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In the Forum: Audio Discussions
In the Thread: Passive transformer based preamp
Post Subject: Re: Further problems with interstage transformers.Posted by Thorsten on: 10/31/2005

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Hi,

 dazzdax wrote:
Thx for this well written and highly educational piece Thorsten! It appears that Romy is not very fond of the Audio Consulting transformers, could you give your opinion regarding those? What is your opinion regarding the use of pure silver wire in transformers?


First, I have no first hand experience of the AC Transformers. Here is what I know about them and how in my experience this impacts on the sound:

1) Primary inductance is 50 - 100H, that is by a factor of 10 to > 20 less than what we ended up with the S&B one. This will seriously impact on the low frequency preformance with sources that have all but the most heroic solid state output stages. I note that Dick Olsher found problems when using the SR with a Lamm LP2 Phonostage, which has around 3KOhm output impedance. I also note that the Dave Slagle Autoformer Volume controls (Intact Audio) have low impedance/inductance as have the Sowter TVC's (85H), which means that if sources have a fairly high output impedance any of these TVC's will experience problems at the bandwidth extremes at much lower source impedances than the S&B TVC and the far eastern "carbon copy" (or should that be amorphous copy?) that is now floating around.

2) Core material is iron/steel in all the lower grade versions (they don't say what the top grade version uses). Our (S&B plus myself) experience was that lowering the nickel content (currently S&B use 80% Nickel Superpermalloy [aka Mu-Metal]) "disimproves" neutrality and transparency, in other words, steel cored (or FE based amorphous) line level transformers are not sonically "wires with gain/attenuations", but fairly strongly manipulative, sonically speaking. It is entierly possible that the colorations and reduction in transparency from this (I also note this with the Opera/DIYHFS Amorphous Iron core equipped TVC's) will be considered to "sound good" by some in some systems, it simply was not the design goal for S&B, that's all.

3) As for silver, S&B have both silver and copper versions of their transformers. I tend to stick with the copper, not just for cost reasons. For utmost transparency silver seems slightly ahead though, but the tonality in my experience becomes slightly washed out, something which may be offset partially by using lower nickel content cores.

Finally, a number of comparisons have been made especially in the HKTA and DJTA Yahoo Groups of various TVC's, including SR & Sowter vs. S&B's earlier offerings (the current MK III are appreciably, if modestly better), it is worth seeking them out.

Ciao T

PS, in my pro-audio days back in east germny we used daisychain several transformers to be able to better hear the effects of core materials, bandpass filter et al. Using Schulze TH-315 Coaxials and even MEG RL-900 Monitors it was difficult to hear with any reliability as much as 4 - 6 daisychanied studio grade line level transformers using high nickel cores and winding techiques that made sure of very wide bandwidth.

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