The Amp Garage

FUCHSAUDIO wrote:When the amp is working, connect then disconnect the nfb. If it's wired right the gain goes DOWN when the lead is connected. That determines phase is correct..

So will the howling, squealing, and hiss if that is present.

You never see these in tube guitar amps, (I do use them where thought to be needed or useful) MLR to the tube recto. Older tube manuals will often list them. Some say all tube rectifiers should have them. Tube rectifiers can only deliver so much current, the limiting resistor keeps it from being swa...

Yes, when the plate to OT connections are not correct, may PP amps will oscillate and any NFB will actually be positive feedback exacerbating the symptoms. If disconnecting the alleged NFB wire improves things, that is a telltale that plate leads are reversed. It can occur in open loop amps or amps ...

I was curious at this point to see what they put in my batch of 47 uF 450V Rubycon caps. It was the same story. The pics tell it.

I found an article on fake Rubycons on ebay and decided to look what kind of "bargain" I fell for so I chopped open a recent cheap "Rubycon" 33 uF 450V axial. It was pretty sickening. There was a small 22 uF 450 v labelled rubycon inside the larger 33 uF 450V labelled can YK type. Worse yet, I open...

I found an article on fake Rubycons on ebay and decided to look what kind of "bargain" I fell for so I chopped open a recent cheap "Rubycon" 33 uF 450V axial. It was pretty sickening. There was a small 22 uF 450 v labelled rubycon inside the larger 33 uF 450V labelled can YK type. Worse yet, I opene...

Yeah, cab vibration can be a bitz. I have an old Crate BV412 and cranked up the whole cabinet will literally rattle an amp to death. Any bad connects or poor wiring will show up in a hurry. It doesn't buzz or make noises, it just resonates with the output and induces vibration to anything on it. Tha...

Cliff, I'm not sure of the brand, they were lot orders from China through eBay, they very well could be Xicon, just not sure. The leads have been pretty good for the most part. BTW, I've noticed if you wrap the lead around sharp edges like a terminal strip has, and you crip it with the needle nose, ...

It was nice to see someone doing things on their own in regards to build layout. I have not gone so far as to PTP one of these. You no doubt learn through all this and gain respect for the original design. I can't even guess how many hours KF spent in the initial design stages before he got the desi...

I got a set of OEM style lightning trannys from TDS who was an early supplier and designed them for Matchless (they still hand wind them at transformer design and supply and on ebay). He told me the OT primary was 4K and the outputs were to 4 and 8 ohm if I recall correctly. The lightning I put them...

Yep, they should spring for all new power filter elytics at the very least. Not doing them will end up costing them more, maybe much more in the long run not to mention almost no reliability. With all new filter caps, it at least has a chance of running somewhat trouble free for a while and maybe pr...

It seems strange the fil winding would be so low, a lot of older PTs are wound for 115 or 117 VAC primary at most, so it's usually the case that when connected to 120VAC mains, they run a tad too high, not a volt or so too low. I would be very suspect of the PT, 2 cents FWIW. A known substitute PT s...

"FWIW, i have a 1500uF (!!!!!) 35V cap on my power tube cathode." Why such a huge cathode bypass cap? 220 uF is about the largest I ever see in vintage amp designs. From Valve Wizard Single Ended power section page: "Cathode bypass capacitor: As with most single ended stages, fully decoupling the ca...

Cool!

reading that resource does make me a bit worried that the currents flowing through the diodes might be a bit much for them to handle. UF4007 is rated at 1000V 1A only. the secondaries are rated at 3A. maybe it would be more prudent to put 5-6A diodes in there? the resource shows a 60s1, which has u...