Reverb enhancements

[glasman]

I have been testing a few new reverb ideas lately and I thought I would post to give you guys a few things to try.

If you read over the accutronics literature, they comment about placing a .0022uf cap across the input from the tank to ground. I had always kinda blown over that part, but in the interest of curiousity I did some testing to see the effects. The tests were interesting. The cap tends to make the circuit act more like a bandpass filter, with (obviously) various cap values changing the center frequency and gain.

Below I posted the results for four conditions. No cap, .0022uf, .0047uf and .015uf (extreme case). Note the .0022uf gives the flattest response while the ,.0047uf and .015uf tend to peak the gain at lower frequencies.

Below 1kHz the response variations are minimal. Tweaking this part could (have not applied the "ear" testing yet) allow getting a little "sparkle" in the reverb. Although my guess is that going to big would cause the reverb to get ringy.

Have fun, be interested in getting comments.

Test conditions:

Swept sin wave.
Measured on an Ono Sokki CF-5220 FFT.

[Bob-I]

I've been using a 500pF cap in that position. I find it smooths out the reverb, although I've never done an analysis like you did. I'll look at that later (I'm colorblind so my daughter will help me)

Thx

[BobW]

Gary,

I'll assume you used the same cap type for each value? Orange Drop, Xicon?

[BobW]

double post

[glasman]

Gary,

I'll assume you used the same cap type for each value? Orange Drop, Xicon?

The .0022 and .0047 were xicon MPP that I had handy. The .015uf was a Xicon 100V polyster (a green chicklet). For space conservation, I would probably end up going with a 100v something or other .

Gary

[BobW]

OK, I should have enlarged the pic. Definitely a peak shifted from about 1.5kHz - 2.5kHz, w/ .015 to 2.75kHz - 3.5kHz, w/ .047.

I imagine a .0068 would work well w/ your tank.

Good info, thanks.

[glasman]

OK, I should have enlarged the pic. Definitely a peak shifted from about 1.5kHz - 2.5kHz, w/ .015 to 2.75kHz - 3.5kHz, w/ .047.

I imagine a .0068 would work well w/ your tank.

Good info, thanks.

Yes the .0047 gives a bit of a bump. I have about 80dB of return gain to work with so not too much of a problem getting a good reverb . The final value will be somewhere between the .0022 and a .0082. You .0068 guess might be about right, This would give good extention to the 2nd harmonic of the highest note on an electric guitar.

You are welcome. I will always share information where I can.

Gary