Tube Amp Archive

Hey paolo, It costs an arm and a leg to get MM trannys sent here to Australia too! Specially seeing as the Oz dollar is about on parity with the PEANUT!!!So I know how you feel!! Anyway you'll soon forget the money and you'll still have the Transformers! One of my JTM's has Marstran/Heyboers in it. ...

I've used MM trannys in a couple of JTM45's, and also two Plexi types. I converted a Silverface Vibrolux to a Dumble type(HybridA based). It didn't turn out too great in the beginning IMO, however I replaced the original O/T with a MM Axiom Tweed bassman O/T and it made a big improvement to the amp....

Thanks blokes. Yes that's possibly what happened. I have replaced pretty much all the coupling/tone caps in the front end as I thought the sizzling was from a leaky cap originally and the Vol pot was making that heavy breathing kind of sound when you turned it. There doesn't seem to be any DC there ...

Well thanks for the suggestions guys! I appreciate it. After trying everything suggested with no luck, I went through the whole front end of the amp, reflowing just about all the solders, replaced the whole dropping string along with a bucketload of other things. The last thing I would have suspecte...

Hi all My D style amp (hybrid A based) has developed a strange fault. When I switch the standby on, I get a sizzling/fryingpan sound for a few seconds. I am assuming that it is something to do with the B+ reaching it's operating point, when it gets to it's quiescent state the sizzling stops and the ...

I have a silverface Vibrolux reverb donor D type amp. I chose to use diodes instead of the 5u4 that it originally had. With a 390ohm resistor now in place of the choke I'm getting over 490v on the plates of my 6L6's. I have to say it's a pretty harsh sounding animal as it is at present and seeing as...

SWT, I asked Gary the question re supply string recently and Scott chimed in with some help.
Check the thread "Help implementing loop please Mr Glasman"
cheers, John

Thanks Scott and Gary for sharing what you know. This has helped me a lot!
Cheers from rainy Oz, John

Thanks Gary, that helps a lot. There you go, 370v at the plate, 20 at the cathode. That's 350v across the tube! As I said, I'm no tube guru for sure, but I would have been convinced that those voltages exceed the specs for the tube. I thought 300v was the max? I probably don't know how to read spec ...

Thanks Groovtubin, but I'm asking about the first stage of the loop, not the whole amp. I'm no amp guru, I just need to know some test/reference points for my own peace of mind. Gary has 370v on the equivalent plate in his Rev a loop schem , but what should the cathode voltage be? It's the voltage a...

Hi Gary, or others who may know. I really need some assurance/help regarding my D/lator type loop. I have a separate node to supply B+ between PI and O/D nodes. Q1: Is one node OK for the whole loop? Q2: The voltage across the first 12ax7 stage of the loop has me worried, at the moment I have 315v a...

Hey Skip Thanks for your replies! I originally used 6.3v heater tap with voltage doubler, 1,000uf on both halves of the doubler into 7812 regulator. ground isolated from chassis. This system was silent until I engaged the relay for PAB, then it was hum city. If I grounded the supply to chassis the h...

I thought I'd just update on this one, since I have fixed the issue I was having. I wracked my brain over this one and still don't know the technical reason for it, so if someone could enlighten me I'd be delighted. I could not get the hum to go while using a relay supply derived from either 6.3v he...

Hey Paddy, thanks mate, I'll try that then and see what happens. I live in Ourimbah about 1 hr north of Sydney. Pretty rural where I am, I can turn my amps up full blast when my wife is out! and I do!! Whereabouts are you in Taz? Don't you love the shipping charges on components for amps???? Cheers ...

Actually on further investigation it may be that the runs of wire to and from the relay may be causing it. If I disconnect the wire going from the treble pot to the relay at the treble pot itself, the hum almost goes completely. I have my relays a little further away from the pots than would be idea...