Advanced Users Guide
Contents
1. There is also a line level OUT on the rear panel This 1 4 Stereo connector can be used to run most stereo headphones However the signal itself is always mono The line output is also useful for running into house sound or a recording rig It has its own level adjustment so that you can adjust the level of your phones once the Lunchbox controls are set where you want them Unlike most headphone outputs this one doesn t mute the internal speaker If you want to do that just use the SPEAKER switch This approach give you total control of what is on or off at any given time For example you can use the Lunchbox to monitor the sound on stage even when routing into the board via the line out Using The Lunchbox With Other Instruments The Lunchbox is not just for guitars In fact the Lunchbox loves a very wide variety of instruments and sound sources Excellent results have been achieved with acoustic guitar pickups harmonica electric piano sax accordion electronic organ traditional string instruments and synths We ve even seen people successfully run an electric bass through the Lunchbox in a small venue Start with the GAIN TONE and REVERB controls all set at midpoint and the VOLUME all the way down Then inch up the VOLUME step by step Season to taste Because of the high available gain some acoustic instruments may tend to feedback if the GAIN control is accidentally set too far up 0901_v02 Mic ing The Lun2. The External Speaker Output There is a 4 external speaker output connector on the rear of the Lunchbox which can be used to power an external cabinet The Lunchbox makes a really good sounding very powerful head With the right cabinet we think you will be stunned by the results If you decide to try this please not the following IMPORTANT rules v This output is fully balanced and high power Connect it only to a speaker cab y Do not use this output for recording or connect it to other amps v Use a speaker cabinet rated at 8Q or higher v Be sure your external cabinet can handle at least 100W I s usually a good idea to turn off the Lunchbox s internal speaker when using an external cabinet to make 100 of the amp s power available to the output This is done by setting the rear panel SPEAKER switch to Off 0901_v02 Additional Inputs and Outputs The Lunchbox can accept a line input from an audio source such as an MP3 player via a standard 1 8 Stereo jack on the rear panel labeled AUX INPUT This input is not affected by the GAIN control but does run through all the other Lunchbox controls The input impedance is 22KQ and the expected signal level is 50mVrms If you need to tweak the relative balance between your guitar and your MP3 player you can use the GAIN control to do it or adjust the output level on your player It is recommended that you disconnect any cables from the AUX INPUT when it is not in use
3. historians and coveted by amp collectors for all its little quirks 0901_v02 Reverb vs Ambience Speaking of quirks the Lunchbox has another one we should probably explain The labeling on our Reverb control may be confusing and really should be called AMBIENCE What this control actually does is add the type of natural short term reflections that emanate from the rear of an open back cabinet These reflections are a big part of why open back amps have such a rich and dimensional sound You can use this knob on your Lunchbox to dial in some nice dimensionality and fullness to your sound But it s a subtle effect and you won t get a Surf sound out of it even if you turn it up farther than you probably should We did it this way because we could the effect was a natural outgrowth of the proprietary technology we use in our signal chain If you want a more conventional reverb sound you will need to plug in an external unit Or of course go record in the bathroom Hey it can be fun Just stay out of the tub that s for the drummer and make sure your wall sockets all have Ground Fault Interrupters Seriously what we would like for you to do if you love your Lunchbox but need a more traditional reverb tone is consider ZT s new 12 Club Series amp It has all of the sound character of a Lunchbox and more in an incredibly powerful and compact enclosure Plus it has a very good sounding more traditional reverb
4. is sure to upset the balance and operation of the whole For example our speaker driver is fully custom and built using special high power components You won t find anything else quite like it So enjoy your Lunchbox and please do send us any and all suggestions you have We take our customers input very seriously Oh and we like compliments too Thanks 0901_v02
5. with more traditional approaches We believe it is time to re think the fundamental design of the guitar amp bringing in advanced audio technology without losing the wonderful benefits of proven classics We offer the Lunchbox amp as proof that ZT has cracked the code It s an amp that is small simple and affordable bringing a whole new level of sound and tone to portable applications And it s an amp with a personality all its own a flexible and adaptable problem solver in the hands of a musician The Lunchbox is layered with responsive tone but powerful and seriously fun to play at the same time Isn t that what classic is all about anyway 0901_v02 Initial Setup When first connecting your Lunchbox before power is applied please be sure to set the controls as follows v REVERB AMBIENCE set to off Fully counter clockwise y TONE set to mid point 12 o clock position y VOLUME set to off Fully counter clockwise y GAIN set to mid point 12 o clock position v SPEAKER switch on rear panel set to On position Towards left side y Now you can apply power and turn up your instrument to the desired level using the VOLUME knob The Signal Path The main input to the Lunchbox is via a standard 1 input on the top panel This input has an impedance of 1MQ 2MQ DC and can accept working signals up to 6Vpp It is protected against RF interference and ground error overloads After the inpu
6. In almost all cases this control should be set high up well above the 50 point on its range This will assure a good tone and low operating noise The only time the gain should be turned down is when a very clean tone is needed for an excessively high signal input such as when certain external effects units are used with the Lunchbox Minimizing Noise The ZT Lunchbox can deliver peak sound pressure levels in excess of 134 dB to a listener sitting 1 ft 0 3 m in front of it Thus even boasting an excellent Signal to Noise Ratio of 85 dB with certain control settings there can still be a residual peak noise level of almost 50 dB in the near field This can be quite audible and is simply a function of how loud the amp is capable of playing and the high gain gt 4 000 that is potentially available We could have put an aggressive noise gate in the circuit like many modern amps do but the tone touch and sustain of the amp would have been negatively impacted The key to low noise is to Keep The GAIN Knob High and Use the VOLUME Knob To Adjust your sound level Yes we realize now that we probably should have reversed the position of these two knobs on the top panel Hindsight is a painful thing We hope you love the Lunchbox so much in other ways that you can forgive us and get used to the drill You can perhaps console yourself with the knowledge that you own a first generation Lunchbox sure to be admired by future
