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Old 19th July 2013, 03:17 AM   #1
kimbal is offline kimbal  Australia
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Default Who makes a Williamson output transformer ?

Hi All;

Does any one know a source for making Williamson output transformers ?

I believe Sowter make one; their type 8950 - but as to how close it is to the original design made by Partridge is is another story.
I understand the transformer made by Partridge had an open loop bandwidth from 2 hertz to 200 khz, where as the Sowter unit starts at 5 hertz; meaning a smaller core.

Has any one compared the Sowter transformer with the Partrdge for audio test comparison ?
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Old 19th July 2013, 06:34 AM   #2
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I found an old article about this William amplifier but 200kHz? No, just 60KHz i read. Was there a newer version of this transformer with better specs?
http://www.clarisonus.com/Archives/A...0Amplifier.pdf


btw Sowter is 5Hz - 70kHz





Quote:
Originally Posted by kimbal View Post
Hi All;

Does any one know a source for making Williamson output transformers ?

I believe Sowter make one; their type 8950 - but as to how close it is to the original design made by Partridge is is another story.
I understand the transformer made by Partridge had an open loop bandwidth from 2 hertz to 200 khz, where as the Sowter unit starts at 5 hertz; meaning a smaller core.

Has any one compared the Sowter transformer with the Partrdge for audio test comparison ?
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Old 19th July 2013, 07:54 AM   #3
kimbal is offline kimbal  Australia
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I'm not aware of a newer version of the Williamson but I recall reading that the output transformer made by Partridge ( ? ) was capable of 200 Khz. If that is wrong then so be it. Either way - whatever the true bandwidth is - it's whether someone makes such today other than just the Sowter version.
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Old 19th July 2013, 09:41 AM   #4
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It may be difficult to find such extreme transformer today, but I would try this for Williamson:

TGL 20/002 Transformator g?o?nikowy (2x EL84 PUSH-PULL) - Lampy Elektronowe On-Line. Najwi?kszy polski sklep z technika lampow?.

Don't be confused about the published specification of the frequency band. It is much wider than specified.
I have used this transformer with QQE03/12 pentode output stage and the frequency response (-1 dB) without GNFB is up to 50 kHz.
With triode or UL output stage the upper frequency limit is presumably beyond 100 kHz.
Primary inductance is 40 H ( 5kΩ @ 20 Hz), but the most important; leakage inductance is low (20 mH a-a) and therefore the use of GNFB is not complex.
And the price is very low too.

I have compared this transformer to Hammond 1608 and the performance of Indel is superior.

Last edited by artosalo; 19th July 2013 at 09:50 AM.
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Old 19th July 2013, 10:24 AM   #5
FoMoCo is offline FoMoCo  United States
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Quote:
Originally Posted by kimbal View Post
I understand the transformer made by Partridge had an open loop bandwidth from 2 hertz to 200 khz, where as the Sowter unit starts at 5 hertz; meaning a smaller core.
Does it really matter? 5Hz is plenty good enough. And, it doesn't really mean a smaller core. The measurement may not have been conducted at full power.
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Old 19th July 2013, 10:38 AM   #6
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Here is some transformer comparison for Williamson (from 1953).
Peerless S-265-Q seems to be the winner.

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD011593
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Old 19th July 2013, 11:30 AM   #7
kimbal is offline kimbal  Australia
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Thanks for that link.

I've never heard of Indel Transformers > .:: INDEL Sp. z o.o. ::. - transformatory, d?awiki, cewki, zasilacze. < but I do have a few audio transformer books in Polish indicating the POLs must know what they are doing with such design. The prices are also very cheap - postage to Australia will be the main killer !

I might give a couple of these transformers a try and see how they sound.
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Old 19th July 2013, 11:50 AM   #8
kimbal is offline kimbal  Australia
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Quote:
Originally Posted by FoMoCo View Post
Does it really matter? 5Hz is plenty good enough. And, it doesn't really mean a smaller core. The measurement may not have been conducted at full power.
Of course it does not matter what the bandwidth actually is - unless you want identical performance. As for the Sowter transformer being measured at full power or not, if it was done at low power ( say 1 watt ) the measurement was made, then the low frequency response will be even worse at high power.

As for core size, halve the frequency and you double the core area.
In the case of a transformer having LOW DISTORTION one of the crucial factors is having a large core to reduce saturation.

Partridge realized that in order to have a low distortion at 20 hertz, the core had to be capable of going some 10 times lower in frequency - hence 2 hertz was the roll off point.
Some pipe organs are capable of inaudible composite sub-bass sounds at low as 8.2 hertz and others at 16.4 hertz.

Equally so, if - 20khz is the upper limit of the audio spectrum, the open loop bandwidth ideally should be 10 times higher ( 200khz ).

The reality is - few output transformers meet such stringent design demands.
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Old 19th July 2013, 11:15 PM   #9
Matt BH is offline Matt BH  United Kingdom
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You are splitting hairs, but hey ho.

Here's where you can actually get one made that will be identical in every way:

http://www.transformers.co.uk/index.asp?pgid=20

It will be extremely expensive but it will also be indentical to the cracking original.

Personally if I could afford it and was that way inclined (which I am not) I would go with the Sowter.

The Williamson transformer really isn't that great. In my opinion it was just a brute force exercise in over engineering.

Cheers

Matt.

Last edited by Matt BH; 19th July 2013 at 11:25 PM.
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Old 20th July 2013, 12:21 AM   #10
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Magnequest in the USA has been building Peerless outut transformers.

MagneQuest Transformers: The top name in tube audio transformers
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