Sound Lab Mini-Synth PLUS with MICRO SAMPLE AND HOLD

Sound Lab Mini-Synth On Steroids This project is a reprise of the Sound Lab Mini-Synth with the addition of a Sample and Hold and several circuit and component value changes to improve performance. Even if you have already built a Sound Lab I would recommend this as a completely new project. Of course if you desire to you can mod your existing Sound Lab to match this project. I will call attention to changes from the original Sound Lab.

This is an ambitious project and I do not recommend it to beginning electronics or synth-diy enthusiasts. If you have already built a sound lab you can do the mods listed here and improve the functionality of your Sound Lab. Please read the entire page and study the schematics before picking up your solder iron (you'll be glad you did). If you already have a Sound Lab and are happy with it as it is then leave it alone. Why mess with success? I built one anew and it looks almost like the artist's rendering above. Except you get the benefit of not making the mistakes I did and having to do lots of rework. There are kludges that will require some skill but nothing really that difficult. Follow the pictures and drawings carefully and you will have a very cool analog synthesizer to enjoy.

This project is kind of like two projects in one and requires 2 circuit boards. A Sound Lab Mini-Synth PCB and the new "MICRO SAMPLE AND HOLD" PCB, both are available for sale below. All of the details for the MICRO SAMPLE AND HOLD are presented the bottom of this page.

Between the schematics, layout drawings, and photos there are over 50 new images here to help you and 16 new PDFs. On many of the kludge photos if you click you will ge a much larger view. I hope you enjoy the project and I know you'll enjoy the outcome. It has turned the cool factor up to beyond 11 on the Sound Lab Mini-Synth.

Well that's enough introduction. Below you'll find the schematics and everything else you need to build this cool project. If you find glaring errors or omissions please let me know so I can correct them. I'll be getting some sound samples up here soon but I need to eat and take a shower first :-) Enjoy!

Buy Sound Lab Mini-Synth And/Or MICRO SAMPLE AND HOLD PCBs via PayPal

Sound Lab Mini-Synth PC Board (6.6" x 3.7")

MICRO SAMPLE AND HOLD PC Board (2.8" x 1.8")

With S2 is in the off state and S3 set to "Trig'd" the circuit functions as follows. When S1 is momentarily pressed it discharges C2 (to about 1.6 volts) through R2 which causes pin 2 of IC1-A to go high. This pushes a positive pulse through C1 and D1 which sets the flip flop made up of IC1-E and IC1-F. IC1-F pin 12 goes high and C3 begins to charge at the rate set by the Attack pot R10 from -8 volts to about 6.5 volts (this voltage is buffered by IC2-B voltage follower) at which point IC1-B's output goes low and IC1-C's output goes high and the IC1-E/IC1-F flip flop is reset by the high logic level presented to pin 13 via D5. This causes IC1-F pin 12 to go low and discharge C3 at a rate determined by R11.

When the "AR Repeat/S&H Trig" switch is in the "AR Repeat" position and the voltage at IC2-B is lower than -6 volts then IC1-D pin 8 goes high and sets the IC1-E/IC1-F flip flop again thus causing the cycle to begin again and subsequently repeat. Notice that I am allowing negative voltages to reach the inputs of the schmidt triggers but that they are protected from drawing high current through their internal protection diodes during that time by the high value resistors in series with their inputs.

When S3 is in the "Gated" position the repeat function is disabled. In this configuration a high level is presented to the "Attack" diode/pot combo as long as S1 is held pressed (because the output of IC1-A is high when S1 is held pressed). Gate mode allows C3 to charge from -8 volts to about +8 volts maximum. When S1 is released a low level is presented to the "Release" diode/pot combo (because the output of IC1-A is low when S1 is not pressed). The output of IC2-B is fed to R15, the AR Envelope output level adjustment pot. The circuit point "AR" is the wiper of R15, which is fed to the AR-Gen switches of the modules.

