Overdrive-II changes iss 1 to iss 2 ?

[Noiseconformist]

Hi,
what are the differences between issue 2 and issue 1 of the Overdrive-II module?
Anything worth modding?
Thanks, Michael.

[Synthbuilder]

what are the differences between issue 2 and issue 1 of the Overdrive-II module?

I think the only differences are small layout changes to suit the newer dotcom power header format. It's also a different board manufacturer.

Anything worth modding?

I now recommend that U7 be a OPA2134. The original schematics show a TL072, but with very large input signal levels this can be pushed into phase reversal which doesn't sound that nice. The OPA2134 is immune to such poor behaviour.

[Noiseconformist]

Thanks for your quick reply, Tony!
Would be an easy swap to try (besides that I don't have one in the drawer).
Michael.

[euphonic]

Anything worth modding?

I now recommend that U7 be a OPA2134. The original schematics show a TL072, but with very large input signal levels this can be pushed into phase reversal which doesn't sound that nice. The OPA2134 is immune to such poor behaviour.

Thanks, for clarifying that change.

As I just built an issue 2 Overdrive-II, I happened to notice that U2 is also different between issue 1 and issue 2. In issue 1 it is an OP275 opamp. But in issue 2 a TL072 is used instead. Is this upgrade of U2 also aimed at preventing the occurrence of phase reversal with very large input signal levels? Or is there another reason behind this change? And would a swap of the OP275 in U2 for a TL072 in an issue 1 PCB be advisable as well, or would that be unwise?

Thanks in advance for any help. But it is purely out of interest, no need to hurry!

[Synthbuilder]

Is this upgrade of U2 also aimed at preventing the occurrence of phase reversal with very large input signal levels?

Technically it's a downgrade. The OP275 is a better op-amp than the lowly TL072.

The reason is simply one of cost. The OP275 used to be around £1.50. Now it's close to £7. U2 does not need to be such an expensive device where a cheaper one works almost as well.

The phase reversal issue is not a problem for U2 because both amplifiers are configured as inverting amplifiers, which means that the input pins of the op-amps sit steadfastly at 0V.

[euphonic]

Technically it's a downgrade. The OP275 is a better op-amp than the lowly TL072.

The reason is simply one of cost. The OP275 used to be around £1.50. Now it's close to £7. U2 does not need to be such an expensive device where a cheaper one works almost as well.

The phase reversal issue is not a problem for U2 because both amplifiers are configured as inverting amplifiers, which means that the input pins of the op-amps sit steadfastly at 0V.

Thanks Tony for the clear explanation! It would never have occurred to me that it is an intentional downgrade to make the design more cost effective! Thanks also for guarding my wallet.