The Amp Garage

I'd suggest doing some reading to get a better understanding of what's going on. This is a nice place to start: http://valvewizard.co.uk/Common_Gain_Stage.pdf The 1987 and 2204 circuits aren't much different from each other, and can be converted without needing a new board or anything. Just a few re...

I'd also add that you might want to pull the lead of V1B's grid stopper in so that the resistor is as close to the pin as possible. You might also try flying its plate wire over the top of the socket so it goes straight to the pin instead of wrapping around the socket.

Oh no now look what I've started lol. I feel the same way. I just want the screeching to stop. :roll: If you want good Bass response on the low E string and in turn better dynamic range then get away from a low core mass 15 watt OT and into something in the 25 watt or better range! Yeah that's partl...

They prefer transgendered. I was wondering if anyone was gonna pickup on that. :mrgreen: :mrgreen: I'm thinking the beefed up Deluxe transformer (#TO26) from Allen Amps will probably be a nice choice. Its a little more expensive than the classic tone models and some of his others but I think the ex...

Thanks, I doubt its a HF oscillation. I've had that amp on the scope many times and I've never seen any HF noise on the output. I suppose its possible when I changed the caps out that something got moved or whatever to cause it but I was pretty careful not to move any wires around. On the scope and ...

A year or two ago I converted my SE express-ish amp into a P-P with 6v6's. I'd ordered some polystyrene caps (Edit: meant to say polyester) and today I finally got around to putting them in. I wanted to try some larger values as the amp was still overly bright. Originally I had .022's throughout. I ...

If you use a 12DW7 I'd recommend putting the AU7 half on the bottom (input) and the AX7 half on top. This should give you optimal gain and performance out of the circuit. Though that's coming strictly from a Hi-Fi perspective. Which way around sounds better you'd have to experiment with to find out....

Well it seems like that solved the problem. I finally got around to trying it in the preamp today, and after disconnecting and reconnecting the power supply at least a dozen times, even with the unit switched on I didn't see any device failures. Here's to it staying that way lol.

Oh of course! Man I can't believe I overlooked that. Most of the MOSFET's I've used in the past had them built in internally. I knew I'd overlooked something. I'll give it a try tomorrow and report back. Thanks!

Well like I said it fails even in a simple common source circuit. I can put up a schematic for that if you really need it but its just a DN2540 with the drain connected to a +15v supply through a 4k75 resistor. The gate is tied to ground through a 10k resistor and the source is also tied to ground t...

So I'm trying to figure out why this particular MOSFET is prone to failure. Its a DN2540, depletion mode N-channel. Its used in a constant current source of a tube pre-amp. It works great in circuit, however the pre-amp has an external power supply, if you don't wait long enough after switching the ...

Thanks, I've never heard that one before. I mostly just use PTP because we have the terminal strips on hand at work and if you're building 1 or 2 of a particular amp its just easier to do it that way I think. Especially if you're building new circuits or layouts that haven't been tried before, if so...

Fixed the hum, was just a leaky tube in V1. Swapped it with the PI and all is good. I think this may be the quietest amp I've ever built. Everything dimed in 1959 mode and its just a very mild hiss. Of course its alot more when you engage the additional gain stage but its about as good as you could ...

Thanks guys! The pre-amp is a pretty standard Marshall 2203/1959. Pretty much copy and pasted that, coupled with a smaller output section. The layout I created myself. It works pretty well. Sounding much better now that I fixed the issue with the NFB loop. I may yet have to put in some shielded wire...

Don't worry I totally get that. I just wanted to point it out in case you weren't aware of it. Pretty much all my builds these days are in the <15w range. I just can't justify the cost and SPL of larger amps. Hell even the 6k6/6v6 amp that I made a post about in the tech discussion that puts out a m...