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Old 17th March 2011, 11:21 AM   #41
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Hi Pieter,

I agree with you, there is too much focus on isolated parameters.

Your statement about DCR is interesting. I would understand why a low DCR is beneficial in a transformer. But could you explain why a low DCR would also be beneficial in a plate choke? Just curious, I have not done comparisons in different DCR plate chokes so have no opinion on this yet.

Best regards

Thomas
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Old 17th March 2011, 11:26 AM   #42
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Sorry, but it was not meant to be agressive.
Let me say it in other words: over the years I have extensively tried different winding techniques to maximize HF bandwidth with high Rp tubes and step-up or step-down ratios, because that is the most difficult area for winders, a major challenge so to say.
Based on experience I know what is about possible, and minus 3 dB with a 7k tube.....forget it. Even for a 300B (700 ohms or so Rp) output transformer this would be a really good spec when also the full low frequency power bandwidth would be there.
It seems to make more sense if you would indicate what you would expect (or require) from this type of interstage transformer. A good winder should say if these requirements could be met.
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Old 17th March 2011, 11:45 AM   #43
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Originally Posted by Vinylsavor View Post
Hi Pieter,

I agree with you, there is too much focus on isolated parameters.

Your statement about DCR is interesting. I would understand why a low DCR is beneficial in a transformer. But could you explain why a low DCR would also be beneficial in a plate choke? Just curious, I have not done comparisons in different DCR plate chokes so have no opinion on this yet.

Best regards

Thomas
Hi Thomas,
For output transformers low DCR's are clearly of advantage (damping / output impedance) because of the low impedance loudspeaker interface.
For interstage transformers and anode chokes this should not be of equal importance because loads are generally high impedance.
Nevertheless in my experience the lower DCR types just sound better, "easier" on the ear. Then one is tempted to search for reasons, and when searching, you want to find something "important" without knowing or able to prove wether it really matters. This forum's ever ongoing thread "John Curl's blowtorch amplifier" with "deep going" discussions on resistance induced noise and eddy currents is a nice exemple of that IMHO.
Maybe one of your points, headroom, is also playing some beneficial role here.
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Old 17th March 2011, 11:54 AM   #44
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BTW, i find your comment about Japan not funny!
Be sure that what has happened in Japan, and what is still going on there, is of major concern for all of us!
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Old 17th March 2011, 12:42 PM   #45
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pieter t,

letīs say itīs a misunderstanding.

So if the old UTC HA-133 is an optimal transformer for the #26, isnīt it possible to produce
a replica on the old data and make it perhaps a bit better?
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Old 17th March 2011, 12:49 PM   #46
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pieter t,

letīs say itīs a misunderstanding.
OK, granted.
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Old 17th March 2011, 12:51 PM   #47
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pieter t,
So if the old UTC HA-133 is an optimal transformer for the #26, isnīt it possible to produce a replica on the old data and make it perhaps a bit better?
You ask me?
I had Tango transformers for comparison, but never had a UTC HA-133.
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Old 17th March 2011, 01:01 PM   #48
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No, no. This was a global question.
Is there a source where you could see the internal winding datas from the HA-133?
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Old 17th March 2011, 01:22 PM   #49
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No, no. This was a global question.
Is there a source where you could see the internal winding datas from the HA-133?
I'm the one using the HA-133, and it's my optimal solution. (Because it's what I've got, but there is no question it is an excellent transformer.) Rated at 30Hz - 40kHz (not sure of dB window) in this application it is good from a little below 30Hz to about 20kHz and is actually pretty flat - way better than -1dB over this range with the 26. Total primary DCR for both windings in series is in the region of 600 ohms.. Split primaries, and multi-tapped split secondaries with a permalloy core. Rated 8mA DC on the primary, I've found it works best at up to 6mA - recollect some odd behavior when run at 8mA. (I've been running this pair for about 10yrs now.)

Here's a good resource for owners of UTC transformers: UTC Data Includes specifications, and connection diagrams for many different types..
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Old 17th March 2011, 01:39 PM   #50
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Hi Kevin,

Checking HA-133 specs I see that primary impedance is indicated being "15k".
We know that transformers in general have no "impedance", but impedance ratios, however I prefer "winding" ratios.
All one can say is that a "15k" primary impedance asks for a minimum value of primary inductance. Though the absolute value measured by some inductance bridge does not tell us everything it gives an indication, and I would say that the HA-133 should have at least 150H. It is a pity that UTC did not give specs of primary L.
Did you ever measured it?
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