Transistor selection and the Ross Comp

Started by rhys, April 28, 2008, 02:09:13 PM

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rhys

A tale of two rosses:

I built one for a friend with the Hammer 3-way recovery switch and a Processareus's clean blend add-on board and the mods suggested by RG.  I thought, I have to have one for myself, so about a year later I finally got around to building one for me.

This time I used a pot for recovery instead of the switch, and I did not add the clean blend to mine (although it's quite cool).  It wasn't as squishy as I'd remembered my friend's being.  Finally, I got the first Ross back from by buddy and compared the two and sure enough, his is way squishier.  Even when the blend knob is set to no clean and the 3-way switch is set to max.  I tried swapping out the ICs and that did not make a bit of difference. 

The only other thing that's different is I used 3904 transistors in by buddy's and I used 5088s in mine.  I know the transistor selection makes a discernible difference with the OS, is it the same with the Ross? 

If its a transistor difference, is there one or two in particular that I should change? 

Here's the layout I'm working from.
http://www.tonepad.com/getFile.asp?id=9

Mark Hammer

I can't see that the three transistors involved in providing the rectified envelope signal have any specific requirements.  The one in front of and the one after the 3080 chip do carry audio signal, though, and variations in those might make a difference.

JDoyle

If the rectifier transistors mattered YOURS would be more 'squishy' because of the increased hFE of the 5088s.

The only thing I can think of off the top of my head is that the Sustain pot in yours may not go all the way down to zero resistance, or you have a different value for the 27k resistor from that pot to the Iabc port on the 3080.