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Old 2nd January 2006, 03:23 AM   #21
Sheldon is offline Sheldon  United States
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If you are not certain, this may be the one. I haven't built it or heard it, but it can be configured for many different output tubes - so go ahead and wallow in indecision with no regrets. http://db.audioasylum.com/cgi/m.mpl?...en&r=&session=

I think it is sold as a kit by diyhifisupply.com. Maybe they sell just the transformer too.

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Old 3rd January 2006, 10:15 PM   #22
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Quote:
Originally posted by ligascon
About Thorsten's phono...well yes, we all should thank him (I did already) but I also thank you for having the guts to ask all the questions that I would be afraid to ask. You're the man.
Wow. I didn't think I had any "The Man"-like qualities, but apparently endless redundant, inane, elementary and redundant questions gets you in. Looks like the bar's been lowered.


Quote:
The mains transformer is from diyparadiso in Belgium but I'm thinking a new one from vt4c.com


Can't seem to find a transformer with these specs on DIYParadiso.com, but I'd bet that Jack at Electra-print could wind one. Hmmm... that vt4c.com looks like an interesting site. Have you ever ordered from them?

Quote:
Please note that filament supply for the d3A is supposed to be 6,3 Volts. Thorsten advices to run in at low 5,5. See, as I told you before I was afraid to ask why and just did it.


Good idea.

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The common mode choke is from rs components.


Got it. Should be 7.5mH, right?

Dave-- this design looks interesting, but I think I'm gonna stay with the DRD.

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If you are not certain, this may be the one. I haven't built it or heard it, but it can be configured for many different output tubes - so go ahead and wallow in indecision with no regrets. http://db.audioasylum.com/cgi/m.mpl...ten&r=&session=
Wow! That's pretty cool. Unfortunately, its probably more than I can spend given the increased number of parts. Mrs. Annan's a nice girl, but not that nice.

Any ideas on the voltage rating for the paralleled caps in the amplifier circuit? I want to make sure that I don't get underrated caps.

Also, Lundahl has the LL1623 rated at a maximum primary voltage of 270V and a primary impedance of 3K, which is different than the specs listed for this OPT on the schematic. Now, I notice that these can be wired in, like, a zillion different ways, so there must be a way to wire the 1623 to get 5.6K primary with 8R out, right?

Also, how can this be rated at 270V when we know there's 620V running through it? I know, dumb question-- but WHY is it a dumb question?

Kofi
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Old 3rd January 2006, 10:27 PM   #23
Tweeker is offline Tweeker  United States
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Thats primary signal voltage, VAC RMS.

Isolation is 3 kV between primary and secondary, 1.5kV between windings and core.
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Old 4th January 2006, 12:28 AM   #24
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by Kofi Annan
Wow! That's pretty cool. Unfortunately, its probably more than I can spend given the increased number of parts. Mrs. Annan's a nice girl, but not that nice.

Any ideas on the voltage rating for the paralleled caps in the amplifier circuit? I want to make sure that I don't get underrated caps.
Kofi
Actually you can do this just as you would any other version, no extra parts. Three substituted parts - an adjustable cathode resistor instead of fixed, and some different taps on the OPT's and power transformers. If you ordered them wound, the extra taps wouldn't cost much more. Might be a bit much for an early project, but as you say, it is kinda cool.

For a specific answer, it would require knowing which caps. Generally, the caps have to be rated for the voltage they will see under any circuit condition. Maybe a 20 percent safety margin beyond that is a good idea. Parallel caps require the same rating as a single caps. Caps of the same type and value can be put in series. Two caps in series split the voltage in half, but as you know from your dealings in the U.N., they may not be inclined to play nice and share equally. So you have to send in some troops in the form of a resistor divider to make sure they play nice. You can see an example of this in Thorsten's power supply as shown in the referenced thread.

Sheldon
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Old 4th January 2006, 09:46 AM   #25
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Quote:
Looks like the bar's been lowered
You dont even know...I lower it every other time, sometimes even without opening my mouth...

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that vt4c.com looks like an interesting site. Have you ever ordered from them?
Yes, I ordered some tube sockets and silver wire. Really serious and no problems at all.

