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Old 28th October 2009, 02:22 PM   #21
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Quote:
Originally Posted by Zen Mod View Post
janneman - have you any info about these xformers ?

winding ratio etc ?

edit : I forgot that in original schematic is written 64:8 ohms

any other info , besides that ?
The original also has a 4 ohms tap but that is not really necessary. And of course the core must have an air gap because it carries the 1A DC bias.

jd
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Old 28th October 2009, 02:51 PM   #22
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Quote:
Originally Posted by janneman View Post
The original also has a 4 ohms tap but that is not really necessary. And of course the core must have an air gap because it carries the 1A DC bias. jd
I want to perform experiments with output transformers instead of current sources and I want to have an universal output transformer for single ended solid state output.

Which exactly parameters must I have to submit to the manufacturer of single ended output transformers, if I know only the load resistance (e. g. 8 Ohms) and the wanted output power (e. g. 10W) respective the wanted output current (e. g. 3A)? I am not familiar with the parameters to core permeability and air gap.

And an additional question: If I haven't p-spice model for the transformer, what value I must choice for the replaced resistor in the drain line (I would say accordingly the winding ratio, but I am not shure)?
Thank you very much for advices
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Old 28th October 2009, 03:08 PM   #23
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Quote:
and the wanted output power (e. g. 10W) respective the wanted output current (e. g. 3A)
Wow 3A, I don't think that is possible.

Maybe you should try parafeed? I.e. just use a toroidal transformer (or custom parafeed tranformer (no airgap))as OT with a dc blocking cap. You could use a Lundahl LL1694 (3A) 40mH or the new LL2733 (3.4A) 100mH as current source.

Because I don't think a single ended output transformer that can withstand 3A of dc would work very well across the frequency range.
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Old 28th October 2009, 04:00 PM   #24
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Quote:
Originally Posted by Bas Horneman View Post
Wow 3A, I don't think that is possible.

Maybe you should try parafeed? I.e. just use a toroidal transformer (or custom parafeed tranformer (no airgap))as OT with a dc blocking cap. You could use a Lundahl LL1694 (3A) 40mH or the new LL2733 (3.4A) 100mH as current source.

Because I don't think a single ended output transformer that can withstand 3A of dc would work very well across the frequency range.

3A should be not a definite condition, but only one example. Maybe it is better to build a SE amp with 200V Vdd, choosing a smaller idle current but a greater winding ratio.
Currently I am talking only about fundamental considerations and the basic parameters, that I need for ordering customized edition of such transformer
By the way, this commercial single ended amp uses output transformer - the only, about I know:
http://www.envogue-24.de/Neue%20Seiten/ear/M100A.html
http://hometheaterreview.com/ear-par...-amp-reviewed/

Last edited by tiefbassuebertr; 28th October 2009 at 04:06 PM.
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Old 28th October 2009, 06:01 PM   #25
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I intend to run my output mosfet at around 100- 150 mA, within the ratings of the specified transformer (One Electron UBT-1). I'll be blowing about 30W per device at that current level and 200-250V drain voltage. This is most likely not within the sweetest spot of the output fet, but I'm not really all that concerned, as the output device will be inside a feedback loop and have some little brothers ahead of it to help straighten it out. This will not be a minimalist amp without global feedback like the one Nelson ginned up, but still one pretty much in line with tube methodology. It would be amusing to slap together a tube front end to drive the mosfet as well. I may do that as a side project after I finish the solid state version. Remember, Nelson designed his amp to be as simple as possible to encourage people to get off their backsides and build something. The concept I've outlined is something I want to uinvestigate for myself. A big depletion mode fet should have as many uses as a cat's got hair...

BTW - thanks to the guys who rooted out the Nemesis schematic (what concept/competing amp Hiraga had in mind when he named the amp, I'd like to know). It's an interesting concept, but not what I have in mind, especially as I'm determined to use the iron I have on hand.
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Old 30th October 2009, 08:30 AM   #26
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OK, this is how far I got on the Nemesis transformer.
I spoke with Per Lundahl and he can do one, based on the LL2410 I believe, but modified with a air gap for the DC bias. Projected price euro 160 each.

