Tube Amp Archive

Thanks! Just signed up. I really hope things get sorted out. Cannot fathom losing a trove of information like this...

Stevem wrote: ↑Tue Oct 07, 2025 10:31 am Here’s some idle current to plate voltage guides .

60% will give far better tube life then the 10% difference between 60 and 70% suggest.

Weber used to have the Jim Jones bias table. I found a copy here (in case folks are interested in more than EL34): https://www.franciselectrik.com/bias/

desertmouth90 wrote: ↑Wed Sep 24, 2025 11:27 am

Reeltarded wrote: ↑Mon Sep 15, 2025 4:37 pm It sounds like two stage plate drive. No CF with input stage, ts, stage two.. a Twin with a Marshall buttock.

whats a CF?

I know it's not my quote, but I'm pretty sure he means Cathode Follower.

Because that's where the big tone is hiding. Nobody complains, the house has great soundproofing and you don't hear it outside, so it's all good. I stick in my earpro and just GO. Hah! My house was built in 1892 before insulation was a concern. Still has original windows, and the only thing between...

I admit, I was afraid of the power, so I built the triode version first (AX84 4-4-0). After chatting with RJ for a while, I bought the parts to try a 6Y6 version. Still haven't built it, but in theory, gets a little closer to "the sound" without melting your face off.

I'm still using an old Xytronic station I got in the early oughts. It still had the dial for temperature control. I bought my son an updated version with a digital temperature select. So far, so good.

I'm sure someone much smarter than me can figure it out, but I don't know what switch will do it...

Edit: Best I can come up with works with an on-on 3PDT. If it was a center off switch, center off would truly be "Off"

Wouldn't that link the cathodes? That's what I couldn't get my head around; keeping the cathodes separate, because the meter would link them.

Japanese Univox (Lafayette) U-320 - designed with a voltage doubler and meant to run 7591's Someone earlier changed the transformer and rewired it for 6L6GC's Owner wants it returned to 7591's The new transformer is putting out 268vac across the secondaries, so running through the voltage doubler g...

Just FYI - doing a reverse number search does, in fact, take you to this name. Identified as a landline in TX. Still just as confused as everyone else, but...hard to say anymore. Maybe if OP could pop back in and check the "I'm not a robot" box?

Fantastic news! Thanks!

Is this the PT330Mi? Are you using both sets of primaries? The data sheet shows the black and white primary connected and the brown and blue connected. If only using one set, I could see that over-stressing that PT.

That's a whole lot of drop on the filament winding...If it were me, I'd try inserting the tubes one by one, or at least in groups (for example, preamp first, then power), and measuring the voltage to try and narrow down where that drop is coming from. I know you have multiple problems to chew on, so...

Just wanna chime in and agree about that little meter. My old meter didn't test caps, so I snagged one of these for less than $20. It's just too easy to use, and if I accidentally cook it, I'm definitely getting another. Nice to have ESR and leakage measurements for caps.

sluckey wrote: ↑Mon May 26, 2025 11:38 pm Look for an old Akaia/Roberts R2R carcase on eBay. I found this one for cheap. It is just what you need...

Funny you mention this...I just fixed an old Akai R2R for my wife's aunt and uncle! Just waiting for the new pinch roller to arrive before calling it done.