 20Hz 20KHz 1 6KHz 16KHz 2 2 cows 2 3 M 2 2 e 2125 Ras Do BIOK BIOK 160 Vk i n i Mae fuer d RUT x5 B N gt 45600 10K 10K 10K 10K 10K UK 10K R R118 SR119 D9 su 7 Vk QUK 2 p UR epus suas AOT tta xs gt ea 4535 7 p ciun pr pa o wees Sak AK dL BE 8748 R 10K iK our our Vii web wen Bak SWDror SWDPDT R ue gt 1 LT 100K dmn 23 lt 5 847 Holt Road Webster NY 14580 9103 Phone 716 872 0010 Fax 716 872 0739 Draw By TZE Rav Sim smear 14 oi Pint Dae Steet 14 of ASBQ 193 James B Franks SEnginesring CLIENTOSS7SI toss TS cT sch 10 Sep 2002 DPX 200 Parametric COMPRESSOR LIMITER APPROVED 9w 1085751 z 3 B D 15 SCHEMATICS 42ajurT 40ss24duio 4221 pn bg 21412u40d YOZ Xdq 8 SI AIHSV
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5. Ses Drawn By Print Date 14 27 46 Rev B enr gt 157 James Franks S Engineering CLIENT98 5751 10s57510 2 SCH 10 Sep 2002 DPX 200 Parametric COMPRESSOR LIMITER APPROVED 2 1085751 1 2 3 4 5 6 7 8 42ajnurq 40ss24dui0 4221 pn bg 214120047q 00 6I 1 2 3 4 5 6 7 8 E GAIN REDUCTION db D38 1037 036 1035 034 033 032 0 030 029 n AR AR AA AR AA AA AA AA AR PA 0l 166 0 8 D49 D48 D47 D46 045 D40 26 1908 2 AA AR AA AR AA AR AA PA 7 20 R Y 12 R 14
6. 1 in out ula D19 D20 271 C49 C53 C57 C59 bt pj 1 _ al 25 IU IU 10 IU 57 8144 14003 INA003 14003 596 15K 4 L 5 mog 95 6 B 10 D21 po T 6 12 koe tE ss al 4 J JL Ashly Audio Inc 2 PEAKBUS1 gt N i Ts 10000 847 Holt Road 144003 144003 020 1 75024 CAS C54 C56 C58 C60 s 47PI413 aii 8 1 7918 1N4003 1U 1U 1U 1U 1U PEAK BUS 2 Webster NY 14580 9103 n 5 2 z KEYSTONE KEYSION KEYSTONE ot erste In 3 I THRES Phone 716 872 0010 Fax 716 872 0739 1U 100V Size Drawn By Print Date 14 27 05 Rev ce ize Sheet 3 4 rint Date 15 16 n7 18 19 ERA m LSIG lt gt B gt 157 James Franks KEYSTONE KEYSTONE KEYSTONE KEYSTONE KEYSTONE N4003 COANN S Engineering CLIENT98 5751 10s575163 5CH 10 Sep 2002 INPUT METER gt i L I T I Qi Qi Q DPX 200 Parametric COMPRESSOR LIMITER OUTPUT METER 77 APPROVED 944065751 1 2 4 5 6 7 8 42ajnurT 40ss24duio 4221 p0n bg 2 4 YOZ Xdq pnubjy 8 Operating Manual DPX 200 Parametric Equalizer Compressor Limiter ASHLY ASHLY AUDIO INC 847 Holt Road Webster NY 14580 9103 Phone 585 872 0010 Fax 585 872 0739 Toll Free 800 828 6308 Internet www ashly com 2002 by Ashly Audio Corporation All rights reserved worldwide Printed in USA 0902 DPX200 0
7. 15dB Filters In i soccer 90dBu Max Level All Filters In 0dBu 0 775 volts rms balanced input Level Controls at Unity 23dBu Pseudo balanced output is single ended signal with bal Max Level One Peak Filter at Max Boost anced impedance 0 3 octave or greater 7dBu ASHLY 15 Operating Manual DPX 200 Parametric Equalizer Compressor Limiter SPECIFICATIONS continued Compressor Limiter Gaini 15dB Frequency Response 0 2dB 20Hz 20KHz ev idea wie eee dion 2 1 Distortion lt 01 THD OdBu 1KHz Attack Time 200uS 20mS lt 0 15 THD 15dBu Release Time 100mS 3Sec 20Hz 20KHz Output to 18dB Output Hum and Noise lt 95dBu Maximum Input Level 23dBu Maximum Output Level 23dBu DPX 100 Power Requirements Input Impedance 20KQ balanced 93VAC 120VAC 50 60Hz 10W Output Impedance 2000 Pseudo Balanced Size and Shipping Weight 19 L x 1 75 H x 6 D 8 lbs 14 DIMENSIONS 6 00 0 5 O 0 0 020 0 0 000000 Ooo O k a E 16 ASHLY LI
8. The compressor limiter provides many so lutions where dynamic signal level processing is required The combination of a parametric EQ and a compressor limiter allows for additional applications such as a full range speaker processor 70 volt distributed system pro cessor mixing console channel insert and frequency sen sitive limiting just to name a few In most cases the DPX 200 should be the last device before the power amp or crossover or right before a recording device or trans mitter 8 1 Parametric Equalizer Applications General Tone Control Like a graphic EQ the parametric equalizer is a very useful device for general tone shaping because the filter s center frequency bandwidth and level are all con tinuously variable To use the power of the equalizer ef fectively you need to translate your idea of the tone you want to produce into a range of numerical frequencies This is simple after a little practice Here are a few refer ences which are useful for starting points Very low bass the wind in a kick drum almost felt as much as heard 40Hz 80Hz The low register of a male voice 200Hz The low register of a female voice 350Hz Lower midrange warmth frequencies 400Hz 1KHz Upper midrange harshness snare drum bite hot sound 2 5KHz 4KHz Sibilance sss sounds cymbal 51271 8KHz 15KHz Try using these starting points as a guide when yo
9. analog recording ASHLY 9 Operating Manual DPX 200 Parametric Equalizer Compressor Limiter Broadcasting Compression has long been used as a tool to make an audio signal appear louder A N ra good example is in broadcasting where competing stations with identical transmit ters and power attempt to sound louder than each other Since they are all restricted with respect to maximum audio level modulation their best tactic is to squeeze the dynamic range of their programs to just a few dB The audio output level of the station virtually never changes and the listener perceives this continuous high level sound as being louder than the same material in an uncompressed form Although both com pressed and uncompressed programs reach the same peak levels the compressed signal stays near peak level more of the time and thus sounds louder This technique makes the broadcast more intelligible over ambient noise and increases the geographical area over which the broadcast is audible to the listener Additionally this compression technique is extremely useful for FM and infrared trans mission systems for the hearing impaired 8 3 Special Effects Compression For Feedback Control A common ritual in sound system set up is equal izing the room to remove feedback This is generally accomplished by turning up system gain to purposely in duce feedback searching for the center frequency of the feedback and then equalizing
10. at that frequency to remove the feedback Once this frequency has been cut system gain is again increased to induce another feedback point and the whole procedure is repeated until the engineer is satisfied that the significant problem frequencies have been corrected The major problem with this approach is that the feedback can easily get out control and the engi neer ends up dashing back and forth between the mixer volume controls and the equalizer controls while every one in the room plugs their ears and prays it will end soon The Ashly DPX 200 can turn this procedure into a fast painless job eliminating loud feedback levels and the possibility of speaker or ear damage Procedure 1 Set up the DPX 200 limiter controls as follows Output level control to 20dB Input Gain control to OdB Threshold control to 30dB Ratio control to infinity Attack time to 5mS Release time to 1 Sec Limit switch IN C 2 Using 1 3 octave 31 band or parametric equalizer set the EQ controls to a flat setting and if the equalizer has an overall volume control boost it by 10 to 15 dB 3 Open up several microphone input channels to a normal operating level with typical EQ settings and turn the console master fader up to a louder than normal setting At this point the system should be well into feed back but the room volume will be constant due to the action of the limiter You can listen to the
