The Amp Garage

I have often needed to drop the value of the resistor that is inline with the bias pot. If it is a 47k or 56k, lower it down to the next value and try again.

I got caught up in the same situation as you when planning my first Marshall style builds ten years ago. I went down the rabbit hole buying Piher resistors, mustard caps, Lemco silver mica and many other NOS parts that were used by Marshall. The two amps turned out fine but after building many other...

The original SLO ran all AC heaters but the newer models produced by BAD are using DC on the first couple of tubes.

These are some of the other Metro layouts that one of the members saved,
https://drive.google.com/drive/folders/ ... 549g-K1iDA

This is the old Metroamp layout that I used for my 2204. This should help you along with your build.
https://drive.google.com/drive/folders/ ... jBAObvpf2g

Any chance that the oscillation is being caused by reversed primary wires on the OT? Have you tried swapping them? If they are reversed and causing positive feedback, that could be messing with the presence pot.

I was going to suggest the Splawn schematic also. I built one last year from that schematic and the plate fed tonestack definitely adds a ton of gain.

It may be a long shot but several folks over the years have reported issues with those black silver mica caps. Some have been faulty right from the get go and others have been damaged from excessive heat while soldering. I have gone to using quality ceramic caps these days because of this. I also wo...

Robrobinette has some good basic, beginner info on one of the most simplest circuits. Aiken's sight also has some good info. Both of these are geared specifically towards guitar amps. As suggested above, learning the basics of AC and DC should be your main priority in the beginning. https://robrobin...

I recently completed a Tweed ODS build that was posted here on the forum several years ago by a fellow member. I included the Framus mid control in the OD section of this amp and it does work fairly well. With the pot on 10, the gain loss is very minimal. When dialing down the pot, you do loose a ti...

I purchased one of Burger's boards last year for a JJ jr build. The board and documentation were top notch and having two foot switchable channels with separate MV's is a nice upgrade. His board also offers a cathode bias/fixed bias circuit option should you decide to build it that way.

I used one of Burger's boards in a JJ jr style build just a few months ago. Excellent service after the purchase and the board was top notch!

This may help you.

http://forum.metropoulos.net/viewtopic.php?f=26&t=15719

The boards changed slightly over the years but this should have the info you need.

I would think think that swapping those carbon comp resistors in the preamp stages for carbon film, or better yet, metal film would help to alleviate some of the hiss.

I know for myself at least, any clips that I hear on Youtube rarely sound the same as sitting in the room with the actual amp. The best bet would be to do what the fellas have suggested...try out as many amps as you can and then let your builder know which ones you liked. Then he has a good starting...