New to forum, gotta MAG+VHT amp question

IMakeBourbon

New Member
Hello every'all,
From Cincinnati and posting here for the first time, thank ya so very much. I'm trying to link up two Mini Amp Gizmos to control a pair of 1990s vintage VHT (now Fryette) Classic (aka CLX) 2x12 combos. I'm planning to make some DIY cables to connect the MAGs and the amps because it has been a real tough year. Shoutout to the staff at RJM who have been very helpful.

Here's my question. The VHTs have five footswitch functions (rhythm, lead, boost, EQ, and loop) and a 6 -pin jack on the amp chassis, and the shield wire per RJM's pinout solders to the #6 pin. So no problem, I'll go and solder that up into a cable, with a 6-pin DIN at the amp end and an 8-pin at the MAG end. Except, now that I think about it...the MAG is eight-pin. It has eight wires in play, but only five of them are controlling functions in the VHT amp. It can control up to eight functions.

Could I—
• install a new 8-pin DIN in the VHT chassis,
• install an 8-wire DIN at the amp-end of the cable, wire up the five footswitchable functions per usual there,
• break out the other three wires from the chassis 8-pin DIN, inside the chassis, to control other functions in the amp, not currently footswitchable?

Such as the spring reverb, which has a 1/4" footswitch jack under the chassis but is not controlled by the 5-function footswitch. I'd have to figure out how to wire those into the existing functions (and some of those functions, like pentode/triode power amp operation, are only controlled by a rocker switch at present; and others, like depth/presence circuit, are not switchable at all). But the way I see it, if the MAG controls eight functions, why not try and take advantage of all eight wires? Thoughts?

Cheers—
 

rjmmusic

Administrator
Staff member
It's dangerous to do if you don't know exactly what the circuit is doing at each point you're trying to control. Most switches can't be connected directly to the Mini Amp Gizmo without causing major electrical problems. To switch those things, you'd have to replace the switch in the amp with a relay that's controlled by the Gizmo. That would isolate the Gizmo from whatever signals are going through the switch.

Controlling reverb might be ok, as long as the ground of the reverb jack is connected to the chassis ground. You might still get a ground loop or noise, but it would probably not be a catastrophic failure like you'd get if you tried to wire the Gizmo to the Pentode/Triode switch.

Kevin O'Connor's classic book The Ultimate Tone has a whole section on amp switching circuits, it might prove useful.
 

IMakeBourbon

New Member
[tried to reply to this earlier and somehow it didn't go through]
Thanks for the advice, RJM. So I'd need to get a relay going before any other switching... I might have figured out the reverb, but for the other items I would engage the services of Fryette to help me, certainly with the pentode/triode switching since there you are monkeying with the power amp. I definitely do NOT know exactly what the circuit is doing!
 

rjmmusic

Administrator
Staff member
[tried to reply to this earlier and somehow it didn't go through]
Thanks for the advice, RJM. So I'd need to get a relay going before any other switching... I might have figured out the reverb, but for the other items I would engage the services of Fryette to help me, certainly with the pentode/triode switching since there you are monkeying with the power amp. I definitely do NOT know exactly what the circuit is doing!

Yeah, getting Fryette to do it for you would be the safest bet.
 
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