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Old 6th October 2012, 12:51 PM   #2081
tcqanh is offline tcqanh  Viet Nam
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Quote:
Originally Posted by andyjevans View Post

I don't use the 26 anymore, but when I did I used two Hammond 156C chokes in series, bolted top to bottom and wired out of phase - all the details are in the thread somewhere. That was a good sound and cheap to achieve. This gives you all the gain of the 26 with a Russian teflon cap in my case. The issue with this setup is hum - the Hammonds are prone to hum pickup so you need to place magnetic components carefully, and well away from the chokes.
Exactly, I did build an 71A preampli with anode choke of 150H. Hum is a bit quite although I isolate power transformer in separate chassis. The preampli lies next to the power ampli, so I don't have any problem on impedance matching. high and midrange of this are fantastic.

I have an idea. Take 27/56/76 or 6J5/ 6SN7 is role of CCS for 26, likes SRPP circuit. That means these tubes are top half, and 26 is bottom half. I will experiment that in near future. That time the schema will be simplest.....

Last edited by tcqanh; 6th October 2012 at 01:16 PM.
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Old 6th October 2012, 01:14 PM   #2082
tcqanh is offline tcqanh  Viet Nam
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Originally Posted by tcqanh View Post
I have an idea. Take 27/56/76 or 6J5/ 6SN7 is role of CCS for 26, likes SRPP circuit. That means these tubes are top half, and 26 is bottom half. I will experiment that in near future. That time the schema will be simple.....
Top half tube is maybe a DHT, I can take 2 windings of filament in out of phase. So no need to get DC filament because AC hum from filament will be a lot canceled together.

... promissing
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Old 6th October 2012, 01:22 PM   #2083
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The "cancelling" of ac in filaments is what a hum-pot tries to do.... it's not good enough for a line amp, firstly because the filament is not perfectly symmetrical, - and secondly because the cathode generates second-harmonics of the filament current.

The sound is much worse as well, because the ac-current generates cross-products with the music (intermodulation).
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Old 6th October 2012, 03:11 PM   #2084
mogliaa is offline mogliaa  United Kingdom
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Quote:
Originally Posted by tcqanh View Post
Exactly, I did build an 71A preampli with anode choke of 150H. Hum is a bit quite although I isolate power transformer in separate chassis.
I had a lovely 71a loaded with Mu follower gyrator. Filaments DC using Rod's regulator and was dead quiet
Go for dc filaments!
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Old 6th October 2012, 06:05 PM   #2085
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What happened with 4P1L on epay? Only 2 sellers left...

One from Ukraine (selling matched pairs) and one from Czech Republc...
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Old 6th October 2012, 06:07 PM   #2086
mogliaa is offline mogliaa  United Kingdom
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Quote:
Originally Posted by Wavebourn View Post
What happened with 4P1L on epay? Only 2 sellers left...

One from Ukraine (selling matched pairs) and one from Czech Republc...
Hi Anatoliy,
Too late, all sold out thanks to us preaching all along the beauties of this valve. I bought about 15,000
Ale
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Old 6th October 2012, 06:59 PM   #2087
Magz is offline Magz  United States
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OK, here are some pics of my completed 26 linestage. First the whole package of PS, linestage, umbilical and remote, then a closeup of the linestage, then the linestage in operation on my workbench.
Attached Images
File Type: jpg 26 Preamp and PS.jpg (426.4 KB, 298 views)
File Type: jpg 26 Preamp Closeup.jpg (354.9 KB, 292 views)
File Type: jpg Preamp Closeup On.jpg (342.8 KB, 286 views)
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Old 6th October 2012, 07:01 PM   #2088
Magz is offline Magz  United States
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Now for some nudies:

First is the Power Supply Internals, then two shots of the linestage internals.
Attached Images
File Type: jpg 26 PS Internal.jpg (404.0 KB, 282 views)
File Type: jpg 26 Preamp Front Inside.jpg (392.9 KB, 283 views)
File Type: jpg 26 Preamp Side Internal.jpg (440.2 KB, 173 views)
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Old 6th October 2012, 07:03 PM   #2089
mogliaa is offline mogliaa  United Kingdom
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Quote:
Originally Posted by Magz View Post
OK, here are some pics of my completed 26 linestage. First the whole package of PS, linestage, umbilical and remote, then a closeup of the linestage, then the linestage in operation on my workbench.
Hi Magz,
Superb job, well done! Very neat! I wish mine could look like that.
Here is my current 26 preamp incarnation with LL2745 and HT using russian glow tubes and dn2540 CCS "a la Gary Pimm"....
Ale
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File Type: jpg mogliaa 26 preamp gen2.jpg (79.7 KB, 184 views)
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Old 6th October 2012, 07:05 PM   #2090
mogliaa is offline mogliaa  United Kingdom
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And another one:
http://www.bartola.co.uk/valves/wp-c...908-171450.jpg
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