Low gain triode recommendation plz

[Tom Bavis]

12A4 is the only tube with the same pinout - mu of 20. Must not be in demand... costs half as much as the 12B4. If you want LESS gain, there's the 7233...

[ilimzn]

There are a number of pentodes and beam tetrodes that have a lowish mu triode strapped, and often come with the desirable combination of high(ish) gm and low Rp, as well as available current - if you can fit them into your design...

[Koifarm]

Originally posted by zigzagflux
6n6p is used in my linestage. Lovely tube. Good suggestion.

However, I would prefer to avoid duplicate tubes in successive stages. Just personal preference; I'm sure it wouldn't hurt.

Thanks, keep it coming !

Then use JJ ECC99 same spec's linear frequentie spectrum and also super sound like 6n6p. I use also 6n6P( in shanling CD-T100se) and ECC99( in SE 813 amp) behind each other.

About the schematic just use one driver tube like 6n6p or ECC99.This works very good. My filisofie is " Less is more".

[Bandersnatch]

hey-Hey!!!,
From the land of the single, octal triode there is 6AH4 and 6CK4 to look at. There are also beefy triodes in dual triode tubes like 6EM7 and 6DN7 to look at.
cheers,
Douglas

[GordonW]

Originally posted by kevinkr
Remember in the case of the typical LTP your gain will be half that of a single triode in common cathode connection (the cathode of the driven section is seeing its internal resistance plus that of the other half of the LTP instead of a low impedance bypass if used, i.e 2X the internal cathode impedance alone) so your gain single ended would be no more than 3 (~10dB) and your differential gain 6 (~16dB). If this is ok the 12B4 may serve just fine..

Given this, the 6BL7 comes to mind. Gain of 15 nominally; in an LTP, it should give a gain of about 7.5, before tinkering. Could probably readily be tweaked (cathode/anode resistors, etc) to get right in the range...

Regards,
Gordon.

[JoshK]

Your design looks a lot like Lynn Olson's Karna. You could take suggestion from him and use the 5687/6H30/7044/6N6P types for first position (he uses 45 in second, 46 is similar enough).

[Bandersnatch]

hey-Hey!!!,
Just a bit of clarity on the gain. A grounded cathode amp will have a gain related to mu wrt ground. A LTP with the same plate loads and B+ will have the same gain but referenced plate-to-plate. Each of the plates wrt. ground will be this gain over two.
cheers,
Douglas

[zigzagflux]

Originally posted by JoshK
Your design looks a lot like Lynn Olson's Karna. You could take suggestion from him and use the 5687/6H30/7044/6N6P types for first position.

It IS the Karna, with a few mods. I am hoping the negative rails w/ CCS is an improvement over resistor biasing. I originally was planning on the 7119, per his suggestion, but again, the gain is a little much for my source of 1.73 Vrms. So, I've pursued the lower mu devices.

Originally posted by Bandersnatch
Just a bit of clarity on the gain. A grounded cathode amp will have a gain related to mu wrt ground. A LTP with the same plate loads and B+ will have the same gain but referenced plate-to-plate. Each of the plates wrt. ground will be this gain over two.

That's my assumption; I basically calculate each stage's gain with the full mu of the tube, as all inputs and outputs are taken differentially. Net result is that I need a input stage with mu=6.5 to have 1.73 Vrms input produce 11.9 V output, equivalent to 35.6W (about the maximum). 12B4 is right there. Little more gain could be beneficial for lower level recordings.

For instance, Neil Young's Harvest seems to be a pretty 'quiet' recording, little more gain might help. But not as much as the 7044/7119/ECC99 types provide - those are just a little hot at a 0.55V input sensitivity.

mu anywhere from 6 to 10 should be really nice, aiming for low Rp.

Anyone NOT like the 12B4 sonics/linearity ? Most of the threads I've read rave about this tube, typically used in linestages.