Arion SCH1

[sevenisthenumber]

Hey guys, I re-cased my SCH1 and want to add a good usable volume control with some boost on tap, any advice for a VERY quiet stage I could add on the out? I dont need a ton of gain just enough to boost above unity a few DB

[Mark Hammer]

It's going to be tricky.  At the very least, I doubt one can simply change a resistor value and expect greater output.

If you look here: http://www.hobby-hour.com/electronics/s/arion-sch1-chorus.php  you'll see that the SCH-1, like so many other chorus pedals, uses the "poor man's Dolby" of treble pre-emphasis (C5/R8) going into the BBD and complementary de-emphasis at the mixing stage (C22/R34 and C23/E35) to restore tonal balance and reduce BBD-related noise.  Goosing the level at the input stage will overdrive the BBD, so you don't want that.  Increasing the gain of the output stage would necessitate adjusting the values of C22/C23 and R34/35, in addition to R36/37, and that's too much monkeying around for me, although in theory it CAN be done.

[sevenisthenumber]

Thanks Mark,
you think adding a simple gain stage would be funky?

[Mark Hammer]

A simple single transistor stage might be appropriate.  I'm not familiar with the insides of the unit so I can't really offer an opinion about whether a pair of those could fit inside the chassis.

On the other hand, if you were handy with surface mount parts, I imagine there could be room.

[sevenisthenumber]

I re case it so I have tons of room. Any suggestions on the lowest noise stage possible in your opinion?

[Mark Hammer]

I wouldn't worry about it.  You're going to get far more noise contributed by amplifying the output of a chorus circuit than whatever you're going to get added by the extra gain stage itself.  Any simple single JFET or bipolar stage should do.

[sevenisthenumber]

Gotcha, thanks. Anyone have any suggestions on a gain stage for volume that is somewhat transparent?