I was searching on the net for project using 12ax7 and 6bq5 and i found this site.
Projekty lampowe
The guy wrote a book about diy audio so he must be serious.
Downloadable PCB board and translation using google seems great.
Projekty lampowe
The guy wrote a book about diy audio so he must be serious.
Downloadable PCB board and translation using google seems great.
Sorry, I only read English.
Please give us a link that goes directly to the amp you mentioned,
not a link to the home page.
Please give us a link that goes directly to the amp you mentioned,
not a link to the home page.
That amplifier looks real good to me.
The amp has what I call a "serial stage" phase splitter. R6 and R7 have the right relative resistor values, depending on the gain of the two triodes. The second of the triodes always needs lower resistance for R6 coming from the first triode plate, than R7 coming from the 2nd triode plate, so that it has the proper amplitude signal at the 2nd triode grid.
[Some amplifiers that use a "serial state" phase splitter set R6 and R7 at equal resistances (wrong). But this amp does it correctly.]
And R5 and R11 are also equal resistance (correct).
R1 and R13 are also the same (correct).
Even though the "serial stage" phase splitter is not my favorite phase invertor, it does have good gain and signal swing, versus a single stage driving a concertina splitter.
This implementation of the "serial stage" phase splitter is good.
There is no dominant RC pole on the first stage. But do not put one there.
As long as the output transformer is the same as the one in the schematic,
and as long as you use the original values for the negative feedback resistor R21, capacitor C9, and resistor R3, that amp should be very stable.
My favorite phase splitter is with a current sink to parallel cathodes, identical plate resistors, and ground the 2nd grid (do use a 1k grid stopper to ground). But that has less gain, and less signal swing.
It is a tradeoff.
But do not modify your "serial stage" phase splitter circuit.
3 of the waveforms look good, but I do not understand the what wave-shape is applied at the amp input, to get the lower left waveform out.
Some sort of overdrive / clipping test perhaps?
The amp has what I call a "serial stage" phase splitter. R6 and R7 have the right relative resistor values, depending on the gain of the two triodes. The second of the triodes always needs lower resistance for R6 coming from the first triode plate, than R7 coming from the 2nd triode plate, so that it has the proper amplitude signal at the 2nd triode grid.
[Some amplifiers that use a "serial state" phase splitter set R6 and R7 at equal resistances (wrong). But this amp does it correctly.]
And R5 and R11 are also equal resistance (correct).
R1 and R13 are also the same (correct).
Even though the "serial stage" phase splitter is not my favorite phase invertor, it does have good gain and signal swing, versus a single stage driving a concertina splitter.
This implementation of the "serial stage" phase splitter is good.
There is no dominant RC pole on the first stage. But do not put one there.
As long as the output transformer is the same as the one in the schematic,
and as long as you use the original values for the negative feedback resistor R21, capacitor C9, and resistor R3, that amp should be very stable.
My favorite phase splitter is with a current sink to parallel cathodes, identical plate resistors, and ground the 2nd grid (do use a 1k grid stopper to ground). But that has less gain, and less signal swing.
It is a tradeoff.
But do not modify your "serial stage" phase splitter circuit.
3 of the waveforms look good, but I do not understand the what wave-shape is applied at the amp input, to get the lower left waveform out.
Some sort of overdrive / clipping test perhaps?
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