In my humble opinion the measurements of Jean-Michel Le Cléac'h have significant value and use. Thank you Jmmlc. However the listening test was not a true 'test' at all, and in real terms means virtually nothing. Indeed it's only value is good-natured 'entertainment value' !
Agree on both counts. Fine work by Jean Michel, no question. But the shoot-outs are fun, nothing more.
I just had a look at the transformer shoot-out measurement results and I found them quite interesting. I was shocked at the number of ringy trasnsformers when subjected to the 10kHz square wave test. Design of wide bandwith transformers has been pretty much beaten to death with a stick over the years, and there are several definitive references. The one that occurs to me off the top of my head is the old MIT Radiation Lab book on pulse generators, which has many practical details for designing wide bandwidth pulse transformers with maximum flatness and fidelity. A lot of the criteria used for radar pulse transformer design are germane for a wide-bandwidth SE audio transformer. I wonder how a transformer desined to those criteria would fare in a listening test? I may have to wind one myself to find out...
It would also be interesting to duplicate the test setup and have a look at some of the transformers I've used so far.
Don't interpret my comments to mean I think the measurements were poorly done or not valid in any way. I was trying to point out the variation between measurable performance data and listening experience. I think that taking the time to do all those measurements was a great undertaking. Kind of wish there was a Magnequest and Electraprint sample in there, too.
SM Brown - I didn't say that the measurements were faulty in any way - my thrust was that a lot of the transformers were poor performers in things like square wave response. How much this affects listenability is a matter of conjecture. My point was that there is enough information floating around to enable making transformers that measure well. How they then sound is another matter. It may be interesting to have a transformer measurement setup at next year's Burning Amp. It doesn't look like a whole lot of kit would be required.
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My point was I didn't want anyone to think I wasn't appreciative of the effort to make all those measurments. No problem. 🙂 I've not been to the festival, but I would if that were on the venue! The iron is SO expensive it would be great to have an opportunity to measure AND listen to samples. Relatively easy to try different caps, resistors, wire, etc.. but really much more difficult to have a variety of SE OPTs on hand to try in your own amp. Personally, I have had the opportunity to try a number - Bartolucci (C core stuff, really nice), Electra-Print, Magnequest (parafeed in a 45 amp), Audio Note, James. Of them all, the AN was the winner in my book, but James came in second. It's all relative, however, because the price point and amps these went in were all over the board. Minimizing at least some of the variable and then listening would be a great opportunity!
As far as transformers are concerned, I've been eating at HoJo's so far. The best I've used have been a set of old Fisher 500B magnetics for my "Kingfisher P-P amp (sounds very nice). All the rest of my amps have been built with either budget Hammond iron (125 series) or Edcor budget series (XSE and GXSE).These amps managed to sound ok, though they probably wouldn't have passed muster at the Triodefest, as they all have a liberal sprinkling of sand, each and every one... In addition, all my designs so far have used global negative feedback, so that the transformer is sort of forced to behave until it just can't.
Anyway, I'm getting ready to graduate to some designs that will use somewhat better iron, and I'm curious to see if I'll notice any difference.
Anyway, I'm getting ready to graduate to some designs that will use somewhat better iron, and I'm curious to see if I'll notice any difference.
vuki said:
>I guess that with an audience large as that room acoustics influences the results
>much more than transformer differences.
Let me say it that way:
The combination of test set-up, method, permission of a wide range of loads (2,3..3,5 kOhms), room acoustic, speakers and music samples made the early phase of the testing random number generation rather than significant... the 'B' bias was obvious, and a number of very good transformers did bite the dust too early.
I have to admit that I decided to drop out of the listening test after a few samples because it became clear that the result of the test would be rather random...
Jean-Michel le Cleac'h's measurements are way more significant than the listening results.
Regards,
mb-de
===
>I guess that with an audience large as that room acoustics influences the results
>much more than transformer differences.
Let me say it that way:
The combination of test set-up, method, permission of a wide range of loads (2,3..3,5 kOhms), room acoustic, speakers and music samples made the early phase of the testing random number generation rather than significant... the 'B' bias was obvious, and a number of very good transformers did bite the dust too early.
I have to admit that I decided to drop out of the listening test after a few samples because it became clear that the result of the test would be rather random...
Jean-Michel le Cleac'h's measurements are way more significant than the listening results.
Regards,
mb-de
===
I was informed from a friend who joined ETF2009 that a Japanese OPT
was proceeded to the BEST 4 level. This OPT uses R-Core construction
(not C-Core).
