Peavey Encore 65 Misc Parts Question

[Dix]

I was talking with regard to a replacement for the one in the reverb circuit. Which is installed with the common center connection not used.

Meaning there was no real need for the use of a dual LDR there. A 4-leg single would have worked just fine rather than the 5-leg dual.

I question whether there was an actual "need" for the use of the duals at all. Other than it was a parts saving move. You want to switch 2 circuits at the same time. Doing that with 1 part rather than 2 would save on parts count, & likely some PCB real-estate to boot. (x2 in the case of the pump circuit switching).

But, as I said, we're not talking about a stereo compressor here. Given the application, does it really matter in this case if say the ground for the "smooth" switch acted a few millisconds faster/slower than the ground for the master volume? (LDR2 in a Rockmaster)

Would not 2 single LDRs with the LEDs wired in parallel work just as well in that spot?

This would all be a moot point if I could get Peavey to get back to me & take my credit card number.

[Enzo]

I see, in the schematic it is a single.

I might surmise that the double used has the two elements wired in series, so twice the off resistance. SInce it is used as a series element in the voltage divider with R39, maybe it makes for better OFF.

[Dix]

True.... but from looking at Tom's test method & his results, it would appear that the "dual" LDRs are more like a "center tapped single" than a "matched pair in a single package".

His "on" resistance values as drawn are end to end. Which would make the 5C3 (which are plentiful on eBay) a drop in replacement for the 5C3/2 for that circuit if that's the case.

Although, even if we assume "matched pair", I have my doubts that the difference between a 10M off or a 20M off is going to be audible. But if that's the case, then the 5C9 has pretty similar response ratings & is 50M dark. So you can get even more "off". Or parallel a resistor to get you down to 20M.

& if the on resistance is an issue, Peavey's only driving these things with about 10mA. So there's plenty of room to go either way with the limiting resistor to adjust that.

Of course, there's always the possibility that my redneck engineering thought process has short-circuited somewhere.

[Enzo]

In this circuit the difference between 20M and 40M is the divider is either 1/45 or 1/90. SO if the difference matters, it has twice the attenuation. In this circuit, the higher the better.

While it won't matter to you or me, when Peavey made these amps, an important consideration aside from electrical specs was availability. They had to have a reliable source of production quantities.