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For the past week or so I have been trying to get a 6dj8 to work in place of the 12at7 that can be used in the attached schem as a substitute for the 6n1p. Why was I doing this you ask? Because I had 6 volts available with the psu I was using from another amp and did not want to add another filament transformer. After days of trying unsuccessfully to get it to work, it finally dawned on me that I had a nice little 12vac to 12vdc solid state transformer left over from a previous project that would work just fine. Soooooo, I changed everything back to the original design this afternoon and evening and now it is playing very nicely thank you. Sometimes we just try too hard.
By the way, this is a very easy and straight forward project if you just build it as designed, with lots of gain. Cheap too. And I do love the sound of the 6bq5. Thanks for all the help and advice you guys gave me. I did learn a lot, even if it was a bit frustrating at times trying to get things into spec. By following the original design everything is right close to what it should be. I think I will go ahead and make this one of my permanent amps and that way I will have both a 6bq5 triode connected PP and a 26/26/45 SET amp for my main system.
Edits: 08/04/17 08/04/17 08/04/17 08/04/17 08/04/17Follow Ups:
But it sounds great. The psu module in the middle started life out as the psu for my 91A 300B clone, then morphed into the 813 amp, and now it will live it's third life as the psu for my triode connected 6bq5 PP amp. It is a very nice psu and is dead quiet with this amp. I designed it with psud2. Even with my ear against the speaker there is absolutely no hum. I am sure the fact it is PP helps. I am so use to fighting hum on SET's it knocks me over to hear nothing at all.Changed over to using 6 volts on the 12at7 filaments as suggested, works just fine. I have a 6A 6.3v winding on the power tranny so it can run the four 6bq5's and the two 12at7's and still have more than 2A left by my count. Thanks for the tip guys, it will make for a neater build.
In the bottom photo the other unit in the center is my everyday filament voltage supply for the bread board panels and the unit on the far left is the everyday psu for the bread board panels. Neither is connected to anything in this set up.
You can see the old front end module in the back ground of the top photo. I will either make a new top plate for this amp or cover the old holes with new pieces of plate and make new holes for the 6bq5 sockets. I really like to repurpose whenever I can, it saves a lot of work and material. Just got to order a few parts (resistors and sockets) and we will get going on the final build. Thanks again for all the help.
Edits: 08/05/17 08/05/17 08/05/17 08/05/17 08/05/17 08/05/17 08/05/17 08/05/17 08/05/17 08/05/17 08/05/17 08/05/17
I think you might be one of the few people here who is actively building at the moment, not just planning or researching. Nice work!
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Buy Chinese. Bury freedom.
Thanks TK. I really do enjoy bread boarding a new amp and listening to it for the first time.
nt
...depending on how you strap the filament. Or maybe I didn't understand your comment about 6V vs 12V for filament thus driving your attempt to use 6N1P.
Still not to late. How do you do it? That makes it even more of a lesson!
Edits: 08/04/17
You would connect one wire from your 6.3V source to the centertap of the 12AT7 filament, and the other wire to both ends of the filament tied together.
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Buy Chinese. Bury freedom.
By placing the two halves of the heater in parallel the heater runs on 6.3 volts.
Pins 4 and 5 get tied together for one connection and pin 9 is the other connection.
Tre'
Have Fun and Enjoy the Music
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