I need help with an amp mod.

[grjeff]

    Can anyone help me with modifying an Ampeg BA-112 combo. What I want to do is install an effects loop and maybe a master volume. The loop is more important to me first.
    There already is an RCA CD input that seams to be a direct line into the power amp section but I would like to have a dedicated preamp out/ power amp in ¼'' connections installed. If anyone can guide me through this, I would greatly appreciate it
Thanks,
Jeff

[brett]

If you can post the schemtic, it will help a lot.  In general, you'll want an SPDT switch that makes and breaks the "hot" connection between pre and power sections.  For safety, though, you'll probably want to output the preamp to a buffer before sending to the effects loop.  For that, I'd use something simple like an emitter follower (and use a hefty BJT like a TIP or BD139).

There's a good chance you'll want an output level control, too.  That'll just be a volume pot before the output buffer.
cheers