While contemplating this circuit remember that the inverters are schmidt triggers and that their inputs must go lower than 1/3 of the supply voltage before their output goes high and then the input must go to greater than 2/3 of the supply voltage before the output goes low. This characteristic is know as hysteresis.

The zener on the external gate is meant to protect against gate signals greater than 9 volts. When the gate is high transistor Q8 will discharge C2 the same way switch S1 does.

Connecting the Sample & Hold Gate output to the Sound Lab

R200 is mounted as shown. Be sure to mount it on the pads shown because there are kludges to follow that depend on it being in the right place. Notice it is the last set of connected pads to the left in the PROTO AREA. One side of R200 goes to the front panel point marked R200 Pin 2 (which is a pin on switch S2 "Internal Repeat/S&H Trig"). The other side of R200 is connected to a wire which is soldered to the end of 100K resistor R1 that connects to the base of Q8. This mod is used to connect the Sample & Hold gate output to the Sound Lab.

These two circuits are practically straight out of the National Operational Amplifiers Databook data sheet for the LM13700. They have linear voltage control but for a sound box they're fine. The transconductance characteristic of these Op Amps makes them perfect for VCAs and VCFs.

In the VCA the control voltage controls the current flow through the amp and subsequent level of the signal at the output. S4 switches the AR Gen control voltage on or off. When on, the level of the AR Generator output pot determines how much the AR Generator controls the signal amplitude at the output of the VCA. S5 switches the LFO control voltage on or off. When on, the level of the LFO output pot determines how much the LFO controls the signal amplitude at the output of the VCA. R19 controls the initial amplitude at the output of the VCA. When S4 or S5 is on it is best to turn R19 all the way down and then up as needed.

In the VCF the OTAs act as voltage controlled resistors which change the pass-band (in band pass mode) and cut-off frequency (in low pass mode) from low (for low control voltage) to high (for high control voltage). The resonance control adjusts the feedback around the circuit and thus the gain at the cut-off frequency. At high resonance settings the filter rings adding harmonics to the filtered signal which give the classic synthesizer wahhhhh sound when the cut-off frequency is swept from low to high. The filter also acts as the mixer as all of the signal sources are presented to its input via attenuation pots (R29, R38, and R44). It is not necessary to turn the inputs to the filter all the way up. When you do so you can overdrive the filter resulting in distortion (which won't hurt anything and you may even like it). With high resonance keeping the inputs low will keep the filter from peaking into distortion.

The input to the VCA is either the low pass output or the band pass output determined by the setting of switch S6. S7 switches the AR Gen control voltage on or off. When on, the level of the AR Generator output pot determines how much the AR Generator controls the cut-off frequency of the VCF. S8 switches the LFO control voltage on or off. When on, the level of the LFO output pot determines how much the LFO controls the cut-off frequency of the VCF. R37 controls the initial cut-off frequency of the VCF. When S7 or S8 is on it is best to turn R37 off or nearly off.

Adding R216 To The Bottom Of The PC Board
	R216 is mounted as shown on the bottom of the PC Board in the vicinity of IC4. It goes between -V and a land that is connected to pins 1 and 16 of IC4.

The sound lab uses two voltage controlled ramp oscillators. IC5-B and IC5-A and associated transistors and components comprise a linear voltage to logarithmic current convertor. The control voltages which are summed by IC5-B range from -8 to 8 volts. The corresponding current ranges from around 1uA to 1mA and since the oscillators go up approximately 1 octave every time the current doubles this gives the oscillator a nice range from a sub-audible 0.6 Hz to beyond human hearing.

The explanation of the operation of oscillator 1 follows (oscillator 2 works the same way using its associated components). Oscillation occurs because as the current is sucked out of the input of integrator IC5-D its output goes high until IC5-C (comparator with hysteresis) pin 8 goes high and turns on the N-Channel FET (Q5) which shorts the integrating capacitor (C8) which causes the cycle to begin anew and subsequently repeat. IC6 is used in a similar configuration.