11. in normal operation the diaphragm is required to accelerate slow down smoothly change direction and accelerate again distorted opera tion requires an instant acceleration instant stop a change of direction and instant acceleration again Since speaker diaphragms are subject to the laws of physics they won t take this kind of punishment for long The diaphragm may shatter or its voice coil may overheat In addition to the damaged caused by sustained overload the speaker may also be damaged by occasional one shot high level overload for example the sound of a microphone falling face first onto a hardwood floor Even if this type of transient doesn t destroy a speaker outright it may damage the speaker surround in such a way as to cause mechanical abrasion and future failure Alternatives For Sound Installations To install a compressor limiter in a sound sys tem using a passive crossover insert it between your mix ing console output and the power amplifier input For systems using electronic crossovers there are two ways to use a compressor limiter It may be inserted between the mixer output and the crossover input in which case it will act on the entire audio frequency spectrum Alter nately if the limiter is inserted between an output of the electric crossover and the input of a power amp it will only affect a specific band of frequencies Recording The Ashly limiter can be used to prevent tape saturation in anal
12. it is engulfed by the noise The noise floor or minimum constant noise level will consist of hiss hum transistor noise tape hiss buzz and whatever noises are inherent in the medium When the program level is considerably higher than the noise floor our hearing masks the noise and it is not a prob lem However when listening to very quiet sections of a program for example a pause between movements of a string quartet the noise can become very bothersome At the other end of the loudness spectrum the limitation on dynamic range is usually distortion either in the form of amplifier overload tape saturation or A to D clipping In most transistorized equipment the transi tion from clean undistorted operation to severe distor tion is very abrupt Therefore it is common practice to operate a piece of equipment at a level that is somewhat below the distortion point leaving a margin of safety for ASHLY 11 Operating Manual DPX 200 Parametric Equalizer Compressor Limiter unexpected transient volume peaks in the music This safety margin is known as headroom and may range from 10 to 25 dB Lowering our standard operating level to leave ourselves some headroom helps prevent distortion but at the same time it moves our average program level closer to the noise floor thereby compromising signal to noise performance It becomes apparent that to get most out of an audio system you have to keep your standard operat ing le
13. only provides it with a control voltage Experience showed us that both are crucial to the overall sound and that if anything the detector s performance is the harder to judge by conven tional measuring techniques While the VCA is doing its job if it has low noise and distortion the detector must con stantly adjust the gain of the audio path in a manner which keeps the level under control while sounding acceptable to the listener This constantly changing gain is a dynamic action while conventional audio measurements like noise and distortion checks are Static at a constant level We became painfully aware of this problem with some of our earlier limiter prototypes which measured fine and sounded terrible This led us to use a purely subjective approach in the design of the detector we did a lot of listening to de termine what sounded good and what didn t Two important features emerged from this re search 1 We designed the detector to let the attack and release times speed up as more and more limiting occurs The compression ratio also increases This lets us main tain peaks fairly close to a constant ceiling level but al lows the illusion of increasing loudness as input level increases thereby preventing complete loss of dynamics when limiting 2 We incorporate a double release time constant When release time was set slow with a single time con stant transients such as mic pops caused a quick re duction
14. release time and a low enough threshold to cause 6 to 10dB of Gain Re duction Try using this effect to help bring out a lead vocal or instrumental solo in a cluttered mix The com pressor is also a great corrective tool when working with 10 ASHLY Operating Manual DPX 200 Parametric Equalizer Compressor Limiter singers whose own dynamic control is less than perfect A little compression helps to keep their quieter lines from becoming buried in the mix Experimentation is highly recommended Voice Over Compression Ducking The compressor limiter can be used to automati cally reduce music to a background level when an an nouncer is speaking In this scheme only the music signal is actually gain reduced by the limiter However the de tector is connected to respond to an announcer s voice instead of the music s peaks Voice Over compression assumes you are already using some sort of mixer to com bine the music and mic signals Use the direct out send of the mic channel to feed the detector input on the DPX 200 Note Be sure to use a mono plug for the detector input Then use the Threshold and Ratio controls to de termine when and by how much the announcer s voice affects the music level De Essing A special type of saturation problem often en countered in recording is the sibilant Ssss sound of the human voice High frequency sibilant sounds can reach very high energy levels so that a voice that is otherwise
