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Old 8th December 2004, 01:11 PM   #1
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Default Balanced DAC to unbalanced preamp (passive) conversions

My balanced DAC outputs are shouting out to be used so I have considered the technologies available and would like to know if anyone has tried any or all of these and have any comments that could help my search for an audiophile-standard converter:

SSM2141-the industry standard?

INA143-An upgrade to SSM2141

THAT1200-This is especially intruiging, sinec they claim some patented techmology which resulst in much better real-world CMRR

The usual bunch of very expensive metal chunks-Sowter, Lundahl, Jensen, etc

I tried an in-expensive "high qulaity audio transformer" from RS Components, made by Oxford Electrical Products, and even though it has a freq range of 20Hz-35kHz, +-1.5dB, it sounds quite good. Bass is not as deep as through the single-ended outputs, but highs are better, cleaner.

Any experiences anyone?
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Old 8th December 2004, 02:46 PM   #2
nuppe is offline nuppe  Sweden
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Default Re: Balanced DAC to unbalanced preamp (passive) conversions

Originally posted by Dr.H
THAT1200-This is especially intruiging, sinec they claim some patented techmology which resulst in much better real-world CMRR

I sent an email to Profusion (That's european distributor) the other day about availability of That's newer chips. They said "The THAT1200 series is due to us soon in sample quantities but the THAT1420 is yet to be released." I don't know where you are located, but i thought maybe you'd want to know if your based in europe.

I have no prior experience with any of the solutions you mentioned, but I have some INA2134 samples inbound this week for a preamp protoype. If i can get some That 1200's i'll try to set up a simple comparison.

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Old 8th December 2004, 03:34 PM   #3
Previously: Kuei Yang Wang
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Default Re: Balanced DAC to unbalanced preamp (passive) conversions


Originally posted by Dr.H
Any experiences anyone?
First, transformers are IMHO the way to go, bifilar type with mu metal core. Too many advantages over any electronic solutions for my taste to sidestep, also, once you account for good quality power supplies, passive components etc the cost of a pair of moderate level handling pro-audio line outputs is not that much higher.

Otherwise consider using a high performance dual Op-Amp (LM6172 comes to my mind), both sections operated as gain of 1 inverers, with the one inverting the negative polarity output also being fed the signal from the Op-Amp inverting the positive polarity output, needs 5 resistors of identical value (high precision) and one dual op-amp (high audio quality) and is likely much better a solution than any single chip solution.

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Old 8th December 2004, 06:06 PM   #4
mcs is offline mcs  Denmark
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I would probably choose the transformers. The OEPs have a reputation for sounding good, but with a slightly distorted low end - the cores are very small after all. I guess that description matches your experiences...

So try some from Lundahl or Sowter.

Best regards,

Mikkel C. Simonsen
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Old 9th December 2004, 06:15 AM   #5
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Thanks for the responses.

I spoke with the THAT distributor in the UK yesterday and he said that they would ship samples to me, so they may be available now.

I have spent more time listening to the pre-amp with the OEP transformer and I must say that it sounds surprisingly good for a $30 transformer! Highs are light, detailed, mids detailed and emotive, but again bass depth is slightly curtailed.
I am sorely tempted to try one of the greats, like Jensen and maybe I can ask them to send me a sample...just one channel to compare with the cheaper OEP.

Implementing the transformer is so simple that it may make sense in terms of parts cost etc to just go for the transformer.

Will let you guys know how this unfolds.

P.S. The rest of the system is a Theta DATA III, Theta Gen Va into the passive pre (a DACT volume pot) followed by a non-regulated LM3875 in non-inverted mode.
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Old 14th December 2004, 05:05 AM   #6
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Well, my THAT samples arrived today and they were kind enough to include not just the THAT1200, but also the -3dB and -6dB versions as well. Time for some comparison with the Oxford Electrical product trannies....
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Old 20th December 2004, 05:56 AM   #7
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Default OEP transformer vs THAT 1200

OK, had a chance to compare two ways to convert balanced audio to unbalanced:

The Oxford Electrical products "high quality audio transformer" from RS Components: Relatively good product, sweet mids, bass somewhat rolled off. Easy to install.

The THAT 1200 chip: Comes in a DIL 8 pin package. Requires just a +-15V power supply, an external cap and two decoupling caps. I also installed the optional anti-RFI circuit ahead of the chips inputs.

Performance of the THAT1200 is staggering vs the OEP transformer-The sound is open, seperated, very detailed, bass is amazingly detailed and powerful, down to the lowest notes. In contrast, the OEP provides a sound best described as warm, "everything mixed together" and indistinct for instrument placement.

The 1200's only drawback was that highs could be spitty and harsh, "digital-sounding", something the OEP smoothed quite well...
I am not sure if this will improve with time, i.e. whether the product requires a break-in period, although I suspect that this may be the case, since after a couple of hours I listened again and the highs seemed somewhat more resolved.

I still need to compare with a decent transformer like Jensen or Sowter or Lundahl though.
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