operating points

mete · 402

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Offline mete

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on: June 16, 2024, 11:09:48 PM
I am trying to understand the circuit and making a simulation. Can someone tell me the operating point, typical grid voltage and plate current values, of the tubes ? I have (on the simulation) -1.7V and 5.2mA for 12AU7 and -32.6V 41mA for 6080. I think they are slightly off (my B+ is high, 204V). Is the design value for B+ 170Vdc (the test voltage in the manual) ?



Offline Paul Birkeland

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Reply #1 on: June 17, 2024, 05:10:26 AM
-1.7V and 5.2mA for 12AU7
The HLMP6000 diode is 1.57V.  The plate current through the 12AU7 will vary with B+ in the stock circuit.

and -32.6V 41mA for 6080. I think they are slightly off (my B+ is high, 204V). Is the design value for B+ 170Vdc (the test voltage in the manual) ?
That is on the high end of what we would expect in the stock circuit in terms of operating current, but again, your B+ is a little bit on the high side. 


Paul "PB" Birkeland

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Offline mete

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Reply #2 on: June 17, 2024, 05:18:30 AM
The HLMP6000 diode is 1.57V.  The plate current through the 12AU7 will vary with B+ in the stock circuit.
That is on the high end of what we would expect in the stock circuit in terms of operating current, but again, your B+ is a little bit on the high side.

Thanks Paul.



Offline mete

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Reply #3 on: June 17, 2024, 11:21:13 PM
The HLMP6000 diode is 1.57V.

Since the LED biases the tube to -1.57V, the maximum signal at input (after volume pot) without clipping can be approx. Vpp=3.2V. Is that correct ?

I saw a reply of yours from 2017,  you explained it in detail, no need to answer this.
« Last Edit: June 18, 2024, 01:20:14 AM by mete »