Dumb idea for an amp mod?

[mynameisjonas]

I mentioned in another thread a while back that I wish I was able to switch between two master volume settings on my amp, and I had a simple idea of how to do that without adding a relay and another pot on the amp, by simply switching in a variable resistor between the existing master volume and ground, and putting that in a pedal:



Is there something really obvious that I'm missing here, or could it actually work?

[Dr Tony Balls]

It should work.

[therizzla]

Surfy Industries does something similar with their remote Drip Switch pedal, you may look into that for inspiration.

[øøøøøøø]

You'd probably want a MBB (shorting) switch, as opposed to a BBM (non-shorting) switch.

I'm not sure exactly what would happen if there was a momentary removal of the master volume's earth connection, but whatever it is would probably not be especially pleasant (loud pop or buzz).

[Dr Tony Balls]

You'd probably want a MBB (shorting) switch, as opposed to a BBM (non-shorting) switch.

I'm not sure exactly what would happen if there was a momentary removal of the master volume's earth connection, but whatever it is would probably not be especially pleasant (loud pop or buzz).

Probably more of large jump in volume. The master here is a voltage divider dumping signal to ground and in between the switch throws it would instead be very briefly a series resistance, which just looks like an increased grid stopper resistance on the following triode with no voltage dump to ground.

[øøøøøøø]

I’d expect this to be perceived as a “pop” since it would be so instantaneous, but either way a MBB switch avoids the issue

[jimboyogi]

Off topic. I'm intrigued by the schematic for the Hiwatt. I've never had a close look at Hiwatts before, and the V3 and V4 arrangement is new and confusing to me.

Is the purpose of V3a cathode follower only there to provide the bias voltage for the fixed bias LTPI V4?

EDIT - I read up on it and yes, that's what V3a is doing. Back to actual topic.

[mynameisjonas]

You'd probably want a MBB (shorting) switch, as opposed to a BBM (non-shorting) switch.

I'm not sure exactly what would happen if there was a momentary removal of the master volume's earth connection, but whatever it is would probably not be especially pleasant (loud pop or buzz).

Probably more of large jump in volume. The master here is a voltage divider dumping signal to ground and in between the switch throws it would instead be very briefly a series resistance, which just looks like an increased grid stopper resistance on the following triode with no voltage dump to ground.

Hmm, yeah that could be... interesting. Running this amp wide open with the preamp gains turned up isn't just loud, it's physically violent. Not exactly something you'd want in a small club, even if it's just a split second.

[mynameisjonas]

Maybe the smarter way to do it is to run the VR to ground in parallel with the ground connection and using a single pole on/off switch on the ground. That way there's no risk of leaving the master wide open in the case of a failed switch.

If this works, I could do the same thing for the channel volumes, thereby giving me 4 different levels of volume and gain that I'm currently using 2 overdrive pedals to achieve.

[OffYourFace]

IDK about you Jonas, but Hiwatts emit a certain upper mid frequency that makes my ear canal feel 'itchy' when they are cranked. IDK how else to describe it.

[mynameisjonas]

I don't know about the itchy part, but they definitely have a certain upper mids bite that's part of the appeal for me. But I've never used a Hiwatt (or my Ceriatone) with a Hiwatt cab, I've always used them with Celestions (greenbacks, V30s, T-75s). I have a pair of Fane F90s in a 2x12 that I keep at home, and that does get a bit hard in the upper mids for my taste.

[JSett]

IDK about you Jonas, but Hiwatts emit a certain upper mid frequency that makes my ear canal feel 'itchy' when they are cranked. IDK how else to describe it.

I know what you mean, it's not too dissimilar to the frequency of a metal fork or knife squeaking on a plate

[mynameisjonas]

You say that like it's a bad thing!

[B.T.]

I mentioned in another thread a while back that I wish I was able to switch between two master volume settings on my amp, and I had a simple idea of how to do that without adding a relay and another pot on the amp, by simply switching in a variable resistor between the existing master volume and ground, and putting that in a pedal:



Is there something really obvious that I'm missing here, or could it actually work?

Ampeg did something similar with their V series amps of the 60’s/70’s. Sold a little box as an accessory, rare as hens teeth. Plugged into the amp out jack. There were 3rd party offerings with a stomp switch to make it like a boost. You could set the amp much louder and have the box set to a lower volume and switch between the two. Pretty cool, and it actually worked quite well.

[mynameisjonas]

There's also the Jimmy Page Hiwatt, with its 'Balance' control. It also had an extra gain stage compared to a DR103 (although wired in a very different way than the OL), and the switch activated a gain attenuation control.