The output of IC6-D (point ZZ) is fed into comparator IC2-A in order to provide a square/pulse wave shaper for Oscillator 2. The control voltage fed into IC2-A pin 2 via resistors R86 and R87 determine the comparator threshold and thus the point at which the output (pin 1) goes high and low. Varying R85 will change the pulse width which will vary the timbre of Oscillator 2 when Rect Wave is selected. S15 permits the LFO output voltage to modulate the pulse width which can cause the output of Oscillator 2 to sound almost like 2 oscillators beating against one another (when approximately 1HZ LFO frequency is used).

S11, S13, S12, and S14 are used to feed the AR Generator, Sample & Hold, and LFO outputs to the CV inputs of the VCOs. When on, you will hear the obvious effect as you advance the LFO and/or Sample & Hold or AR Generator output adjustments.

S9 causes Oscillator 2 to sync to the frequency of Oscillator 1. This provides some very cool timbres which you will hear if you turn on Sync and then tune Oscillator 1 lower than Oscillator 2 and sweep Oscillator 1 upward in frequency.

Adding The Fine Tuner Pot Support To The Board

R208 is mounted as shown and one side goes to the front panel point named "R208 Pin 1". The other side of R208 gets attached to a wire that goes to the end of R63 that connects to pin 6 of IC6. R207 is mounted as shown and one side goes to the front panel point named "R207 Pin 1". The other side of R207 gets attached to it's neighbor R210's lead. R210 is mounted as shown and one side goes to the front panel point named "R210 Pin 1". The other side of R210 gets attached to both the lead of it's neighbor R207 and a wire that goes to the end of R62 that connects to pin 6 of IC5.

Adding The Improved Sync Circuitry To The PC Board
	R225 is mounted as shown on the bottom of the PC Board in the vicinity of IC6. It goes between -V and a pad that is connected to the gate of Q6.

	If installed, clip the leads of and remove components C21, C12, R103, and R71. Desolder and remove the remaining portions of the leads of these components. Make a tripod out of D11 (1N914), D12 (1N914) and R72 (20K resistor) by connecting the cathodes of the two diodes and a leg of the resistor as shown and apply solder to the connected leads. After making the tripod, insert all three components at once and only then solder them in place. Insert the anode lead of D12 into the component hole for the side of R72 that connects to pin 8 of IC6. Insert the anode lead of D11 into the component hole for the side of R103 that connects circuit point "S9-2". Insert the other lead of R72 into the component hole for the side of R72 that connects to the gate of Q6.
Additional Views For Clarity

The modulation selectors and the square wave generation circuitry was moved onto it's own page for clarity. This page is pretty self explanatory and if it's not you may be considering building the wrong project. There are some changes from the original though.

Adding The Level Shifting Inverters In The PROTO AREA

As you can see here the points on the circuit board which were formerly the outputs of the ramp oscillators are now fed into the inverting level shifters. The outputs of the inverting level shifters are fed to the rest of the circuitry just as the old points used to be. Whereas formerly the S10-2 PCB circuit point connected to the front panel at point "W" now the output of IC8-B connects to the front panel at point "W". Whereas formerly the R29-1 PCB circuit point connected to the front panel at point "E" now the output of IC8-A connects to the front panel at point "E". The schematic describes what you see here so I'm not going to give a blow by blow on this kludge. There are photos that tell the tale as well.

This is what I mean when I say you need to solder adjacent leads/pads together. This is because these pads are not connected unless you connect them unlike other sets of pads in the PROTO AREA that are connected together by lands.

The original sound lab used the noise from the transistor EB junction to create a "digital" noise by feeding it into a comparator and lagging one of the comparator's inputs. The improvement described below creates a higher amplitude white noise and should work with most 2N3904 transistors. It also adds filtering to reduce the feedthrough of power supply noise by adding capacitors at two places in the noise generation circuitry. If you can find some 2N2712 (old school noise transistor) you will probably be able to lower the gain of this circuit. To increase the gain you can make R100 higher in value. To decrease the gain you can make R100 lower in value. Ideally you want about +/- 5 volts (10V P-P) of noise at IC7-D pin 14.

