Here's the schematic I drew from the description:
An externally hosted image should be here but it was not working when we last tested it.
Eric,
Why don't you ask him?
His ID is an open secret...
http://www.diyaudio.com/forums/member.php?s=&action=getinfo&userid=3984
Cheers,
Why don't you ask him?
His ID is an open secret...
http://www.diyaudio.com/forums/member.php?s=&action=getinfo&userid=3984
Cheers,
I wish more people would put the current flowing through the different paths in tube amp schematics. It really helped me to understand Thorsten's 45 Monkey schematic.
How's this:
How's this:
An externally hosted image should be here but it was not working when we last tested it.
Now for the real question... Will the following work? I read in TubeCad something to the effect that regulating the g2 of a pentode is nearly as good as a regulated supply. The OC3 should give a nice stable voltage.
However, is this going to result in the world's most expensive relaxation oscillator (reg. tube and capacitor in parallel)? There are two parallel capacitor paths for the OC3 that I can see: 22 uF + series 100 Ohm and 22 uF + series 11 kOhm. I don't know enough to determine theoretically whether this will oscillate or just plain blow up
.
Thanks for your help.
However, is this going to result in the world's most expensive relaxation oscillator (reg. tube and capacitor in parallel)? There are two parallel capacitor paths for the OC3 that I can see: 22 uF + series 100 Ohm and 22 uF + series 11 kOhm. I don't know enough to determine theoretically whether this will oscillate or just plain blow up
.Thanks for your help.
An externally hosted image should be here but it was not working when we last tested it.
Replace the 22uF g2-k bypass with the 0C3.
Alternately, you might try two in series, one to the screen, one to the 2A3's cathode (pulling the 22uF and 6.8uF bypasses). This would cause a mild upset in the 235V at the cathode, but nothing Mr. Ohm can't tell you how to design around.
Last possible regulative addition I can think of would be a 3-4V zener in the cathode of, or fixed bias to the 6BQ5. Note this would be detrimental, as no tube will be exactly to spec, causing a different plate current to flow, and hence screwing with the 2A3's bias.
Tim (not like I care, I would never insult the GOT with so much wasted voltage
)
Alternately, you might try two in series, one to the screen, one to the 2A3's cathode (pulling the 22uF and 6.8uF bypasses). This would cause a mild upset in the 235V at the cathode, but nothing Mr. Ohm can't tell you how to design around.
Last possible regulative addition I can think of would be a 3-4V zener in the cathode of, or fixed bias to the 6BQ5. Note this would be detrimental, as no tube will be exactly to spec, causing a different plate current to flow, and hence screwing with the 2A3's bias.
Tim (not like I care, I would never insult the GOT with so much wasted voltage
)Sch3mat1c said:
Thanks Tim. The God of Triodes?
I will eventually get around to trying this version out. I figure that it's like anything containing chocolate, caramel and pecans: if I can't make a good sounding amp using an EL84 with a 2A3, I might as well give up!
An externally hosted image should be here but it was not working when we last tested it.
Hi,
As others mentioned, the OC3 would have to substitute for the for the 22uF capacitor.
HOWEVER, I would STRONGLY advise against doing this. The circuit as shown with the resistor divider includes a negative feedback loop, though only at DC and extremely low frequencies from the output valve cathode to the screengrid of the Driver pentode.
Most DC coupled amplifiers have not got very good operating point stability and often tend to "run away", sometimes to the point of cherry red anodes in the output valve(s). The DC feedback in the original schematic kills that tendency for good. By "stabilising" the Screengrid Voltage you remove this feedback not only at AC but also at DC.
BTW, under NO conditions try to use a zenner diode in the EL84 Cathode, you need to be able to adjust the voltage there to ensure the Amplifier operates at the correct operating point. Different driver and output valves will bias differently, you need to be able to correct for this.
Sayonara
As others mentioned, the OC3 would have to substitute for the for the 22uF capacitor.
HOWEVER, I would STRONGLY advise against doing this. The circuit as shown with the resistor divider includes a negative feedback loop, though only at DC and extremely low frequencies from the output valve cathode to the screengrid of the Driver pentode.
Most DC coupled amplifiers have not got very good operating point stability and often tend to "run away", sometimes to the point of cherry red anodes in the output valve(s). The DC feedback in the original schematic kills that tendency for good. By "stabilising" the Screengrid Voltage you remove this feedback not only at AC but also at DC.
BTW, under NO conditions try to use a zenner diode in the EL84 Cathode, you need to be able to adjust the voltage there to ensure the Amplifier operates at the correct operating point. Different driver and output valves will bias differently, you need to be able to correct for this.
Sayonara
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