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Old 28th April 2013, 09:39 AM   #11
AJT is offline AJT  Philippines
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Quote:
Originally Posted by centraltexastubeguy View Post
Howdy, Folks:

For the amplifier currently in the conceptual stage, I'll want a new manufacture PP output transformer, and for budget reasons it should be an off the shelf as opposed to a custom (unless someone knows of a competent custom winding house that is competent compared to off the shelf).

The topology is still up in the air but most likely it'll require separate screen windings with about a 20-30% ratio relative to the plate windings. Not ready to specify the complete transformer yet, just wanted to give y'all an idea of the class. This is for HI FI.

So, the question: who are the off the shelf providers out there with whom any responder has experience and what are the respective opinions about each?

Thanks!

Rene
i suggest that you pm BudP, Bud Purvine, who is member here, he can surely help you out, if i recall correctly, he is from the Washington state area...
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Old 28th April 2013, 07:36 PM   #12
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Hammond 1650R. The "R" version is a real sleeper.
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Old 30th April 2013, 02:38 AM   #13
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Default What's the budget?

Quote:
Originally Posted by centraltexastubeguy View Post
interesting how at least 2 of the names I'd expected to show up right away have not. Maybe in a couple of days!
Rene
James, Hashimoto, Tamura, Tango, Magnequest......
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Old 30th April 2013, 03:39 AM   #14
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Quote:
Originally Posted by Salectric View Post
Hammond 1650R. The "R" version is a real sleeper.
Curious, how so? (Note, I'm not saying it isn't, just curious about the basis for your opinion on the 'R')
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Old 30th April 2013, 06:21 PM   #15
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I have used two pairs of 1650R OPTs so far and have been very pleased eac thime with the sound. The R version was first recommended to me by Douglas Picard (Pak Protector) for his E-Linear design, and I later learned it is used by at least one custom builder whose PP monoblocks sell for over $30K. I can't say that it is the very best sounding OPT because I haven't compared it to others using the same circuit, but I can say that it sounds very good.
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Old 30th April 2013, 06:50 PM   #16
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thanks for all the input so far, hope it continues! OK, I'll reveal a bit more: My design will be using sweep tubes which generally means lower PP load resistance than other tubes (lower plate voltage at higher current). I'm almost convinced that this will be a conventional G1 drive but I do want to operate in UL mode. Rather than a tapped or tertiary winding transformer, I'm leaning toward a MOSFET circuit to allow adjustment of both the nominal G2 voltage and the percentage of plate swing which will be coupled to the G2. All the simulations I've run plus a considerable amount of investigation by others in this group have convinced me that the optimum "tapping" is somewhere in the 20-30% and not in the 40% range.
with an off the shelf unit, if all else fits, I can always simply ignore any existing G2 taps.
I'm encouraged by the endorsements of both Edcor and Hammond as they are inexpensive units, bears more investigation. The kicker may wind up being the low load Impedance (I think in the order of 3K or so, still running what ifs on that), the higher current and whether CFB will be incorporated.
Keep them coming! This hopefully is helping others in their thinking process.

Rene
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Old 30th April 2013, 11:01 PM   #17
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There is no magic % for UL operation. There are some historical values that soon became standard but actually the percentage depends on device first of all.....
If cathode feedback is used I am not sure that a mosfet follower driving G2 is a better solution than a pentode with regulated screen voltage.
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Old 30th April 2013, 11:02 PM   #18
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^good choice in dropping the "ultralinear" with sweep tubes...
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Old 30th April 2013, 11:25 PM   #19
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Power.

How much power, what class of operation. How much low end response. Which tubes at what voltage = plate impedance calculation. etc.

Otherwise it is just a list of manufacturers.

The actual specifics *change everything*.

20-30w PP iron is easier in general than 100watt+ iron... for example.

The ideal spec is like 10Hz -- 100kHz. Good luck.
But it could just about be done... in general you'd want to reach for that limit... for maximum performance.

Don't forget core material counts too...

In short, everything is a variable and every transformer is a trade-off.
Choose your poison!

_-_-bear
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Old 1st May 2013, 03:44 AM   #20
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Thanks for the comments, all. I would like to get back on topic which is: what are the best PP transformers in the 30-100W range. Based on personal experience, not just hearsay.
My reason for revealing a bit about the topology under consideration was to aid in the flow of input regarding transformer sources.
So, yes, a list of manufacturers but put thru the filter of individual experience. That will be greatly appreciated!
Thanks again!
Rene
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