Single-Ended Pentode Redux

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Nick
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#91 Re: Single-Ended Pentode Redux

Post by Nick »

Well, I think it may be at a nice point, its low current, and seems to work well, regulators may be adding complexity where its not needed. The multiple feedback loops will only tend to increase PSRR anyway.
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#92 Re: Single-Ended Pentode Redux

Post by simon »

At least in PSUD the optimum R isn't always the lowest on the face of it, I've sometimes found adding R removed overshoot or ringing. Now whether this sounds better or worse is another matter, and I feel a Dr Low Mu moment coming on :lol:
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#93 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

In that case chaps, I'll leave it at that. Thanks for the help everyone. A box beckons.
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#94 Re: Single-Ended Pentode Redux

Post by simon »

It would be interesting to try changing the R of the second choke Steve. Perhaps try 50, 200 and 1000 as well to see what happens?
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#95 Re: Single-Ended Pentode Redux

Post by pre65 »

simon wrote: Wed Jan 26, 2022 8:19 pm It would be interesting to try changing the R of the second choke Steve.
How can you change the resistance of a choke ?
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#96 Re: Single-Ended Pentode Redux

Post by steve s »

Your in a catch 22 with low resistance chokes, the lowest are always the heaviest..
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#97 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

pre65 wrote: Wed Jan 26, 2022 8:49 pm
simon wrote: Wed Jan 26, 2022 8:19 pm It would be interesting to try changing the R of the second choke Steve.
How can you change the resistance of a choke ?
He means change it in PSUD. :mrgreen:
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#98 Re: Single-Ended Pentode Redux

Post by pre65 »

Cressy Snr wrote: Wed Jan 26, 2022 9:00 pm
pre65 wrote: Wed Jan 26, 2022 8:49 pm
simon wrote: Wed Jan 26, 2022 8:19 pm It would be interesting to try changing the R of the second choke Steve.
How can you change the resistance of a choke ?
He means change it in PSUD. :mrgreen:
Ah. :wink:
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#99 Re: Single-Ended Pentode Redux

Post by Nick »

Yes changing things change things :-). But if you want a low impedance supply and you need one or you will throw away the regulation of a choke input supply, then you need to remove resistance. It will alter the Q of the circuits but that's the art rather than craft bit.
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#100 Re: Single-Ended Pentode Redux

Post by simon »

Yes change in PSUD :lol:. It was an "exercise for the reader" - adding R in circuit can be done with a bit of series resistance next to the choke.

As Nick says it's a bit of an art. More R might look better in PSUD, but does it sound better?
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#101 Re: Single-Ended Pentode Redux

Post by Paul Barker »

Cressy Snr wrote: Wed Jan 26, 2022 4:52 pm PSUD sim:
Screenshot 2022-01-26 at 16.51.48.png
20 h @ 451 ohm is strange. is it an anode load choke with limited dc current capability? , doesnt sound like a power supply choke which would have a larger core, so larger window to use thicker wire and get resistance around 100 ohm.

Anyway, what does it look like if you pretend its 100 ohm, and do you have a means of testing actual inductance. Alarm bells going off in my head. I bought a cheap pair from China 10h cant recall the current capability promised. Anyway core was about 1/8th the size we would use in the west during the valve era, measured inductance was 3h. No fekin use at all. Not even as a paper weight as the paper would fly away.
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#102 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

https://www.sowter.co.uk/acatalog/E_A_S ... 16-p3.html
It’s the top one in the list.
It’s only supposed to go in the bias smoothing circuit but it works perfectly well in the position in which I am using it because the current is low. Yes the resistance is not ideal but you use what you’ve got.
A2ABAE23-AD14-49D9-A476-BC97FF668128.jpeg
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Last edited by Cressy Snr on Thu Jan 27, 2022 8:56 am, edited 1 time in total.
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#103 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

simon wrote: Wed Jan 26, 2022 8:19 pm It would be interesting to try changing the R of the second choke Steve. Perhaps try 50, 200 and 1000 as well to see what happens?
There you go:
Screenshot 2022-01-27 at 12.39.44.png
Screenshot 2022-01-27 at 12.39.44.png (98.63 KiB) Viewed 1395 times
Screenshot 2022-01-27 at 12.38.39.png
Screenshot 2022-01-27 at 12.38.39.png (99.18 KiB) Viewed 1395 times
Screenshot 2022-01-27 at 12.37.50.png
Screenshot 2022-01-27 at 12.37.50.png (99.72 KiB) Viewed 1395 times
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#104 Re: Single-Ended Pentode Redux

Post by Paul Barker »

Cressy Snr wrote: Thu Jan 27, 2022 8:29 am https://www.sowter.co.uk/acatalog/E_A_S ... 16-p3.html
It’s the top one in the list.
It’s only supposed to go in the bias smoothing circuit but it works perfectly well in the position in which I am using it because the current is low. Yes the resistance is not ideal but you use what you’ve got.
A2ABAE23-AD14-49D9-A476-BC97FF668128.jpeg
Apologies. Actually all the chokes are quite high dcr, and those you have look small. But as they’re Sowter They’ll be what they say they are.

I see that for Simon you’ve modelled at 20h 50 ohm. I doubt if you could find that beast. Go low resistance you would have to buy a choke with large current capability: unobtanium boatanchor.

You might find a Fender output transformer for use with single ended 6v6 which might be 20h perhaps more and 250 ohm. They’re cheap on eBay. Leave secondary open.
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#105 Re: Single-Ended Pentode Redux

Post by simon »

Interesting Steve. There's no overshoot so must be a pretty good PS. The 50R sim has visible ripple - would be interesting to see what the ripple is for each after the HT has stabilised.

Notionally they each have the same H and C so the difference is R. Less is better but there may be a trade off in ripple. More C would reduce the ripple but also slow the transient response. If you couldn't hear the ripple it's probably not an issue. But it's a good example of the trade offs.
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