Repairs, Maintenance & Upgrades > Preamps, Modifications & Upgrades

Does this look aftermarket to you guys?

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aron:
If not, any schematic lying around?

It's a preamp that was in my friend's Rhodes. Apparently bass/treble and volume. Bass/Treble is on a concentric pot.

http://www.diystompboxes.com/pedals/photos/topofrhodesboard.jpg
http://diystompboxes.com/pedals/photos/sideofrhodesboard.jpg

I going to fix it (the pot fell out), but I wanted to see if I could get more info.

Thanks in advance.

Aron

Rob A:
Hey Aron, cheers on your immensely useful site. I was just reading it earlier today as it happens.

The 9V battery makes it conclusively aftermarket--there were no battery-powered pre's to come out of the Rhodes shop.

What is the IC?

aron:
Thanks Rob!!!!!

The IC is sanded. This guy was a early pioneer of copy protection!

Aron

Rob A:
Kind of a puzzler--if it were an opamp you'd kind of expect back-to-back 9V. The only audio amp IC I can quickly recall that runs single-sided supply (LM386) is not exactly audiophile material.

You think that's what we're looking at? I love how it's zip-tied in the socket.

axg20202:

--- Quote from: "Rob A" ---Kind of a puzzler--if it were an opamp you'd kind of expect back-to-back 9V. The only audio amp IC I can quickly recall that runs single-sided supply (LM386) is not exactly audiophile material.

You think that's what we're looking at? I love how it's zip-tied in the socket.
--- End quote ---


Standard op-amps can be run either by a single voltage rail (unipolar) or a dual voltage rail (bipolar). There are countless millions of guitar pedals running op-amps from a single 9v battery supply (and without using a charge pump to get bipolar power), so the power arrangement in the photos is nothing unusual.  Judgin by the low component count, the IC is probably being hooked up in its simplest form as per typical op-amp datasheets, with two  simple passive tone controls thrown in.

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