7. ZT AMPLIFIERS APPLICATION NOTE 0901 2000 02 Lunchbox2 Advanced Users Guide The ZT Amplifiers Lunchbox2 is a product unlike any other musical instrument amplifier currently available This Application Guide was developed to help the advanced user understand its unique features and characteristics The Guide is not intended to replace the Owners Manual It is assumed that the reader is already familiar with the basic features and operations of the Lunchbox2 Our purpose here is to explain more detailed technical concepts to help the serious user get the most from their sound Topics Include e Lunchbox design philosophy e Initial setup e Signal path e Gain and volume controls e Minimizing noise in real use situations e Reverb vs Ambience e External speaker output e Additional inputs and outputs e Using the Lunchbox with other instruments and sound sources e Mic ing the Lunchbox e Understanding amplifier power e About modding ZT Amplifiers Inc 2329 Fourth Street Berkeley CA 94710 USA www ztamplifiers com 1 510 704 1868 Design Philosophy The ZT Lunchbox is the result of many years of study into the sound feel and science of the world s best musical instrument amplifiers Our goal was not to clone or model any particular product Rather we have tried to understand in a methodical way what technical factors give an amp great tone flexibility and playability As a group of experienced au
8. chbox When making a recording or running through a house PA a great sounding amp really deserves to be mic d Direct feeds are convenient sometimes necessary but they rarely capture the full tone the player is hearing Because the Lunchbox uses a very unique speaker which is also smaller than most adjustments to your usual approach might be worth trying Getting really good recordings always involves experimentation but here are some general tips v Start with the microphone directly in front of the driver s dustcap about 6 back from the grille Cardioid LD condensers are the first choice if available Cardioid SD s are good too An Omni SD can capture a very accurate sound but you might have move it in closer to the grille and play with side to side positioning A spot about halfway between the center dustcap and the outer edge surround of the speaker will often work well The classic dynamic guitar amp mics can work of course but be prepared to try a variety of setup positions to get the tonal balance you want Remember the Lunchbox can be Loud and it concentrates a great deal of sound energy into a small area Unless you are an unusually soft player you will probably have to engage the pad on your mic Using a foam windscreen is also a good idea since the driver can create bursts of air when driven very hard 0901_v02 Understanding Amplifier Power Nobody has come up with one numbe
9. dio scientists and passionate musicians we set out to learn what makes a classic amp survive for generations giving artists of many styles and genres a consistently great playing experience over the years ZT s research investigation was clean slate We didn t assume we knew any secret magic formula we set our own techno biases aside Likewise we did not assume that conventional wisdom is always all that wise What we found is that guitar amps are fantastically complex systems Many aspects of the overall product design interact with one another under real world playing conditions Sections of the electrical circuit influence each other the electrical system interacts with the acoustical system etc Some of these interactions are well known to amp aficionados and designers Others have been underrated or overlooked entirely Thus we soon came to realize that guitar amps have plenty of mysteries to reveal and plenty of room for improvement in areas that musicians would appreciate Eventually ZT started collecting real practical insight into wnat makes great amps tick In our view optimization between electrical acoustical and mechanical subsystems is the key to bringing more tone power smaller size and lower costs into the picture By applying sophisticated technical understanding to overcome limitations that have previously been considered facts of life ZT is able to re write some of the rules while working in complete harmony
10. r that can fully represent the power capability of a guitar amp RMS is a very conservative approach but it misses the issue of dynamic power and real world musical signals At the other extreme Peak Power can readily be inflated to the point where it is not a reliable indicator of anything In fact the actual power of any given amplifier varies widely at different frequencies Every amplifier company has their own procedure for stating the power capability of their products which ideally should be done within the boundaries of accepted technical standards and legal requirements Here is our thinking on the matter which we believe results in specifications that are both conservative and useful The internal speaker of the Lunchbox is nominally 6Q with a DC resistance of 5 3Q Electrically the amplifier output stage runs differentially using a 48V rail The output stage can source in excess of 41Vp or 28Vrms into the speaker load This yields the following typical specs Maximum Instantaneous Peak Power 280W Musical Peak Power 236W RMS Power 130W Sustained Average Music Power 200W Finally Two Words About Modding Please Don t Sooner or later most of us get the urge to modify or improve our amps by replacing various parts But remember the Lunchbox is not like other guitar amps It is a highly integrated and optimized system combining electrical acoustical and mechanical subsystems Replacing any element of this combination
11. t stage preamp the signal is sent to an analog GAIN pot on the front panel and then into a diode overdrive network Thus the GAIN knob controls the input sensitivity and allows an analog overdrive to be applied to the signal if desired Following this analog input preamp the signal is converted to 24bit PCM digital at a 44 1 KHz sampling rate In the digital domain ZT s proprietary dynamics and EQ signal processing are implemented Also a TONE control with characteristics closely following a vintage stack is applied Finally adjustable Ambience processing is done allowing the user to obtain the sound of an open back cabinet a closed back cabinet or anything in between At this point the signal is converted back to analog and routed to the power amplifier The output amp section is carefully designed to constantly adapt to the signal characteristics and the instantaneous power supply behavior The amp itself is a pair of Class A B output stages running fully bridged across the speaker load The result is very high RMS power with extraordinary additional peak dynamics on top of that together with a natural progressive overdrive characteristic 0901_v02 Gain and Volume Controls Normal adjustments to the sound level should be made using the VOLUME control only This knob affects the signal levels at all inputs and outputs The GAIN control is used to set the amount of signal drive and natural distortion that is achieved
Download Pdf Manuals
Related Search