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Old 13th January 2010, 01:42 PM   #71
Previously: Kuei Yang Wang
Join Date: Nov 2002

Originally Posted by hornperfect View Post
Thorsten, what are your thoughts re autoformers vs transformers issue?
Well, strictly as a pure volume control there is little to choose, I am sure different devices from different manufacturers sound different and may be preferable to one or the other for a range of reasons.

What I find attractive with a true transformer as VC is that it can be employed in a wide range of "unorthodox" applications and that it can break earth/ground loops and so on.

An Autoformer simply can never do that and the performance gained with the unorthodox applications certainly convinces me.

Ciao T
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Old 13th January 2010, 01:46 PM   #72
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Join Date: Jan 2007
oh definitely, that's a great feature of a transformer. though dave slagle used to say that it's not a way to sort the ground loop out but to fight it at its very source. can't agree more.
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Old 10th April 2013, 07:50 PM   #73
gander is offline gander  United States
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Location: Denville, NJ USA
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Originally Posted by Peter Daniel View Post
Well, the comparison is not that simple. The TVC can actually work as stand alone preamp, offering 6dB gain, high input impedance and low output impedance, it can be wired for phase reversing and unbalanced to balanced (and opposite) conversion, all without any additional active circuitry.

Can your Lightspeed do all that?
Well said. And this isn't even the best quality of a TVC. With every signal there is power (watts), which is voltage times current. With a resistor type attenuator, the voltage drops, but the current does not proportionally increase, resulting in a loss of power. With a TVC, as the voltage drops, the current increases, maintaining the original power (less a small amount for the transformer windings).

ALSO, as the voltage drops, the impedance drops by a factor of squared. So, LOTS of punch and detail at low volumes.
More info about TVCs here:
FAQ for transformer volume contr

I have a Promitheus TVC, made in Malaysia (standard version, not reference).
Transformer Volume Control

I plugged it in at the home of the head of my audio club, who has a Jadis 4-chassis tube preamp, a truly high end machine (one of the channel power supplies was not working, so he didn't have a preamp at that time). My little Promitheus TVC was at least the equal of that incredibly expensive tube collection, according to the owner. And the Promitheus (basic) is only about $500US. Of course the better the core and the transformer, the better it will sound. And Promitheus offers their reference c-core transformers with the TVC, for a bit higher price of course.

And this is just one company. Check out Sowter:
They offer transformers with taps that you can use to build your own TVC.

Companies are coming out with TVC preamps claiming theirs is the best, but you can pay 1/20 of the price and get a damn fine preamp.

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