Melos SHA-gold photentiometer replacement DIY

Sorry the DMM is a digital multi-meter. If you don't have one and don't know how to check resistance,skip that suggestion.

The schematic for your preamp which I found on the web shows a standard stereo pot. "potentiometer" 6 pins. One ground, one input and one output per channel.

Take a look at it. It should have a sticker on it somewhere that says 50k or 100k. Those are the most common values anyway. Or if your going to have the work done for you have them check it for you. If it is indeed 50k and you have the physical room for that stepped attenuator it will work and be a nice improvement.

I do want to do the all the mods I'm planning myself...
Upgrade the attenuator, caps, resistors, tube sockets and power supply

If you're 'rather clueless' and do not own a DMM, I am not sure you should be performing these mods yourself...you could do your amp, or worse, yourself, quite a bit of damage.
Just sayin'...
byron

Agree with Manistory.

You need to test with DMM to check a correctess of your DIY otherwise if you just turn it on, you'll have a large possibility to burn something in the circuit board especially with tube equipment. Also it's good to know what is Votage V, Current I, Resistance R, Impedance Z, Reactance X, Inductance L, Capacitance C, Freequency W, Power P, Measurements units of above listed.

Start with cheap equipment first to practice soldering, measurements (I to actually feel that you're not ready to DIY mod your preamp and practicing on cheap equipment will actually give you a cursory look to estimate yourself) etc and than exersize your DIY when you feel ready to take a risk.

Also having a camera to picture 'before' scenario would be very helpful in any tech DIY projects. I use Nikon D3000/Nikkor 18 - 55mm lens.

Disclosure: I'm part-time studio tech/full time software engineer.

Have you talked to Chris Johnson at partsconnexion.com?
try info@partsconnexion.com and he will get back to you.
If anyone would know, he would.