cheap input transformers

[dfuruta]

Hi,

Forgive me if this has been discussed - wasn't quite sure how to find it in a search.  Does anyone have recommendations for cheap transformers (less than $30) for the input on a mic preamp?  I've used Edcor xfmrs, but am wondering what else is out there I don't know about.

This is (obviously?) not for a high fidelity circuit.  I can work with different ratios, and am mostly interested in hearing any positive results you've found with cheapies.

 

[Max Willis]

You can use Edcor, OEP and Neutrik, all of them are cheap

 

[CJ]

you need shielding for mic levels, mu metal and copper, these metals are expensive nowadays,

you also need a nickel core which is expensive,

so you might try ebay for some used stuff,

Jensen has that 1:10 for 79 bucks which is a great transformer,

 

[PRR]

How cheap are you?

24V:240V power transformers are 1:10 ratio and you will never overload them. Use single-lump windings; when pri and sec are on separate legs of the core there will be large loss in treble. $10 to free.

The 2-bit ($3) wax-dip transformers for pocket radios are still around, the 2K:10K model has quite good response if driven low-Z and not too much bass.

Both are un-shielded. Keep them FAR from wall-power supplies and you may get away with it; or embrace the buzz.

The XLR-1/4" adapters *with* transformers often work remarkably well, and you get an XLR with it. They have modest shielding. If you gut the 1/4" shank you can mount the can so the XLR comes out the back of the box and run the secondary leads into your preamp. $25.

Car-sound suppliers have the RCA-RCA ground breaker which is two 1:1 transformers with a little shielding, $25.

Nickle lowers distortion, and indirectly extends treble by allowing similar bass in a smaller device. But not "cheap".

 

[Humner]

Nickle lowers distortion, and indirectly extends treble by allowing similar bass in a smaller device. But not "cheap".

Sorry to hijack the thread, but I'm curious about this. How much smaller can Nickel core transformers be?

I have a nickel core transformer with similar power handling (+20dbm at 20hz) to another transformer(but unsure of core type) however this nickel core transformer is almost half the physical size and weight of the other transformer. Is that to be expected? Both are used for similar applications - isolating 600:600

 

[Max Willis]

Both Neut

Does anyone have recommendations for cheap transformers (less than $30) for the input on a mic preamp?

The Neutrik ntm4 is mu metal shielded
http://www.neutrik.com/en/accessories/transformers/ntm4

OEP offers a mu metal shield can for their transformers

Both the Neutrik and the OEP shielded are less than $30

 

[john12ax7]

Altran is another budget friendly brand.

 

[dfuruta]

Interesting, didn't know about most of those - especially hadn't considered those 1/4 to xlr transformers PRR mentioned.

I'm not finding a source on the neutriks under $40 some (which, I guess, is still relatively cheap) - anyone have a lead?

Any thoughts on using steel cans or similar for shielding?  Too thin to do much?

 

[Max Willis]

Interesting, didn't know about most of those - especially hadn't considered those 1/4 to xlr transformers PRR mentioned.

I'm not finding a source on the neutriks under $40 some (which, I guess, is still relatively cheap) - anyone have a lead?

Any thoughts on using steel cans or similar for shielding?  Too thin to do much?

Try to call your local Neutrik dealer for a quote.

Or go for the OEP transformer

 

[Anthon]

OEP would be under 30 bucks, but they come without a shield. (you need to buy it separately).

If you don't want hi-fi and you want cheap - why not winding your own? I'm sure it would be a great experience and who knows - maybe you will end up with something special.

 

[dfuruta]

If you don't want hi-fi and you want cheap - why not winding your own? I'm sure it would be a great experience and who knows - maybe you will end up with something special.

It's true it'd be educational!  But, I suspect by the time I had a usable transformer it wouldn't be cheap 

 

[gyraf]

Monacor's LTR-110 is a cheap and almost decent 1:1+½ transformer - with a bit of work on zobeling it can give alright results.

From it's basic sound, I suspect there's quite a bit of Ni in it's core..

Jakob E.

 

[Audio1Man]

Hi All

An inexpensive way to shield input transformers is to slide a short Copper pipe or a Galvanized nipple over the transformer.

Duke

 

[JohnRoberts]

Hi All

An inexpensive way to shield input transformers is to slide a short Copper pipe or a Galvanized nipple over the transformer.

Duke

A copper tube could be like a shorting turn, but still isn't as effective as mu metal.

I recall tooling up some cheapo mic preamp transformers for use in install amps, and the chinese vendors we talked to didn't know what mu metal was at first. They finally figured it out, to get the business.

JR
 

 

[Audio1Man]

Hi All

An inexpensive way to shield input transformers is to slide a short Copper pipe or a Galvanized nipple over the transformer.

Duke

A copper tube could be like a shorting turn, but still isn't as effective as mu metal.

I recall tooling up some cheapo mic preamp transformers for use in install amps, and the chinese vendors we talked to didn't know what mu metal was at first. They finally figured it out, to get the business.

JR
 

Hi John

Yes, we need a shorted turn around the transformer to keep the Magnetic and or the Electric fields from coupling into the transformer windings.

Duke

 

[gyraf]

Copper will work for electrostatic shielding. Any thickness will do, as long as it's conductive.

For magnetic shielding, we need a soft-magnetic shielding material.

Iron or mu-metal. The thicker, the better - as magnetic shielding is about diverting the magnetic field, not stopping it (which is not possible).

So a piece of iron tube, with screw-on iron caps in both ends is probably the best of the cheap solutions. But be aware it could be mistaken for bombware.

Jakob E.