A-10 clone from Crimson Transformers

rackmonkey

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Came across this randomly on ebay. An A-10 reproduction from Crimson.

https://www.ebay.com/itm/Crimson-Audio-Transformers-CT-A10-UTC-A-10-equivalent/124186059462?hash=item1cea10e2c6:g:srIAAOSwGPdeuxyD

Crimson have been around forever, and I own a couple of the SM-57 bodies w/different transformers in them they've made for ages. I also own a couple of DI transformers from them. All are good products.

I sent a message to John, the owner, asking how he went about it without the original lams (or if he managed to find some old stock). This was his response:

Hi Bryan,

The original lamination is certainly not available to me (and I don't think anyone else and I've been making transformers since 1978) and that has always been a huge problem in making a clone. The physical size and shape of the lamination is inextricably tied to the resistance and inductance in any transformer. In my mind and experience, the relationship between those 2 define the sonic nature of a transformer more than anything else outside of the actual turns ratio.

We found a way to modify a standard lamination, and together with a custom winding form, create a "package" that has almost exactly the same length per individual turn as the original. With that in hand, we needed to combine it with the other inhabitants of transformer world - materials and manufacturing techniques - in the right mix to come up with something that could duplicate the original. It took a lot of calculations and too many protos checked against the original to count, but we were finally able to match the T/R, FR curve, THD, inductance and resistance of the original.very, very closely. The A series contains elements of almost everything I have ever learned about transformers and transformer construction. I'm pretty sure it's one of those "I had to go there before I could get here" kind of things for me.

Now that we have cracked the "A" code, the A24 is ready for take off, to be followed by the A11 and A20.
.


The header they managed to source would seem to make it drop-in as a replacement, as the footprint is the same size as the A-series footprint.

Interesting development, with all the usual caveats about the difficulty of an endeavor like this. I went ahead and dropped the dime for one and will test it when it arrives.
 

lassoharp

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but we were finally able to match the T/R, FR curve, THD, inductance and resistance of the original.very

It would be nice to see those numbers in their 3 pg PDF "data sheet" . . . . . . . after all, those numbers are data.
 

rackmonkey

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I sent an email asking about that. Will update.

This is interesting. They make a 5 lead version with the windings connected in series internally for 1:10 ratio (plus a shield ground), for $20 cheaper ($75). Looks like they'll do a custom ratio on the same platform for about the same price:


This 5 lead option also makes it much easier to generate custom variations. The A10 is historically significant, but it’s also a great mic input xfo package. It’s large size and hum bucking construction would produce great results as a 1:2, 1:8, or 1 to almost anything. FYI - most custom variations will cost about the same as the base CT-A10L
 

Winston OBoogie

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Hey, hadn't heard of those, thanks.  A-10 is a good one to be kicking off with.

Just out of interest, does anyone know if dear departed Oliver Archut's A series of transformers are  still being made.  I suppose I could/should just email TAB and ask now that I thought of it, doh  :-\

I'd like to try one of Crimson's as a mic in anyway.

Cheers
 

rackmonkey

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Last time I emailed Oliver's people, they said that the A series was still a work in progress. This was maybe 2 or 3 years ago. I never saw any for sale on their site. But I haven't checked in a while.
 

Winston OBoogie

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rackmonkey said:
Last time I emailed Oliver's people, they said that the A series was still a work in progress. This was maybe 2 or 3 years ago. I never saw any for sale on their site. But I haven't checked in a while.

OK gotcha.  Yeah wasn't sure if they'd ever been completed or?  Thanks dude.
 

rackmonkey

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Just went back and looked on their site for the first time in a while, and whaddya know...they are selling an A-10, A-24 and A-26.

Minimum order 10 pcs.
 

Winston OBoogie

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rackmonkey said:
Just went back and looked on their site for the first time in a while, and whaddya know...they are selling an A-10, A-24 and A-26.

Minimum order 10 pcs.

OK, good to know  Ollie finished the A24 too.  Can't remember what the A-26 is,  15K:600 ?   

10 pcs min is too rich for my blood but, I'll hold a thought for them being available at a fair premium in singles maybe.

Thanks again for the Crimson A-10  info
 

shabtek

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Jeff S sells an a-11 remake that is likely made by crimson and marketed for use as a DI "31.5:1 ratio to be used for some absolute blissful magic"

anybody have one and care to do a sweep?
 

rackmonkey

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Looks like it's definitely made by Crimson. Good catch.

Maybe someone will have one and be willing to sweep it.
 

Winston OBoogie

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Heya Shabtek,
got your message, cool, thanks.
Just letting ya know your inbox is full dude
See ya
 

shabtek

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Sweep of utc top, ct a10 bottom.
.7dB difference in step up.
vert scale is 1dB
source 600 Ω
load 100k Ω
dcr of windings ≤10%
 

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shabtek

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utc has little more 'dirt' @ 0dBu 20Hz

.69% vs .263%. thd+n
 

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emrr

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I wonder what the UTC tolerance really is.  I had a pile of 10 once, and there were obvious sonic differences when comparing. 
 

rackmonkey

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Good question. I've had to sort A-11's for reasonable matches in a couple of different dual mic pres. Discernible differences even between units with the same can color.  And that was leaving the early black can units out.

The Crimson follows the shape of the high end well in the bode plot. Small-ish step up level differences are to be expected.

The "dirt" part is interesting. This is where core materials will make a difference. It'd be interesting to see numbers at several different levels.

But pretty promising so far, IMO, especially when you compare the differences to other vintage "clones". The Cinemag "equivalent" of the UTC O-12 and the Sowter version of the UA 175 OT for example. Quite a lot of sonic ground between the originals and the modern subs.

Thanks Shab.
 

justinheronmusic

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How do these compare sonically to the Sowter 4383? Would it be worth swapping the Sowter for the CT-A10 in my DLA2A?
 

CJ

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good news to hear!  nice pricepoint,  evilbay prices have become insane over the last few years,

 
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