It's not similar. 12AU7 is practically identical to ECC82 (noval-9pin) and electrically similar to 12SN7/6SN7/6N8S (oktal-8pin) and 7N7 (loctal-8pin). There are differences in the heating and the arrangement of the legs. ECC99 is similar to 6N6P/6H30 (noval -9pin).
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No
Are little different
The 6h30 has lower Rp
And 6N6 is a little bit different from 6H30
Ecc99-12bh7- ecc82 can be considered similar
The Ibiasvis around 1 ma. Too low
If we consider 7 ma as bias and - 4 volt as point of job on the R3 can be 56o ohm
The R2 to have half of Va on anode will be 22 k ( 27k) 2 w
R4 = 560 ohm
R5 = 22k 2 w
Try with this
It is a start point
Those are good values, the only question is whether the power supply supports the increased anode currents. 1mA through 12AU7 is very little. It is rather for 12AX7.
What I’m trying to understand, on a much more basic level, is what is causing the left/right voltage discrepancy? Going to have to look into that. As well as reducing the voltage to 300vdc from the existing 324vdc.
But I’m having to put this on hold for a couple of days, daughter’s graduation tonight and I have the kids this weekend.
But I’m having to put this on hold for a couple of days, daughter’s graduation tonight and I have the kids this weekend.
That power supply will be OK for higher anode currents. You will only change that resistor in CRC to adjust the voltage. the power supply is not stabilized, so the voltage can change depending on the voltage in the network and the consumption of the tubes. I think you would get a better sound with a Salas SSHV2 or some similar stabilizer. And the voltage would not be variable.
https://www.valvewizard.co.uk/mufollower.html
I would repackage yours into this. It is practically identical. The advantage is that the anode current is twice as small, 7mA instead of 14mA per channel. And I think it sounds better than existing schematics. My only thought is that the heather power supply would have to be stepped up to 1/4 high voltage.
I would repackage yours into this. It is practically identical. The advantage is that the anode current is twice as small, 7mA instead of 14mA per channel. And I think it sounds better than existing schematics. My only thought is that the heather power supply would have to be stepped up to 1/4 high voltage.
Those numbers are almost identical, left to right. What discrepancy are you talking about?
The two tubes (even two halves of a real tube) are not the same, unless you really go through a lot of them and select a pair matched with identical halves. As @Merlinb said, they are pretty close to each other.
The grid voltage on the right triode looks a bit low, it is probably influenced by the impedance of the voltmeter you are using to measure.
The grid voltage on the right triode looks a bit low, it is probably influenced by the impedance of the voltmeter you are using to measure.
I have to adjust pretty much every build as my house has a transformer right in front and I see higher than usual voltages. Ranging from 123 to 125. I’ll look into the salas
Less than 3% difference is pretty darn good, not a discrepancy.
It is not about accuracy, but about input impedance. The grid voltage is supplied via 560K R6 resistor. That will form a voltage divider with the input impedance of your Fluke. I tried to look into the datasheet but it does not state the value, which I find strange.
PS For example, my BK 393 multimeter has a 10Meg input impedance. If you look at the simulation above, you connect a 10 Meg resistor from grid to ground (my multimeter), and the grid voltage goes from 69V to 56V.
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