15. spond by restoring the gain to normal Thus when the level is within a specified safe range the limiter has no effect When an occasional peak occurs the limiter re sponds This situation is completely analogous to manual gain riding except that it occurs faster and more consis tently Compression A very significant difference in dynamic range is achieved simply by changing the relationship between nomi nal signal level and threshold as a result of either increas ing the GAIN and or decreasing the THRESHOLD control The most interesting effect to be noted however is seen by comparing the original input signal with the output signal The quietest portions of the original signal will be effec tively increased in volume while the loudest portions of the original signal will be decreased In effect both ends of the dynamic spectrum will be pushed toward the middle This is quite different from simple limiting where only loud peaks are subjected to gain reduction More than anything else it is this double ended effect which distinguishes compression from limiting Com pression is further differentiated from limiting by care ful selection of attack and release times When limiting is employed to protect an audio system against transient volume peaks and possible overload attack time is usu ally set as fast as possible consistent with distortion free performance Release time would also be relatively short so that
16. the output signal would be restored to nor mal as quickly as possible after the transient Compression is frequently used to keep over all signal level within a specific dynamic range and for this application slower attack and release times are usually chosen This approach is analogous to our manual gain riding example where our operator is fad ing the music up and down to keep it fairly constant but is doing it slowly enough so that the listener is un aware that the gain is being altered Voltage Controlled Amplifiers Early VCA s were based on vacuum tubes with a remote cutoff characteristic The tube would sim ply change its gain in response to a changing bias volt age Tubes developed for this purpose did an excellent job in fact they could exceed the noise and distortion performance of today s best solid state VCA s Unfor tunately they also had some serious disadvantages pe culiar to tubes change of gain and matching as aging took place heat microphonics high cost and the need for both high voltage and filament power supplies Over the years the need for good low cost solid state VCA brought about many innovative ap proaches A good example is the electro optical at tenuator where a photocell is used as one leg of a potentiometer Since the photocell behaves as a true resistor distortion and noise are very low Unfortu nately the response time of photocells is slow and un predictable so their us
17. until feedback occurs Once you have induced the feedback by boosting its frequency quickly turn down the filter s level control to about 6 dB to suppress or notch out the feedback frequency 5 Again slowly increase the master level at the mixer until feedback is heard If a new feedback frequency is heard then repeat step 3 with the other parametric filter to find and suppress the new frequency If the original feedback frequency is still heard then adjust the first filter s level even lower The bandwidth control may be ad justed full clockwise to produce a very sharp notch so that a severe feedback frequency can be attenuated by as much as 15 dB without degrad ing the frequency response with noticeable notches Note Very sharp bandwidth lowers the maximum equalizer input level because of the high filter gain necessary to obtain such a nar row bandwidth Only use bandwidth control full CW 05 Octave in severe cases Console Channel Equalization Many mixing consoles provide only simple equal ization for individual channels If your console has chan nel inserts you can patch your parametric equalizer into 8 ASHLY Operating Manual DPX 200 Parametric Equalizer Compressor Limiter a channel that s being used for something important and use it to tailor the sound of this channel exactly the way you want Large Room Equalization Large rooms tend to suffer from multiple reflec tions with long time delay
18. where the shelf flat tens out The inner concentric knob is the level control for that filter and indicates the decibel level of the flat portion of the shelf relative to the unaffected signal The frequency range on the low shelf is 40Hz 400Hz while the hi shelf range is 1 6KHz 16KHz Both filters have a 15dB boost or cut and can be switched in or out A green LED turns on when the filter is engaged 4 ASHLY Operating Manual DPX 200 Parametric Equalizer Compressor Limiter 6 10 2 ac 15 dB Input Output Level dB Clip Th 2 4 6 8 12 14 16 18 20 18 15 12 9 6 3 0 3 6 9 20 gt 20900026 d L o 10 2 33 lt Ae gr ONC PK m 10 10 Phantom 20 2 5 15 4 22 dB o0 9 4 1 Threshold Ratio Attack Level In Power 5 5 Parametric Filters Two 20Hz 20KHz parametric filters allow cus tom tailoring of EQ points most useful for feedback con trol resonance compensation or other types of frequency specific voicing Each parametric filter consists of three main controls frequency bandwidth and level Also an in out switch for each filter facilitates easier setups by allowing comparisons between filtered and unfiltered sig nal A green LED turns on when the filter is engaged Frequency The outer concentric frequency con trol determines the filter s peak frequency or the point tha
19. ASHLY DPX 200 Parametric Equalizer Compressor Limiter Operating M anual ee 1 05200020002 209000000 0e iz 6KHz 16KHz LES amp NN amp pio cy 7 4 10 roo 45 5 10 4 20 48 yon tery o is A c 0 2 15 2 hE wre ats e 2 mo 2 00 FS of d e 2 e 2 2 E ay Freg Attack Release Output Level Irr ASHLY AUDIO INC 847 Holt Road Webster NY 14580 9103 Phone 585 872 0010 Toll Free 800 828 6308 Fax 585 872 0739 Internet www ashly com Operating Manual DPX 200 Parametric Equalizer Compressor Limiter Table Of Contents 1 INTRODUCTION 2 UNPACKING aod be segs ben eae Eee Hee dine Sead PRU Ea ERR eae TRA 3 AC POWER REQUIREMENTS 4 MECHANICAL INSTALLATION 5 PARAMETRIC EQUALIZER CONTROLS 5 1 Equalizer Input Select Switch 5 2 Gal Rees ROG Ree MAES She Rees Pee Bee X9 Phantom POWE o wie do JA Shelving Filters 222 m be eee e qe qe eR ae 3 5 Parametric eR Red ee ERE ERA EE 5 6 EQ Clipping CREAR EVE RS G
20. Compressor Limiter Troubleshooting Tips No Output Check AC power Is the power switch on Check input and output connections are they reversed Are you sure you have an input signal Controls Have No Effect Is the limiter in out switch in Perhaps the ratio control is set too low to produce an audible effect or the input level is below threshold Is the threshold LED light ing up If not lower the threshold setting or increase the gain Do not expect to hear any effect when the input level is below threshold since the unit is simply a linear amplifier at those levels 14 ASHLY Operating Manual DPX 200 Parametric Equalizer Compressor Limiter When Using Heavy Compression Background Noise Is Noticeable During Quiet Sections Of The Program As defined in the section on compression quiet program material is effectively made louder while loud peaks are made quieter When the program source is thus raised in volume its noise floor is also raised in volume by a proportionate amount This is not a defect in the compressor limiter but an unavoidable side effect of the gain altering process If the noise becomes a problem the solutions are to either decrease noise at the program source or use less compression Excessive Hum Or Noise Hum is often caused by a ground loop between components Try using the suggested balanced input and output hookups if the other pieces of equipment used in conjunction with the DPX 200 have balance