Please note that some components that were formerly in the circuit have changed in value. R226 and R227 are connected in series and mounted where R96 used to go. A .22uF capacitor (C25) goes between the junction of the two resistor leads and ground. This helps filter the supply going to the emitter of Q7. A 30K resistor (R228) goes between the base of Q7 and -V. A .22uF capacitor (C26) goes between the junction of Q7's base and the lead of R228 to ground. This capacitor also filters the supply used to generate the noise on Q7. The impedance to the input of IC7-C has been reduced making it less susceptible to noise. C15 was formerly .1uF and R97 was formerly 1M. C15's value has been increased to .22uF and R97's value has been reduced to 20K. The gain of the first stage of noise amplification has been reduced. IC7-C used to supply a gain of about 4700 (R100 used to be 4.7M and R98 was 1K). Now with R100 at 200K and R98 at 4.7K the gain of the first stage is about 42. IC7-C's output no longer feeds both inputs of IC7-D via 1M resistors. Instead it's output now feeds the non-inverting input of IC7-D via R95 (which has been changed to a 10K resistor). IC7-D is now used for a second inverting gain stage for the white noise adding another factor of about 50. R229 is connected between the inverting input of IC7-D (pin 13) and IC7-D's output (pin 14). R230 goes between IC7-D's inverting input and ground. Several photos of the required kludge from several angles are shown below to aid you in performing it.

The LFO is the same as the Super Simple Ramp and Sawtooth LFO. Notice that the switch is changed to be center off so the circuit produces a triangular wave too. This was suggested by synth-DIYer Harry Bissell (I remembered the little email logo H^) that came with the suggestion.) thanks. Additionally, you can change the range of oscillation for the LFO with the range switch. In low range a 2uF cap (C13) is placed in parallel with the integrator capacitor (C14) to reduce the range of frequency provided by the Frequency pot R90.

Two 9 volt batteries power the circuit and the two by-pass caps absorb the larger current spikes.

Improved Noise Generator Kludge

	Here we see a view of the kludge that shows how IC7-D is made into a gain stage. R230 (2K resistor) is mounted where C17 used to go. This accomplishes connecting IC7-D's inverting input to ground via 2K of resistance. R229 (100K resistor) is mounted using one hole from the former R99 and one hole from the former R101 thus placing it between the inverting input of IC7-D and IC7-D's output. Notice that you must connect a small wire between the lead of R229 connected to IC7-D's output and the other side of the former R101. The new values of R100 (200K), R97 (20K), R98 (4.7K) and R95 (10K) are clearly visible in the photo. C17, R99, R102, and R101 are no longer used in the circuit.
	Here is the meat of the kludge. R226 and R227 are connected in series and the two non-connected ends go in the holes of the former R96. A .22uF capacitor (C25) goes between the junction of R226 and R227 and ground which is the lead of R98 that both C25 and C26 are soldered to. One end of R228 goes into the hole that Q7's base used to go into. The other end of R228 gets solderd to the base of Q7 which is bent upward to accomodate the connection. A .22uF capacitor (C26) goes between ground (the same ground point used by C25) and the junction of Q7's base and R228's lead.
	Top view for clarity.
	Side view for clarity. Note the point where capacitors C25 and C26 are grounded by soldering them to the end of R98.
	A clearer shot of the connection of the base of Q7 to the leg of R228.

Parts Layouts And Panel Wiring

PC Board Parts Legend Please note that the components that are no longer used in the Sound Lab Mini-Synth PLUS are shown on the side for clarity. The PC Board still has these legends on it. Just leave these components off if building anew or remove them if you are modding an existing Sound Lab.

PC Board To Front Panel Wiring The front panel diagram has letters that correspond to these letters. Connect a wire (of sufficient length) from the board to the panel at each pair of corresponding lettered points. There are two points "W" and "E" that are shown below on the Inverting Level Shifters to Front Panel Wiring drawing. Remember to connect those too. As noted above some of the components shown on the board legend are not used in the Sound Lab Mini-Synth PLUS. Points X1, X2, and X3 go to the jack panel.

