Small Push-Pull Amp.

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Cressy Snr
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Re: Small Push-Pull Amp.

Post by Cressy Snr » Fri Jul 19, 2019 10:15 pm

Paul Barker wrote:
Fri Jul 19, 2019 9:28 pm
Nowt wrong with triode strapped valves. Some prefer gk71 over gm70. I liked 813 triode connected as much as I loved 211 for their unique stand out extra not heard in most amplifiers. Entirely different to each other yet only mood or tastes depending on which way your preference lies.
Just having a laugh Paul. My 13E1 OTL is a triode strapped Tetrode after all.
If you think your system could sound better than it presently does, please believe me, it’s not your fault. The only thing you are guilty of, is not telling your wife how much you spent to get it to sound this bad. (Herb Reichert)

Cressy Snr
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Re: Small Push-Pull Amp.

Post by Cressy Snr » Fri Jul 19, 2019 10:27 pm

6336A curves:
Image

260 ish on the anodes and 90mA idle current at 80 ish Vk looks decent to me.

2K5 loadline.
If you think your system could sound better than it presently does, please believe me, it’s not your fault. The only thing you are guilty of, is not telling your wife how much you spent to get it to sound this bad. (Herb Reichert)

Cressy Snr
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Re: Small Push-Pull Amp.

Post by Cressy Snr » Sat Jul 20, 2019 12:58 pm

Some working out (not mine, but why reinvent the wheel)

Image

The blue line gives 26.1W plate dissipation per section, plus the 31.5W of heaters. This means having to shift 83.7W of heat from a bottle the size of a KT88
The green line at 23.5W per section is a little cooler at 78.5W to manage. The valve is designed to manage this, but it’s a bit warm. I’ll probably go for the green line, even though the max distortion is slightly higher at full power.

Driver needs to swing 160V pk-pk, so a simple 6SN7, or 12AU7 cascade will easily manage it on a shallow load line.
If you think your system could sound better than it presently does, please believe me, it’s not your fault. The only thing you are guilty of, is not telling your wife how much you spent to get it to sound this bad. (Herb Reichert)

izzy wizzy
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Re: Small Push-Pull Amp.

Post by izzy wizzy » Sat Jul 20, 2019 2:17 pm

I see you're plotting as a single valve. So is this a SE amp now?

I've just been playing around with composite curves for PP amplifiers for the first time for the GM70 PP amp and I think it comes out as different to playing around with single sets of curves.

Cheers,
Stephen

Cressy Snr
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Re: Small Push-Pull Amp.

Post by Cressy Snr » Sat Jul 20, 2019 2:40 pm

izzy wizzy wrote:
Sat Jul 20, 2019 2:17 pm
I see you're plotting as a single valve. So is this a SE amp now?

I've just been playing around with composite curves for PP amplifiers for the first time for the GM70 PP amp and I think it comes out as different to playing around with single sets of curves.

Cheers,
Stephen
Yes, It’s now SE. I have some Hammond 1627SE output transformers off Steve S (which I still need to pay him for) that are good for 130mA DC and its a shame to leave them lying about. I also have experience with the 6336A and know how good it sounds as a single stereo amplifier valve.

I could have gone big with the 1950s 13E1s I have, but you’re talking 200mA before they start singing in SE; which would have meant having another custom pair of OPTs made to replace the Majestics that I sold, years ago. I don’t have that sort of dosh to chuck around these days.

I’ll have to start another thread.
If you think your system could sound better than it presently does, please believe me, it’s not your fault. The only thing you are guilty of, is not telling your wife how much you spent to get it to sound this bad. (Herb Reichert)

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