21. IP EQ Master In Out gt LINE InpuT GAIN 4 BAND 31 5 PARAMETRIC EQ 30 Line 1 ko 1 2 3 4 Individual EQ Band In Out EQ OUTPUT EJ LIMITER CHAIN 1 t CLIP INPUT OUTPUT METERS Y NN GAIN 2 VCA oi N OUTPUT LEVEL GAIN REDUCTION DISPLAY LIMITER RATIO Ed OUTPUT CHANNEL DETECTOR IN OUT ATTACK CIRCUIT lt DETECTOR RELEASE NSERT THRESHOLD NA This will only be caused by too much signal which will show on the Clip LED If the LED is not flashing there is an overload within another product in the signal path Adjust the relative gain of each component in your chain to keep everything at a com fortable level Excessive Hum or Noise Hum will usually be caused by a ground loop between components Try using the suggested bal anced input and output hook ups if the other pieces of equipment used in conjunction with your equal izer have balanced inputs and outputs Noise excessive hiss can be caused by in sufficient drive signal Make sure you are sending nominal 0 dBu line level signal to the equalizer Most noise problems occur because gain is applied to au dio signal
22. There is a common but incorrect notion that lim iting always implies the use of an infinite ratio Although there are times when an infinite ratio is desirable there will be situations where infinite or limiting ac tion is neither appropriate nor necessary In fact it should ASHLY 5 Operating Manual DPX 200 Parametric Equalizer Compressor Limiter T ASHLY 2 Model DPX 200 Made In USA iic Phantom s amp C y 100 120VAC 50 60Hz 12W 11 p id Compressor Limiter Detector Return Ducking Input Use Mono Plug For Ducking RING Detectar Send Detector Output Ser be noted that an infinite ratio setting is likely to cause noticeable side effects in the sound and may not be us able on programs where subtle control is desired 6 4 Attack Time The response of the compressor limiter to signal levels above threshold is further defined by the attack time control Attack time is the amount of time it takes to attenuate the output level after threshold has been reached For very fast transients such as hand claps snare drums or other percussive sounds a fast attack time is usually desirable so that the limiter can respond in time to control the peak level On other types of program ma terial a slower attack time may be preferred An abrupt attack may on some material square off the top of a waveform producing a distorted sound The DPX 200 pro vides co
23. advantageous to use balanced connections when running signal more than ten or fifteen feet although par ticularly noisy environments may require that even short patch cables be balanced Unbalanced connections are used mostly for short distance high level signals OdBu nominal Most exter nal EMI noise pick up will be ground Inputs are 20KQ active balanced using preci sion 1 metal film resistors outputs are 2000 pseudo balanced which means they have balanced impedance with a single ended signal source and can be wired bal anced or unbalanced When possible we recommend balanced connections between all components in your system If inputs are used unbalanced the signal should be on the connection and the connection must be tied to ground or signal loss will result While a mono phone plug used as an unbalanced connection will auto matically ground the ring of the jack XLR s will not automatically do this so attention must be given to proper wiring 7 3 Chain Switch The chain switch on the back panel allows the output of the parametric equalizer to be fed directly to the input of the compressor limiter with no external cable required When the chain switch 15 in the input connec tors to the compressor limiter are removed from the cir cuit while the equalizer outputs remain functional 7 4 Compressor Limiter Detector Loop Ducking The DPX 200 com masked under the noise floor of the signal assu
24. arametric Equalizer Compressor Limiter Gain 1 40Hz 400Hz LT Bone SE 1 TE 16KHz 0 Shelving 2 D Norm Bandwidth an D Norm eu ae 40 3 043 1 Norm Norm 3 0 3 4 10 ASHLY E el oe 315 2 Model DPX 200 a 2 3 4 EQ Parametric Equalizer 2 O Compressor Limiter 4 Clip 0 e eK tih 400 20k O 8 QU 24 9 OR QU 291 Or J 77 15 Hz gt J 8 gt Input Select ZNoctaves FEE Pea ivel a9 Fred 4 MECHANICAL INSTALLATION The DPX 200 mounts in a standard 19 inch equip ment rack The mounting screw threads vary with differ ent rack manufactures and you should refer to your rack instructions for proper hardware An oval head or flat head screw with a plastic countersink washer is preferred to protect the finish of the DPX 200 under the screw This unit is housed in a rugged steel case and will tolerate moderate abuse However for road systems which may be dropped or otherwise subjected to extreme forces we recommend some rear support for the chassis to prevent bending the front panel when these forces oc cur For installations where it is desirable to protect the front panel controls from tampering or accidental misadjustment use the Ashly security cover Installation is simple and does not require removal of the equipment from your rack See your Ashly dealer for details A
25. d inputs and outputs Noise can also be caused by insufficient drive levels Make sure you are sending a nominal 0 dBV line level signal to the unit 12 WARRANTY INFORMATION Thank you for your expression of confidence in Ashly products The unit you have just purchased is protected by a five year warranty To establish the warranty be sure to fill out and mail the warranty card attached to your product Fill out the information below for your records Model Number Serial Number Dealer Date of Purchase 13 SPECIFICATIONS Parametric EQ Input Connection Line in 1 4 Phone Jack XLR Output Connections 1 4 Phone Jack XLR 20KQ Active Balanced 2000 Pseudo Balanced 10KQ Unbalanced 100Q Unbalanced Gain Line input to 15dB Max Output Level 23dBu Input Connection Mic Low Z Balanced XLR Mic Input Pad Attenuator OdB out 20dB In Frequency Response 2dB 20Hz 20kHz Gain Mic input 20dB to 55dB THD 20Hz 20KHz lt 03 4dBu Shelving Filter Frequency Range midpoint of slope LOW eet ur wee 40Hz 400Hz Output Noise 1 6KHz 16KHz 20Hz 20KHz unweighted Shelving Filter Amplitude 15dB All controls at unity gain vts lt 1094 Peak Filter Freq Range 20Hz 20KHz EQ Peak Filters In lt 93dBu Peak Filter Bandwidth 3 1 3 to 1 20 Octave EQ Peak and Shelving Peak Filter Amplitude
