There are some options here...
Cavalli: Cavalli Audio
Millett: Pete Millett's DIY Audio pages
HeadWize: HeadWize Library - Projects
Aikido: John Broskie's Guide to Tube Circuit Analysis & Design (Octal All-in-One LSA/HPA)
Cavalli: Cavalli Audio
Millett: Pete Millett's DIY Audio pages
HeadWize: HeadWize Library - Projects
Aikido: John Broskie's Guide to Tube Circuit Analysis & Design (Octal All-in-One LSA/HPA)
Hello,
You are asking about SET headphone amplifiers. You do not say transformer output or not.
I have been trying several versions of SET headphone amplifiers. I am using an Aikido line stage with up to 20 volts output (more than plenty) to drive the power tube. To start you do not need a high dollar tube or output transformer to work with, after you make refinements you can add more expensive parts.
I have tried 6BX7, you only need one tube with two triodes in the single envelope. Also 12B4A, 6G6G, 45, triode strapped 6L6GC, 5763, and others. They all work. I have 307A to try. The tubes that sound best with HD 600 300Ohm headphones are the tubes with the lowest plate resistance. The 6BX7 and triode strapped 6BQ6GBT I like the best. I have had the 6BQ6GTB running for several months. At this point I am going to move the 6BQ6GTB amplifier off the breadboard into a pretty box. This tube working into this headphone only needs to swing a couple of volts and produce less than 0.1 watt (way less) to cause hearing damage. With little voltage swing or little power needed there is very little distortion. The difficult part was obtaining output transformers made for headphones in the range of 300 ohms. I called Edcor and talked up output transformers. I paid a design fee and they made 5K : 300 ohm 3 watt transformers with a UL tap, model #GXSE-300-5K ~ $20.00 each. The tube idles at 150 volts plate ~22 volts on the grid at 50ma. Sounds very nice The Zo is ~23 ohms. I also had Jack at Eletra-Print make output transformers. The Eletra-Prints sound some better. I think the 50 ma idle current helps get solid output from both transformers.
DT
All Just for fun!
You are asking about SET headphone amplifiers. You do not say transformer output or not.
I have been trying several versions of SET headphone amplifiers. I am using an Aikido line stage with up to 20 volts output (more than plenty) to drive the power tube. To start you do not need a high dollar tube or output transformer to work with, after you make refinements you can add more expensive parts.
I have tried 6BX7, you only need one tube with two triodes in the single envelope. Also 12B4A, 6G6G, 45, triode strapped 6L6GC, 5763, and others. They all work. I have 307A to try. The tubes that sound best with HD 600 300Ohm headphones are the tubes with the lowest plate resistance. The 6BX7 and triode strapped 6BQ6GBT I like the best. I have had the 6BQ6GTB running for several months. At this point I am going to move the 6BQ6GTB amplifier off the breadboard into a pretty box. This tube working into this headphone only needs to swing a couple of volts and produce less than 0.1 watt (way less) to cause hearing damage. With little voltage swing or little power needed there is very little distortion. The difficult part was obtaining output transformers made for headphones in the range of 300 ohms. I called Edcor and talked up output transformers. I paid a design fee and they made 5K : 300 ohm 3 watt transformers with a UL tap, model #GXSE-300-5K ~ $20.00 each. The tube idles at 150 volts plate ~22 volts on the grid at 50ma. Sounds very nice The Zo is ~23 ohms. I also had Jack at Eletra-Print make output transformers. The Eletra-Prints sound some better. I think the 50 ma idle current helps get solid output from both transformers.
DT
All Just for fun!
Last edited:
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