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Old 30th November 2012, 10:47 AM   #5711
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A resistive attenuator doesn't provide any isolation.
If the hiss is generated by the DAC output circuit, and if any volume margin available, providing some attenuation in input will increase the signal/noise ratio, thus reduce the hiss by the ratio of attenuation. 2 resistances, not a big deal.
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Old 30th November 2012, 10:55 AM   #5712
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Please, don't do that (audio trasfo). they are terrific if not super hight quality, and will destroy all the performance of your set-up. And they are super expensive if high quality.

May-be you have some margin of gain ? Add a resistance bridge or a potentiometer to reduce the volume and so, the noise of the DAC.
That's a broad generalization that could apply to any piece of electronics, not very constructive.. An example of a very nice xformer with stellar performance (not cheap ~$190,00 but very good imho)
http://www.jensen-transformers.com/datashts/dm2xx.pdf
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Old 30th November 2012, 11:04 AM   #5713
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If the hiss is generated by the DAC output circuit, and if any volume margin available, providing some attenuation in input will increase the signal/noise ratio, thus reduce the hiss by the ratio of attenuation. 2 resistances, not a big deal.
Sure - but if the problem is some ground loop or HF oscillation interaction with the DAC, as opposed to a pure DAC problem, we don't just want to attenuate the problem, we want to get rid of it.
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Old 30th November 2012, 11:38 AM   #5714
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not very constructive.. An example of a very nice xformer with stellar performance (not cheap ~$190,00 but very good imho)
"Oh lord, oh won't you buy-me a Mercedes Benz..."
60% the price of the amp, for something you cant assure it will solve the issue ? Very constructive, indeed.
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Old 30th November 2012, 11:42 AM   #5715
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60% the price of the amp, for something you cant assure it will solve the issue?
So how many times do I need to repeat "I am suggesting a cheap one (or getting one on loan) to see if the galvanic isolation solves the problem"?
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Old 30th November 2012, 03:05 PM   #5716
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You're quite right Julf, just wanted to reply to imho a to broad generalization about audio x formers.
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Old 30th November 2012, 03:09 PM   #5717
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You're quite right Julf, just wanted to reply to imho a to broad generalization about audio x formers.
I agree, Mark - audio transformers can be surprisingly good, and even their error modes aren't too bad (limited "ultrasonic" range, soft clipping when overdriven).
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Old 30th November 2012, 03:58 PM   #5718
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Default Additionally...

Some nCore users have reported excellent improvements in sound quality when coupling a DAC to the nCore via a tranformer of some type. Output transformers in the DAC, TVCs, and input transformers in the amp have been reported to result in sound quality improvements.
I noted that one DAC I tried with the nCore produced a course grainy noise floor (still only audible with an inch from tweeter), and have come to suspect that the nCore is sensitive to RF on its input (as are many class D amplifiers).
So, as Julf is pointing out, there may be additional benefits to reducing the gain of the Mytek DAC via a transformer which would justify the high price. Also, going amp direct, using a transformer to step down the voltage a little increases the current drive vs using a resistor based solution, and I find having higher current availability is a good thing when driving amplifiers directly as well.
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Old 30th November 2012, 04:14 PM   #5719
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I noted that one DAC I tried with the nCore produced a course grainy noise floor (still only audible with an inch from tweeter), and have come to suspect that the nCore is sensitive to RF on its input (as are many class D amplifiers).
sounds like what my DAC was outputting. kind of like a modulated buzzing noise.
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Old 30th November 2012, 06:45 PM   #5720
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I agree, Mark - audio transformers can be surprisingly good, and even their error modes aren't too bad (limited "ultrasonic" range, soft clipping when overdriven).
Well. it is a little like tube amps (because the use audio transformers ? ;-). Quite a natural sound, kill the magic of very fast systems.
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