Ross Compressor Cap changes - "muddy and dark" fix

[snorky]

Hey all,

Just finished a Ross Compressor using a PCB and directions from GGG.  After digging around here for tips, I used a 220pF cap instead of the .0022uF referenced in the parts list (C2).  HOWEVER, it still really sounded dark and muddy, and basically unuseable when I got everything together.  

After more digging around, I saw 2 references to changing the cap that runs off pin 6 of the IC in parallel with a 150k resistor (C11 on the GGG layout).  I had initially used a .01uF but changed to a .001uF (.001uF is shown in the tonepad schematic and parts list).

This did the trick!    I haven't used the pedal much at all yet, but it's MUCH MUCH better.  More transparent with nice sustain etc.  This was the most "involved" project that I've done, and I'm really happy I found the answers here on the forum.  I'm just posting to leave a reference for future Ross builders.  It sucks to put so much work into a project, and not have it work at all well.  I haven't used compressors much, but this pedal seems to give really good sustain, and doesn't color the sound too much with these small changes.

Ciao!

- Mark

[brett]

The DYNA compressor is similar in many respects to the Ross, but doesn't have the low-pass filter that cuts so much treble.  The Tonepad site shows how to build a switchable Dyna/Ross, but the Dyna is so much better (IMO) that the switch is rarely used.

cheers

[Jay Doyle]

Brett,

I feel the opposite. I have built both and have never ended up using the dyna. I feel that the ross has a much smoother FWR and doesn't mis-fire and 'pump' or 'breathe' because of the extra low pass filtering. Of course my guitar is bright as it is and I don't mind losing a little high end. I use single coils.

Obviously, your results may vary with this project!  

Snorky,

Good job posting this 'for the record' as it were.

Another thing that is rarely mentioned, if at all, is to solder the .01uF cap that goes across the power supply, directly onto pin 7 and pin 4 of the OTA. This has really help me with noise, esp with a high quality film cap.

Jay

[phillip]

When I built my modified version of the Ross Compressor a couple of months ago, my chief complaint was that it cut way too much treble for my liking, even using the TonePad capacitors values, which are correct to the original Ross.

When it was switched on it muddied up the signal coming from the Telecaster to my Twin Amp.  With the Tele/Twin combination I rather like to keep my treble response fully intact since it's part of my "sound."

Are there any ways to help bring back some of the treble in the Ross circuit?  What would happen if one replaced the 220pF capacitor on the input with a smaller value, say 100pF or 150pF?  It seems like this would lessen the treble loss a bit.

Phillip

[snorky]

I'm not smart enough to suggest anything.  I hope someone else can.  You're sure you have all the correct cap values?

- Mark