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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 9:47 am 
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Joined: Mon Mar 22, 2010 1:10 am
Posts: 238
I am considering something like this... raise the cathode R till it is around 20V above the G1 voltage? Possible?

http://www.tubemaster.de/DIY/Grafik/EL84-2A3DC.GIF

my B+ can potentially go up to 500V Smile


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 10:34 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7251
Location: Pleasant Hill, California
You may use some Zener between base and emitter of high voltage transistor.

But in such case you may consider something like Meteor of Michael Koster.


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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Sat Apr 09, 2011 7:50 am 
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I love my 4P1L amp!!!!! LOVELY SOUND!!!!


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Sat Apr 09, 2011 8:18 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
quikie22 wrote:
I love my 4P1L amp!!!!! LOVELY SOUND!!!!


Congratulations! Applause

How did you end up with driving it?

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Sat Apr 09, 2011 8:38 am 
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Joined: Mon Mar 22, 2010 1:10 am
Posts: 238
with driver tube = 6P15P

tested 2 ways...

1) borrowed an IT ... think i will go with IT. (earlier bad sound due to poor load selection, sounded incredible after correction).... now.. to order my IT will be my coming headache... Smile

2) In the meantime, will use cap coupling with 50uF motor run caps... also sounds very very good...

also did as you suggested, added high quality cathode bypass caps for 4P1L.

4P1L sounds very very real...


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Sat Apr 09, 2011 8:29 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
We auditioned today my 4P1L prototype with this speakers:

Image

Sounds very nice and real, but on some music material 5W per channel is not enough to reproduce peaks driving such speakers. Horns would be more than adequate, or bi-amping with separate amps for woofers. Such a way single 4P1L per channel would be enough.

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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Sat Apr 09, 2011 8:54 pm 
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Joined: Mon Mar 22, 2010 1:10 am
Posts: 238
wow, nice speakers.

Mine are used on a single-driver high efficiency speaker (94dB). 5 W is sufficient but I agree, transients may not be handled well.


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Mon Apr 11, 2011 9:30 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
quikie22 wrote:
wow, nice speakers.

Mine are used on a single-driver high efficiency speaker (94dB). 5 W is sufficient but I agree, transients may not be handled well.


Actually, they are handled extremely well, due to absence of a coupling capacitor to the grid of an output stage, no cathode resistor shunted by capacitor, and very stiff regulated PS. It clipped, but continued to work nice immediately after that, as if nothing happened. 2 of us (me and Jim who designed speakers) heard this moment, but the audiophile Frad who were with us did not recognize it, so unusual for SE amp was this behaviour.

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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Tue Apr 12, 2011 1:54 am 
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Joined: Mon Mar 22, 2010 1:10 am
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wavebourn wrote:
Actually, they are handled extremely well, due to absence of a coupling capacitor to the grid of an output stage, no cathode resistor shunted by capacitor, and very stiff regulated PS. It clipped, but continued to work nice immediately after that, as if nothing happened. 2 of us (me and Jim who designed speakers) heard this moment, but the audiophile Frad who were with us did not recognize it, so unusual for SE amp was this behaviour.



Yes. I noticed this behaviour with the GU-50 amp. The Cathode follower drive topology with fixed bias really is a very good design.

What I meant about 4P1L being unable to handle transients was that it would clip due to the limited headroom from the tube's low power.

Would have liked to do the same thing with the 4P1L with cathode follower, but unfortunately need to work within the constrains of the parts I have. Saving up money to get a transformer for negative voltage supply, but decided that maybe should try the interstage transformer at least once.


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Tue May 10, 2011 9:43 am 
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I finally drew the schemo of the amp, as it is now.


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gubernator-7-1-sch.jpg
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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!
 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu May 12, 2011 4:32 am 
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As the 4P1L are paralleled, do we need to match them and how much "difference" is allowed between tubes if we need to match?

I know you posted previously that 4P1L are very close, but are they close enough to work in parallel?


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu May 12, 2011 7:39 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7251
Location: Pleasant Hill, California
quikie22 wrote:
As the 4P1L are paralleled, do we need to match them and how much "difference" is allowed between tubes if we need to match?

I know you posted previously that 4P1L are very close, but are they close enough to work in parallel?


Sure, I selected almost identical tubes. And since they are very linear, paralleling does not increase distortions, rather the better is match, the better they share power between them.

Question: how do you select halves of 2A3 paralleled inside of the single balloon?

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu May 12, 2011 8:31 am 
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wavebourn wrote:
Question: how do you select halves of 2A3 paralleled inside of the single balloon?


LOL Good question Smile


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu May 12, 2011 8:39 am 
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Joined: Mon Mar 22, 2010 1:10 am
Posts: 238
If my output transformer has got 2.5K taps and 5k taps as well as 8ohm and 16 ohm taps, is it better to use 2.5k:8ohm or 5k:16ohm if I am using an 8 ohm speaker and paralleled 4P1L?


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu May 12, 2011 8:48 am 
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Шаман, типа...

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Posts: 7251
Location: Pleasant Hill, California
I would try both and find better power and frequency response.
When used 5K/16 Ohm for 8 Ohm there should be better low end, but loss on DC resistance higher.

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