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Should be 7.5mH, right?
Yes

Quote:
Any ideas on the voltage rating for the paralleled caps in the amplifier circuit?
The Ducati Motor Run that I got are rated 450 VAC...that should give you some safety margin even if I run B+ at 650 DC Volts.

Quote:
there must be a way to wire the 1623 to get 5.6K primary with 8R out, right?
Yes, its listed as ALT B on the factory PDF. The Lundahl part is what I used but you should feel free to try any other brand. Im sure that either electra-print or magnequest should have suitable chokes and trannies...its your call.

Good luck with all the preparations. Take care,

Luis
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Old 6th January 2006, 12:26 AM   #26
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Quote:
Thats primary signal voltage, VAC RMS.
Thanks!

Quote:
Actually you can do this just as you would any other version, no extra parts. Three substituted parts - an adjustable cathode resistor instead of fixed, and some different taps on the OPT's and power transformers. If you ordered them wound, the extra taps wouldn't cost much more. Might be a bit much for an early project, but as you say, it is kinda cool.
Yep. Kinda cool, but might be too much for me on this go 'round.

Quote:
The Ducati Motor Run that I got are rated 450 VAC...that should give you some safety margin even if I run B+ at 650 DC Volts.
OK-- this is confusing to me since I thought that I would need to multiply the 450VAC x 1.414 to get a total DC voltage rating of ~636V, which would not accommodate the 650VDC. I have found some 420VAC rated motor run caps that I would have like to have used in the PSU, but my calculations indicate that this would only be ~593VDC-rated and would not work.

Of course, nothing in the universe have proven more consistently wrong than my calculations, so are the motor run caps rated conservatively or am I not calculating this right?

Quote:
Yes, its listed as ALT B on the factory PDF. The Lundahl part is what I used but you should feel free to try any other brand. Im sure that either electra-print or magnequest should have suitable chokes and trannies...its your call.
I figured that one out after I posted... thanks!

I'll probably stick with the Lundahl OPT, but I may mix it up a bit with the PSU and chokes.

Also, did you use motor run caps in the amp circuit, the PSU or both?

Yours in ignorance,
Kofi
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Old 6th January 2006, 03:20 AM   #27
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by Kofi Annan
so are the motor run caps rated conservatively or am I not calculating this right?
Kofi [/B]
Yes, generally so. They are designed for pretty severe AC duty, so the AC ratings reflect that. example: http://www.cornell-dubilier.com/misc/hot.htm

Sheldon
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Old 6th January 2006, 12:33 PM   #28
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Thanks!

Even more questions:

So, does that mean I could safely use a 370VAC-rated motor run capacitor for the power supply?

Also, can you(ze) tell me how many mA I the circuit consumes or what would be the recommended mA rating for a power transformer? I may be having one wound and I know that this question will come up.

Kofi
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Old 6th January 2006, 12:48 PM   #29
Sherman is offline Sherman  United States
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Quote:
Originally posted by Kofi Annan
Thanks!

...
So, does that mean I could safely use a 370VAC-rated motor run capacitor for the power supply?
...
Kofi

If you wish to be conservative multiply your AC rating by 1.4 to get the DC rating. In this case 518 VDC. And that is working voltage. They can take higher voltages for short periods of time (as when charging up).

I've had motor run (and make sure they are motor run not motor start) caps in my SE KT88 monoblocks for about a year now. The PS voltage is 425, max voltage on the caps as the PS stabilizes over the first 30 seconds or so is 560. I think the caps work great.

Having said all that I've been told I can safely double the AC rating for DC use but I'm too much of a coward... er, uh, I mean conservative, yeah, that's it; conservative, with electricity to try that (so far).
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Old 6th January 2006, 03:11 PM   #30
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by Kofi Annan
Thanks!

Even more questions:

So, does that mean I could safely use a 370VAC-rated motor run capacitor for the power supply?

Also, can you(ze) tell me how many mA I the circuit consumes or what would be the recommended mA rating for a power transformer? I may be having one wound and I know that this question will come up.

Kofi
Quite likely on the 370 caps. But if you're worried about it use 440AC caps. It's a very common motor run value.

How many ma? Depends on the circuit, but no higher math required here. Just add up all the current sinks - bias for each tube and any bleeder resistors, etc.. If you are not sure of the transformer quality, overrate by 20%. If you have one wound, just give the winder your circuit.

Sheldon
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