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Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

01A question
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Old 10th November 2015, 09:42 PM   #11
sumotan is offline sumotan  Indonesia
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Thanks Andy yes I am going to build that preamp.
I prefer going with tube rectifier instead for HT
supply.

Thanks again
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Old 10th November 2015, 09:51 PM   #12
andyjevans is offline andyjevans  United Kingdom
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Tube rectifier is OK. I use AZ1 mesh. Any mesh rectifiers are the best - AZ11 is the same, different base. I thought Ale used a tube rectifier?
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Old 10th November 2015, 10:09 PM   #13
sumotan is offline sumotan  Indonesia
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Looking at the schematics I believe it was connected to a Salas HV supply
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Old 10th November 2015, 11:03 PM   #14
andyjevans is offline andyjevans  United Kingdom
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Ale brought round his preamp - the one on his blog - and we listened to it in my system. I remember his power supply was shared with his 4P1L preamp but not what was in it. He probably did have a Salas reg, but that would come after the rectifier. Use an AZ1 mesh if you want the best.
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Old 10th November 2015, 11:17 PM   #15
sumotan is offline sumotan  Indonesia
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Thanks again for the advice Andy. Will hunt around for some AZ1. Btw why does globe version sound better then ST. Any idea Andy ? Actually I like the looks of ST more.
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Old 11th November 2015, 06:54 AM   #16
Hylle is offline Hylle  Denmark
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What is the technical reason for these old types of tubes to be better than others?
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Old 11th November 2015, 08:02 AM   #17
andyjevans is offline andyjevans  United Kingdom
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The AZ1 mesh is audibly better than the solid plate version, so technically it's the mesh. No idea why.

I think with globes and ST versions it depends a lot on the state of the tube - some of these are almost 100 years old.

Basically the 01A has a thoriated tungsten filament, like the 801 and 10Y and some other highly valued tubes. I'm sure somebody could say why this makes a difference - not sure myself.

Actually it's a bit more complex. You can tell by applying voltage to the filament. Thoriated Tungsten will be much brighter than coated cathode type. Original 201's were Tungsten. These draw 1 amp and light very bright. Later tubes were marked 201A or 01A and used Thoriated Tungsten. These drew .25 amps and were not as bright but still very noticeable. More recent 01A's used coated cathodes. Some of these can barely be noticed in lighted areas. Believe these tubes should have been marked 01AA but not everyone did this. If you find tubes marked 01AA they have coated cathodes but so do later 01A's.

01 = 1 amp filament
01A = 250 ma filament
01B = 125 ma filament
01C = 60 ma filament

More information and pictures here:
http://vinylsavor.blogspot.co.uk/201...th-ux201a.html

Last edited by andyjevans; 11th November 2015 at 08:17 AM. Reason: incomplete
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Old 11th November 2015, 08:57 AM   #18
sumotan is offline sumotan  Indonesia
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Hi Andy
Thks for the explanation. My own thoughts was that if the difference in volume between ST & Globe had any effect on the tube itself. Perhaps shape of the glass might even affect the sound. Sounds berserk right ?
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Old 11th November 2015, 02:04 PM   #19
euro21 is offline euro21  Hungary
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01A question
Don't forget to mention, that 01a is very sensitive to the load.
My breadboarded 201a preamp (SSHV2, 22R filament bias -0.25A Rod Coleman regulator- , cascode CCS load- 5mA-, 0.47uF - 100k load) was able to fall 3dB at 10kHz due to the 5m coax cable (connected to the oscilloscope)!
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Old 11th November 2015, 02:20 PM   #20
sumotan is offline sumotan  Indonesia
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Why would you need should a long coax cable Euro21 ?
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