26. e gis 3 7 EQ Master SWwiteli e dd 6 COMPRESSOR LIMITER 8 SUNG MM ise asa sens ET 6 2 Threshold iio Bore ET sce ex Redes e te v ae ER MMC rr GA Attack Time whe take whee 6 5 Release Trme wa ccc cta iad Hades ood Rew ESS 6 6 Output Level e norte poll ere a ples alle ae 6 7 In Out S WIteli wha eR ERR UA ERES Meee OSRAM NE AMA 6 8 Threshold Gain Reduction Display 6 9 Input Output Meter 7 CONNECTIONS AND CABLES 7 1 Balanced and Unbalanced Audio Connections 7 2 Inputs and Outputs rr Re eee UR Re a Eee edad eee ces AS Chain 2544 dre Dra ds 7 4 Compressor Limiter Detector Loop Ducking 8 TYPICAL APPLICATIONS 8 1 Parametric Equalizer Applications 8 2 Compressor Limiter Applications 8 3 Special V uS RO 9 DESIGN THEORY 10 BLOCK DIAGRAM
27. e in a fast peak limiter is really not feasible Also the matching between units is very poor so that stereo tracking is not possible without te dious hand matching of photocells Another approach uses a field effect transis tor FET as a variable resistor Here at least the re sponse time is fast in the nanosecond range but matching between units is still poor requiring hand matching for stereo An additional problem is that a 12 ASHLY Operating Manual DPX 200 Parametric Equalizer Compressor Limiter FET will only act as a pure resistor with very small sig nals applied so it is necessary to attenuate an input signal before the gain control FET and then amplify it again Of course this results in less than ideal noise performance and imposes a frustrating trade off less noise more dis tortion A number of VCA s based on the exponential volt age current characteristic of a bipolar junction transistor have been used One of the most common is called a transconductance amplifier Using the inherent match ing obtained by integrated circuit technology these de vices have very predictable control characteristics Tracking within 1dB over a 40dB range is common Not only do the control characteristics match well from unit to unit but they can easily be made exponential loga rithmic so that even increments of control voltage pro duce even increments of gain change in decibels The response time is also very
28. er a 100 1 frequency range about 6 6 octaves and a 70 1 bandwidth range with no more than a 2 dB amplitude error at center frequency At its sharpest setting the filter has a of about 35 and generates a response curve with 3 dB points only 1 20 octave apart making feedback control possible with no audible side effects Each filter is placed in the feed back loop of a summing amplifier to produce the desired frequency response Since a separate summing amplifier is used for each band no interaction between bands oc curs Compressor Limiters The Need For Gain Control The human ear excels in its ability to detect an extremely wide range of loudness levels from the quiet est whisper to roar of a jumbo jet When we attempt to reproduce this dynamic range by means of amplifiers tape recorders CD players or radio transmitters we run into one of the fundamental limitations of these electronic media limited dynamic range Amplifier dynamic range 18 quite good and is adequate for most musical program material However some types of audio equipment such as cassette tape recorders have a very narrow useful dy namic range What is it that compromises the dynamic range of this equipment The useful operating region of a piece of audio equipment is squeezed in between noise and dis tortion As program level decreases it approaches what is known as the noise floor and if the volume of the program material goes lower still
29. fast The problem with simple transconductance am plifiers is that like FET VCA s they can handle only very small signals so the noise performance is poor A num ber of linearizing circuits have been devised to minimize this problem but even the best transconductance amplifi ers have an equivalent input noise of about 80dBv which compares poorly to straight linear amplifiers The best analog compromise to date is the class AB current ratio multiplier Early implementation of this circuit used two matched pairs of transistors one pair of NPN s and one pair of PNP s The problem here is that excellent matched integrated NPN pairs were avail able but integrated PNP s were not The PNP s had to be hand tested and matched Careful trimming was neces sary for low distortion and even minor temperature changes made re trimming necessary because of differ ing characteristics between the two types The Ashly VCA The Ashly VCA is an integrated current ratio mul tiplier circuit It has low noise 90dBv low distortion 05 excellent response time and tracking and does not suffer from thermal drift The noise and distortion are at state of the art levels and the circuit is consistent in mass production with minimal trimming and no hand selection of transistors Detectors It would seem that of the two components in a compressor limiter the VCA is the more critical since the audio passes through it and the detector
30. feedback at any level you like by simply varying the limiter output level control although below a certain monitoring level the feedback will stop 4 Try to determine the feedback frequency and then equalize it by adjusting the center frequency band width and boost cut controls of your parametric equal izer Note a graphic equalizer can also be used although with less accuracy After eliminating the problem fre quency try to further define it by sharpening up the band width reattacking the frequency control and making the cut shallower if possible 5 As soon as the first feedback frequency has been removed the compressor limiter will automatically bring up system gain until another feedback point is in duced Repeat the equalization procedure until it becomes impossible to distinguish individual predominant feed back frequencies 6 Write down EQ marks for safekeeping if nec essary and return all mixer EQ master gain and com pressor limiter gain controls to normal operational settings Altering the Texture of Musical Instruments It would be impossible to mention here all the ways that compression is used to create new sounds with familiar instruments Some typical uses are 1 Creating a fatter kick drum or snare sound 2 Thickening acoustic guitars 3 Adding punch and sustain to electric bass or guitar In general use a gentle compression ratio say 4 1 with a 10 mS attack time 0 1 Sec
