Dual triode - can both sides be run in parallel ?

[Justin Thomas]

I'd thing the effects are the same, regardless of which dual triode he is using. As in, more than a single by itself but less than in series. I'm not expecting it to compete with a 12AX7.

Justin

[Helmholtz]

I'd thing the effects are the same, regardless of which dual triode he is using.

The principles yes, but not the results. Clipping characteristics and clean headroom strongly depend on input stage gain. And the different triodes vastly differ in gain (G).

6SN7 : single triode G=14, 2 triodes in parallel G=16, 2 triodes in series G=196 max.
12AX7: single triode G=57, 2 triodes in parallel G=76, 2 triodes in series G=3,249 max.

Generally 2 triodes in series introduce additional odd harmonics as the signal is inverted twice.

[Bloomfield]

Another option to get more gain with a 6SN7 would be to set it up as a cascode. Never tried it myself but there is some information here:

http://www.valvewizard.co.uk/cascode.html

[HaroldBrooks]

Another option to get more gain with a 6SN7 would be to set it up as a cascode. Never tried it myself but there is some information here:

http://www.valvewizard.co.uk/cascode.html

Nice ! Always learn something new here !

[Mick Bailey]

Doug Hammond's Firefly uses a cascode front end and it works superbly.

[Helmholtz]

Another option to get more gain with a 6SN7 would be to set it up as a cascode. Never tried it myself but there is some information here:

http://www.valvewizard.co.uk/cascode.html

Good idea!

A cascode is another way of wiring 2 triodes is series. Achievable gain with the 6SN7 is around 100 (a little more than with the ECC82 in Merlin's example), using a plate resistor of 67k @ Ip=1.9mA.

[HaroldBrooks]

Another option to get more gain with a 6SN7 would be to set it up as a cascode. Never tried it myself but there is some information here:

http://www.valvewizard.co.uk/cascode.html

Thanks Bloomfield. I think I am going to try this and see how it works out, but on one of my "rolling test lab" hi-fi chassis amps first. I have a few that run 6J5 tubes in V1, so I believe I can sub a 6SN7 in the same Octal Socket, and rewire the whole thing to work as a cascade. This wouldn't breach the integrity (if there is any left !) of the initial Zenith Hi-Fi design of the amp in question, as it is my understanding that a 6SN7 is basically two 6J5 tube in one glass envelope, so it should work out nicely, as long as I adhere to the adjustments necessary for the Cascode.

[HaroldBrooks]

Good idea!

A cascode is another way of wiring 2 triodes is series. Achievable gain with the 6SN7 is around 100 (a little more than with the ECC82 in Merlin's example), using a plate resistor of 67k @ Ip=1.9mA.

Thanks for figuring that out Helmholtz, I rely on you to be the brains behind whatever low level "Experimental" stuff I am doing at this point !

By the way, part of my mixed heritage is from Germany, and my Father spoke fluent German and was a big clock repair man and fabricator, amongst other hi-level things. Hope to visit Germany in the not to distant future !