OEP A262A7E For Mic Splitter

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Ricardus

WILL SOLDER FOR FOOD
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No longer in NY and below the Mason Dixon line.
Has anyone used the A262A7E to build an isolated mic splitter?

If I'm reading the specs PDF right, I should be able to get a dual split out of each transformer? Wire the primary in parallel with a single input, and then I should be able to take each winding of the secondary to its own isolated output?
 
0.5H is a very low inductance for mic signal.
It is an output xfmr designed to be driven with an almost zero ohm source.
You need at the very least 2H (actually 5H is the absolute minimum I would use).
You also need to consider it's not shielded nor humbucking, which makes it very sensitive to magnetic fields.
You may have to put them in a dual box made of thick steel (1.5mm at least) or expensive mu-metal.
Individual cans are available on their site. (£5 each)
Model A187A11C is better suited (2.82H), but AFAIK is not shielded.
 
mjrippe said:
If you are looking for inexpensive mic splitter transformers, I have some Sescom ones available.

I'm looking for a bunch down the road if my friend wants one of these boxes he's described to me. The OEP stuff is good and inexpensive, so I'll go that route.

I'll be designing some small PCBs and will make 4-channel modules that I can turn into any size splitter he needs in groups of 4.
 
abbey road d enfer said:
0.5H is a very low inductance for mic signal.
It is an output xfmr designed to be driven with an almost zero ohm source.
You need at the very least 2H (actually 5H is the absolute minimum I would use).
You also need to consider it's not shielded nor humbucking, which makes it very sensitive to magnetic fields.
You may have to put them in a dual box made of thick steel (1.5mm at least) or expensive mu-metal.
Individual cans are available on their site. (£5 each)
Model A187A11C is better suited (2.82H), but AFAIK is not shielded.

Cool Awesome suggestion.

Yeah. I know about the mumetal can they offer because I used them on the OEPs in my Boh Hansen DI builds. Sadly I can't find a dealer with this particular OEP in the US.

Do you have any other suggestions for good, inexpensive PCB mount transformers other than the OEP?
 
Ricardus said:
Cool Awesome suggestion.

Yeah. I know about the mumetal can they offer because I used them on the OEPs in my Boh Hansen DI builds. Sadly I can't find a dealer with this particular OEP in the US.

Do you have any other suggestions for good, inexpensive PCB mount transformers other than the OEP?
When I was in business, I had my own custom xfmrs made. They were a much bigger core (EI44) and cost about $6 in quantity of 100.
I had them made by a non-specialist winder, who didn't know a thing about audio, so it took a couple of prototypes to get a working product.
 
Newmarket said:
Intersetingly, and for clarity, it's listed on the Carnhill website under "Line Input Transformers"
Well, OEP is a power xfmr winder that got inadvertently in the audio business.
I did business with them in the early 90's, when I transferred manufacturing to the UK, originally for small power xfmrs.
Since I'd had a positive experience with subcontracting audio xfmrs to non-specialist winders in France, I did the same with OEP. I don't think they had anyone in the company that knew of frequency above 400Hz and dBu.
They became our main source of audio xfmrs, until we ceased using output xfmrs in our products. Then they added them to their standard catalogue.
As far as I can see, their technical knowledge in audio has not much improved.
 
Newmarket said:
Intersetingly, and for clarity, it's listed on the Carnhill website under "Line Input Transformers"
https://carnhill.co.uk/products/line-input-transformers/
If used with the windings in series, the inductance will be 2H. Also note that the inductance figure quoted is measured at 1KHz. It will undoubtedly increase as the frequency drops and could easily equal or exceed Abbey's 5H requirement at 20Hz (which is where it matters).

I have pointed out to OEP on more than one occasion that an inductance measurement at 1KHz is not useful and I am trying to get them to measure it at a more meaningful 100Hz instead.

Cheers

Ian

Most line input transformers these days are designed on the assumption that they will be driven by a very low impedance source
 
ruffrecords said:
If used with the windings in series, the inductance will be 2H.
certainly. However, for use as a mic splitter, that would result in a 6dB loss that would probably be unacceptable.

I have pointed out to OEP on more than one occasion that an inductance measurement at 1KHz is not useful and I am trying to get them to measure it at a more meaningful 100Hz instead.
Is there anyone there that understands that? It wasn't the case when I did business with them. they didn't even have an audio generator.
 
ruffrecords said:
If used with the windings in series, the inductance will be 2H. Also note that the inductance figure quoted is measured at 1KHz. It will undoubtedly increase as the frequency drops and could easily equal or exceed Abbey's 5H requirement at 20Hz (which is where it matters).

I have pointed out to OEP on more than one occasion that an inductance measurement at 1KHz is not useful and I am trying to get them to measure it at a more meaningful 100Hz instead.

Cheers

Ian

Most line input transformers these days are designed on the assumption that they will be driven by a very low impedance source

Have you had any response on the frequency issue ?
And thanks to Abbey for the background info'.
 
abbey road d enfer said:
certainly. However, for use as a mic splitter, that would result in a 6dB loss that would probably be te].
I agree. It is also not really a what I would call a line level transformer (apparently as said by Carnhil) since it has 3% distortion a 0dBu at 20Hz.
Is there anyone there that understands that? It wasn't the case when I did business with them. they didn't even have an audio generator.
I have no idea what test gear they have. I have spoken mostly with Chris Smith who has been most helpful in customising their transformers to my requirements and making the measurements I asked for, all at no charge. I even got the specially wound versions for the same price as the regular production version.

Cheers

Ian
 
ruffrecords said:
I have spoken mostly with Chris Smith who has been most helpful in customising their transformers to my requirements and making the measurements I asked for, all at no charge. I even got the specially wound versions for the same price as the regular production version.
Shows they are caring for the audio market.
 
abbey road d enfer said:
Shows they are caring for the audio market.
I agree. Chris wound three variants for me until I found one that met my spec. Then I purchased just ten of them at no extra cost. I like that kind of service for the small end user.

I have to say I have had great service from transformer manufacturers and the community. When I wanted to design a low profile version of a transformer originally designed for me by CJ, I decided on the required laminations and nobbins. These were not your usual EI laminations but UI ones. Generally speaking these are not readily available to the man in the street. However, I contacted my local transformer manufacturer ElectroMag who had made some of the original CJ design for me. They are in the trade, and although they do not normally use these lams and bobbins they agreed to but some for me. I had to buy enough to to make about 20 transformers. Then I sent a couple of sets to Volker who kindly transferred CJs design to the new format and make me a prototype. This tested better than expected so I passed Volker's design to Electromag who made as many as they could from the remaining material. In the end it performed better than the VTB2291 it was replacing for very nearly the same price.

Similarly, Brian Sowter has always been very helpful in creating variants of existing products for me, usually without charge.

Cheers

Ian
 
Here stateside, I have had good experiences with Edcor.  They have a small fee for initial setup/prototype, then a flat rate for any number of production.  My design was a replacement power transformer for a tube mic and several have been installed with no issues.
 
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