Hyperlinear line preamp

[Original Burnedfingers]

Anyone ever built a Hyperlinear circuit? If so would it be worth the trouble?

[Bandersnatch]

Originally posted by burnedfingers
Anyone ever built a Hyperlinear circuit? If so would it be worth the trouble?

Never heard of it as some special circuit. Got any information to share I could study?
cheers,
Douglas

[smoking-amp]

Hyperlinear

maybe this:
http://www.diyaudio.com/forums/showt...79#post1462379

[Original Burnedfingers]

I did a search here but didn't turn up anything when I started this thread. I had come across an interesting circuit using a 6SJ7 and EBC33.

Http://www.veiset.net/Hyperlinear/index.html

I would like to try it but don't know where to find any EBC33's and was wondering if another tube would work.

[smoking-amp]

Yup, same one.

I would think that just about any tube suitable for a cathode follower circuit should work in place of the EBC33.

A low capacitance HV Mosfet follower should work nicely too. (Fairchild FQP1N50, FQP2N90 or STmicro STM2NK60Z, STM2NK90Z ... some Zetex and Supertex depl. mode parts too)

I would also suggest dropping the voltage on the pentode's screen by 50 volts or so (below its plate) by some means (zener, neons,... or just tap down on R5 but will increase the gain too) and increasing the B+ by the same amount (to compensate the screen V back to its original value). This will lower distortion further for most pentodes, but testing the dist. versus the drop voltage would be required to find the best operating point, since some screen current variation will null out some of the 3/2 power law plate current.

Don

[AKSA]

I've done a few sums on this one, and I reckon around 120K plate resistor, 82K screen resistor, 4K cathode resistor. The triode CF would have around 12K on its cathode.

I agree, however, you would need to suck it and see; this is a simple interconnection, but all the voltages are interdependent.

The question is: do you run the pentode at recommended Ip of 2.9mA (the operating point chosen is around 1.1mA from what I can see) or 6mA, the triode recommendation..... and where do you place the screen wrt the plate; my figures assume around 25V below plate for G2.

It would all be a question of trying it out, and listening for the various operating points. I would try to go for more triode than pentode operation to get the favourable harmonic spectrum.

Cheers,

Hugh

[wrenchone]

Hmmm... This sounds like a natural to try with one of the many pentode/triode duals. Riffling through the specs, some obvious suspects will come to mind.

[jane]

I did build a prototype (6SJ7/6R7) of this circuit and found it quite good sounding, so I decided to build a working preamp. I choose the EBC33 most because they where red and sexy looking and they are pin compatible with 6R7.
Compeered to a classic common cathode/cathode follower the output resistance and distortion are lower, but that is hard to spot at modes level. I use this preamp every day, most because of its ability to deliver plenty of clean voltage swing into a power amp with a ~15k reflected load input transformer.
All in all, a simple circuit that performs quite well.



Hyperlinear was just a word I made up, thinking of ultralinear screen feedback in output pentodes.

Jan E Veiset

[AKSA]

Thanks Jan,

Have you tried - and this is a very good sounding mod - a simple resistor from kathod of CF to kathod of input pentode?

In your design it would be a large value; start with 470K, and reduce the pentode kathod resistor to maintain the same -4.5 Vgk.

I applaud your clever design; great topology!

Cheers,

Hugh