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Old 19th April 2011, 03:29 PM   #1
nickds1 is offline nickds1  England
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Default Info wanted on OPT....

I've just been given the OPT from a Velleman K8011 monoblock amp - its a toroidal BEAST (90W). Its marked "ZD 043".

The Velleman manual is at

Does anyone have the spec for this xfrmr?

"The whole plan hinged upon the natural curiosity of potatoes" - S. Lem

Last edited by nickds1; 19th April 2011 at 03:34 PM.
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Old 19th April 2011, 03:37 PM   #2
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It should be a type ZD043

Primary: 2 x 1K, taps at 1/3
Secondary: 4 and 8 ohms
90W max

bandwidth: 2Hz to 125kHz (-3dB/1W) (probably with feedback applied)
Real tubes have top-caps
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Old 30th April 2013, 07:59 PM   #3
M Gregg is offline M Gregg  England
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Has anyone used these transformers for other tubes...

It seems a strange primary impedance..

M. Gregg
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Old 30th April 2013, 08:39 PM   #4
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Default PPP?

Originally Posted by M Gregg View Post
Has anyone used these transformers for other tubes...

It seems a strange primary impedance..

M. Gregg
Sounds like something meant for 4 or more tubes in PPP (i.e. trioded EL34s) or 6c33
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Old 30th April 2013, 11:59 PM   #5
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By 2 x 1K they actually mean 2K anode to anode (Raa) even though to be technically correct 2 x 1K would actually mean 4K Raa. It is one of those annoying little snippits of information posted to the web which is quite missleading.

So 2K Raa with what seems like 30% Ultralinear taps is what it really is. It will suit a quad of the usual suspects ie. EL34, 6L6, KT77, KT66 in parallel push pull. You could also use 4 off 6550 or KT88 at slightly lower voltage to keep the power down to the 90 Watt level.

6 off 6L6 is one more option at lower B+

At lower B+ it would also suit 8 off 6V6 or EL84 or 4 off sweep tubes like 6CM5, 6DQ6 etc.

Heap of options.


Last edited by gingertube; 1st May 2013 at 12:02 AM.
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