Merry new year!
After a long time with no updates, I just posted the design of a single-ended amp using the PL-177 tube. About 15W single-ended pentode with plate-to-grid feedback... it was a fun project!
You can find the details here: http://www.pmillett.com/PL177.html
Pete
After a long time with no updates, I just posted the design of a single-ended amp using the PL-177 tube. About 15W single-ended pentode with plate-to-grid feedback... it was a fun project!
You can find the details here: http://www.pmillett.com/PL177.html
Pete
That is Beautiful!
Can you turn up the volume a little bit please, I want to hear it.
The values of C2 and R3 to the grid of the output tube are inside the plate to grid feedback loop. I suspect that is what causes the little bump at 30Hz. That could sound nice.
I once built a 4-65 Amp in triode mode (almost all the current was in the screen, which is rated at 10W diss, almost no current in the plate). That tube was not good for my circuit.
It might have worked a little bit better in Tetrode mode, and with a much higher B+ and higher primary impedance on the output transformer.
You located a winner tube.
Thanks for sharing.
Can you turn up the volume a little bit please, I want to hear it.
The values of C2 and R3 to the grid of the output tube are inside the plate to grid feedback loop. I suspect that is what causes the little bump at 30Hz. That could sound nice.
I once built a 4-65 Amp in triode mode (almost all the current was in the screen, which is rated at 10W diss, almost no current in the plate). That tube was not good for my circuit.
It might have worked a little bit better in Tetrode mode, and with a much higher B+ and higher primary impedance on the output transformer.
You located a winner tube.
Thanks for sharing.
I just added a little info on that to the web page. The glass part is a borosilicate glass "sight tube" from McMaster-Carr (https://www.mcmaster.com/#catalog/122/3682/=15r3ls2). I designed the top and bottom aluminum parts to fit the tube, which are glued to it with a transparent silicone glue. Landfall Systems (www.landfallsystems.com) machined the metal parts for me.
Pete
Clarence Beeks to Billie Valentine (Eddie Murphy): "We say Happy New Year around here."
You too must have been watching Jamie Lee Curtis on New Year's Eve.
Not sure why that would be. I used a special high temperature silicone designed to glue glass, not the regular caulking stuff...
Dammit, I wish I had known about that stuff before!
I used some marine grade silicone in one of my amps, but obviously it wasn't good for prolonged high temperature use. Sent from my LG G2 with CM13 using Tapatalk
Well, I built an amp with Zout in that neighborhood and it sounded fantastic, although I can't say I wasn't bothered that that number didn't end up lower. I guess that's the curse of being an engineer.
Did you by chance take time to measure DCRs in the Hammond output transformers? Are they on the high side?
In any case, your amp is a thing of beauty. And thanks for pointing out a manufacturer of quality enclosures. I've been looking for something like that for some time now.
Looks like 0.7 ohms, on the 8 ohm tap. Is that high? I've actually never compared them...
I've only ever owned one SE transformer myself, the Edcor 25W 5k:8. I measured 85 Ohms on the primary and a 0.39 Ohm secondary, which translates to a total minimum copper loss of 0.53 Ohms referred to the secondary.
I built a breadboard amp that drove the transformer from a mofet source follower and I measured a 0.6 Ohm Zout on the secondary, so core losses appear to be much smaller in magnitude than copper losses.
I have a 5k Ohm Hammond 1628SE manufactured in 1998.
The primary has 406 Ohms DCR.
It weighs 11 pounds, and has lots of lamination material to do quite a bit of power at low frequencies without saturating, and lots of inductance in the primary for very good low frequency response.
The 406 Ohms accounts for about 0.7 dB of the power loss of the transformer. The DCR of the secondary accounts for most of the rest of the power loss of the transformer.
The transformer is quite large, and there is quite a bit of leakage reactance that reduces the frequency response above 20kHz.
The primary has 406 Ohms DCR.
It weighs 11 pounds, and has lots of lamination material to do quite a bit of power at low frequencies without saturating, and lots of inductance in the primary for very good low frequency response.
The 406 Ohms accounts for about 0.7 dB of the power loss of the transformer. The DCR of the secondary accounts for most of the rest of the power loss of the transformer.
The transformer is quite large, and there is quite a bit of leakage reactance that reduces the frequency response above 20kHz.
That's quite a bit more DCR than the Edcor. Edcor transformer weighs in at 9.4 pounds and has a 2 inch tall stack of EI-150 for a core. I assume the Hammond is EI-150 as well. How tall is the stack?
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