What's wrong with the 12AV7? Try this out!

[rsumperl]

Hello everyone,
Can I get some opinions on the triodes in these tubes:
http://tubedata.milbert.com/sheets/093/6/6M11.pdf
http://tubedata.milbert.com/sheets/123/6/6BH11.pdf

Thanks,
Ray

 

[smoking-amp]

Both triodes have large 2nd harmonic distortion similar to a 12AT7. (notice the variation of plate curve spacing for a tilted load line and the non-constant Mu curves) The 6BH11 having the strongest dist. But note the gm versus current curves are nearly flat ramping, this will work well in differential mode (CCS tail) where the 2nd harmonic cancels and the two tube gm's can sum to a constant for low 3rd harmonic. (opposite ramps in diffl mode sum to a constant gm)

 

[rsumperl]

Thanks for the info. That's exactly how I was hoping to use either one. My thought was to use the pentode as a first stage of amplifcation then feeding into a phase inverter/splitter.

Ray

 

[smoking-amp]

Interesting idea. I see the 6BH11 is on the $1 list too. Maybe I should pick up a few. Another approach would be to use two nine pin tubes with Triode+Pentode in each. Then some hope of getting a matched pair of one pair at least. But a CCS tail on the splitter pair guarantees equal outputs anyway. Just need some adjustment for the bias on one side for equal idle currents. Comes down to the cost of a 12 pin socket versus two 9 pin sockets I guess, and some filament current.

 

[SY]

Interestingly, the input tube is a 12BZ7; the 12AV7 is apparently the driver. That tube is supposed to be equivalent to a pair of 12AX7 paralleled- the distortion spectra, OTOH, are a whole different thing. Very nonlinear with lots of high order distortion.

Don, I have not seen inordinately high 2nd in 12AT7 spectra. And Kevin, the 12AX7 actually challenges and may beat the D3a for linearity- as long as it's not loaded, which makes design a bit more of a challenge. The D3a is still the low noise champion, though.

 

[msallen021]

I've experimented with them in the second stage of a phono stage where the signal levels were low, and in a few other applications - they do work well as phase splitters

The 12AV7 tubes are being used as phase splitters in the Graaf GM200... the 12BZ7 is only used if you use the balanced input - if the single ended input is used this is bypassed.The drivers are a pair of EFL200 dual pentodes (incidentally, these use DECAL sockets which are just about unobtainable).

I do agree that my earlier experience with Graaf amps (the 5050) matches yours, in that they have a rich sound (dark would be perhaps too strong a word..) but the GM200 does not have this characteristic - it has an immediate sense of being stupendously quick - far more than the 5050 or the NuForce Ref 9V2 SE, and has a full/rich but spacious sound to it. Very appealing and this, along with really outstanding soundstaging, is what makes it stand out from others. If it has an area of failing it is that noise is audible when listening close to the speakers but this becomes completely inconsequential the minute the music starts - all you can say is WOW!! I put new tubes in 3 months ago, along with an hour-meter and I am already at over 300 hours - just totally addictive!