MC transformers survey

[Marik]

Hello folks,

I am wondering what people would expect from a GREAT MC transformer.

The reason I am asking is we manufacture high quality toroidal transformers for ribbon and condenser microphones and looking if there would be a market if we come up with transformers for MC application.

What would be the parameters people are looking for that application: source impedance, operating levels and headroom, ratio, core materials, shielding, cost, what people are missing in the current commercial MC transformers, etc. etc. etc.

Please post your thoughts here, and who knows, we might come up with something that community would be interested in.

Best regards,
Mark Fouxman
Samar Audio & Microphone Design

[makaiyumtony]

Hi Mark
I prefer the sound with a MC step-up transformer than the high gain phono, all my friends and mine are custom made from Electric Print Audio, with silver, different cart need different load, gain 10 times is good for most low out-put carts, the only big issue is hum pick up, in my experience, better with a round housing then it can be 360 degree turn when it install into phono amp's surface to adjust hum pick-up. one more interest thing is a double housing, the transformer and inter and out side housing all isolate, transformer's iron and out side housing ground to the chassis, but the inter housing connect to a 10 to 15 dcv (open circute voltage only no current ), will make the sound quality change , if people don't believe that then try switch from 3v to 20v listen the different, you will get the answer
regard Tony Ma

[SY]

Low secondary DCR, high CMR, 1:10 to 1:20 (strappable), low LF distortion. It would preferably not ring with a 10k-47k load paralleled by 150pF.

[jcx]

another transducer xfmr requirement could be sensitive audiophile IEM - not iBuds, 200->1K US$ from UE or JH Audio for example

these may have 135 dB SPL re 1V sensitivity and the only sensilbe interface to any audio source is a step-down transformer

[Marik]

Originally Posted by makaiyumtony

Hi Mark
I prefer the sound with a MC step-up transformer than the high gain phono, all my friends and mine are custom made from Electric Print Audio, with silver, different cart need different load, gain 10 times is good for most low out-put carts, the only big issue is hum pick up...

Tony,

Toroidal transformers pick up MUCH LESS hum than EI (is it what Electra Print uses?) or even UI cores. In fact, in most of the cases we don't use any shielding for ribbon microphone transformers (usually, ratio of about 1:30--1:40).

So here would be another question, do folks make their own enclosure for the stereo pair? Then what material they usually use? Iron, mu-metal, etc.... If so, then most likely it won't need any shielding. On the other hand, we could pot the transformer in a mu-metal can, no problem, which should be more than adequate. It'd add some $15-$20 to the final price.

Originally Posted by SY

Low secondary DCR, high CMR, 1:10 to 1:20 (strappable), low LF distortion. It would preferably not ring with a 10k-47k load paralleled by 150pF.

From top of my head, I'd think for 2.5 Ohm source we could get the sec. DCR in some 5-10 Ohm range, depending on a transformer. If needed, we could go even down. Would it be good enough?
With our automatic winding machinery we use sectioned winding, so with those values the ringing should be way out of bandwidth.

The strappable would be no problem, however, what initially we were looking at is to make a range of transformers to custom fit a range of specific cartridges. In other words, instead of one generic transformer (kinda "fit it all" size) to make a range of different transformers highly optimized to each individual cartridge. The main questions here would be:

1) Is the optimized design would be something what people will be interested in, or some more "generic" types would have more appeal, and

2) What popular cartridges people use and how many transformer models would cover MOST of the cartridges out there.

Please keep them coming.

Best regards, M

[makaiyumtony]

Hi Mark
I am a DIYER, I did the enclosure by myself, not too many materials for me to shoose I use copper pipe with caps from pumping supply, the double housing not work for hum, hum can be reduced by turning direction, (different location of the phono amp get difference) add dcv to the inter enclosure result in sound quality change, add 3v sound soft but up to 20v that sound too hard like CD, so 13v is just good for my cart and amp, I don't know why ? maybe those voltage potential erase the self capacitor and self inductance of the wire
Tony Ma

[SY]

Would it be good enough?

One would think. A 2R DCR cartridge stepped up 10:1 will have an effective resistance of 200R, so the DCR you're talking about will barely affect the noise.

[EC8010]

Foil E/S screen between primary and secondary. Balanced leakage capacitance and inductance at each end of the primary. Primary winding floating. Yes, the primary ought to be good enough to give a nice CMRR with a balanced floating source. 1:10 ratio should cope with most cartridges. Lowest cartridge DC resistance I've seen is 3 Ohm; 10 Ohm seems to be typical.

[Scott594]

I'm currently using a Denon DL-103R, and a copy of a Mac head amplifier which has 4 set of inputs (10, 20, 40 & 100 ohm) allowing adjustment to suit the cartridge's output characteristics. What suprised me is how significant these input taps are, and that the cartridge prefers the 20 ohm input despite the cartridge being rated for a 40 ohm load. Based on this, and the variations of input impedance among different preamplifiers (which would be reflected to the cartridge), I would think that a multi-tapped primary would be a very desirable feature. It would allow use with most equipment, and experimentation by the user to best suit his system and tastes.
I've been wanting to try some transformers, but have been hesitant because I would most probably have to go through quite a few to hit the combo which works the best. I'd buy something with adjustable input taps because I'd be fairly confident there would be a setting that would work well.

[oshifis]

Inductance is another important parameter, just like for tube output transformers.