[E55l2]

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[FullRangeMan]

Yes and no.....

That means you have to measure a lot to say if one transformer is better then another transformer and even then its a matter of interpretation....

But there are some rules to see if a transformer is  good or not. In general : good frequency response without any resonance, low copper losses and good low loss core materials.

This is interesting, how is the range from a superior freq. response?

[E55l2]

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[E55l2]

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[FullRangeMan]

Where did you get such bad result?

If I remember well its a OPT for guitar amp;
if I found the page I will inform you.

[FullRangeMan]

in general, -3dB,  7Hz-80kHz or better. But more importend what is happens after the -3dB point for the high frequencies. Any resonances have to be damped so that a 10kHz squarewave still looks good.

How to stop that resonances? It woud be a wood table instead of metal or other mechanical resonator as Sorbothane? I have see something in the FM Acoustics.
Its that black square:

[E55l2]

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[FullRangeMan]

Wow a famous expensive brand.
In all cheap amps I had all of them had the SS rect bridge solded wire, in the image above this expensive FM Acoustics amp use a blade connector.

[E55l2]

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[FullRangeMan]

E55l2, I always wants to know why this other famous and expensive hi end maker do it, he remove 2 bolts from the EI transformers in this preamps?

[J-Pak]

Yes and no.....

That means you have to measure a lot to say if one transformer is better then another transformer and even then its a matter of interpretation....

But there are some rules to see if a transformer is  good or not. In general : good frequency response without any resonance, low copper losses and good low loss core materials.

Also, if there are no good datasheets or any data from the manufacturere avoid it. Avoid companies as Tribute and Lundahl because they give no good information about what they make. Look at Amplimo/ Plitron or Tango, Monolithmagnatics, Tamura.

Monolith Magnetics do have impressive low frequency response with their amorphous SET transformers. Now they are going into Finemet game, but very expensive, nearly 3000 Euro for a pair of 300B SET finemet OPT.

It is about 480K Yen+ shipping from Japan.

WOW  For frame of reference I paid $1200 for a pair of X10s a few months before ISO Tango closed. I ended up not going 211 route so I need to sell them at some point.

ISO Tango used to be good value transformers, prices went up a lot prior to their closure. I don't see any reason to use them now with a pair of 211 OPTs coming in at nearly $4500 (granted JPY is strong)...

[Steve]

Sometimes a electrical resonance can be killed with a snubber circuit. Resonance in a negatief feedback amplifier can lead to instability problems

If you see a frequency response as this:


expect a square wave as this:



It's a Audionote transformer. (performance is poor)

I agree E55, and as you and others have mentioned earlier, there are other expensive, not so hot brands out there. Thank you for posting such. And over the years, the hype on many forums has been unless one uses X, Y, or Z expensive brands, one's amps, other trannies are junk. By the way, losses are minimal in almost any descently designed OPT. Flea amps are about the only amps that this becomes critical.

Back on page 6, and shown below, I provided an actual measured 10khz response from an entire amplifier, not just the OPT. There was no resonance control incorporated, no global negative feedback, no output stage voltage feedback, just a typical open loop circuit. Frequency response is
-1db at 5 hz, and -3db at 75khz. Notice no overshoot at all, not a hint of zing, just excellent response. (I am retired and not selling anything.)


 
I mention this as an object lesson that X, Y, or Z expensive brands are not all that is out there, and that the rest of the circuitry also influences the quality of the component, sonics.

Cheers
Steve

[FullRangeMan]

Steve any opinion on the transformers w/removed bolts?

[Steve]

Steve any opinion on the transformers w/removed bolts?

Not nearly enough information FRM. Can you borrow a signal generator and scope to measure? If not, is there a college near by who will allow you, or a student/professor to measure said amp?

Cheers
Steve

[ACHiPo]

Steve any opinion on the transformers w/removed bolts?

I'm also interested in this question.  I've been tweaking my Gustard DAC, and one of the recommended tweaks is to remove the steel bolts and sit the torroids on cardboard.  I've done both, replacing the bolts with nylon.  Things seem to be a tad better, but it's pretty subtle.  I'm trying to understand why having a conductor running through the middle of the torroid would be a bad thing?

[FullRangeMan]

Not nearly enough information FRM. Can you borrow a signal generator and scope to measure? If not, is there a college near by who will allow you, or a student/professor to measure said amp?

Cheers
Steve

I cant do it Steve these +$5K preamps are not mine, these are web photos.

[FullRangeMan]

I'm also interested in this question.  I've been tweaking my Gustard DAC, and one of the recommended tweaks is to remove the steel bolts and sit the torroids on cardboard.  I've done both, replacing the bolts with nylon.  Things seem to be a tad better, but it's pretty subtle.  I'm trying to understand why having a conductor running through the middle of the torroid would be a bad thing?

My guess is that interferes with the magnetic flux of the transformer during operation.
But the toroidal core is stable without screws but not the laminated core, it can open it self without screws during operation.

[ACHiPo]

My guess is that interferes with the magnetic flux of the transformer during operation.
But the toroidal core is stable without screws but not the laminated core, it can open it self without screws during operation.

I'll noodle on it--it's been entirely too long since I have electricity and magnetism.

[FullRangeMan]

Just received these: monos 48steps custom model at no extra cost,
free shipping, fast email reply.
http://www.khozmo.com/products_dale_shunt.html

[FullRangeMan]