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Old 11th January 2010, 11:35 AM   #21
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Check out this doc I translated.
http://basaudio.net/pubs/dhtrob_psu.pdf
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Old 11th January 2010, 01:55 PM   #22
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Hello,

why not using a high GM pentode in pentode mode :

- no Miller effect
- no bypassing cathode capacitor (local CR)
- only one stage drive, no preamp needed

Philippe
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Old 11th January 2010, 02:40 PM   #23
jrenkin is offline jrenkin  United States
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Quote:
Originally Posted by Bas Horneman View Post
Check out this doc I translated.
http://basaudio.net/pubs/dhtrob_psu.pdf
Great article! Thanks for posting it.

The article mentions two follow up articles. Would you happen to have access to those? I will search, but time is limited at work...
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Old 11th January 2010, 02:46 PM   #24
jrenkin is offline jrenkin  United States
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Wow, Bas, I didn't realize you translated that. Great work and much appreciated. Learned from it already.
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Old 11th January 2010, 03:38 PM   #25
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Quote:
The article mentions two follow up articles. Would you happen to have access to those? I will search, but time is limited at work..
Glad you like it.

I will post the second article but to be honest you don't learn anything new. (That is the reason I did not translate the third article) It's more of the same just on a different amp if I remember correctly.

There is another article on psud someone wrote for my diymag. I'll see if I can seperate that and post it here.
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Old 11th January 2010, 03:52 PM   #26
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PhillippeS,
Can you please clarify something in the schematic you presented? There is a junction (I think) below the 27K and above the 47uF where this path to ground crosses the lead out of g2. does this all connect there at that 4-way junction? Or does the wire from the 27K to the 47uF cross-over the lead out from the g2 without actually making a connection there?

Bas,
that was a perfect article! It really answered alot of questions I had about power supplies. I was wondering how one measures the power transformer output resistance/impedence you were mentioning in the article (I think an example had a value of 710R). Is this a simple measurement with a multimeter across the secondaries, basically the DCR of the secondary windings or is it something more than this? If so, how does one calculate it or is it something given in the manufacture data sheet of the transformer (If so, I don't think I have seen it before).

I was wondering what the advantage/disadvantages were of using the D3a in Triode vs. Pentode as well other than the obvious of higher output in pentode. Why would you choose one over the other is what I think I am asking?

To date it has been suggested to me to connect the D3a in triode and that has been my plans so far. I don't think I need the extra gain from a pentode connection either. Also, the pentode requires more parts and is a bit more complex....I want to keep it as simple as possible. I have never worked with zeneers either to date. I think the schematic shows x3 51V zeneers, when a zeneer is purchased are there any other ratings other than voltage I should concern myself with?

Thanks again to all,
Jeff
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Old 11th January 2010, 04:03 PM   #27
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Hi Jeff,

Quote:
I was wondering how one measures the power transformer output resistance/impedence you were mentioning in the article (I think an example had a value of 710R). Is this a simple measurement with a multimeter across the secondaries, basically the DCR of the secondary windings or is it something more than this? If so, how does one calculate it or is it something given in the manufacture data sheet of the transformer (If so, I don't think I have seen it before).
Here is an answer to your question. Otto Axel wrote an article for my mag to do just that.

http://www.basaudio.net/pubs/DIYMAG_2006_2.pdf page 10-13.
Thanks again to Otto Axel.
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Old 11th January 2010, 10:43 PM   #28
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I promised you to draw a schematic and here it is.
I have drawn the shunt mod, and the output stage as well, but I didnt check values, but used the ones you gave me. The shunt mod has one disadvantage, at full volume it still acts as a voltage divider 2:1. But the d3a has a gain of 70x, so the 35x left is still plenty. I presume you don't have a pre-amp? because if you do, I would leave the potmeter out.

Sorry it is a little late, but I had to put some Ikea furniture together.... Billy the bookshelf x 6

Good luck!
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Old 12th January 2010, 01:56 AM   #29
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Pauldune,
Thanks alot it looks great. I think the only difference is I have 0.33 Russian PIO's I will be using.

I was wondering if I should maybe place some resistance to bring the voltage down some on the CCS....maybe a B+ of around 300-325 rather than the full 435v for the output stage. This should decrease the heat and sinking I will have to use for the CCS. Or am I mistaken? If it is a good idea to bring the B+ down a bit for the CCS is there a particular voltage you would target?

Is there any way to use the CCS for the 300B stage as well? Just curious, I haven't seen this before and I am sure there is a reason. Maybe it is just I haven't seen it too. Not sure. Either way, any use for this for the output stage at all?

Jeff
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Old 12th January 2010, 03:37 AM   #30
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BAS,
Great magazine! thanks, I learned alot, perfect explaination of how to use PSUD2 and the output impedance tool.
Jeff
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