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Old 8th March 2013, 04:55 PM   #551
Pano is offline Pano  United States
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Cool. You have the screen tied to ground? And it runs 4V on the heaters, right?
I suppose you are getting a lot of gain out of it.
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Old 8th March 2013, 05:32 PM   #552
FRUGIVO is offline FRUGIVO  Spain
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you're right
is a high gain triode nearly 80
http://www.shinjo.info/frank/sheets/010/p/PC900.pdf

Last edited by FRUGIVO; 8th March 2013 at 05:38 PM.
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Old 10th March 2013, 06:20 PM   #553
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I'm just making a back-up 4P1L PSE amp for the one I use every day. I use a modular system with top plates 4mm thick alu, 275mm long. Widths are 50mm, 70mm or 100mm. Here's my output stage on a 50mm strip. It has four loctal sockets wired up to the filament bias resistors which are parallel 2x 25ohms, 25W on top and underneath, series 2x 1.2ohms 7W, Welwyn W22. So 12.5 plus 2.4 = 13.9 ohms for bias. These get hot so are well within ratings, in fact passing about half spec. (50W rating for 25W actual) They should have 19v bias on them. Current is about 1.3A. Plate voltage should be about 260v, giving 240v across the two tubes for about 30mA each. The two 1.2ohm resistors under the chassis can be fine tuned in size to alter the bias.
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File Type: jpg 4P1L_PSE-OPstage.jpg (930.1 KB, 631 views)
File Type: jpg 4P1L_PSE-OPstage1.jpg (950.5 KB, 605 views)

Last edited by andyjevans; 10th March 2013 at 06:22 PM.
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Old 10th March 2013, 06:43 PM   #554
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Here's the present amp. Audio Note Trans-152 OPTs. On the extreme right are two glow tubes giving 180v on the input stage of 4P1L into Hammond 126C. This is all fed by my 26 preamp, as shown in the schematics a few posts back. For the new amp I'll be using O-netics OPTs. The front of the amp is made up of standard 19" subrack parts - two horizontal rails, top and bottom, with an anodised sheet of aluminium in between. All the top plates screw into the horizontal rails with the usual 2.5mm screws. I can change any of them as needed, and I have a LOT of spare ones with various project bits on!
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File Type: jpg 4P1L_PSE_Amp AN152.jpg (950.4 KB, 591 views)

Last edited by andyjevans; 10th March 2013 at 06:53 PM.
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Old 16th March 2013, 08:06 AM   #555
FRUGIVO is offline FRUGIVO  Spain
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Default #26+4pl1

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behind hedlund horn
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Lowther DX4 speakers
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power
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sounds nice and very detailed
having fun
do it yourself
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Old 16th March 2013, 10:12 AM   #556
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Quote:
It drives a pair of infinite baffle columns of around 21 litres with Mark Audio Alpair 10s (Mk.1).
Hi Andy,

Can you post a picture of these as well? Is it a standard enclosure, or your creation?

Thanks, Erik
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Old 17th March 2013, 01:11 PM   #557
Pano is offline Pano  United States
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Looking good, guys!
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Old 17th March 2013, 01:27 PM   #558
stajo is offline stajo  Sweden
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behind hedlund horn

sounds nice and very detailed
having fun
do it yourself
A masterpiece!
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Old 17th March 2013, 05:11 PM   #559
FRUGIVO is offline FRUGIVO  Spain
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A masterpiece!
know little orthodoxy but,,, funny
thanks!
more pict.
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Old 17th March 2013, 06:02 PM   #560
RajkoM is online now RajkoM  Bosnia and Herzegovina
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know little orthodoxy but,,, funny
thanks!
more pict.


Wow....looks great!
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