The Amp Garage

Thanks nuke! I kind of want to use bias modulating trem on this amp, but we'll see. The power amp is a Bassman AA864, and there may not be enough swing to get the trem to sound nice enough. With R.G. Keen's circuit as he described I can use part of it only to get the bias modulating trem, and probab...

Thanks R.G.! Yah I'll have to see how well it will work out in this amp. It might be a better approach to use the triode elsewhere and use a MOSFET as you suggest. This amp is quite complicated, with three separate amps in one head basically, all sharing the power transformer. I've done the best I c...

I have an amp that I was working on years ago that I want to get back to. It is basically 3 amps in one head, with a common power transformer, separate output sections, phase inverters, and output transformers in one chassis, and I am adding a preamp chassis where each of the 3 preamps will be separ...

There has been some activity at some of the MEF forums. The Sunn page is back up. (link below) Pickup forum and wider MEF is still down, but Tboy must be getting things back up! Yay!!! Once things are back up, we should all contribute to site costs and the time it takes for him to maintain it. Greg ...

I just tried the link I had for the Sunn section of the MEF (https://forum.sunnstillshines.online/) and it says

Maintenance mode

Site maintenance in progress

The pickup forum link is still showing a 404 message.

Maybe there is something going on with it though. Fingers crossed!

Greg

Hi Chris,

Welcome back to the amp community! All of us old timers miss the old days with AX84, and now with Ampage/MEF too. It's good there are still a few sites around like TAG and Hoffman and MEF2 that are dedicated to the craft.

Greg

Depending on exact circuit, parallel input triodes can result in more than doubled input capacitance. Might mean something like 300pF. The increased low pass filtering and lowering of the PU resonance are likely to be audible. It was audible in my case. The crisp highs that might otherwise be there...

One of the concessions with running a parallel stage is that the tone has a bit of high end loss. I noticed this in an amp I built that is using a parallel input stage, but every time to tried to get more high end the amp would squeal so I ended up living with it.

Greg

Yes some of the MEF community has started up the MEF2. We encourage all former members to join, and if anyone has information on how we can reach Tboy (the operator and host of the old MEF) then we would like to do so in order to save all the data from the old site and make it available again for ev...

That is crazy! But I guess we shouldn't be surprised....lots of tin plating with no lead added makes for lots of tin whiskers in modern electronics. 60 years is quite a good life before the problem manifested. Here's a NASA webpage that documents satellite and other failures due to tin whiskers. The...

For an active mixer, Fender did it with one of the Bassmans, AA864 I think. Most people didn't understand that circuit and modify that channel and get rid of it, but an active mixer can work very well and results in better bandwidth and less reduced gain when compared to a resistive mixer. If you ha...

Reading this thread, I am wondering if the saggy voltage doubler and lower screen voltage may be exactly what I was missing. I'm almost tempted to go gut it again and try. Anyways, this is a great discussion and some amazing work on these amps. Thanks for sharing! The 1484 power supply isn't really...

It's a great forum with some old timers around that has a lot of great info. You'll be very welcomed there R.G., even though all forums have seen a drop in activity since FB took everyone away. I'm sure Doug will fix the issue, whatever it is. There is a great schematic resource on the Hoffman site ...

I don't know him, but may ask around to see if anyone I know in the music/amp community does. For amp builders and repair techs it is a relatively small group of people outside of the big names everyone knows. I am up north of Seattle by about an hour. You're up a little further than my friend Wolf...

I know he's in the PACNW in WA state somewhere, but aside from that I have no idea. Greg Should I start knocking on some doors? It's a pretty small amp community up here... Do you know where Chuck H lives? I seem to remember it was somewhere up towards Bremerton, or Port Orchard, but he could have ...