I was looking for a lower cost alternative to the 12AY7 for a guitar amp I am building. I noticed that the 6bc4 has close to the same mu and the transconductance is similar as well as the plate resistance. I was wondering what the group thought about the feasibility of using two of these for a simulation of a 12ay7 in phase inverter service. I will be using them at their maximum plate voltage. Thanks.
ECC83 or 12AX7 is very similar.
6BC4 has incorrect heater current and you will need two but if you have them, why not.
6BC4 has incorrect heater current and you will need two but if you have them, why not.
Why do you say 12ay7 is expensive ?
12ay7 price is similar to 12ax7 if you talk new tubes from JJ
There is no need to buy NOS 12ay7.
^^ This, i see $13.95 at tubedepot. And i am forced to ask, why 12ay7 as P.I.? You would be better off using 12ax7 or better yet 12at7. How about 6J6 with a common cathode, free if you are in USA., other wise postage and i'll mail a few out.
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Short answer: even Fender did not use the 12AY7 as it was intended to be used; and everybody and their bassist replaced 12AY7 with 12AX7. You can too.
You need two of three factors to begin to describe a triode. Mu alone is not enough.
rp is often the next factor considered. 12AY7 25K, 6BC4 5k. 5:1 difference!!
Next note that 12AY7 is plotted to 10mA, 6BC4 to 40mA. This hints that 6BC4 may be 4 times as "fat" as 12AY7. Big cathode.
If you re-scale both plots so 300V 10mA are the same size, you see 6BC4 is going up much faster than 12AY7. It IS a fatter tube.
At zero grid, 6BC4 will pass 10mA at 77Vp. 12AY7 needs 210V to reach 10mA.
You "can" stuff 6BC4 into a 12AY7/12AX7 circuit. Triodes are remarkably tolerant. But I don't see the point. It won't bias-up or amplify or clip anywhere like a 12AY7.
And I can't see using "low audio hiss" 12AY7 in a power stage driver. If you want low-gain driver, use 12AT7 12AU7 or gimmick some values.
You need two of three factors to begin to describe a triode. Mu alone is not enough.
rp is often the next factor considered. 12AY7 25K, 6BC4 5k. 5:1 difference!!
Next note that 12AY7 is plotted to 10mA, 6BC4 to 40mA. This hints that 6BC4 may be 4 times as "fat" as 12AY7. Big cathode.
If you re-scale both plots so 300V 10mA are the same size, you see 6BC4 is going up much faster than 12AY7. It IS a fatter tube.
At zero grid, 6BC4 will pass 10mA at 77Vp. 12AY7 needs 210V to reach 10mA.
You "can" stuff 6BC4 into a 12AY7/12AX7 circuit. Triodes are remarkably tolerant. But I don't see the point. It won't bias-up or amplify or clip anywhere like a 12AY7.
And I can't see using "low audio hiss" 12AY7 in a power stage driver. If you want low-gain driver, use 12AT7 12AU7 or gimmick some values.
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damn, do we really need to expose the virtues of the 6bc4? it is a 1 dollar tube afaik...
expect a lot of them gobbled up at Stans...
expect a lot of them gobbled up at Stans...
I'm not building a Fender. I am building a modified wreck which is built on the edge of stability and is pretty persnickety when it come to components, (at least that is what I'm reading). I was just looking to find a cheaper alternative to the 12ay7 and keep it as close to the values of that tube. Something like a 6av6 as a single triode version for the 12ax7. Two dollars as opposed to 30 dollars for a vintage used tube was where I was coming from. I guess I will just experiment. I must have missed the rp value. I thought I read it as closer. Thanks for the information. That's what I was looking for.
Don't get too excited about it. It is an RF amp tube for grounded grid use in TV tuners. This use requires gain control. Look at the Mu curve on the last page of the data sheet. The Mu varies from 21 at low currents to 49 at high current. I haven't smashed one, but it must have a variable Mu grid.
It will generate copious amounts of second harmonic, which may be OK as a PI, but there are better choices.
There is a good use for this tube...but I won't "expose" it here. Those who who have already ventured into this tiny little corner of the DIY world will understand.
The 6AT6 and the $1 6AQ6 (similar to the 6AT6, but has a 150 mA heater) are possible PI choices. I have used the 5965 for PI, but it has a higher Gm and lower Rp than the 12AY7, but does work nice.
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