Guys does it look good to you?
This is a baxandall + output buffer (just to make use of the other TL072) stage of an Overdriver.
I raised R15 to tame the voltage gain a bit when the bass is all the way up.

Better place U1 before C7..
(unless there is another very low output impedance Bax driver already..)
Or, depending on rest of the circuit, use it for +4.5V bias voltage stability..

Looks fine to me.

+1 what Antonis said, the buffer would be more use ahead of the bax, unless it's already driven by a low impedance op-amp output or something similar. In that case, use it to buffer the Vref voltage.

I like the trick with the unequal resistors on the bass control too. I don't think people do that sort of thing enough. Often it makes sense to have more of one than the other, but there's always this idea that we need as much as we can get. In reality, many times controls that are a bit more limited (to the "useful" range, instead of the "looney") are much more helpful.

Quoteuse it to buffer the Vref voltage

Or after the volume pot.

Thank you guys, i may place it before the bax then, although the bax seems to work ok, the output impedance of the stage before is about 100-150 ohms (500hz-1kHz) though so maybe even the voltage stability is a good idea.

By buffering the Vref, do you mean to place the follower so the +4.5V from the divider is connected to the + input? So the 4.5V source looks into a massive impedance and won't get loaded?

Quote from: FiveseveN on November 04, 2023, 02:25:36 AM

Quoteuse it to buffer the Vref voltage

Or after the volume pot.

Yeah, another good suggestion.

Quote from: Lino22 on November 04, 2023, 07:50:53 AMBy buffering the Vref, do you mean to place the follower so the +4.5V from the divider is connected to the + input? So the 4.5V source looks into a massive impedance and won't get loaded?

Yes, but the point is to provide a low impedance Vref source for the *rest* of the circuit, not really to provide a high impedance for the 4.5V divider (although it does that too).

I've just realized that the Overdriver / Power Boost are used with their Volume knob half way down very often. Now that brings Zout up to 7k. Is that ok?

7K isn't that bad.

Quote from: GibsonGM on November 04, 2023, 09:41:37 AM7K isn't that bad.

Isn't so good , also..

P.S.
Is everything OK, SIR..??

Quote from: Lino22 on November 03, 2023, 02:33:46 PMGuys does it look good to you?
This is a baxandall + output buffer (just to make use of the other TL072) stage of an Overdriver.
I raised R15 to tame the voltage gain a bit when the bass is all the way up.

It depends on how much you want the 12'O clock position to be flat.  It would be more normal to raise both R12 and R15.  That would reduce the amount of bass-boost and the amount of bass cut and leave the 12'O Clock position flat.

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Some examples:

Schematic:


Response

I've done something similar a few years ago. Just in case it may contain some useful pointers, here's the thread:

https://www.diystompboxes.com/smfforum/index.php?topic=126139.0#msg1205139

Andy

Quote from: Rob Strand on November 04, 2023, 03:52:19 PM

Quote from: Lino22 on November 03, 2023, 02:33:46 PMGuys does it look good to you?
This is a baxandall + output buffer (just to make use of the other TL072) stage of an Overdriver.
I raised R15 to tame the voltage gain a bit when the bass is all the way up.

It depends on how much you want the 12'O clock position to be flat.  It would be more normal to raise both R12 and R15.  That would reduce the amount of bass-boost and the amount of bass cut and leave the 12'O Clock position flat.

---

Some examples:

Schematic:


Response

Thank your Rob! This is very helpful.