I could not identify its entry number. I suppose it is #26 or #27. Does anyone know ?
was proceeded to the BEST 4 level. This OPT uses R-Core construction
(not C-Core).
I could not identify its entry number. I suppose it is #26 or #27. Does anyone know ?
Eventually, I have identified the entry number of the R-Coreded transformer
from the attached photo. It was #27 although the below Web page indicates
#28 as I suspect it is wrong.
Attachments
Hello,
Pierre-François Brand the owner of both N°27 and N°28 informed me that N°27 is a Spanish transfomer on EI core and N°28 a Softone RW-20
See: Softone RW-20 Single-Ended Audio Output Transformer
The H2 and H3 distortion curves of that transformer show a feature alos shown by few other measured transformers. That curve shows peaks and dips a bit similar to a comb effetc.
I once correlated this behaviour to a "singing transformer", that means a transformer emitting a sound on test signals (secondary loaded by a resistor).
It is possible that the vibrations at resonance frequencies depending on the size and shape of the transformer modulate partly the magnetic field in the gap...
Best regards.
Jean-Michel Le Cléac'h
Pierre-François Brand the owner of both N°27 and N°28 informed me that N°27 is a Spanish transfomer on EI core and N°28 a Softone RW-20
See: Softone RW-20 Single-Ended Audio Output Transformer
The H2 and H3 distortion curves of that transformer show a feature alos shown by few other measured transformers. That curve shows peaks and dips a bit similar to a comb effetc.
I once correlated this behaviour to a "singing transformer", that means a transformer emitting a sound on test signals (secondary loaded by a resistor).
It is possible that the vibrations at resonance frequencies depending on the size and shape of the transformer modulate partly the magnetic field in the gap...
Best regards.
Jean-Michel Le Cléac'h
As I attached the photo in my previous post, the transformer with
#27 indicated by yellow paper is same as RW20 whose exterior
looking and the color coordination of the wires are seen in the Web which you quoted.
Please confirm it to Pierre-François Brand, again.
Hello,
After having done the necessary verification, Pierre-François Brand confirmed that the N°27 is the Softone RW20 transformer.
Pierre-François Brand says that N°28 and N°27 are inversed on the list of the shootoot as we can see on
http://www.triodefestival.net/uploads/ETF09/shootout.jpg
The Softone came in the 1/2 round and lost again N°5.
Here is a copy of P.F. Brand's message (in French language)
"JM,
Le 27 est bien le softone, arrivé en 1/2 finale, la liste European Triode Festival - ETF2009 Shootout est inversée entre mes transfo 27 et 28...
PFB"
Best regards from Paris, France
Jean-Michel Le Cléac'h
After having done the necessary verification, Pierre-François Brand confirmed that the N°27 is the Softone RW20 transformer.
Pierre-François Brand says that N°28 and N°27 are inversed on the list of the shootoot as we can see on
http://www.triodefestival.net/uploads/ETF09/shootout.jpg
The Softone came in the 1/2 round and lost again N°5.
Here is a copy of P.F. Brand's message (in French language)
"JM,
Le 27 est bien le softone, arrivé en 1/2 finale, la liste European Triode Festival - ETF2009 Shootout est inversée entre mes transfo 27 et 28...
PFB"
Best regards from Paris, France
Jean-Michel Le Cléac'h
Thank you very much for your re-confirmation.
Would you please correct the Web which you quoted for the
honor of R-Core. I haven't known R-Core's ability for Audio Use
until this result.
Hello ja2dhc,
I am in no way in charge of the webpage you mention but I'll try to contact one of the webmaster of the site and ask him to modify the file.
Best regards from Paris, France
Jean-Michel Le Cléac'h
I am in no way in charge of the webpage you mention but I'll try to contact one of the webmaster of the site and ask him to modify the file.
Best regards from Paris, France
Jean-Michel Le Cléac'h
An externally hosted image should be here but it was not working when we last tested it.
Softone RW-20 Single-Ended Audio Output Transformer
R-core is made by rolling a long uncut silicon steel strip.
I wonder how a gap is created in core (magnetic path) to make SE output transformer????????
I was informed from the president of Softone as follows:
For SE use OPT, R-Core is cut at the center (see attached photo).
The cutting sections are polished. Gap retaining film is inserted
between cut faces.
After the windings are assembled, inductance is adjusted by a screw
on the fastening metal belt (see attached photo).
For PP use OPT, no gap is applied on R-Core.
Attachments
- Status
- Not open for further replies.