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Old 24th December 2012, 04:07 PM   #331
regal is offline regal  United States
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That's what I a using it is actually representing a pair is parallel. Oddly he doesn't give a single model.
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Old 24th December 2012, 04:10 PM   #332
mogliaa is offline mogliaa  United Kingdom
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The pair are half-triodes, not two 4P1L in parallel
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Old 24th December 2012, 04:13 PM   #333
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Quote:
Originally Posted by Rod Coleman View Post
Hi Ale,

Yes, if the 47K grid resistor is moved to connect across the CCS only - then connect one end of the IT secondary to the bias, the other end to the grid. No other connexions at the grid needed.

This way, the grid sees the bias voltage, but the IT winding feels none of the dc current.

With a high quality IT, this will give an excellent solution!
Hello Rod,

Sorry my ignorance what's IT?
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Old 24th December 2012, 04:18 PM   #334
mogliaa is offline mogliaa  United Kingdom
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Hi Felipe,
It's an interstage transformer like the LL1671 used in my diagram
Feliz Navidad!
Ale
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Old 24th December 2012, 04:24 PM   #335
mogliaa is offline mogliaa  United Kingdom
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Quote:
Originally Posted by Rod Coleman View Post
Hi Ale,

Yes, if the 47K grid resistor is moved to connect across the CCS only - then connect one end of the IT secondary to the bias, the other end to the grid. No other connexions at the grid needed.

This way, the grid sees the bias voltage, but the IT winding feels none of the dc current.

With a high quality IT, this will give an excellent solution!
Cheers Rod, should have thought that one myself!
Here is the updated circuit, I think it should perform well and also can be easily tweaked to get the 4P1L output stage with a 20K grid bias resistor only...
Have a great Christmas!
Ale
Attached Images
File Type: png 6C4C:4P1L PSE version 02.png (42.1 KB, 467 views)
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Old 24th December 2012, 04:38 PM   #336
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Quote:
Originally Posted by mogliaa View Post
Hi Felipe,
It's an interstage transformer like the LL1671 used in my diagram
Feliz Navidad!
Ale
Thanks Ale,
Merry Christmas to you too.
Felipe
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Old 28th December 2012, 11:30 PM   #337
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I just got around to doing some measurements of my 4p1l linestage,
20ma thru a single dn2540 and -12.4v @ 600ma using the phonostages 6e5p and 6c45pi's (shunted with 39r) heaters in filiment bias using coleman reg.

pretty happy for a newish project with lots of refinements available.

2nd harmonic at -85 db and 3rd -97
snr outside of the 50hz which i'm struggling to measure due to soundcard issues (noisy pc i think) is-100 to about 2k then -110+ up to the 40k i measured
and the bandwidth is about the same as my 192khz soundcard at half volume.
great tube!
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Old 4th January 2013, 08:19 PM   #338
mogliaa is offline mogliaa  United Kingdom
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I did some tests using the 4P1L as a driver in filament bias. Linearity is outstanding in triode mode as measured before, but was keen to see the performance in pentode mode. I tweaked my breadboard to run in pentode albeit it wasn't optimal but still got THD=0.58% @ 200Vpp which is really good for a driver!

4P1L Driver Tests | Bartola Valves
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Old 8th January 2013, 06:07 PM   #339
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Default No second ?

Just to throw in a thought after all the earlier discussion of 2nd harmonic and cancellation & which tube is more linear etc etc .
Why would you want to minimise all of the 2nd harmonic ? ;o)
If I had a pre-amp with 2nd harmonic at 70dB down, and one with no measurable 2nd-harmonic, I know which I would prefer !!
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Old 8th January 2013, 06:22 PM   #340
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Quote:
Originally Posted by IslandPink View Post
Just to throw in a thought after all the earlier discussion of 2nd harmonic and cancellation & which tube is more linear etc etc .
Why would you want to minimise all of the 2nd harmonic ? ;o)
If I had a pre-amp with 2nd harmonic at 70dB down, and one with no measurable 2nd-harmonic, I know which I would prefer !!
No, you don't. Try first.
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