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Old 13th February 2013, 07:49 PM   #511
mogliaa is offline mogliaa  United Kingdom
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Here you go Andy. You can get in theory up to 2W with 40Vpp drive when biasing the pair at full tilt = 250V, 80mA. Just a reference:
Click the image to open in full size.
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Old 13th February 2013, 08:02 PM   #512
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Try 2K4 load, and up to +12V drive. 5W output from a paralleled pair.

Also, try to apply constant positive voltage on G3, you may need less positive swing in A2.
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Old 14th February 2013, 01:37 AM   #513
Pano is offline Pano  United States
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What are you thinking for voltage on G3?
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Old 14th February 2013, 05:56 AM   #514
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Quote:
Originally Posted by Pano View Post
What are you thinking for voltage on G3?
I am talking, to get curves when some positive voltage, like +12V, is applied to G3, instead of connecting it to anode or to ground. Triode curves of pentodes shift such a way to the left, closer to the Y - axis.
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Old 14th February 2013, 06:48 AM   #515
mogliaa is offline mogliaa  United Kingdom
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I can redo the A2 swing loadline yes. For positive G3 bias I need to trace curves again, may be in the future as am not with a lot of time at the moment unfortunately
Ale
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Old 14th February 2013, 09:00 AM   #516
45 is offline 45  Italy
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Quote:
Originally Posted by andyjevans View Post
I was wondering about driving PSE 4P1L with 2C22, pretty much half a 6SN7. I'm wondering if it would work in two stages if I had 2v coming out of my DAC, like an ODAC for instance. I have Mark Audio Alpair 10s. It would be marginal. Right now I get about 0.5v from my DAC with 3 stages, 26>4P1L>4P1L.
Why don't you use an ECC40? You would get 2W out, as shown by Ale, with 0.5V rms in.
You can use the ECC40 both for min. THD and tune it for H2 cancellation being the main component of the spectrum.
There you have a two-stages PSE with 5 valves only....

Last edited by 45; 14th February 2013 at 09:03 AM.
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Old 14th February 2013, 04:02 PM   #517
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I have an amp with a ECC40 input. I can see your point about the gain, but I prefer DHTs. I suppose I should look at a 2-stage amp. It certainly makes sense, but the only tube I know that sounds remotely like a DHT is the 2E22, and I'm not sure about that either. I do transformer couple, so one thing I should look at is sneaking in a 2x step-up somewhere. I suspect the likely place for more gain is in the DAC stage somewhere. I'm only inputting 0.5v to my preamp, and it can't be hard to improve on that!
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Old 14th February 2013, 06:10 PM   #518
mogliaa is offline mogliaa  United Kingdom
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Hi Anatoliy,
I think I got it right here reflecting your experiments. Yes, 5W in A2 with 2k5 load with only 50Vpp:
Click the image to open in full size.
Cheers,
Ale
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Old 14th February 2013, 06:45 PM   #519
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Thank you Ale!
In my experiment I had about 220V on anode, so at clipping level of H2 was slightly less, level of H3 was slightly high, so dynamic distortions caused by "rectification" of an envelope were slightly lower. However, in the original schematic negative supply for cathode follower need to have more voltage, because despite of almost cut-off of output tube on clipping hard clipping of the current source was still audible.
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Old 15th February 2013, 11:27 AM   #520
RajkoM is offline RajkoM  Bosnia and Herzegovina
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Quote:
Originally Posted by 45 View Post
Why don't you use an ECC40? You would get 2W out, as shown by Ale, with 0.5V rms in.
You can use the ECC40 both for min. THD and tune it for H2 cancellation being the main component of the spectrum.
There you have a two-stages PSE with 5 valves only....

ECC40 direct coupled to 4P1L looks promising.

Question for 45 and Andy.

Do you have practical experience with smaller B+ on ECC40, say 130V/6mA op.point.

Also, if there is any difference in sound quality between Long glass Miniwatt ECC40 and Short glass Tungsram ECC40?

Tnx.
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