31. in gain and a slow fade up making the action of the limiter very obvious With the double time constant release from gain reduction after a brief transient is al ways fast with a slower release after a sustained over drive When choosing a compressor limiter you can see that it is very important to listen to it in your particular application and see that it sounds the way you want There are lots of these devices with seemingly excellent specs which sound very different with real program material applied to them Peak Or RMS There are several ways of looking at a signal to determine its level A peak detector looks at the maxi mum voltage a signal reaches regardless of it s waveform while an RMS root mean square detector looks at the energy in a signal regardless of the short term voltage levels This makes a peak detector the correct choice for preventing clipping overmodulation or tape saturation while an RMS detector can be used to restrict material to a given loudness When an RMS limiter is used to pre vent clipping the result is unpredictable For instance a flute and a snare drum which are limited to the same RMS level might have peak levels as much as 30dB apart Use peak limiters to prevent clipping ASHLY 13 Operating Manual DPX 200 Parametric Equalizer Compressor Limiter 10 BLOCK DIAGRAM Distorted Sound MIC DPX 200 Block Diagram INPUT p roh 5 h Te CL
32. level control is provided to fully cut or restore up to 18 dB of system gain For unity gain set the control to 0 NOTE When the compressor limiter is switched out the output control still functions 6 7 In Out Switch This switch enables you to quickly hear the com pressor limiter in or out of the audio chain When the switch is in the out position all limiting and compres sion controls and functions are bypassed with the excep tion of the gain and output controls which continue to function as straightforward level controls 6 8 Threshold Gain Reduction Display As soon as the threshold level is reached the yel low LED illuminates Depending on how far the input level rises above threshold successive red LED s will il luminate indicating gain reduction Gain reduction can best be described as the difference between input level and the resulting change to output level For signals below threshold there will of course be no gain reduc tion that is a 10dB increase in input will yield a 10dB increase in output For signals above threshold however output level will increase only to the extent that the ratio control allows With a high ratio say 20 or so it will take 20dB of increased input level to increase output level by IdB With a gentler ratio of 3 1 input signals above threshold will be gain reduced at the output by 1 3 In other words with threshold set at OdB a signal peak at 12 dBV that is 3 1 compressed rati
33. ming there is little or no gain following the unbalanced signal If a gain stage does follow a signal or if externally sourced noise per 1515 use balanced connectors 7 2 Inputs and Outputs Tip 4 Ring Sleeve Gnd pressor limiter has a TRS In sert DETECTOR PATCH point which can be used as a ducking input or in con Tip J Sleeve Gnd B Stereo Phone Plug 594 ed used for balanced junction with an equalizer to produce frequency sensitive limiting Various uses of the detector patch are discussed The DPX 200 uses two dif 8 Mono Phone Plug used for unbalanced under TYPICAL APPLICA ferent audio connector types 1 4 TIONS a z m o TRS tip ring sleeve phone jacks XLR pins are NES and three pin XLR connectors will al num gereg e e pm low interfacing to most professional connecte RENE audio products Ashly TRS balanced sd connections use the tip as and the de m ring as signal with sleeve used for ppm ground Ashly XLR connectors use Audio Connector Types pin 2 and pin 3 with pin 1 ASHLY 7 Operating Manual DPX 200 Parametric Equalizer Compressor Limiter 8 TYPICAL APPLICATIONS By itself a parametric equalizer is useful for gen eral tone control feedback control room resonance cor rection individual microphone voicing and many other applications
34. ntinuously variable attack times from 200 micro seconds to 20 milliseconds 6 5 Release Time Another parameter which affects compressor lim iter performance is release time or the time required to restore system gain to normal after the input signal has fallen below threshold level Again proper release time will depend on the type of program material being processed and the way in which the limiter is being used When subtle limiting is desired slow release times are often chosen to avoid condition referred to as pumping or breathing This occurs when overall gain is modulated up and down by repeated peaks which are followed by quieter intervals If the release time is set too fast then the overall level will jump up and down producing an objectionable and unsettling effect Note that in some cases an individual track or channel which seems to be pumping may sound acceptable when heard in context of a complete mix A unique feature of all Ashly compressor limit ers is the incorporation of a double release time con stant When a conventional compressor limiter is adjusted for slow release times transients such as mic pops may cause a severe reduction in gain followed by a slow fade up making the action of the limiter very obvious With the double time constant release from gain reduction af ter a brief transient is always fast with a slower release after a sustained overdrive 6 6 Output Level Output
35. o at 3 will produce only 4 dB 12 3 at the output and 8 dB of gain reduc tion has occurred 12 dBV input minus 4 dBV output 8 dB reduction 6 9 Input Output Meter Select While the gain reduction display accurately rep resents the action of the limiter comparing input to out put levels in real time is somewhat more intuitive and is made simple using the input output meter select switch 6 ASHLY Operating Manual DPX 200 Parametric Equalizer Compressor Limiter INPUTS are Active Balanced OUTPUTS May Be Wired Balanced Or Unbalanced The input meter takes its signal just after the gain con trol and will indicate input signal level regardless of out put levels or limiter settings The output meter display takes its signal from the actual output of the unit so ev ery control that affects the output will also have an effect on output meters Used in conjunction with the gain re duction meters input output meters prove to be an ex tremely useful diagnostic tool when working with system dynamics and level control 7 CONNECTIONS AND CABLES 7 1 Balanced and Unbalanced Audio Connections Balanced signal connections are preferred in pro audio applications because of their improved immunity to induced hum and noise A properly shielded and wired balanced input stage on any audio product will reject most unwanted noise RFI EMI picked up by the cable as well as minimize ground loop problems Therefore it is always