Fine Tuner Support Kludge To Front Panel Wiring The fine tuners mixer resistors, R209 "VCO-2 Mod VCO-1" resistor and the resistor used in switching the Sample & Hold gate to the AR Generator are shon here. Remember to put the components as shown so that the various mods don't interfere with one another.

Inverting Level Shifters to Front Panel Wiring In addition to the panel connections shown above in the PC Board To Front Panel Wiring section above you need to connect a wire (of sufficient length) from the board to the panel at points "W" and "E" shown here. These points are the inverted, level-shifted (formerly ramp now sawtooth) oscillator outputs.

Sound Lab Mini-Synth PLUS Panel Wiring Diagram (Rear View) Click this image for a larger one or click here for a PDF version. Wire the points on this diagram to: the corresponding points on the PC Board (including kludged connections), the MICRO SAMPLE AND HOLD PC Board, and the jack panel. For connecting the flying components I use a variety of methods including, shrink tubing, nylon wire ties and nylon wire tie anchors, terminal strips, etc. The main point is to make sure the connections are secure and that they don't short to anything. Also if you use 1/2 watt resistors for the flying components they have thicker more stable leads. Note the key at the bottom of the diagram. The various colors indicate where the point gets connected: Green: to a kludged component Blue: to the MICRO SAMPLE AND HOLD PC Board Pink: to the jack panel Yellow: to the Sound Lab Mini Synth PC Board. Pot values with an A (A100K for example) are audio taper. All others are linear taper.

Sound Lab Mini-Synth PLUS Panel Legend (Front View) Click this image for a PDF. In order to print it in the proper size set the PDF print setup to "legal size (11" x 14")" paper.

