Line Level Transformer Box HELP

[APMrecording]

Hi, I'm considering building a box with line level transformers to insert on the output of some transformerless mic pres and compressors I have. My knowledge in electronics is very limited so I'm seeking help to make sure the transformers I'm looking at will work.

I'm considering using a Carnhill vtb2280 because it's Carnhill and it's possible to wire it 600 600 or 150 600 which would be interesting to try.
It's a gapped design, will this work or should I use an ungapped transformer?
One alternative I'm considering would be the Edcor WSM 600/600.

 

[CJ]

you do not need a gapped design unless there is DC on the output which you hopefully do not have, maybe there might be a few mv if it is an opamp output but that is no big deal,

level is important, how many dB does the mic pre put out?

usually around 24 dB will work without overloading, unless you want overload, then you could use something rated at 10 dB,

API 2502 will work also if you want unlimited bandwidth, 

and Carnhill is good, the Neve output, ungapped version would be nice, can't vouch for the Edcor, never used it,

 

[ruffrecords]

The ungapped 600:600 Carnhill is the 2281. Sowter also do a number of 600:600 transformers that you could use. I have found Edcor XSM series to be surprisingly good - hard to measure any differences from Carnill equivalents. They used to be very cheap (about $15) but looking at their web site is seems they have put up the prices to nearly $24.

Cheers

Ian

 

[APMrecording]

Thanks for the info, I'll be going with an ungapped design for sure.

The mic pre (single tube, transformerless design) has a maximum output level of 27dBu, and the compressor has a maximum output of 20dBu.
I want to be able to overload the transformers, so I'm more inclined to the Edcor WSM instead of the XSM due to the lower maximum input voltage (10vrms for the WSM and 50vrms for de XSM).
I love the Neve sound and I would love to get Carnhill transformers, but unfortunately, I can't get info on these values for the Carnhill VTB2281.

The Sowter's are a bit too expensive, at this point I'm just looking to experiment.
Is there any other transformer you guys would recommend for such a project?

Thank you!
Antonio

 

[MountCyanide]

If I were to use transformers for effect I'd grab a smaller one made of steel like the Cinemag CMOQ3S or the easy-to-find-on-eBay Jensen JE-123s.

 

[APMrecording]

Thanks for the tip @MountCyanide, the Jensen JE-123s sounds like a good candidate.

I believe the Edcor WSM is also a steel core.

 

[ruffrecords]

Nearly all output transformers are steel cored because that is the only material that can sustain enough flux without becoming enormous.

You will find it very difficult to overload the Carnhill; they are at least twice the size of of the Edcor XSM. I have put +32dBu into a 2291 wired 2K4:600 without it saturating.

Apart from core size, the other think that makes transformers distort is frequency. Above 100Hz of so, distortion is more or less independent of frequency. But below that distortion increases as the frequency lowers so you will find it much easier to add transformer distortion to bass.

Transformer get an undeserved bad press for distortion. They are largely benign until overload, just like op amps. However, transformers have the happy property of lower intermodulation distortion relative to their harmonic distortion than almost any other device which means when the do distort, it does not sound godawful (unlike op amps).

Cheers

Ian