mike stehr

Report post Posted 6 hours ago 09/14/2020 > SETI Said : A gift from IBSlammin. LuxmanPP triode 50ca10. Just completed cap replacement and putting it back to factory as it has been modified. Going to bring it up this week. I love the Luxman Me too...

A bread-board of this circuit, created by an retired EE audio friend of mine. Frustrated with the price of interstage transformers along with lousy bandwidth and goofy ratios, he experimented using a cheap Allied SE to PP interstage transformer connected as SE to SE. Square waves ring like crazy, until one bridges the interstage with the 0.1uF capacitor. The cap more or less brute forces the interstage to give better bandwidth, or gives the best of both worlds. (advantages of cap coupling and interstage coupling) It's a circuit that makes SET luddites cringe. But it will output a decent square wave at 30kHz, with strong bass at 30Hz. The 6EA7/bridged Allied IT front end circuit can run upwards of 120 volts peak to peak if I recall...I could be wrong. It's rather difficult to clip this amplifier for what it is. Personally, I think John Warren won this thread...

I want to build a pair when I'm a bit more flush...

I'm pretty sure it's a "V" or "W" type filament structure. Initially, the amplifier had the TJ tubes set-up at 2A3 spec, with regard to plate voltage and cathode/filament current/voltage. Being specified as a 300B tube, we wanted to try it dialed up as a 300B. The gentleman I bought the project from, scrounged up another PS transformer so we could get the higher plate voltage for 300B spec. I used the amplifier like that for maybe a year. But I then wanted to go back and convert the amplifier back to 2A3 specification, because I wanted to try different 2A3 tubes. So I used the original PS xformer for lower plate voltage, and have used 2A3 since then. The TJ tubes starting waning in emission after using them specced as 300B. Don't know why, they claim to be a 300B. The tubes were run well within the plate voltage and cathode/filament current/voltage. 70% of total dissipation rating if I recall...

Breadboards? Here's a SRPP using a 6SL7 to drive a 71A. DC heating, because directly heating with 5 volts AC is a challenge I really doubt I can pull off. Polypropylene/oil caps used for cathode/filament bypassing. James universal OPTs. The circuit shined on my LaScalas I had at the time. Not much gumption at 800 milliwatts a side, but it sure had a nice sound.

Sort of reminds me of the TJ voice of music globes I have. They have a 300B solid plate anode structure, with a 2.5 volt filament. They had this lush sound about them...nice sounding. My only complaint is they didn't last very long with regard to emission.

From Kenosha, Wisconsin...heh