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Re: MIke, womderfully informative reply!

>if you check on lundahl's website the published airgap for most of their PP models is .001" (or 25u).... this indicates to me that (in the gretest of likelihood) there is not a spacer per se that is added to the gap... my hunch is that the airgap is derived experentially by the manner in which the faces are finished (or not so finely finished on purpose) before the core is assembled<

Not according to Per Lundahl himself - in a talk he gave to the Munich Triode Mafia in my own apartment a couple of yesrs ago - and repeated at the European Triode festival last December. He has positively stated they intentionally use a spacer to get known and repeatable air gaps in their P-P OPT's - and also in their power transformers.

>I never argue with what folks hear or don't hear. And consider it to be unassailable. With that said... it doesn't mean that I am not surprised by what people report hearing<

I can agree with that!

>And this is one of those cases.... you say 1 mil unbal dc and a ST 70 trans sonically goes to the devil???<

In my differential poweramp circuit - in my system intomy speakers from my souces - yes. It looses a lot of downward dynamic range - which is like room ambience, micro dunamics, but more than just that.

>the quantitative analysis would not support such a finding that at one mil dc of unbal plate current the device goes to hell in any objective manner at all... <

Can understand that. But some claim copied CD's sound better than the original - which also has no basis in conventional theory.

>which isn't to challenge, per se, your subjective findings but just to point out that on first blush it is hard to quantitatively support your subjective findings<

No argument. But I would find it real interesting to know why.

>another point I kept thinking about the last few hours is... comparing a James, a ST70, a Tamura, etc... in the same circuit and then concluding that you liked the Lundahl's better than the above units... was due to the presence of 1 madc of unbal plate current... that blows my mind a bit... <

That I didn't say, Mike, and nothing like it! And if what I did say could be taken to mean that - that is NOT what I meant!

I prefer the Lundahl's in *my* amps for many reasons - mostly to do with their performance to price ratio, and that they deliver on time, and are made in Europe, and are small in relation to their performance etc etc etc. And to date - I haven't found any OPT that sounds better - in my amps in my system - and ALWAYS for crucial tests, no matter what the brand/type, with the currents balanced to better than 100uA.

>in the same way that folks take 10 different chokes... all with different L's, different C's, different flux densities, different core mats, different insulations, perhaps different levels of workmanship, different enameling on the wires, and etc... and then are able to conclude that the unit with the lowest DCR sounds best... when they have not isolated the dozens of variables that goes into how a transformer might sound or behave...<

Totally agree with this. One can hear what one does - but to give techical reasons for such a preference is where many seem to loose the plot.

>... in some sense... I think the same thing has perhaps occurred here...<

Nope!

> once you consider all the variables btwn the three different tranneys... that you liked A better than B, C, and D...<

That's what I said.

> it seems to me to be a bit of a stretch to say that you liked A better soundwise cause it sounded better with X amount of unbal plate current...<

That I didn't say! As above.

> you might have liked A "better" for lord knows how many reasons... but I'm from Missouri that this preference would rest on A's alleged ability to carry 1 madc of plate current better than units B, C, and D.<

I liked A because it sounded better to ME in MY circuit - which I have to admit is rather unique.

>the top dog peerless critters are expensive but no more so than the top dogs from Tango and Tamura to mention just two competitors<

Would like to try your big dogs one day...

>I hope I've not appeared to be picking on you.... as this is not my intent at all<

If it's intelligent (and it is) I can take it!

> Rather... I wanted to point out that you should not (and perhaps cannot) make a generalization that PP EI tranneys cannnot accomadate unbal dc plate currents... this is too broad of a statement<

Fair enough - and not too many people are making my amp designs!

Allen


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