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What do you think of this mashup amp?
What do you think of this mashup amp?
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Old 9th February 2018, 01:59 PM   #11
kodabmx is offline kodabmx  Canada
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Originally Posted by john_tracy View Post
That was 50mA total or 25mA/section. I used a cathode CCS "tail" with the B+ CCS fed shunt reg. The tubes would initially have ~-3V grid bias. When they were "done" it had dropped to less than -1V. 6 months to a year max.

Unless you need 25ma (I used a 6N6P to drive an interstage transformer flawlessly at 14ma) bias it colder and it'll last for years. The same thing happened with 6P1P with me. I biased them hot (18W, 50% over maximum) with an LM317 CCSink in the cathode. When I started they biased at -14V however, about 6 months later, when I sold the amp to a friend, they were only at -6V! Thing still sounded fine though, just less power. Of course I gave him a new set of tubes with it and showed him how to lower the bias current to whatever he liked.


EDIT: Just saw you don't like the sound of them running colder. 4 6N6P is cheaper than 1 6N30P though...

Last edited by kodabmx; 9th February 2018 at 02:08 PM.
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Old 9th February 2018, 02:07 PM   #12
kodabmx is offline kodabmx  Canada
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Less elegant maybe, but you could use triode strapped 6P1P instead of the 6N6P. They will use more power, but they will last far longer and you will have more headroom. Plus they are extremely inexpensive for the time being.
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Old 10th February 2018, 05:29 AM   #13
PRR is offline PRR  United States
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First you regulate the voltage. Then you regulate the current. Then you put it on a big capacitor which smooths the voltage. By this point the electrons don't know what to do! Well, actually they will do what they want to do.

Will it work? Yes.

Is it a total waste of low-cost Silicon? I say it just makes more build-time (and more ways to go wrong) without any likely audio advantage. (But it is your baby, and everybody's baby is beautiful to the parent.)

_I'd_ replace 30 connections with 2.
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Old 10th February 2018, 04:31 PM   #14
zacster is offline zacster  United States
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Originally Posted by PRR View Post
First you regulate the voltage. Then you regulate the current. Then you put it on a big capacitor which smooths the voltage. By this point the electrons don't know what to do! Well, actually they will do what they want to do.

Will it work? Yes.

Is it a total waste of low-cost Silicon? I say it just makes more build-time (and more ways to go wrong) without any likely audio advantage. (But it is your baby, and everybody's baby is beautiful to the parent.)

_I'd_ replace 30 connections with 2.
I don't think the build time will be much in any case. And the cost is pretty small too. Whether it makes a difference or not is really the only issue. But you are right in that I could put it together without that and it would also work, and maybe I will. The VR is already in place so just drop the CCS. I could always add it later.
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Old 11th February 2018, 05:27 PM   #15
stocktrader200 is offline stocktrader200  Canada
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I got 30w with the same transistor count. 12ax7 > 2N5551 splitter > supertriode 6922 > transformer with 150v B+
no global NFB. maybe the best sounding amp i have made
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