36. og recording Also with modern trends toward inexpensive digital recording it remains neces sary to protect against input overload With digital re cording the information stored on tape hard disk optical disk etc is either a 1 or 0 so actual signal level on the tape is not the concern it is with analog recordings in fact it is not even a user controllable parameter What is of concern however is the signal level applied to the A D analog to digital converters If clipping occurs at the converter input stage the resulting distortion is most un pleasant and will be recorded digitally as if they were part of the original audio signal forever mixed with the audio To prevent converter distortion while preserving the extended dynamic range of digital recording look up the max input level of your recorder converter and set up the limiter as follows Set Gain to 0 Set Threshold to 2 3 dB below max converter input Set Ratio to 10 Set Attack to 2 mS Set Release to 2 Sec Set Output level to 0 Ne If you are exceeding threshold frequently your input signal is probably too high and should be turned down Of course every situation is different so experi mentation before final recording is always a good idea but this is a good starting point To obtain a gentler limiting action at the expense of some dynamic range decrease the threshold to 15 and the ratio to 3 5 This is also a good starting point for
37. ote that the gain control is always active regardless of the setting of the EQ master switch 6 COMPRESSOR LIMITER CONTROLS 6 1 Gain The Gain control is used to adjust incoming sig nal level to the VCA circuit It is always active so switching out the limiter function has no effect on this control Used in conjunction with the input output level meter display this control is useful for setting up optimal system levels This control should normally be left at 0 to achieve accurate threshold calibration 6 2 Threshold The threshold control has a range of 40dB to 22 dB allowing applications from low level compres sion to high level limiting The threshold control de termines the audio level above which gain reduction occurs When the threshold LED comes on that means that gain reduction is beginning to occur due to input signal peaks exceeding the selected threshold in dB 6 3 Ratio This control determines the resultant change in output level to changes in input level for all signals above threshold The numbers printed around the ratio con trol are calibrated in db and indicate the increase in input above threshold required to produce a 1db in crease in output This can be expressed conveniently as a ratio If the output remains constant no matter how high the input level we have an infinite cc input output ra tio It should be remembered that the ratio control has no effect on signals which are below threshold
38. s long reverberation times and ring modes all of which lead to reduced intelligibility and a generally muddy sound As sound travels long distances through the air high frequencies are attenuated more than low frequencies In general large rooms ben efit from some low frequency roll off high frequency boost and attenuation of ring mode frequencies 8 2 Compressor Limiter Applications As the functional name implies a compressor limiter can be divided into two basic categories limiting and compressing When used as a protective device to prevent audio levels from overloading systems such as tape recorders power amplifiers speakers or transmit ters it is generally referred to as a limiter It may also be used to create special effects and unusual sounds for recording and musical performance by deliberately reducing the dynamic range of a signal creating a much louder or fuller sounding signal without increasing the loudness peaks in which case it is referred to as a compressor The Limiter As A Protective Device The DPX 200 compressor limiter section pro vides fast and accurate gain control for the prevention of sound system overload due to unexpected transients Sound system distortion is usually the result of amplifi ers running out of power in which case nice round wave forms turn into harsh sounding squared off waveforms Looking at it from the perspective of the speaker dia phragm this means that whereas
39. s too late in the chain For best performance apply gain to individual source signals as early as possible like at the mixer input preamp section As gain increases it also boosts the noise content of that signal Any cumulative noise built up in a mixed sig nal will only be increased by using an equalizer as a gain device so make every attempt to operate the 11 Equalizer Troubleshooting Tips No Audio Output Check AC power is the pilot light on Check in out connections are they reversed Are you sure you have an input signal Is the correct input selected Is the gain control turned all the way off EQ Controls Do Nothing Is the individual filter or master EQ switch 1n Is the bandwidth set too narrow to be heard The lowest and highest frequency filters may be beyond the range of the program material or speakers and may produce little or no audible effect Peak Light Flashes or Stays On the Time If the peak light flashes the signal level to the equalizer is too high or a particular filter is boosted too much Turn down the gain or switch the EQ filters If it is on all the time disconnect the input and output cables If it is still on the unit must be returned for service equalizer with as little gain as possible Note Unshielded cables improperly wired con nectors and cables with broken strands of wire are very common problems Use quality cables with quality cor rectly wired connectors 11 1
40. shly Security Cover Installation 5 PARAMETRIC EQUALIZER CONTROLS 5 1 Equalizer Input Select Switch The DPX 200 equalizer input is selectable be tween line level or mic input each with its own connec tor The line level input is used for normal signal processing while the discrete mic input provides more gain for those applications where the DPX 200 is used as acomprehensive mic preamp Press the input select switch in for line input and out for mic input 5 2 Gain A single knob dual function gain control is used for both mic and line inputs When the mic input is se lected the gain range is from 20dB to 55dB A 20dB pad switch on the back panel allows for nominal OdB mic input level When line level input is selected the gain control range 15 to 15dB Unity gain for line level signal is 0 5 3 Phantom Power 48 phantom power is provided to the mic in put XLR for use with condenser microphones The phan tom power switch is on the back panel and a red LED near the power switch indicates that phantom power is turned on 5 4 Shelving Filters The nature of a shelving filter is such that the fre quency response ramps up or down to a plateau and then levels off again hence the term shelf The DPX 200 has a low and high shelving filter for general tone control or correction Using the outer concentric knob the calibrated frequency tick marks indicate the halfway point between unaffected signal and the frequency
