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Transformers for Balanced to SE conversion.

post #1 of 32
11/1/09 at 9:26am
Thread Starter 
So, the addition of two monoblock amplifiers has me left with a lack of space to fit my two racks side by side.

Sadly, the only possible alternate location for the "digital" rack requires approximately 25 feet of cabling between the DAC output stage and the preamplifier. Now, the DAC output stage has balanced outputs, whilst the preamplifier only has unbalanced inputs.

With the notion that balanced cable runs can be longer than SE without picking up hum/noise along the way, I was thinking that I can move the rack, implement 25 feet of length of balanced cabling, and then perform the Balanced/SE conversion near the preamplifier.

To do so, I could either go with an active solution [opamp?] or passive [transformers]. I would prefer the latter, and was looking for suggestions for a suitable pair of transformers I could mount into a small box with a pair of XLR and a pair of RCA connectors. Put this close to the preamp and problem solved.

So, any suggestions for a nice pair of transformers? Cinemag is an option, but am not sure which ones to pick. Lundahl is another, but I am a bit hesitant to leave the "affordable" category.

However, I understand performance is paramount at this link in the chain, so I would be up for anything reasonable.

Much appreciated.
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post #2 of 32
11/1/09 at 9:59am
DRV134 for chip and LUNDAHL LL1527 for transformer.
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post #3 of 32
11/1/09 at 12:58pm
Jensen doesn’t get much audiophile mention but are big in pro/oem transformers

they also have basic packaged stereo pro-to-consumer isolators ~ US$200 if you didn't want to make a box

JENSEN TRANSFORMERS, INC. - ISO-MAX® Audio Isolator Products
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post #4 of 32
11/1/09 at 2:37pm
Quote:
Originally Posted by bidoux View Post
LUNDAHL LL1527 for transformer.
Impedance is too low. The 1690's are more appropriate.

Lundahl: http://www.lundahl.se/pdfs/datash/1690.pdf
Cinemag: http://cinemag.biz/line_input/CMLI-15-15B.pdf
Jensen: http://www.jensen-transformers.com/datashts/11p1.pdf
Electra-Print: Electra-Print.com Moving Coil/Low-Level Input
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post #5 of 32
11/1/09 at 2:41pm
Quote:
Originally Posted by InSides View Post
So, any suggestions for a nice pair of transformers? Cinemag is an option, but am not sure which ones to pick. Lundahl is another, but I am a bit hesitant to leave the "affordable" category.
CineMag CMLI-15/15B.

What's the input impedance of your preamp?

se
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post #6 of 32
11/1/09 at 3:07pm
Quote:
Originally Posted by bidoux View Post
DRV134 for chip
DRV134 is a differential line driver (i.e., does unbalanced-to-balanced conversion), which is the opposite of what's needed here. The correct counterpart is INA134, a differential line receiver.

However, I think the THAT1206 is a better device.
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post #7 of 32
11/1/09 at 4:10pm
Thread Starter 
Quote:
Originally Posted by Koyaan I. Sqatsi View Post
CineMag CMLI-15/15B.

What's the input impedance of your preamp?

se
24kOhms. I had looked into the Cinemag, but the typical application notes schematics show the transformer in combination with active parts.

Is that necessary? If I go transformers, the idea was to keep it passive and off the grid. Also, Cinemags are a bit difficult to source since I am in Europe.

I had thought that the Lundahls are quite a bit more expensive, but I see that the price for the Lundahl LL1527 is quite good, and I can get it locally.

Quote:
Originally Posted by amb View Post
DRV134 is a differential line driver (i.e., does unbalanced-to-balanced conversion), which is the opposite of what's needed here. The correct counterpart is INA134, a differential line receiver.

However, I think the THAT1206 is a better device.
Thanks, Ti. I will look into the THAT.
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post #8 of 32
11/1/09 at 4:56pm
Quote:
Originally Posted by InSides View Post
I had thought that the Lundahls are quite a bit more expensive, but I see that the price for the Lundahl LL1527 is quite good, and I can get it locally.
Quote:
Originally Posted by dsavitsk View Post
Impedance is too low. The 1690's are more appropriate.
.
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post #9 of 32
11/1/09 at 5:00pm
Quote:
Originally Posted by amb View Post
DRV134 is a differential line driver (i.e., does unbalanced-to-balanced conversion), which is the opposite of what's needed here. The correct counterpart is INA134, a differential line receiver.
I was thinking of unbalanced to balanced conversion, sorry
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post #10 of 32
11/1/09 at 5:22pm
Thread Starter 
Quote:
Originally Posted by dsavitsk View Post
Impedance is too low. The 1690's are more appropriate.
Apologies, I must have missed your original post.

Looks like the Jensen's are a very viable option, and at a good price. Now to see whether they would be willing to ship to Europe.
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post #11 of 32
11/1/09 at 5:31pm
Quote:
Originally Posted by InSides View Post
24kOhms. I had looked into the Cinemag, but the typical application notes schematics show the transformer in combination with active parts.

Is that necessary?
Well, you're going to be using it in combination with active parts too, won't you? I mean, your preamp's not passive is it?

Quote:
Also, Cinemags are a bit difficult to source since I am in Europe.
Not hard to source. Just order direct from CineMag.

Quote:
I had thought that the Lundahls are quite a bit more expensive, but I see that the price for the Lundahl LL1527 is quite good, and I can get it locally.
As Doug mentiond, the 1527 isn't well suited for your particular application and recommended the 1690 instead.

se
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post #12 of 32
11/1/09 at 5:32pm
Quote:
Originally Posted by InSides View Post
Looks like the Jensen's are a very viable option, and at a good price. Now to see whether they would be willing to ship to Europe.
CineMags are just as good and cost less. And yes, they'll ship to Europe.

se
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post #13 of 32
11/1/09 at 5:58pm
Just as a side note...

The owner of CineMag is Tom Reichenbach. Tom's father, the late Ed Reichenbach, used to work for Altec designing transformers. He later started his own company, Reichenbach Engineering.

It was Ed Reichenbach who designed and manufactured the transformers sold by Deane Jensen under the Jensen Transformers name, until Jensen began manufacturing them in-house (which I believe happened when Ed retired).

Tom/CineMag owns all of Ed's engineering work, which includes the original designs Reichenbach Engineering did for Jensen.



se
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post #14 of 32
11/1/09 at 6:33pm
Also look at the Sowter 3575
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post #15 of 32
11/1/09 at 6:56pm
Quote:
Originally Posted by dsavitsk View Post
Also look at the Sowter 3575
Yeah.

Though Sowters aren't a transformer you actually want to "look" at if you know what I mean.



se
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