Tube Amp Archive

I like this LTPI calculator: https://www.ampbooks.com/mobile/amplifier-calculators/long-tailed-pair/calculator/ I did try using some of the calculators on that site, but I think the low voltages I plan on using send them into a tizzy so I wasn't too sure how accurate Mr. Kuehnel's calculators were....

I feel like I've been officially labeled a disturber of the peace! But I'm glad it stirred up some good discussion. lol I certainly wouldn't directly couple the PI to the power tubes. I planned on using screen and grid stopper resistors anyway so oscillation shouldn't be an issue. Reading that data ...

I did exactly that in my 4-4-0. 12ax7 drives those little triodes too hard. I was too lazy to modify the circuit, so I swapped that in. Much better. Cheers! I noticed on the 12AU7 data sheet that even with a single triode they showed using 100k plate resistors and like 2.2k cathode. So I figured a ...

With 5 volts peak and I was figuring about 120 volts on the plates of the PI that should leave me with plenty of voltage swing at the outputs of the PI even with a relatively large 45k tail, but to be fair I haven't done the maths yet since I was still settling on what tube to use for the PI, and wh...

Dang, some weird designs using cathodyne PIs lol. Guess everyone wants more juice with an LTP and so just naturally use a 12AX7. Oh well, time to throw something together and tinker until it works I guess! Shouldn't be too hard to get in the ballpark I guess using the standard values for a 12AX7 LTP...

Spitballing a PP guitar amp using a pair of 6EH5/6CA5 for power tubes. Little suckers only need like 4.5 volts peak to get to full power so I don't necessarily want to use a high gain PI like a 12AX7 LTP and have to attenuate the signal either before or after the PI. So I got to thinking about using...