Sound Lab Mini-Synth PLUS Jack Panel Wiring Diagram

Sound Lab Mini-Synth PLUS Battery Connection

Sound Lab Mini Synth PLUS Project Parts List

Qty.	Description	Value	Designators
1	CD40106 Hex Inverter	CD40106 14P DIP	IC1
1	LF442 Dual Op Amp (or equiv.)	LF442 8P DIP	IC2
3	LF444 Quad Op Amp (or equiv.)	LF444 14P DIP	IC5, IC6, IC7
1	TL072 Dual Op Amp (or equiv.)	TL072	IC8
2	LM13700 Dual gM Op Amp (or equiv.)	LM13700 16P DIP	IC4, IC3
2	MPF102 N JFET (or equiv.)	MPF102 T092	Q6, Q5
10	Silicon Switching Diode	1N914 (or equiv.)	D1, D2, D3, D4, D5, D7, D11, D12, D9, D10
1	9.1V Zener Diode	1N5239B (or equiv.)	D8
6	Transistor NPN(s)	2N3904 T092	Q8, Q4, Q1, Q3, Q2, Q7
4	Ceramic Capacitor(s)	.001uF	C2, C1, C8, C9
1	Ceramic Capacitor	.0047uF	C14
5	Ceramic Capacitor(s)	.1uF	C10, C11, C20, C19, C24
3	Ceramic Capacitor(s)	.22uF	C15, C25, C26
2	Ceramic Capacitor(s)	100pF	C7, C6
1	Non-Polarized Aluminum Cap	1uF	C22
1	Non-Polarized Aluminum Cap	2uF	C13
2	Ceramic Capacitor(s)	560pF	C5, C4
1	Tantalum Capacitor	2uF	C3
2	Electrolytic Capacitor(s)	100uF	C16, C18
4	Audio Taper Potentiometer(s)	100K	R29, R38, R44, R27
2	Audio Taper Potentiometer(s)	1M	R10, R11
12	Linear Taper Potentiometer(s)	100K	R15, R19, R48, R37, R58, R55, R205, R202, R85, R209, R90, R92
18	Pot knobs(s)		Knobs for all pots
1	Trim Pot	100	Scale adjust trimmers
10	Resistor 1/4 Watt 1%(s)	100K	R68, R69, R74, R54, R57, R73, R63, R62, R207, R208
2	Resistor 1/4 Watt 1%(s)	10K	R64, R65
4	Resistor 1/4 Watt 1%(s)	1M	R67, R66, R56, R59
2	Resistor 1/4 Watt 1%(s)	2K	R60, R61
2	Resistor 1/4 Watt 1%(s)	39K	R52, R50
5	Resistor 1/4 Watt 1%(s)	470K	R225, R206, R204, R203, R201
2	Resistor 1/4 Watt 1%(s)	47K	R75, R76
19	Resistor 1/4 Watt 5%(s)	100K	R4, R14, R12, R1, R200, R24, R28, R18, R79, R77, R78, R210, R86, R217, R219, R218, R220, R93, R229
3	Resistor 1/4 Watt 5%(s)	10K	R199, R26, R95
1	Resistor 1/4 Watt 5%	130K	R20
4	Resistor 1/4 Watt 5%(s)	150K	R30, R33, R39, R16
1	Resistor 1/4 Watt 5%	15K	R36
5	Resistor 1/4 Watt 5%(s)	1K	R22, R23, R45, R34, R35
5	Resistor 1/4 Watt 5%(s)	1M	R8, R9, R2, R87, R91
3	Resistor 1/4 Watt 5%(s)	200K	R31, R89, R100
9	Resistor 1/4 Watt 5%(s)	20K	R42, R40, R47, R43, R46, R70, R72, R80, R97
4	Resistor 1/4 Watt 5%(s)	220K	R82, R84, R221, R83
1	Resistor 1/4 Watt 5%	270K	R222
2	Resistor 1/4 Watt 5%(s)	27K	R17, R216
1	Resistor 1/4 Watt 5%	2K	R230
2	Resistor 1/4 Watt 5%(s)	2M	R5, R13
1	Resistor 1/4 Watt 5%	30K	R228
1	Resistor 1/4 Watt 5%	33K	R21
1	Resistor 1/4 Watt 5%	3M	R7
2	Resistor 1/4 Watt 5%(s)	4.7K	R81, R98
1	Resistor 1/4 Watt 5%	4.7M	R3
2	Resistor 1/4 Watt 5%(s)	470K	R226, R227
1	Resistor 1/4 Watt 5%	475 ohm	Scale adjust resistors
4	Resistor 1/4 Watt 5%(s)	47K	R49, R32, R223, R104
2	Resistor 1/4 Watt 5%(s)	510 ohms	R6, R94
1	Resistor 1/4 Watt 5%	6.2K	R224
1	Resistor 1/4 Watt 5%	620K	R25
1	Resistor 1/4 Watt 5%	7.5K	R88
4	SPDT Toggle Switch (center off)		S7, S11, S12, S16
6	SPDT Toggle Switch		S3, S6, S10, S20, S21, S22
1	SPST Mom. Push Button N/O		S1
8	SPST Toggle Switch		S5, S8, S4, S9, S15, S14, S13, S17
1	DPDT Toggle Switch (center off)		S2
1	DPDT Toggle Switch		S18
1	DPST Toggle Switch		S19
2	9V Battery Connectors		For B2 and B1
2	Battery(s)	9V	B2, B1
4	Phone Jack(s)	1/4" Jack	J1 (and Osc-1 CV, Osc-2 CV, and Gate In)

Miscellaneous

• 1/16" Thick aluminum plate for mounting the pots and switches.
• Wood or other material for case construction.
• Assorted hardware 1" 6-32 nuts and bolts, 1/2" #8 wood screws, etc
• Digital Volt Meter and a Signal Tracer or oscilloscope for testing.

Yet another single chip sample and hold but I managed to tweak portamento out of this one.

Input voltages to be sampled arrive at VIN and are fed into U1B's non-inverting input. U1B's non-inverting input is also biased up to about 4.8 volts by R7 and R2. The NFET switch likes when the voltage it is sampling stays positive so we help keep it that way with this bias network.

