My last project, completed, PP with KT88 EH, with timing mode, anodic voltage, and bluetooth, Toroidy output transformers, Alps potentiometer, Kendeil electrolytic capacitors, Nipon chemikon. The laser-cut housing, painted in an electrostatic field, still has meters to connect. On and off, with smart socket mode with Tuya application and local push button.
Attachments
uriy52,
I like your schematic! Thanks for posting!
The amplifier looks great too!
I am sure it sounds really good. But here are a couple of ideas for you . . .
1. GU32: Measure DCR1 from plate 1 to the center tap; measure the DCR2 from plate 2 to the center tap.
Then, set the 30k resistor until:
(plate 1 to center tap voltage drop) / DCR1 = (plate 2 to center tap voltage drop) / DCR2. That makes the plate currents equal.
The output transformer will "love you" for that: (no early lamination saturation when the quiescent currents are matched).
2. Replace the 56k pot, and the 47k resistor, with 47k 0.1% resistors. The concertina signal voltage balance will match perfectly (unless your 6N2P is gassy, then grid current destroys the balance).
Gassy tube? . . . Then replace it.
. . . Well, I see now . . . the setting of the 30k pot, unless it is centered exactly, and even if the 150k resistors are matched, the load on the concertina is not equal, and so the 56k pot can solve that. Yes, we still need to set the GU32 plate currents equal, so I do see the need for the 56k pot, to make up for a non centered 30k pot.
Have fun listening!
(I bet you already are)
I like your schematic! Thanks for posting!
The amplifier looks great too!
I am sure it sounds really good. But here are a couple of ideas for you . . .
1. GU32: Measure DCR1 from plate 1 to the center tap; measure the DCR2 from plate 2 to the center tap.
Then, set the 30k resistor until:
(plate 1 to center tap voltage drop) / DCR1 = (plate 2 to center tap voltage drop) / DCR2. That makes the plate currents equal.
The output transformer will "love you" for that: (no early lamination saturation when the quiescent currents are matched).
2. Replace the 56k pot, and the 47k resistor, with 47k 0.1% resistors. The concertina signal voltage balance will match perfectly (unless your 6N2P is gassy, then grid current destroys the balance).
Gassy tube? . . . Then replace it.
. . . Well, I see now . . . the setting of the 30k pot, unless it is centered exactly, and even if the 150k resistors are matched, the load on the concertina is not equal, and so the 56k pot can solve that. Yes, we still need to set the GU32 plate currents equal, so I do see the need for the 56k pot, to make up for a non centered 30k pot.
Have fun listening!
(I bet you already are)
Last edited:
OK, send me your email, I will send You Saturday or Sunday /Im sitting with my grand children/.
PS unit for heating 20V is power unit 20V/40W from ebay. No hmm, no hisss, very clear
This amp is a crazy idea I had for long time that finally got built. It is a 17 watt stereo EL84 amp (basically a Dynaco ST35) built in the style of a classic McIntosh. It took forever, but turned out surprisingly well. I expect some double-takes from McIntosh experts who would know that an "MC217" never existed 
Here also is a link with more details on the build saga:
https://lensprojects.com/2022/03/03/a-tube-stereo-amp-built-in-the-style-of-classic-mcintosh/
Here also is a link with more details on the build saga:
https://lensprojects.com/2022/03/03/a-tube-stereo-amp-built-in-the-style-of-classic-mcintosh/
Nice!This amp is a crazy idea I had for long time that finally got built. It is a 17 watt stereo EL84 amp (basically a Dynaco ST35) built in the style of a classic McIntosh. It took forever, but turned out surprisingly well. I expect some double-takes from McIntosh experts who would know that an "MC217" never existed
Here also is a link with more details on the build saga:
https://lensprojects.com/2022/03/03/a-tube-stereo-amp-built-in-the-style-of-classic-mcintosh/
View attachment 1031947
ECC832's-This amp is a crazy idea I had for long time that finally got built. It is a 17 watt stereo EL84 amp (basically a Dynaco ST35) built in the style of a classic McIntosh. It took forever, but turned out surprisingly well. I expect some double-takes from McIntosh experts who would know that an "MC217" never existed
Here also is a link with more details on the build saga:
https://lensprojects.com/2022/03/03/a-tube-stereo-amp-built-in-the-style-of-classic-mcintosh/
View attachment 1031947
What I'm using as well, in my SCA35 hybrid 6GM5 PP-
Q- did you try the 7247's as shown in original schem? Or perhaps a 12DW7?
Just wondered if your curiosity had gone there...
Jim