Yes it was classic SRPP, very similar to what you presented, 300V regulated B+ and 1K (820 also) cathode resistors.
The interesting thing about the SRPP is there is a definite null in THD if you vary the load resistance. The amps these drove had 68K input impedance. No longer remember what the optimum value was, and pretty sure it varied a bit from tube to tube!
Yes it was very transparent, I currently use transformer coupled DHTs which come with their own set of issues.
I would give the 6SN7 a try if you can get some, they are definitely better. (8 - 10mA @ 350V - 400V plate supply)
The interesting thing about the SRPP is there is a definite null in THD if you vary the load resistance. The amps these drove had 68K input impedance. No longer remember what the optimum value was, and pretty sure it varied a bit from tube to tube!
Yes it was very transparent, I currently use transformer coupled DHTs which come with their own set of issues.
I would give the 6SN7 a try if you can get some, they are definitely better. (8 - 10mA @ 350V - 400V plate supply)
Probably not to the extent I could today, but it measured well, as consistent across all of the samples built (with given tubes). It was designed for use with my power amps then available at the time. (I sold a lot more of those)
The 6CG7/6FQ7 is worth experimenting with. I find it very good.
6SN7 are pretty common here comparatively speaking, although the really good NOS ones are a bit harder and more expensive to find these days.
The 6CG7/6FQ7 is worth experimenting with. I find it very good.
6SN7 are pretty common here comparatively speaking, although the really good NOS ones are a bit harder and more expensive to find these days.
In most cases the SRPP optimum load resistance is significantly smaller than the SRPP output impedance, so you get lower distortion at the expense of lower gain. OK if you know what the load impedance will be and it is in the relevant range. In most audio circuits it isn't so the SRPP gives no real advantage. In most cases a mu-follower will be better.
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