OT: Show us your DIY tube amps

[alancohen]

I have a question for you guys.What do you think are the best sounding Tubes for you die hard tube guys. KT88's

"Best" tube is like catching mercury. Kind of like what is the best driver for a speaker. The circuit it's in makes a big difference, just as the enclosure and even room parameters also affect the end result for a speaker. And eventually the answer comes down to what you prefer.

I have KT88s in my cathode follower. I love it. It is warm and musical, but not as transparent as the EL-509s in my output tranformerless amp. In a transformer-coupled amp, the OTs make a huge difference and really good ones can cost a small fortune. The law of diminishing returns is in full force here.

I'm currently awaiting my newest toys which will be a pair of 300B output transformerless monoblocks. That's a real trick since "In an OTL, the cathode is connected to the speaker. A 300B triode has a directly heated cathode. That means the cathode is the filament. This places the filament in direct electrical contact with the speaker." Eliminating the A/C hum on the filament has been cleverly achieved in this circuit by using a separate power supply running at 25Hz instead of 60Hz to heat the filaments. There will still be a hum, but below audible levels. Pretty cool. So in effect you get the best of both worlds. No transformer between tube and speaker to color the signal and the bliss of a 300B. Actually 8 of them..ouch!

As far as "replacing tubes all the time", again, it depends on the circuit. A well designed amp should be able to provide many years of service for the tubes. Reliability is job #1 for an amp designer.

AB, you're more than welcome to stop by and listen to both...anytime.