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Old 20th January 2013, 07:58 AM   #2321
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Hi Abe,

The preamp circuit looks about ready to build, I'd say.

For the Filament's raw dc, please aim for about 6.7Vdc.
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Old 20th January 2013, 08:09 AM   #2322
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In the Filament raw dc, a value of 60mH seems very high. The Filament Regulator will reject a large amount of ripple, so even if the raw dc has 50mV or so, you can still build a very quiet preamp.

One choke to try is the Hammond 159ZJ (10mH 5A, 160mOhm)
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Old 20th January 2013, 08:14 AM   #2323
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When you are modelling the high value capacitors in a power supply, please double-check the ESR given in the data for the caps.

For example, the Panasonic TSUP series of parts is recommended, where the ESR is 38mOhm for 22000uF.

http://panasonic.com/industrial/incl..._aec_ts-up.pdf


adding the correct ESR to the model will make a big difference to the accuracy of the ripple model.
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Old 20th January 2013, 09:51 AM   #2324
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Here's the type of filament supply I use. I strongly recommend filament bias rather than battery grid bias. I've tried both. With filament bias you eliminate the capacitor on the input. I consider it important to eliminate all capacitors that could influence the signal path, and to use polypropylene caps in the PSU.
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Old 20th January 2013, 12:07 PM   #2325
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Do you like the chassis distribution for #26? The heatsink inside the chassis without pcbis for Salas SSHV2 shunt regulator. The empty centered space inside the chassis is for the TVCs.
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Old 20th January 2013, 12:16 PM   #2326
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if you ,I turn the top/under panel ,like the air hole is in the front ,ie under the tube

this plate are alu ? you need non magnetic...a must
better wood at last
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Old 20th January 2013, 12:22 PM   #2327
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That's a nice looking chassis! Where did you get it?
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Old 20th January 2013, 12:27 PM   #2328
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I believed that was better than the HV heatsink was better ventilated than the valves.

Yes it's all aluminium.
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Old 20th January 2013, 12:32 PM   #2329
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Quote:
Originally Posted by andyjevans View Post
That's a nice looking chassis! Where did you get it?
Thanks, it's a Galaxy Maggiorato form modushop - hifi2000, the exact model is code 1NGXA288 230mm x 280mm

1x frontal in aluminum 10mm oxidized silver
1x back in aluminum 3mm oxidized black;
2x flanks in aluminum of 10 mm oxidized black ,
2x covers in alu 2mm oxydized black

Dimensions:
Width: body 230mm, inner useful 210mm
Height: 80mm
Depth: 280mm
Weight: 2,0 KG

Web link: modushop.biz
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Old 20th January 2013, 12:44 PM   #2330
regal is offline regal  United States
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Merlin,

I have been designing something similiar (SSHV's + coleman regs) for a headamp.

How are you going to handle the power supplies? I understand the Coleman doesn't like the dc supply to the filaments to be run on the same umbilical as the pre filtered B+. My experience is that its best to keep all power transformers as far as possible from the OPT's. I've literally measured -25db per foot 60hz reduction separatig output transformers from power transformers. Three chassis just seems crazy to me.

I have often wondered if for an amp like this if it would be best to just make the power supply chassis AC only, and do the rectification for both the regs and B+ in the amp chassis. It always makes sens to "transmit" ac rather than DC, but I don't know how much buzz the 26's would pick up from rectifiers in close proximity.

Last edited by regal; 20th January 2013 at 01:10 PM.
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