VVR2 into 1960s AC15 build

[plook]

Has anyone here put a VVR2 into an AC15 (trem/vib 1960s schematic)? Just need to get it confirmed that I tap into C41 and pin 3 of EZ81.

[martin manning]

It would help if you posted the schematic for the amp you are working on, but generally you would place the VVR after the rectifier and the reservoir capacitor.

[plook]

Sorry about that. Here are some pictures of the schematic i used to build the amp. including layout. I don't have digital copies of them, just printed copies, so i took pictures with my phone. I actually made an attempt at the VVR today and it didn't work. I connected to C41 for the plates of the EL84s and pin 3 of the EZ81 and nothing. the amp worked as normal except when the VVR pot was turned up around 70% it gave a horrible hum. It had no impact on tone or volume.

Would appreciate any help on fixing it.

[martin manning]

Here's how I'd do it.

[plook]

Thank you. I'll go and try that now. Really appreciate it. I'll let you know if it works out.

[plook]

Still not working. Can you confirm which leg of the EZ81 rectifier should connect to the right leg of the switch/pot? I have it on pin 3. I made a fresh VVR with new parts just to be sure and i have other amps i fitted the VVR to a few years back, but the difference here is that i have never done it to an EZ81 rectifier. I'll sketch out what i have done and will add that.

[plook]

Here is a rough sketch of my layout

[martin manning]

In the layout snip above, I meant to indicate where to insert the VVR, as shown below.

[plook]

Perfect! Thank you so much. At first the on/off/volume didn't have any sound until about 50% turned and the other channel volumes needed to be turned way up, but after a few minutes it all came in to perfection.

I am so grateful for your help and you've made me really happy today.

[martin manning]

You're welcome. Have fun playing!

[plook]

I've noticed that the trem/vib fades to near nothing as i engage the VVR more. Is it lowering the voltage on the trem tube too much? Is there a way to isolate it so normal voltage hits the trem circuit?

[martin manning]

To do that you'd have to create a separate branch in the power supply to keep the voltage supplied to the trem oscillator up where it normally operates. If you are just looking to reduce the volume of the amp, and you want to use the trem, I think an easier solution would be to switch to a PPIMV.

[plook]

I'll do some investigating. I did add a PPIMV to a tweed Pro about 10 years ago and i never liked the tone of that, was too compressed and smooth. It used a double pot i seem to recall. I'll have a good think. Thanks again.

[ChopSauce]

Some people - I could read - even implemented a PPIMV combined with a VVR. The only comment I could read was "that was fun", though...