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Old 30th June 2009, 05:10 PM   #1
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Default Tube amplifier

Hi everyone, just wondering as I am about to build my first tube amplifier is the attached design o.k. and also does anyone know a suitable replacement tube for a 6AU6 driver tube and a 5Y3G rectifier.
Here is the amplifier schematic...
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...and the power supply schematic.
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Old 30th June 2009, 05:53 PM   #2
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Why do you want to replace the 6AU6? Looks like it's a pretty cheap tube. Found them here: http://www.esrcvacuumtubes.com/vacuu..._6A3-6CZ5.html

as well as the 5Y3G.

The only comment that I have is that there is a lot of feedback in that design...
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Old 30th June 2009, 06:23 PM   #3
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I need a replacement for the two tubes as I live in the UK and cannot find a UK supplier that stocks them. I don't want to order form the US because of the high postage costs. Also, if a suitable replacement can not be found could someone possibly give me a website address of a UK supplier that stocks the 5Y3G and the 6AU6.
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Old 30th June 2009, 08:31 PM   #4
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EF94 is same as 12AU6 - can you find that one? 5Y3 should be available, (perhaps Russian) but U50 or almost any GZ... number will do.
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Old 1st July 2009, 02:28 AM   #5
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Other than the cathode sleeve, the GZ30 is pretty much a 5Y3. Make sure to take the B+ from pin 8, not pin 2.

A 6AU6 data sheet is here .

A German EF94 data sheet is here.
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Old 1st July 2009, 07:12 AM   #6
colinB is offline colinB  United Kingdom
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Hi,

A good source for valves in the UK is Langrex. They stock all the valves you need for your build.

http://www.langrex.co.uk/

Cheers
Colin.
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Old 1st July 2009, 10:40 AM   #7
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I don't know who Michael Holden is, but that design bears a more than passing resemblance to
this design from J.E. Calvert in 2001
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Old 1st July 2009, 10:44 AM   #8
chrish is offline chrish  Australia
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Quote:
Originally posted by ray_moth
I don't know who Michael Holden is, but that design bears a more than passing resemblance to
this design from J.E. Calvert in 2001
On the link you refer to, the schematic is credited to the RCA Receiving Manual, so perhaps it is from there...

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Old 1st July 2009, 10:51 AM   #9
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Yes, you must be right, I didn't notice the label in the schematic. I was going by the credits at the foot of the page -

Composed by J. B. Calvert
Created 30 October 2001
Last revised 2 November 2001


Looking at the circuit, the operating points are strange, don't you think? Whoever runs a 12AU7 with a 220k plate load? 330k for a 6AU6 plate load is also odd, because it suggests a very low plate current for a tube that, as far as I know, runs best with about 3 to 5 mA plate current.
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Old 1st July 2009, 11:18 AM   #10
Gordy is offline Gordy  United Kingdom
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If Langrex run out, and if you can't source them in the UK, then Antique Electronic Supply has both tubes in stock. (Don't get hung-up on the price of postage. The last time I ordered from them it was only about 25. Instead think about the overall cost of getting the job done quickly and effectively).

Their site: http://www.tubesandmore.com/
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