Exar OD-1 Over Drive  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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VitaliiBobrov
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Post by VitaliiBobrov »

I was lucky to get Exar OD-1 in good condition for a reasonable price, so I thought I must trace it. Many legends are around that pedal, and pricing on the used market went too far, significantly after JHS added it as one of the modes in Bonsai pedal. I hope my trace will help reduce insane prices on those, sometimes higher than vintage TS ones.
Exar OD-1 Over Drive
Exar OD-1 Over Drive
I got my unit with a box and price tag on it that says 370,000 PLN, and it was made in 1993. In 1993 that amount was about 21$.
Exar OD-1 price
Exar OD-1 price
The PCB is standard for series 1 Exar pedals - single-sided, with no silkscreen. I knew from JHS Show and Polish forums that it should be a TS clone with some changes to a few values, but nobody mentioned actual changes.
Exar OD-1 PCB bottom
Exar OD-1 PCB bottom
It was also known that it uses the AN4558 op-amp - 4558 variant made by Matsushita (Panasonic). This one is quite rare.
Exar OD-1 AN4558
Exar OD-1 AN4558
The circuit was easy to trace since it was not big, but I had difficulty verifying the ceramic cap value because it was color-coded.
Exar OD-1 PCB top
Exar OD-1 PCB top
No surprise, it appeared to be a Tube Screamer clone with some differences in input/output buffers, pots value/taper, and asymmetrical clipping. Not as many changes as I expected, but as a result, it sounds pretty good. I compared it side-by-side with Ibanez TS7 and TS5, and I love OD-1 better. I also have JHS Bonsai and compared it in XR mode - it is close, but IMO (subjective, I know) OD-1 has more harmonic content. Attached is the schematic with buffered bypass parts omitted. So everyone can build their own Exar OD-1, even using TS PCBs.
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exar-od-1-schematic.pdf
Exar OD-1 schematic
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VitaliiBobrov
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Post by VitaliiBobrov »

I got a chance to check another OD-1 unit, slightly earlier production circa 1990. It has exactly the same PCB, but black color textolite, components values are the same. The only difference that that unit uses JRC4558D IC instead of Panasonic one, initially I thought that all of them should have AN4558 inside.
Exar OD-1 circa 1990
Exar OD-1 circa 1990
Exar OD-1 JRC4558D
Exar OD-1 JRC4558D

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