Then I got in contact with Jack Elliano of Electraprint Audio. He can do one for about $ 75, and he is willing to sell me a prototype which can be tested and then if necessary to be returned to him for final design. However, the shipping to my home in Holland is $ 50 each way, so I may end up with $ 100 in shipping for a $ 75 xformer. Since I have a perfectly working Nemesis with the original xformers, I think I'll pass for the new xformers.

I suggest that someone in the US will take this on, the shipping will be (much) less, but he/she must be able to measure the xformer as to freq response, undistorted power and preferably distortion versus frequency. Anybody game?

jd
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Old 30th October 2009, 08:48 AM   #27
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Quote:
Originally Posted by tiefbassuebertr View Post
I want to perform experiments with output transformers instead of current sources and I want to have an universal output transformer for single ended solid state output.
I'm about to start mucking around with using SE (and PP) OPTs as inductors.

This has the advantage that a small inductor in series with the main inductor will deal with the parallel C issue.

The downside with this is the DC offset due to winding R. But the numbers look pretty much the same as as running DC (or PP DC) on the primary of a normal or garden type tube OPT.

IE. If you have an SE OPT, it can handle a certain N x I without saturating. It frankly doesn't care whether that is applied at the primary or the secondary.
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Old 30th October 2009, 09:24 AM   #28
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Quote:
Originally Posted by janneman View Post
OK, this is how far I got on the Nemesis transformer.
I spoke with Per Lundahl and he can do one, based on the LL2410 I believe, but modified with a air gap for the DC bias. Projected price euro 160 each.

Then I got in contact with Jack Elliano of Electraprint Audio. He can do one for about $ 75, and he is willing to sell me a prototype which can be tested and then if necessary to be returned to him for final design. However, the shipping to my home in Holland is $ 50 each way, so I may end up with $ 100 in shipping for a $ 75 xformer. Since I have a perfectly working Nemesis with the original xformers, I think I'll pass for the new xformers.

I suggest that someone in the US will take this on, the shipping will be (much) less, but he/she must be able to measure the xformer as to freq response, undistorted power and preferably distortion versus frequency. Anybody game?

jd
BTW This transformer is sized for 1.3A DC bias so it is perfect for the IXYS SE amp as discussed here. Pout about 12W with 40-45VDC supply.

jd
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Old 30th October 2009, 11:36 AM   #29
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Now would not be a good time for me to commit to more projects It does sound like fun though.
However, I happen to have 2 Hammond 195T5, 100mH, 5A, 0.64 ohm Chokes. Naturally these are for powerline freqs but what would be expected of them as a choke load in a configuration like the Delite. Possibly for the upper ranges since 100mH probably would not cut it in the bass region? I'm concerned the laminated core will contribute to much of it's own nonlinearity
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Old 30th October 2009, 04:03 PM   #30
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Quote:
Originally Posted by janneman View Post
OK, this is how far I got on the Nemesis transformer.
I spoke with Per Lundahl and he can do one, based on the LL2410 I believe, but modified with a air gap for the DC bias. Projected price euro 160 each.

Then I got in contact with Jack Elliano of Electraprint Audio. He can do one for about $ 75, and he is willing to sell me a prototype which can be tested and then if necessary to be returned to him for final design. However, the shipping to my home in Holland is $ 50 each way, so I may end up with $ 100 in shipping for a $ 75 xformer. Since I have a perfectly working Nemesis with the original xformers, I think I'll pass for the new xformers.

I suggest that someone in the US will take this on, the shipping will be (much) less, but he/she must be able to measure the xformer as to freq response, undistorted power and preferably distortion versus frequency. Anybody game?

jd
good advice and good idea.

here another source: about the URL
EXPERIENCE electronics - Home
I see datasheet of this transformer:
http://www.experience-electronics.de...er/DBEA265.pdf
Unfortunately it was be optimized for the single ended tube output (high voltages) about
EXPERIENCE electronics - Monoblock Single Ended 30 W
But this company makes also custom specific versions.
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