Voltage at the output of U1-B is presented to the source input of Q2 (PN4391).

U1-A and associated components (R4, R5, C9, C4 R13, D3 and R12) comprise a single op-amp pulse generator. The rate at which the pulses occur is determined by the setting of R13 and the size of C4. The values shown give a good range of from approximately .5 HZ to about 50 hz. The leading edge of the pulses is fed via C1 and R9 and Q1 to the gate of Q2. The pulses turn on Q2 causing a sample of the voltage at pin 7 U1-B to charge C7 (polystyrene or other low leakage cap). When Q2 turns off C7 holds the voltage and presents it to U1-C high impedance buffer. I found that the LF444 was the lowest leakage (highest impedance) op-amp and resulted in minimum droop. My experiments with TL074 showed a lot more droop so it's worth finding the LF444.

U1-C biases the sampled voltage so that it is back to the levels it had prior to being biased by U1-B. The voltage at U1-C's output pin 8 is presented to C8 via 1M Glide pot R20, and R15 20 ohm resistor. U1-D buffers the voltage on C8. When R20 presents resistance between pin 8 and pin 12 of U1-D the voltages slide from sample to sample. The more the resistance the slower the glide between samples. The lower the resistance the faster the glide with the glide being imperceptible at minimum resistance.

The output of U1-D feeds the Output Level pot R22 via R16 from point CV1. Point CV2 can also be used as a source for the sampled voltage output.

The sampling pulse is about 4 mS wide and is also used as the trigger output via D1 and R6 (marked as GATE). It started out as a gate (I didn't originally have the diode across R13) but when the output of the oscillator was square I could hear a perceptible drop in the output voltage when the square wave went low. I tried EVERYTHING to get rid of it to no avail. My solution was to make the pulse narrow enough so that if there is still a drop as the pulse goes low it happens so quickly after the sample that I can't hear it so good enough is good enough.

MICRO SAMPLE AND HOLD PC Board Parts Legend

MICRO SAMPLE AND HOLD PC Board Parts Values

MICRO SAMPLE AND HOLD Panel Connection Details Connect the circuit points shown below to the corresponding front panel points. Wire the power connections to the extra power pads on the Sound Lab PCB.

MICRO SAMPLE AND HOLD PCB Layouts

Qty.	Description	Value	Designators
1	LF444 Quad Op Amp	LF444 14P DIP	U1
2	PN4391	PN4391 T092 (or equiv.)	Q1, Q2
3	1N914 Sw. Diode(s)	1N914 (or equiv.)	D2, D1, D3
1	Ceramic Capacitor (S)	.01uF	C1
1	Ceramic Capacitor (S)	.47uF	C4
1	Ceramic Capacitor (S)	10pf	C9
3	Ceramic Capacitor(s)	.1uF	C2, C5, C8
2	Electrolytic Capacitor (S)(s)	1uF	C3, C6
1	Polystyrene Capacitor	.01uF	C7
1	Linear Taper Pot	100K	R22
1	Linear Taper Pot(s)	1M	R13
1	Audio Taper Pot(s)	1M	R20
1	Resistor 1/4 Watt 5%	100 ohm	R18
2	Resistor 1/4 Watt 5%(s)	100K	R8, R5
1	Resistor 1/4 Watt 5%	1M	R4
1	Resistor 1/4 Watt 5%	20 ohm	R15
1	Resistor 1/4 Watt 5%	200K	R11
1	Resistor 1/4 Watt 5%	20K	R7
1	Resistor 1/4 Watt 5%	30K	R2
1	Resistor 1/4 Watt 5%	33K	R14
2	Resistor 1/4 Watt 5%(s)	39K	R3, R9
2	Resistor 1/4 Watt 5%(s)	4.7K	R12, R6
2	Resistor 1/4 Watt 5%(s)	470 ohm	R16, R21
1	Resistor 1/4 Watt 5%	47K	R10
2	Resistor 1/4 Watt 5%(s)	75K	R17, R19