41. t is boost or cut peak filter as the name implies has a symmetrical rise and fall around the center fre quency as opposed to the plateau nature of a shelving filter For maximum frequency resolution on the para metric filter a frequency range switch divides the cali brated frequency labels by 10 meaning that if the frequency control is set at and the range switch is then pressed in the frequency is now 100Hz instead of 1KHz Tick marks on the face panel are calibrated to ISO 1 3 octave center frequencies Bandwidth The inner concentric bandwidth control determines how broad or narrow the peak filter coverage is and is expressed in octaves For general tone control use a broader bandwidth For notching out feed back frequencies use a narrower bandwidth Being able to optimize bandwidth for the job at hand is the main reason parametric equalizers are preferred for notching and feedback control Level As with the shelving filters the level con trol boosts or cuts the frequency by up to 15 dB at the filter peak 5 6 EQ Clipping The equalizer section has its own clip LED in case both the EQ and comp limiter are wired indepen dently All critical signal points within the parametric EQ are monitored for signal level which exceeds 19dBu 5 7 EQ Master Switch The EQ master switch allows easy comparison between filtered and unfiltered signal A green LED next to the switch turns on when the four filters are engaged N
42. that each component s electrical specifica tions are within tight tolerances before becoming part of the circuit assembly Each finished unit is then tested twice before leaving the factory guaranteeing you a worry free professional product for many years Please read this instruction manual thoroughly before operation so that you may realize all the features and benefits the Ashly DPX 200 has to offer 2 UNPACKING As a part of our system of quality control every Ashly product is carefully inspected before leaving the factory to ensure flawless appearance After unpacking please inspect for any physical damage Save the ship ping carton and all packing materials as they were care fully designed to reduce to minimum the possibility of transportation damage should the unit again require pack ing and shipping In the event that damage has occurred immediately notify your dealer so that a written claim to cover the damages can be initiated The right to any claim against a public carrier can be forfeited if the carrier is not notified promptly and if the shipping carton and packing materials are not avail able for inspection by the carrier Save all packing mate rials until the claim has been settled 3 AC POWER REQUIREMENTS A standard IEC 320 AC inlet is provided on the rear panel to accept the detachable power cord shipped with the unit Units distributed within the United States ASHLY 3 Operating Manual DPX 200 P
43. u want more or less of these types of sounds Adjust by ear from there It is always a good idea to remember that a little equalization usually works out much better than a lot and that there are many audio problems which cannot be solved with equalization alone Feedback Control The parametric equalizer is a powerful tools when applied to eliminating feedback problems On a tradi tional graphic equalizer the fixed filter center frequen cies are insufficient when the frequency of feedback oc curs between two slide faders or is extremely narrow The continuously variable center frequency and bandwidth of a parametric equalizer allows very sharp notching of feedback frequencies The following procedure outlines how to use a parametric equalizer to suppress feedback frequencies 1 Start with all the EQ switches out except the master EQ switch in and the gain at 0 2 With the entire PA hooked up and turned on slowly increase the sound level at the mixer until feedback is heard then lower the level by about 3 dB so that feedback does not continue 3 Start with one of the two parametric filters by setting the level at 0 bandwidth set fairly sharp about 3 oct and adjust the frequency control to where you estimate the predominate feedback frequency to occur 4 Push in the filter s EQ switch and increase its level control by about 6 dB Now sweep the frequency around where you have estimated the feedback frequency
44. undistorted breaks up on the esses producing a raspy un desirable sound With analog recording to magnetic tape high frequencies tend to saturate the tape sooner and com bined with the internal high frequency boost record pre emphasis on standard tape decks the need to control sibilants becomes apparent The solution is frequency dependent limiting which is easily accomplished with the DPX 200 By in serting an equalizer into the Detector Patch point and boosting the equalizer at high frequencies in the vicinity of the sibilant the limiter s detector circuit becomes more sensitive to this particular range of frequencies and so will limit the bothersome sibilants more than other fre quencies Realize that this technique is very different from simple equalization Equalizing a sibilant vocal by cut ting high frequencies would result in a loss of important high frequency information at all times whereas de essing has no effect whatsoever on the signal except at the in stant of the sibilant At that moment the Ashly limiter will reduce overall gain Frequency response is unaf fected and the sibilant is controlled 9 DESIGN THEORY Parametric Equalizers The heart of Ashly parametric equalizers is a unique bandpass filter circuit Basically a state variable type this filter is trimmed and optimized to provide excel lent transient response and a wide range of frequency and bandwidth adjustment Each filter can be tuned ov
45. vel as high as possible without risking distortion Gain Riding One solution to the noise vs distortion trade off is to keep your hand on the level control and manually adjust gain to suit the program Indeed there are times when this approach is entirely satisfactory However in most types of music there are instantaneous short dura tion volume peaks or transients which would be difficult to anticipate and impossible to respond to with manual gain riding you simply could not bring the level down fast enough In many situations this can present real prob lems For example in recording an extra burst of enthu siasm from a lead singer might overload the capabilities of your recording tape causing ragged distortion and ne cessitating another take In sound reinforcement a sud den burst of energy through the system can blow fuses or even damage loudspeakers In addition to the problem of response time with manual gain riding it also requires your constant atten tion which takes you away from more important jobs The need for a fast acting reliable automatic gain control is answered by limiters and compressors What Compressors and Limiters Do Limiting In any musical program are constant changes in loudness It is the job of a limiter to detect when the vol ume has exceeded a predetermined maximum safe level and to then turn down the volume When the incoming signal returns to its original level the limiter should re
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