Current thinking :) on Audio-grade vs Standard grade Toroids in PSU!!

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Some talk about a screen between primary and secondary windings (a copper screen?).
Then there can be a mu-metal screen around the whole trafo?

and that makes it an audio grade? man, i must be making audio grade traffos without knowing it.....:D

i am also fond of putting copper screens in between windings of my diy traffos...copper tapes are now easily available....:cool:

i thought that was a good practice to help in the noise...
 
The permeability of the iron core has a lot to do with the larger heavier 'traditional' torroids too, not just the winding tension, insulation, interlayers, vacuum sealing, etc

If you're prepared to spend up big for a special transformer, any potential benefits will depend on the associated power supply - there's a balance in there somewhere of $s spent for perceived improvement.

As for the Hart Kit for the JLH amp, I'm in agreement with "ctrlx" in that you maybe could look at a replacement power supply and use a local Canterbury transformer - a 50-0-50 (or better yet, a dual 0-50) 300
va should be readily available from them
 
I was hoping someone would share first hand subjective impressions of any of these "audio" transformers.

Having compared dozens of different transformers i fail to notice many common features that actually relate to the sound. Yes, electrostatic screens are marginally better and so is low flux density but those do not explain why some transformers sound really bad. General construction type (EI, C, dblC, R) obviously has some importance, but again, it is not decisive.

For the record, contrary to general consensus, i find some of the worst sounding transformers to be EI types, yet other EIs are brilliant.

Perhaps most frustrating was trying to find an appropriate transformer for the filaments of my DHT power amp. R-cores, towards which i have always been ambivalent, sounded much better than anything else.

So how does replacing a standard toroidal with an "audio" type actually affect the sound? Surely someone has compared this at least with transformers from Toroidy.pl
 
.........As for the Hart Kit for the JLH amp, I'm in agreement with "ctrlx" in that you maybe could look at a replacement power supply and use a local Canterbury transformer - a 50-0-50 (or better yet, a dual 0-50) 300 va should be readily available from them


Thanks for waking this one up James.....need to get back on the horse, following a festive hiatus!!


The Hart Kit 'Parts List'...describes the transformer as 300VA 50-0-50....not sure what you mean by the better option of a dual 0-50.
FWIW...the transformer I'm replacing is an ILP 73033...and old online pages from ETI (around '87 I think) just list the spec as : 300VA 50-0-50.
Should also say that I'm easily confused :)


Keeping in mind that I have two of these monoblocks, not sure that I should be creating an alternative PS for one of 'em, and effectively make it different to the other. So...hanging back from that at the moment, and looking for a direct transformer replacement....so will be checking out Canterbury windings.
 
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When I had a contact with toroidy, they told me that the audio grade were designed to be less likely to vibrate and produce mechanical noise. Any experience on how silent the standard grade ones are ?

that is operating well below the knee of the magnetization curves, you are farther away from core saturation when we do this....this is the reason i run my traffos at lower flux densities than commercial offerings..
 
The Hart Kit 'Parts List'...describes the transformer as 300VA 50-0-50....not sure what you mean by the better option of a dual 0-50.
FWIW...the transformer I'm replacing is an ILP 73033...and old online pages from ETI (around '87 I think) just list the spec as : 300VA 50-0-50.
Should also say that I'm easily confused :)

dual 0-50 is quite standard with anteks i have seen, this enables you to use dual bridge rectifier configurations...

2416d1498953002-dual-bridge-rectifier-pcb-dbrb.png
 
Hi Kev,
I had a look at the circuit diagram as I've forgotten just about this version of the JLH amp - it uses fully regulated supplies both for the front end and the output stages so my advice would be to just go with the Canterbury units when they resume after the break, and yes, a centre tapped 50-0-50v is same as the original - keep it the same.

Just a curious thing, why has the transformer failed without killing off the regulated supplies?
Oh yes, the electrolytic caps are getting quite old now and could probably do with replacement - same thing for the other amp.
 
Hi Kev,
I had a look at the circuit diagram as I've forgotten just about this version of the JLH amp - it uses fully regulated supplies both for the front end and the output stages so my advice would be to just go with the Canterbury units when they resume after the break, and yes, a centre tapped 50-0-50v is same as the original - keep it the same.

Just a curious thing, why has the transformer failed without killing off the regulated supplies?
Oh yes, the electrolytic caps are getting quite old now and could probably do with replacement - same thing for the other amp.
Thanks James...waiting for reply from Canterbury as it happens.
Will be replacing the PS Electrolytics...at least.
TBH...I may have contributed to the demise of the toroid (cleaning!)...by allowing some moisture to get into the windings....can't be sure now:eek:
The big caps on this monoblock are definitely 'iffy'...one has some evidence of leaking...and both respond very oddly to my multimeter...both showing continuity to 'casing'...and from different pins...so they're going! :)
I'm assuming this was originally a standard grade toroid, so I'll replace with same.
Would a pic help clarify if this is a standard grade toroid??
 
