Boss OD-1

[thermionix]

I realized the other day that I had a 4741CP quad opamp.  It was a freebee from a box of random bits, never soldered but condition otherwise unknown.  I've never played an OD-1 of any sort, but here was a chance to try one of the "good" 14-pin ones.  Yeah I know the RC3403 is more coveted, but supposedly the 4741 sounds just as good.



So I breadboarded it tonight, and got no sound.  I quadruple-checked my connections, and then read voltages.  No Vref on pins 14/13.  Fourth opamp dead.  Bummer.  So much for the free chip.

It dawned on me after I pulled it all off the breadboard that I should have stuck a TL074 in there just to check the circuit function.  But I doubt that would sound anywhere near the same.  My point of reference is subbing a TL071 in place of a 741 in a Distortion+, which sounds terrible.

Datasheets for the 4741 and 3403 mention "performance equal to or exceeding the 741" or similar.  But I'm wondering if anybody knows if the sound is about the same as 741, and if so, has anybody here built a "14 pin" OD-1 with four 741s?  The 4741 claims to be a quad MC1741, but I don't know how that relates to the 741.

[thermionix]

Okay, seems MC1741 is just the Motorola version of the 741.  So, disregard.

[Mark Hammer]

You should be able to stick a plain vanilla LM324 in there.  Will it sound identical?  I don't know.  But it comes closer to a quad 741 than a bifet would.

I made mine with a 3403, omitting all the FET-switching circuitry, and I kind of like it.  It won't change anyone's life, certainly, but it sounds nice.  I installed a 3-position DPDT toggle that leaves it stock in the middle position, adds more bottom in one of the side positions by supplementing C5, or adds more bottom and trims the top by sticking a cap in parallel with the clipping diodes in the other side position.

[thermionix]

It won't change anyone's life, certainly, but it sounds nice.

Pretty much my expectation.  I never had any intent to build one, but when I noticed I had the 4741, figured I'd check it out on the bb at least.  I see 3403s are still available cheap at Mouser, so I might grab one some day.

[Renegadrian]

Back in the forum after some time, resurrect this old post but the topic is the same, quad od-1.
built one with socketed chip (to try tl074 and others) and asym 1n4148 diodes.
There's sound but it it sputtery and fuzzy and sinthy...any hint!?

[willienillie]

Can you post pin voltages?  What schematic did you work from?  I seem to recall one floating around that was missing a resistor, but I could be thinking of another circuit.

[iainpunk]

It dawned on me after I pulled it all off the breadboard that I should have stuck a TL074 in there just to check the circuit function.  But I doubt that would sound anywhere near the same.  My point of reference is subbing a TL071 in place of a 741 in a Distortion+, which sounds terrible.

this is not necessarily the case, where a Dist+ clips the opamp, the soft clipping diodes prevent the op amp from clipping. you can put 50 different ic's in a tube screamer and you would hear to much difference, where the dist+ sounds different between two of the same type of opamp.

do you have the 2sk30ay's in the circuit, or have you left out the switching and bypass parts of this schematic? because you can leave out those and the in and output buffer, since they are only there to make it a buffered bypass, for ease of production and cheaper switches.

[Renegadrian]

 iainpunk  maybe you didn't read well my post you replied to an old post not mine.

[Renegadrian]

Can you post pin voltages?  What schematic did you work from?  I seem to recall one floating around that was missing a resistor, but I could be thinking of another circuit.

schem is THIS ONE, vero layout I personally made from this perf HERE

[willienillie]

You need another cut, bottom row, just to the left of R6.

[Renegadrian]

You need another cut, bottom row, just to the left of R6.

that was DEFINITELY it!!!
thx for the help, now it sounds as it should...simple and nice od!