DOD fx35 octaver - replace 1458 with tl072?

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I have the dod fx35 octaver. I didn't use it for ages, but recently I noticed that it could be useful for a certain sound, compared to what can I get out of my (vintage) bass-whammy.

The schematic (not sure if it's _really_really_ correct to the actual circuit):
http://www.freeinfosociety.com/electron ... odfx35.gif

But the dod octaver has some noise floor. Question is what could I expect by replacing the 1458 opamps with say tl072? Or tlc2272. From what I saw in the diagram, imo these opamps could be replaced without any further ado. (Plus the DC current consumption would stay almost the same, based on what datashets show.)

At the same time I'd replace the input buffer RC values with ones that fit "my sound" better, i.e. 100nF / 6k8 / 1M, metals for good luck .



Any opinions on that, did anybody mod the dod boxes this way before (I would think so ...) ?

[analogguru]

The schematic (not sure if it's _really_really_ correct to the actual circuit):

At least Q1 is drawn wrong....

But the dod octaver has some noise floor. Question is what could I expect by replacing the 1458 opamps with say tl072? Or tlc2272.

You cannot expect a change in the noise floor because most of them work at unity gain and the most gain is 4 (or 12 dB) in U2A.

At the same time I'd replace the input buffer RC values with ones that fit "my sound" better, i.e. 100nF / 6k8 / 1M, metals for good luck.

6k8/1M will not have much influence on the sound.

analogguru

[bool]

It tracks better with bigger input cap (just "attached") ... it isn't earth-shaking tone diff, but it feels "more 3D" when playing, and it seems to sit-in-mix better if di'd.

I'm still unsure about the opamp swap, but theoretically isn't it so that sallen-key's will be less noisy with tl072 as well and will exhibit less opamp-input loading - I wonder how may this impact the octave'd tone? Won't be earth shaking either, but may get more "open" sound ...


It's sort of -should-I-stay-or-should-I-go- ...