Back then, the toroids were pretty big and heavy but seemed to be exceptionally good for sound - I remember getting Avel Lindberg to build some big 1kva units and they weighted nearly 12 kg! A/L were regarded as the benchmark toroid transformers that Levinson, Krell, etc used - I think the Polish and mid European trannies are regarded as "the best" trannies these days

Out here in Oz, we saw a lot of the UK made ILPs and PowerTrans and I still use some of these today in my class A amps - big, heavy but good trannies.

The Canterbury trannies that I've used seem to be pretty good - they seem to be the smaller sizes that you see from Farnell and RS - and I think will be perfectly okay with your regulated supplies, except there's a lot more rubbish on the mains these days that seem to get past the Shafner line filters and so maybe investigate the idea of adding a simple mains dc trap between the switch/fuse and primary of the trannie - I've found this to be quite useful in the simple power supplies that I tend to use.
 
Got this comment from former member pieter t:

"The difference between stock toroidal power supply transformers and so called "audiograde" toroidal power supply transformers is not specified.
What generally is meant with "audiograde" is that manufacturers use transformers with higher power rating than necessary for the job.
Toroids are very efficient transformers because of their electromagnetic geometry; form and absence of air gap mean comparatively low power loss.
This means that, for a given power, toroids are smaller than their EI or whatever counterparts.
Another "technical" advantage is that toroids have rather low strayfields.
Dimension and weight are important economic reasons to use toroids.
The problem however with many toroids is core excitation, expressed in flux density T.
Everyone using toroids is familiar with the inrush "oomph", requiring NTC resistors or other means not to blow fuses, and sometimes "DC blockers" to prevent core saturation.
This high inrush current comes from the fact that, because of the efficient electromagnetics, the toroid responds instantaneously when line voltage is switched on.
EI, and other transformers with some sort of airgap and/or less efficient geometry respond less brutal; they therefore have less inrush current.
Winding toroids with less inrush current is not so difficult but normally not done.
To do so, flux density must remain low, preferably maximum 1 T, instead of the "standard" 1,7-1,8 T for off the shelve toroids.
For lower flux density it is necessary to wind more turns on a given core.
More turns mean more required winding space, hence a larger core is required for a low T toroid with the same power as a "stock" high T toroid.
So here "better" is larger, heavier, more expensive.
When you need a high quality toroid with even lower strayfields, find one with low T, and preferably a screen between primary and secondaries (ask the manufacturer for the specs).
A very good, but less acknowledged alternative in the "audiophile" arena is a power supply transformer wound on a c-core (in between toroid and EI for efficiency).
With a c-core it is easy to apply minor air gapping to prevent hectic inrush current, so we don't need NTC resistors or other "inrush current fighters" and DC blockers.
Besides, unlike toroids, c-core transformers (like EI transformers) can be wound tightly, with no "crossing" of windings, so there is less risk of noise caused by resonance (Monolith Magnetics is a manufacturer doing high quality c-core transformers)."
 
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Hello,
I am no technician at all regarding electronics but it seems the last post contains more information than all other post together.
Maybe there are more technicians that know like Pieter how to make a near perfect or the ultimate one.
It is probably 100% true that a 300VA double c core made by Pieter will sound better than a 600 VA big mushroom. It also seems to get more and more and more ( yes triple) important to create as much "" isolation " between primary and secundairy side because there is so much garbage coming from the mains. I remember that in the nineties the French l'audiophile magazine already wrote that some EI core provided with a screen sounded so good because of their limited bandwidth.
Greetings, Eduard
 
there is a basic reason why audio application of a toroid transformer is more challenging.
the rectifier current only flows during a small portion of time,at the peak of the voltage.so the peak to avg current ratio is very high, and the resistance of the copper has a big effect. for audio use the copper crosssection need to be much bigger than for ac lighting use. usually a higher rating transformer is chosen, but specifying a bigger Cu crossection does the job as well.
 
Have you confirmed the primary voltage rating and the physical size of any replacement part are the same as OEM part?

It is plausible that a new part rated for say 230V, may become a problem when replacing a 240Vac rated part, as the flux level may already be sitting higher at 230Vac. Some transformers may also provide a primary voltage tolerance.

Some transformers may have all fly leads coming from one location, or separated, so orientation and lead dress may become a problem.

Can you elaborate on how you concluded the transformer was faulty, given it is a 40 year old amplifier?
 
I find the toroidy transformers to be excellent. I have a number of them in power amps, utterly silent, no hum, easy orientation and with low apparent stray field. At least as good as the audio spec, dersted, goss band, 700va part I have from Cantebury. For the money I find them hard to beat.
 
I find the toroidy transformers to be excellent. I have a number of them in power amps, utterly silent, no hum, easy orientation and with low apparent stray field. At least as good as the audio spec, dersted, goss band, 700va part I have from Cantebury. For the money I find them hard to beat.
Thanks. for this....hoping to get an order off in the next couple of days, before the 'fun' starts after January 31st:)
 
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