I did some calculation without knowing the requested output impedance.
One of my favourit tubes Telefunken ECC85 is a good tube for the job.
Output voltage about 3 Vrms with 28 Ohm I/V resistor. Output impedance between 10 and 20K.
Ronny
One of my favourit tubes Telefunken ECC85 is a good tube for the job.
An externally hosted image should be here but it was not working when we last tested it.
Output voltage about 3 Vrms with 28 Ohm I/V resistor. Output impedance between 10 and 20K.
Ronny
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Google brought me here: I'm looking for a new output stage for my TDA1541. I'm using a 28 Ohm I/v resistor with a 6211 SRPP. I am deeply in love with the sound but seriously lack gain. The 6211 is extremely microphonic btw. I was looking for tubes with a mu of around 100 and the 6N2P seemed a good candidate. After reading this the D3a seems a better choice, but I haven't made up my mind yet
Source impedance with an SRPP using tubes with high rp will be excessively high. Depending on implementation the impedance could approach almost half of the tube's rp, but typically will be at least 20% of it. A mu follower would give you both more gain (maybe up to 6dB more) and a much lower output impedance. High transconductance types like the D3A are your friend because of their low rp - crank lots of current through them..
Hi,
I'd say forget the 12AX7 SRPP for this application, forget a mu-follower using the same valve as well.
A D3A based circuit is much, much better if you can source the valve.
Other than that, and I haven't really looked into it, an Aikido topology using a valve with a mu of 40 (a la E80CC, 6085) could be a tempting alternative perhaps.
Cheers,
Source impedance with an SRPP using tubes with high rp will be excessively high. Depending on implementation the impedance could approach almost half of the tube's rp, but typically will be at least 20% of it. A mu follower would give you both more gain (maybe up to 6dB more) and a much lower output impedance. High transconductance types like the D3A are your friend because of their low rp - crank lots of current through them..
I'd say forget the 12AX7 SRPP for this application, forget a mu-follower using the same valve as well.
A D3A based circuit is much, much better if you can source the valve.
Other than that, and I haven't really looked into it, an Aikido topology using a valve with a mu of 40 (a la E80CC, 6085) could be a tempting alternative perhaps.
Cheers,
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