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Old 31st January 2012, 02:38 AM   #521
John L is offline John L  United States
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Quote:
Originally Posted by rmyauck View Post
So on PS trans it would probably be better to spend on higher mA rating as George mentioned would be a + on his site.

I found a thread in AK with a guy who builds DHT SE with low Watt tubes (Under 10W) & swears by the 28 lb Hammond 1642 SE 5K 75W rated OPT. Pretty pricey to try , but you probably get what you pay for.

Hammond Mfg. - "Classic" Single Ended Tube Output Transformers - (1627 - 1642 Series)

Randy
$300 times two will definitely get you started on a big bucks unit, won't it?
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Old 31st January 2012, 03:07 AM   #522
rmyauck is offline rmyauck  Canada
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That's just a drop in the bucket if you start looking at the line of C-core SE lineup from Audio Note.

Audio Note Output Transformers, A,B,C
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Old 31st January 2012, 03:24 AM   #523
John L is offline John L  United States
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I wonder what justifies the price on those units?

Do you think they use pure silver instead of copper? After all, silver is the world's best conductor. And I'll bet you there would be a lot of silver in some of them.
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Old 31st January 2012, 06:03 AM   #524
rmyauck is offline rmyauck  Canada
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Your right it looks like Ag is part of the reason,along with the expensive cores.

Audio Note

There group B PP OPT's look interesting as affordable, but they don't believe in UL though so one is out of luck for that option. They explained the B series are 50% under rated too.

Audio Note

Audio Note

PDF'S @ partsconnexion have more info too!

Last edited by rmyauck; 31st January 2012 at 06:14 AM.
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Old 31st January 2012, 07:35 AM   #525
Ian444 is offline Ian444  Australia
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I would think the 25W Edcor OPT's would be more than enough. 20Hz to 20kHz at 25W.

Regarding the 2 power trannies, 300V vs 285V, hmmm, interesting choice. Nearly 20V difference in B+. The 285V one might run the heaters on the high side, but that is an easy fix (if required). 20V too much on the B+ is not so easy to fix. I haven't used Edcor trannies so I have no idea of their ratings vs actual measurements in an amp.
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Old 31st January 2012, 02:24 PM   #526
John L is offline John L  United States
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Doesn't George state that a rated transformer at 300V works fine, even though the makers have a tendency to make them slightly over that amount? I would have to go back and reread his expose on the project and tubes, but believe he found that any 6GQ5/EL84 tube could take it.

Some of the other associated tubes, now that would be a different story. But I intend to keep to the above tube. I'm still undecided.
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Old 31st January 2012, 02:56 PM   #527
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John L,
Go with the 300-0-300. Build it stock. Start with a 5U4. After power-up, measure voltage on the plates, if its too HI, change to a 5Y3 or some
other 5 volt tube. If its low add to 2 SS diodes to make a full bridge.
The power supply can be tweeked a bit.
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Old 31st January 2012, 04:32 PM   #528
John L is offline John L  United States
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Quote:
Originally Posted by brucetassin View Post
John L,
Go with the 300-0-300. Build it stock. Start with a 5U4. After power-up, measure voltage on the plates, if its too HI, change to a 5Y3 or some
other 5 volt tube. If its low add to 2 SS diodes to make a full bridge.
The power supply can be tweeked a bit.
At first, I thought of using tube rectification, but have now changed my mind. And I have changed my mind for one over-riding reason.

You all will have to pardon me, but I am a very artistically inclined person. I work in the interiour design field, and make high dollar items for interiour designers. My Mother thinks she and Dad wasted all that money sending me to private HS and the Citadel, not to mention my own expenses in attaining a masters degree in Physical Anthropology. And I am constantly bemoaning the fact that I never went to collage and earned a degree in geology. I am doing my utmost to get my grandson pointed in that direction. Hell, Eugene Shoemaker is my intellectual hero.

