If the tube is paralled you can't bias the cathodes separately.They are PRARALLED,meaning they are connected together.Same with the plates.You parallel the working components of each triode and they become one big tube.
Fatter sounding but not a huge gain boost.I like 18 watt amps with paralled triodes.They sound yummy.
If the tube is paralled you can't bias the cathodes separately.They are PRARALLED,meaning they are connected together.Same with the plates.You parallel the working components of each triode and they become one big tube.
Fatter sounding but not a huge gain boost.I like 18 watt amps with paralled triodes.They sound yummy.
Respectfully, I think that you can use separate cathode resistor/cap networks. O'Connor writes about a "Tweed mixer" where two triodes have separate grids and cathodes but shared plate resistor.
So I guess the question I should have asked is "why?"
So I guess the question I should have asked is "why?"
if you run both sides of a 12ax7 in parallel and would like to bias each side differently (say 820 on one cathode and 2.7k on the other) and you would like to use a shared plates resistor, how do you pick the value?
How does it compare to the same bias set up with separate plates resistors?
Are there any sonic or other advantages or disadvantages to a shared plate resistor?
......because there is only one frequency.
play more than 1 string at onceI think eleventeens argument still holds since each tube *see's* the same thing. To make it work, I'd think you'd need 2 guitars playing 2 different songs, or maybe same song just *delay* one guitar by some amount of time :dontknow:
playing 1 note or six notesI'll buy six notes, HBP answered that question for me in another thread, but 1 note is 1 frequency? and my understanding of heterodyning is you need 2 different freqs beat against each other? since most players use lots of notes I guess it's kinda an academic thing more than a real world thing. :dontknow:
The concept of combining two frequencies to obtain a resulting mixed or composite frequency, was employed prior to audio amps in the field of radio. The Super Heterodyne receiver being one example.
......because there is only one frequency.
What if you play more than 1 string at once, now you have more than 1 frequency?
Quoteplaying 1 note or six notesI'll buy six notes, HBP answered that question for me in another thread, but 1 note is 1 frequency? ... since most players use lots of notes ...
Both forms of "mixer" involve substantial loss of potential voltage gain and maximum output.
The cathode mixer is especially bad.
"Passive" resistor mix with make-up gain as needed is usually a better plan.
| "The isolation is perfect with none of the "tone sucking" that I got from mixing resistors. " [/t]
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> how is the common plate mixer losing gain? Seems like it would be >1 with...
"Potential gain".
You add one triode, you expect gain of 15-50. With two triodes in the pot, 225-2,500.
The plate mixer will have gain of less than half what each tube will do as a plain stage. Also maximum output tends to be much less.
You will in general have "better" (engineering) result with resistive mix then tube gain, or with two tube gain and a passive resistor mix after that (plates not parallel). The resistors can usually be figured to isolate any reasonable amount.
Try it. It may be fine.
If you don't want any added gain, an active feedback mixer does that with improved isolation.