Single-Ended Pentode Redux

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Paul Barker
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#46 Re: Single-Ended Pentode Redux

Post by Paul Barker »

Thanks Steve , and I’m pretty sure that the Russian versions Phil uses are within a Whisker of the nos ones I’ve got! I.E. one tube I’d think you were mad waxing lyrical about a Nos valve when tube rolling.

I get tube rolling which is sometimes a huge benefit with few detractors. Sometimes though a matter of which blend of character you feel at the time, but not enough difference to matter once you’re ears are tuned in.
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#47 Re: Single-Ended Pentode Redux

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but not enough difference to matter once you’re ears are tuned in.
So why bother?
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#48 Re: Single-Ended Pentode Redux

Post by Paul Barker »

In those cases you learned that, and don’t waste any more money.
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#49 Re: Single-Ended Pentode Redux

Post by Thermionic Idler »

Cressy Snr wrote: Mon Jan 17, 2022 2:33 pm
Thermionic Idler wrote: Sun Jan 16, 2022 7:30 pm Steve - I'd be interested on your thoughts on the sound of the JJ 6V6 versus the old stock ones - I've only ever used old stock in the 6V6 driver position of my 300B's, but have been pondering trying some new JJ's as I think one of the ones in there at the moment is going weak.
Right!
JJ 6V6S are very good indeed. Nice fat bass and more extended treble compared to the old Brimar, Mazda and Sylvania. Some people think they have a hint of the 6L6 presentation in the sound they make. I was quite impressed with them TBH. They sound slightly different to the older valves but this is by no means a criticism of them. They are just as valid a proposition as the old ones, in my amp at any rate.
Excellent news. Thanks, Steve, I may well pull the trigger on a matched quad from HotRox.
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#50 Re: Single-Ended Pentode Redux

Post by Paul Barker »

https://www.audio-talk.co.uk/phpBB2/dow ... hp?id=8593

Inject feedback before the coupling cap please?

Take out feedback cap voltage affect on driver is <1 volt! Bin the 2.2 cap size coupling cap for grid load resistor. Edit, youre 100n is 3 hz with that grid load great!
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#51 Re: Single-Ended Pentode Redux

Post by Paul Barker »

additional trick if you want, I’d do it, use the current of output tube to make bias for driver from a voltage devider on output tube cathode, which will be small fraction at output tube so stay unbypassed on the bottom resistance only, i.e. take bypass to this node not ground. Get some tiny amount of feedback for output tube. at node wire up cathode of driver current flow of driver added to output tube current flow to calc bottom resistor, Output impedance of driver fixed, and full cathode feedback of driver remains. which always sounds improved to me.
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#52 Re: Single-Ended Pentode Redux

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dit, youre 100n is 3 hz with that grid load great!
Remember the "grid load" the coupling cap sees is 512k in parallel with 62k, though the anode is moving in the -ve direction from the grid, so not so sure anymore exactly what it sees.
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#53 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

Cheers Paul,
All sorts of stuff you can do with wires, sockets and things on a bit of wood. Don't know why I've often resisted that route to getting a decent amp. :roll:
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#54 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

This is it now, reverted to conventional DC coupled plate-to-plate feedback.
6v6done100timesbefore.png
6v6done100timesbefore.png (54.31 KiB) Viewed 1948 times
Last edited by Cressy Snr on Mon Jan 17, 2022 8:15 pm, edited 1 time in total.
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#55 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

Wonder what would happen if I pulled a stunt like this :twisted: :
Screenshot 2022-01-17 at 19.52.11.png
Screenshot 2022-01-17 at 19.52.11.png (52.58 KiB) Viewed 1942 times
I'm going to try this tomorrow. It'll either be a laugh or there'll be a fecking big bang.
Such fun :lol:
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#56 Re: Single-Ended Pentode Redux

Post by Paul Barker »

Nick wrote: Mon Jan 17, 2022 4:28 pm
dit, youre 100n is 3 hz with that grid load great!
Remember the "grid load" the coupling cap sees is 512k in parallel with 62k, though the anode is moving in the -ve direction from the grid, so not so sure anymore exactly what it sees.
Me neither, if bass is crap Steve get a bigger coupling cap.
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#57 Re: Single-Ended Pentode Redux

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Cressy Snr wrote: Mon Jan 17, 2022 7:53 pm Wonder what would happen if I pulled a stunt like this :twisted: :
Screenshot 2022-01-17 at 19.52.11.png
I'm going to try this tomorrow. It'll either be a laugh or there'll be a fecking big bang.
Such fun :lol:
I dont know about this one.

Ill just check what output impedance of triode stage is.

assming operating point is 170v gain 66 ri llk. using those figures plate impedance goes up from 11k to 37k // with 22k = 13k8
Last edited by Paul Barker on Mon Jan 17, 2022 9:30 pm, edited 2 times in total.
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#58 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

Needs a hi gm pentode really, I would have thought (12Gn7, D3a) but it’ll be a laugh to try it with a triode.
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#59 Re: Single-Ended Pentode Redux

Post by izzy wizzy »

Cressy Snr wrote: Mon Jan 17, 2022 7:53 pm
I'm going to try this tomorrow. It'll either be a laugh or there'll be a fecking big bang.
Such fun :lol:
E-linear innit. Some folk like it. Shouldn't go bang.
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#60 Re: Single-Ended Pentode Redux

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izzy wizzy wrote: Tue Jan 18, 2022 5:08 am
Cressy Snr wrote: Mon Jan 17, 2022 7:53 pm
I'm going to try this tomorrow. It'll either be a laugh or there'll be a fecking big bang.
Such fun :lol:
E-linear innit. Some folk like it. Shouldn't go bang.
My mother loved Trype, tbh its the one food, oh no, one of two (winkles) I never actually tried.

So that odd thing Steve penned is a thaing! As they say in the hill country. E Linear. Norman Crowhurst would turn in his grave.
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