But that aside, I know full well the importance of that tiny concept of 'beauty' and the 'Golden Ratio'. Humans, even other animals, are genetically predisposed to favour the Golden Ration(1/1.6) The most beautiful people have a face that upholds that ratio. Its just in our genes to be attracted to this symmetry.

I have a HP monitor that is of the 16:10 aspect ratio(1/1.6), but now monitors are all made with the new HD wide screen 16:9 ratio, which is not the Golden Ratio. I love that monitor because it is pleasing to my sense of beauty. The monitor I am typing on now, is a newer one, and it uses the new HD standard. And normally I would hate it, because my sense of beauty notices this. But HP uses a ploy to ease the sense of beauty problem by making the bottom frame bar bigger than the top bar. This artificially makes the monitor look more pleasing, and it helps reassure my subconscious, and if I had one of those with thin framing, it would drive me crazy.

Well, there is a 'beauty' problem with this project. The tubes are not symmetrically aligned because the PCP is set up so the tube sockets are just not artistically aligned. The rectifier is also off in left field. From an aesthetic point, it makes the amplifier 'wrong' to the eye, and in need of being hidden from view. This is why so many console 'pulls' are rebuilt into more pleasing units.

Perhaps George will find a way to correct this in the future. And perhaps he did try it, but couldn't get the PCP to allow for it. I'm not sure, but I am thinking of finding a way to elevate the tube sockets from the board.

Doing this is straight forward: just drill the holes and run the connection from the board to the decking above.

But that presents some problems. And If I remember correctly George has tried to discourage this process, but I will have to reread the construction manual. The more that parts are separated from each other, the easier it is for magnetic fields to create hum and distortion. So in order to make the distance as little as possible, I could position the tube holes, but raising the board close enough to the deck would be tricky if I wanted to make the wire connections as close as possible.

I have to think this thing through more before making a decision, but I really want to have the finished product be something that people will want to admire.

And don't get me wrong, I chose this kit because it offers the best bang for the buck, is a proven winner, and has more than enough participants here, who can help get me out of any binds I may have. And I really expect to have a few, because I am new to making my own amplifiers.

I've just got to think of some way to be able to solder tube sockets on the decking, position the PCB properly, and then solder the connections to the board, doing it in such a manner that the distances are as short as possible. I think I have something in mind but haven't finalized it in my mind yet.
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Old 31st January 2012, 05:48 PM   #529
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John L
What are you going to use, tube or SS diodes? It mades a big difference. If you use SS diodes alone, the B+ WILL be too high with a 300-0-300vac transformer. Tube rectifiers drop considerable voltage and that drop was anticipated in the design. If you use SS only, you will need to use a power transformer with a lower secondary voltage. Not having tested the amp with SS only, I cannot recomend a voltage value. Moving the rec tube is possible but opens up a can of worms...
If you want to use SS diodes, leave the tube socket off and solder the diodes directly on the PCB without a socket and get a power transformer with a lower secondary voltage. George shows a picture of this configuration in the assembly manual.
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Old 31st January 2012, 06:03 PM   #530
John L is offline John L  United States
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Quote:
Originally Posted by brucetassin View Post
John L
What are you going to use, tube or SS diodes? It mades a big difference. If you use SS diodes alone, the B+ WILL be too high with a 300-0-300vac transformer. Tube rectifiers drop considerable voltage and that drop was anticipated in the design. If you use SS only, you will need to use a power transformer with a lower secondary voltage. Not having tested the amp with SS only, I cannot recomend a voltage value. Moving the rec tube is possible but opens up a can of worms...
If you want to use SS diodes, leave the tube socket off and solder the diodes directly on the PCB without a socket and get a power transformer with a lower secondary voltage. George shows a picture of this configuration in the assembly manual.
Oh. I'll have to think about this a bit more. Where can I put that tube so it looks like it really belongs?

Will there be any real problem with moving the tube sockets around a little bit? Also, I intend to construct transformer covers, which have steel sheet fit inside and soldered in place. That would naturally add magnetic shielding I believe.
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