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Old 12th January 2013, 12:52 PM   #381
mogliaa is offline mogliaa  United Kingdom
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Originally Posted by mogliaa View Post
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
Improved Pentode driver by adding a parallel resistor to the gyrator output and managed to halve distortion: THD=0.27% @ 200Vpp, 4P1L is a great driver candidate indeed!
http://www.bartola.co.uk/valves/2013...driver-test-2/

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Old 12th January 2013, 02:31 PM   #382
regal is offline regal  United States
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Originally Posted by ikoflexer View Post
Using a 4p1l in the first stage but a 307A (triode connected) in the second stage gives you this. Not much of a difference. Of course, this is just simulation, not reality.
That looks really nice, unfortunatey the supply of the 307A is rather hit or miss I have often wondered if there was a russian equivilant. Any chance you could point us to the 307A model you are using ?



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Originally Posted by mogliaa View Post
Improved Pentode driver by adding a parallel resistor to the gyrator output and managed to halve distortion: THD=0.27% @ 200Vpp, 4P1L is a great driver candidate indeed!
4P1L Pentode Driver (Test 2) | Bartola Valves

Ale
Is there an advantage of a DHT pentode, vs a 6c4pi ? I guess I always considered the little space tube as being a better driver.
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Old 12th January 2013, 02:37 PM   #383
mogliaa is offline mogliaa  United Kingdom
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Some will argue the sound of a pentode driver is better. I haven't tested the 4P1L pentode driver in filament bias, but it looks promising on the bench at least!
Ale
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Old 12th January 2013, 03:34 PM   #384
regal is offline regal  United States
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Originally Posted by mogliaa View Post
Some will argue the sound of a pentode driver is better. I haven't tested the 4P1L pentode driver in filament bias, but it looks promising on the bench at least!
Ale

For my 4p1l-4p1l idea it would be interesting to have a switch to throw the driver into pentode mode for low efficieny headphones that need more gain, or is the bias too different ?
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Old 12th January 2013, 04:00 PM   #385
mogliaa is offline mogliaa  United Kingdom
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When Listened to 4P1L-4P1L made me think I wanted a different sound, too clean perhaps :-)
Either way, you could bias driver on Vgk=-5V and operate the 4P1L in both pentode and tetrode with filament bias.
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Old 12th January 2013, 06:08 PM   #386
regal is offline regal  United States
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Originally Posted by mogliaa View Post
When Listened to 4P1L-4P1L made me think I wanted a different sound, too clean perhaps :-)
Either way, you could bias driver on Vgk=-5V and operate the 4P1L in both pentode and tetrode with filament bias.
Just check your website wow a lot of interesting new stuff.

I guess the next logical question would be does the 4P1L Pentode driver stage have the kuhnas to drive your 4-65a directly, making it a 2 stage amp instead of three stage could be beneficial ?
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Old 12th January 2013, 06:45 PM   #387
mogliaa is offline mogliaa  United Kingdom
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Thanks, I've been working a lot lately on my 4-65a Amp.
I thought about 4P1L as a driver, hence all the testing lately. eBoz used D3a in triode and others used pentodes. However, I already built the filament bias supply for the 46 and the 46 driver in filament bias (yes, hefty thing I know) is very promising....
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Old 13th January 2013, 02:14 AM   #388
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Originally Posted by Wavebourn View Post

Some people believe that others prefer tube amps because of added distortions, despite experiments don't prove that. You can't model result of absense of nasty distortions adding something that is irrelevent. Like water from a glass cleaned by gasoline may look better than from glass cleaned by water that contained some clay, but it will not taste better. Adding to the glass of water cleaned by gasoline a bit of clay you can't improve it's taste.
best analogy ever
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Old 13th January 2013, 02:14 AM   #389
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4P1L is too clean, too much like SS. I like 26 better. (in my preamp)
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Old 13th January 2013, 06:18 AM   #390
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4P1L is too clean, too much like SS. I like 26 better. (in my preamp)
Hmmm... If SS was as clean as best tubes, why would I need tubes at all?
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