Spring reverb/effects loop PCB

[imJonWain]

  I've been working on a reverb/effects loop PCB to replace the one in my Laney AOR and would love some input/peer review.  I've modified the stock reverb driver and recovery quite a bit already but would like it to look a little cleaner and add some more stuff that there isn't sufficient room for on the stock board.  Luckily from the factory the effects loop and reverb section is all on a seperate PCB mounted to the back of the amp so it's really easy to mess with or replace anyway. 

The reverb section I used is completely taken from a Rod Elliot article on reverb driving and recovery but is also somewhat similar to the stock scheme Laney uses in their amps normally.  The rest is more or less the same as the stock laney loop/buffer.  I've added points to have a switch on the back of the amp to bypass the whole loop/reverb section as well.       


1.  Anyone have any experience with the compression/limiter circuit by rod Elliot?  I haven't actually tested that part of the circuit but figured why not since I had space and can just jumper over it if I don't want to use it.  It seems to look/work fairly simple.

2.  Stock the effects loop buffer seems to cut some highs from the sound vs when it is removed completely from the circuit.  Do you think lowering the low pass filter cap a bit on the mixing/recovery opamp might help this or is it more related to impedance interaction differences (tube to tube vs opamps to tube)?  The corner frequency is 22.5kHz stock which is above hearing range but looking at a bode plot it does cut frequencies over 10k by bit.  I don't know if that's really noticeable but I plan to order some caps this week and do some testing on that.

3. Anyone see any glaring errors or see anything you think should be changed?

4. Any fancier or more interesting ways to do the effects loop or buffering?

 
Thanks!

-Jon

Rod Elliot link:
http://sound.whsites.net/articles/reverb.htm

[ElectricDruid]

The corner frequency is 22.5kHz stock which is above hearing range but looking at a bode plot it does cut frequencies over 10k by bit.  I don't know if that's really noticeable but I plan to order some caps this week and do some testing on that.

I don't know about the other stuff, but if the corner frequency is 22.5KHz, you won't hear much difference at 10K. It's only -3dB at the corner frequency, remember, and the just-noticeable-difference is about 1dB. An octave below 22.5K, the difference will be very close to that threshold (Sound is complicated, because it depends on both the frequency and the volume of the signal, but still...). The decisions you make about where these "upper frequency" limits should go will influence the overall tone and character of a whole system, but changing one on its own rarely makes enough of an impact to be significant. So I wouldn't worry too much, especially for an effects loop, where the sound won't come back the same it went out anyway!

HTH,
Tom

[imJonWain]

cool, that's what I was thinking, thanks for the input!  I ended up finding a few component size mistakes on my own, oops!