The amp I started asking questions about in 2016 is finally under construction. All of the modules, power supplies, regulators and audio circuits are finally assembled and ready to start to prototype layout and grounding. I ended up with Coleman regs for the filaments and I am running the 6072 SRPP from them also using the cathode bias on the VT52 to lift them. B+ is running from a single 21st century miada based more on the noise performance than needing any kind of rock-solid supply. My target for the VT52 is 25-27ma at 250V RL=10K but I could only find one set of unofficial curves to pick that point from and not quite sure it is right. The object was to get the load line across the linear part of the curves but keep dissipation low to hopefully let the NLA tubes live a long time. Next up is to start carving metal which is not really my favorite pastime.
Anyway… no further questions yet, just pumped up to be getting so close on a long simmering project.
Here is a shot of the completed audio boards, the ground buss is broken in to individual stages so I can experiment with the grounding scheme to find the quietest option. There are a few things I would do differently with the boards but nothing that bugs me enough to go through the hassle of rebuilding them.
Marty
Anyway… no further questions yet, just pumped up to be getting so close on a long simmering project.
Here is a shot of the completed audio boards, the ground buss is broken in to individual stages so I can experiment with the grounding scheme to find the quietest option. There are a few things I would do differently with the boards but nothing that bugs me enough to go through the hassle of rebuilding them.
Marty
Attachments
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Yes, first shot is the Rankin circuit. I bought a pair of sylvania VT-52 nos out of an army re-tube kit years ago from an old ham and have been scheming projects for them off and on since. I'm planning on a 5RU rack mount chassis in the old style to pay homage to the original use.
Ahh that sounds like an excellent project. I look forward to seeing the end result. I'm currently waiting for a pair of 45s to arrive so I can start tinkering.
Best of luck with the build!
Best of luck with the build!
Did you ever finish this amp, @martyh ? I am considering using VT-52 in a headphone design. Recently picked up a pair to check out, here next to a pair of type 50.
One thing that has me perplexed is their max plate dissipation. I know no datasheet exists, and many treat it as if it is a 45. But it has the same plate structure as the Western Electric VT-25A, which had a 15W rating.
https://lampes-et-tubes.info/tt/tt018.php?l=
Moreover, there are reportedly VT-52 rebranded as 6A3s, which would suggest a 15W rating. The owner of the now defunct VT52.com also rated them at 15W. Let me know if you ever came across that spec.
One thing that has me perplexed is their max plate dissipation. I know no datasheet exists, and many treat it as if it is a 45. But it has the same plate structure as the Western Electric VT-25A, which had a 15W rating.
https://lampes-et-tubes.info/tt/tt018.php?l=
Moreover, there are reportedly VT-52 rebranded as 6A3s, which would suggest a 15W rating. The owner of the now defunct VT52.com also rated them at 15W. Let me know if you ever came across that spec.
