Relam Edcor Transformers?

[tk@halmi]

I was wondering if anyone has taken a stock WSM600/600 and replaced the core with 50% Ni lams? Where would I get such material in the US?

As I understand it would reduce low frequency distortion, but reduce headroom a bit also. If the new core would cost less than $10 it may be worth trying it. Less than $20 for a decent output transformer is not bad in my opinion.

Thanks ,
Tamas

 

[CJ]

Tamas, you can get 50/50 from Mag Metals. They might send you a free sample but you have to pay shipping. The lams won't help the high end, that's determined by the turns/coil structure. You could rewind it on a nickel core, but by then, the only thing that is original is the bobbin.

I do not know if going to 50/50 will help low end distortion. It might even make it worse if the flux levels are already too high. The main advantage of the nickel lams is that you need less turns to get the same amout of inductance as you would have on the M6 core. This means less capacitance which means better high end.

When nickel starts to distort, it does so in a nastier way than M6. At least from what I have seen on the scope. M6 will distort in a more gradual manner, whereas nickel tends to run clean until saturation is approached, then it gets ugly in a hurry. In situations where you have to take a lot of flux, M6 is used. But this is mainly in SE and push-pull outputs. All the McIntosh, Marantz, One Electron, Electraprint and other botique output iron is usually wound on an M6 core.

Measure the lam and post the dimensions. I might have some 50/50 for that x-former. Who knows, a 600:600 might benifit from a relam job since thare is only a 1:1 turns ratio.

 

[NewYorkDave]

[quote author="tk@halmi"]I was wondering if anyone has taken a stock WSM600/600 and replaced the core with 50% Ni lams?[/quote]

Why? It's an $8 transformer, for pete's sake. And you're making the assumption that the performance needs to be improved. You get a lot for your eight bucks. My friend Brian made some pretty thorough measurements of the WSM600/600, and here are some examples of its performance (low-Z source, 600-ohm load):

Response: -1dB at 6Hz and 300kHz

THD:
1 kHz, 0 dBm = 0.0085% +10 dBm = 0.005% +20 dBm = 0.0025%

100 Hz, 0 dBm = 0.03% +10 dBm = 0.015% + 20 dBm = 0.05%

50 Hz, 0 dBm = 0.055% +10 dBm = 0.035% +20 dBm = 0.18%

20 Hz, 0 dBm = 0.07% +10 dBm = 0.085% + 20 dBm = 0.7%

Spot checks at LF and + 20 dBm: 40 Hz = 0.3% 30 Hz = 0.45%

Insertion loss (600-ohm source and load): 1.5dB

My own measurements agree with Brian's, although his testing was more extensive than mine.

 

[PRR]

> -1dB at 6Hz and 300kHz ...... 50 Hz... +10 dBm = 0.035% ... + 20 dBm: 40 Hz = 0.3%

This is astonishingly good audio performance, even for a much more expensive transformer. You really don't need +20dBm at 40Hz, and 0.3% of iron-distortion is not the least offensive. At more musical tones and levels, distortion is point-oh and simple 3rd Harmonic, you won't hear that behind musical sounds.

A more embarassing test would be a 600Ω source. But these days, it is generally easier to have a zero-Z source than a 600Ω source.

 

[tk@halmi]

[quote author="NewYorkDave"]Response: -1dB at 6Hz and 300kHz

THD:
1 kHz, 0 dBm = 0.0085% +10 dBm = 0.005% +20 dBm = 0.0025%

100 Hz, 0 dBm = 0.03% +10 dBm = 0.015% + 20 dBm = 0.05%

50 Hz, 0 dBm = 0.055% +10 dBm = 0.035% +20 dBm = 0.18%

20 Hz, 0 dBm = 0.07% +10 dBm = 0.085% + 20 dBm = 0.7%

Spot checks at LF and + 20 dBm: 40 Hz = 0.3% 30 Hz = 0.45%

Insertion loss (600-ohm source and load): 1.5dB
[/quote]

I see.
Jensen charges at least $35 for a transformer with similar specs.

 

[NewYorkDave]

I forgot to mention a couple of things...

First of all, I measured the primary of the WSM600/600 at 6.9H and 41 ohms DCR, and the secondary at 6.8H and 44 ohms DCR.

Secondly, if you call Edcor to order transformers, be sure to ask for the "old style" with the low winding resistance. According to a friend who bought some recently, Edcor has been altering some models of matching transformers by using smaller wire to bump up the primary inductance at the request of one of their bigger customers. But this results in much higher winding resistance and greater insertion loss if used in an actual 600-ohm circuit. Edcor sent him the "right" transformers after he called them to ask about the high DCR, but you might want to be specific when you place your order. I hope they give the "new style" transformers their own part #s to avoid further confusion.

 

[CJ]

Hmmm, the ol black UTC A-20 had about 8 H of L, and gray version about 20H. Both are pretty flat, have about 70 ohms dcr, and about 1000 turns pri and sec.

So, if you wanted to change your "black" wsm to a gray version, a lam swap would do the trick. What is the cross sectional dimensions of the core?
We can calculate flux and see if the core would handle 15 db.

This would bump you up to about 16 H which is 2 k ohms at 20 hz, thus extending the bottom end down to 10 hz with 1k.

7 H is only 440 ohms at 10 hz.

What kind of core? EI? UI?

Do a listen test first. Remember, music is hardly a steady sine wave from a sig gen.

 

[tk@halmi]

As far as I know they are EI cores. I have ordered a few of these. They should be here by end of next week.