Circuit Bin

From down the back of the filing cabinet at AVA.

These circuits have been aquired over time, downloaded for repairs in hand, to answer repair questions, or exploring design ideas (an all electronic Lesley rotating speaker effect for one). They are here because they are not of ANZ manufacture and there is no other specific place for them, but they are fairly typical of the sort of thing an amp tech will have coming across the bench.

This is not intended to be exhaustive but only to provide representative examples, particularly for stomps and Fx.

Anyone who wants to add, attribute or remove a circuit should e-mail;

Amplifier Circuits

Acoustic

Acoustic 360/361 Service Manual. Caution: 11Mb PDF

Ampeg

1. svt6146b-circuit

BOSE

1. bose-1801-preamp
2. input-circuit

Fender

1. bl_delux - Blues Deluxe
2. fbassman - Bassman
3. fchamp - Champ 12
4. fndr60a - 60-Series part-A, fndr60b - 60-Series part-B
5. fstudio85 - Studio 85 Fully solid-state
6. concert_6g12.pdf 6G12 circuit and layout, 2x 6L6's, “Harmonic Vibrato”
7. concert_6g12a.pdf 6G12 circuit and layout, 2x 5881's, “Harmonic Vibrato”
8. showman_6g14.pdf 6G14 circuit and layout, 4x 6L6's, “Harmonic Vibrato”
9. showman_6g14a.pdf 6G14 circuit and layout, 4x 5881's, “Harmonic Vibrato”

HAG

HAG 39 - 2x ELC84/6GW8's

Marshall

1. 1987 Power
2. 1987pre
3. 2204pre
4. 2205pow
5. 2205pre
6. 2210pow
7. 2550 Amp
8. 2550 Power supply
9. j9po1002 - JCM900 100W
10. j9pow100 - JCM900 100W (2100, 2101, 4100, 4101, 4102)
11. j9pow50 - JCM900 50W (2500, 2501, 2502, 4500, 4501, 4502)
12. j9pr_mv2 - JCM900 Power (2500, 2501, 2503, 2100, 2101)
13. j9pre_mv - JCM900 Pre (2500, 2501, 2502, 2100, 2101)
14. jcm900du - JCM900 (4500, 4501, 4502, 4100, 4101, 4102)
15. marshal_1-2205-preamp
16. marshal_2-2205-op+psu

Rockit

Rockit Super Sustain 130 - power stages

Stomp and Fx Circuits

Note: LDR = Light Dependent Resistor, Cadmium Sulphide (CdS) cell

1. biphase - Bi-Phaser

   The original used 4558 and 741 op-amps. Today we could use the TL07x or TL08x single, dual or even quad FET input op-amps and improve the distortion and residual noise. While there are super-dooper quiet op-amps available, the LM833 is an almost perfect dual audio amplifier at a very cheap price.

2. ibnzbe10 - Ibinez five one octave band equaliser

   The rank of op-amps on the right side are configured as gyrators or simulated inductors. These act as series-resonant LC circuits with C10 etc taking the role of the C and the op-amp and C9 etc setting the value of the simulated inductance L.

   Each acts as an acceptor resonator in its band, and the dip in impedance is fed via the control to the main amp feedback circuit, giving boost or cut.

3. ibnzpt90 - Ibinez Phaser, MP-P01001A
4. jordan_bosstone note value corrections
5. korgngt1 - Korg Noise Gate
6. korgoct1 - Korg Octave Divider
7. korgpeq1 - Korg Parametric EQ (I have no idea what the unique field effect devices IC1-3 are.)
8. korgphs1 - Korg Phaser (ditto)
9. korgtnb1 - Korg EQ/buffer (KLM690)
10. mu-tron3

    Op-amps A2, 3 and 4 comprise a state variable filter that has low-pass, band-pass and high-pass outputs, and can be tuned with two series resistance elements.

    The mystery component, “OB05” or “O805”, is a LED to dual LDR opto-coupler. One of the LDR's goes between A2 and A3, and the other between A3 and A4.

    The light is a LED or LEDs (because filament lamps are polarity insensitive). R23 should be selected to give a LED current of 20mA or less.

11. mxrdistp - MXR Distortion

    A very straight forward distortion pedal suitable for beginner construction, can use just about any available op-amp and the diode clamp can be tweeked to taste. Note: the input tip and ring contacts are drawn transposed; ring is power, tip is signal.

12. octavia - Bob Starr's Octavia frequency doubler.

    Uses a common LM386 audio power amplifier, a common transistor radio transformer, and full-wave rectifier.

13. purple - The Purple Pedal by C.Steele

    Four stages of heavily clipped gain

14. reverb - springline drive and recovery by Robin Tomtlund

    Note: the springline driver uses current feedback so the outer of the RCA connectors driving the line must be isolated from ground.

15. uniflash Bob Starr again with a complex way to flash a small globe, unless you want tight control for LDR's.
16. fxboxsch-hfj - Hi-Fi John Fuzz, 4x PNP, diode clipper, easy mod to NPN silicon
17. fxschem-hfj - Hi-Fi John Boost/Distortion clipper, any op-amp, +/-9V
18. reverb-hfj - Hi-Fi John Stand alone reverb, valve
19. fxloop1-valvewizard - Fx loop send/return using valves.
20. 6BM8 Single Tube Reverb by Eric Barbour.
21. Bass-Treble boost.
22. comp1 - valve compressor.
23. Jen Wah-Volume pedal
24. Preamp/buffer by Rod Elliot, ESP
25. Phase Shift Oscillators - by Bill Bowden
26. Three simple boosters

<<<OzValveAmps