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Old 2nd January 2012, 11:54 AM   #1491
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I like the multiple chassis plan.

Comments:

- where we have silicon rectifiers in a hybrid bridge, there may be some ringing in the transformer current during the turn-OFF of the rectifiers. The shape of the current pulse depends on the capacitance and inductance of the transformer, but it usually helps if you have 47nF (stacked MKT) and a series connected 47 to 100-ohm (carbon composition 0.5W) to snub out the pulses. If you can sense the dynamic current and view on a scope, you can optimise the values, but the ones given will work quite well in most cases. For the HV side a 1500V rated cap is required.

- If the Mallory caps are more than 5 years old, I would recommend avoiding them in audio circuits. Nothing sounds worse than stale Elkos. Mouser has Nichicon KX, and Panasonic TSHA/HB or TSUP and Farnell has the Panas, and these will be very hard to beat in the HV positions.

I think many folks like the IXYS FeTs in CCS circuit, so K & K's advice should be fine. I think that some IXYS types need a few more volts (gate-source) to regulate at 10mA. This is usually an advantage, since the lower cascode device then operates with higher Vds (means lower capacitance = better isolation).

Looks like you are ready to start building.... enjoy the work!
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Old 2nd January 2012, 11:58 AM   #1492
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For the Filament raw dc, the snubbers are connected as in the diagram.
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Old 2nd January 2012, 02:05 PM   #1493
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Rod,

Thanks for the reply.

If I understand you correctly I need to build the filament supply to what you posted/schematic.

Don't know if I quite understand the change to the power HV supply. Is there another way for me to make it that would be better? Would like to stay with a tube rectifier but to be honest I haven't used a transformer without a CT before so this is all I could think of.
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Old 2nd January 2012, 02:18 PM   #1494
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Is this what I need to do for the high voltage supply?
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Old 2nd January 2012, 02:30 PM   #1495
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Yes, have a look at my 26 preamp HT supply here. I recommend adding a shunt regulator (e.g. Salas) for a quieter preamp

http://www.diyaudio.com/forums/tubes-valves/190857-4p1l-dht-line-stage-post2806229.html

Cheers, Ale
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Old 2nd January 2012, 02:32 PM   #1496
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Apologies, posted the wrong URL. Have a look at post 168 of the 4P1L thread...
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Old 2nd January 2012, 03:03 PM   #1497
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Quote:
Originally Posted by Original Burnedfingers View Post
Is this what I need to do for the high voltage supply?
Yes, that looks good. The Fairchild UF4007 works well in this position.

With the RC-snubber, I believe that the hybrid bridge works just as well as the tube rectified full-wave circuit.


We are in good company, too:
Lundahl Transformers - Hybrid power supply
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Old 2nd January 2012, 03:30 PM   #1498
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Ok, if I build the filament supply per your changes on the schematic you posted it will be good to go. Right?

Second, the changes to the HV supply the RC snubber and that will be good also.

Waiting to hear back on some CCS boards the IXYS fets you told me to go with.

Thinking along the lines of copper base plate with maybe Walnut base for the line stage chassis.

I appreciate the input and improvements that you told me about. I really feel like the humming #26 will finally get completed and I can complete a project that I started years ago.

One more thing.... should I be thinking about a AZ1 rectifier instead of the #80 I was going to use?
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Old 2nd January 2012, 03:38 PM   #1499
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Quote:
Originally Posted by Original Burnedfingers View Post
Ok, if I build the filament supply per your changes on the schematic you posted it will be good to go. Right?
Yes. Be sure to use the Hammond choke (28mH at 3A) to ensure that it bucks the voltage down to about 17V.

Quote:
Originally Posted by Original Burnedfingers View Post
Second, the changes to the HV supply the RC snubber and that will be good also.

Waiting to hear back on some CCS boards the IXYS fets you told me to go with.

Thinking along the lines of copper base plate with maybe Walnut base for the line stage chassis.
Copper base will be useful as well as beautiful. May need varnish or some protection though!


Quote:
Originally Posted by Original Burnedfingers View Post
I appreciate the input and improvements that you told me about. I really feel like the humming #26 will finally get completed and I can complete a project that I started years ago.

One more thing.... should I be thinking about a AZ1 rectifier instead of the #80 I was going to use?
We should not have to tolerate humming 26s any more! Many builders here have got this right now.

I haven't compared the AZ1, but I know that some contributors have tried them.
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Old 2nd January 2012, 03:39 PM   #1500
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Not necessarily. The 80 is a great rectifier. No need to go for an AZ1 unless you have a mesh one around :-)
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