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I have a hum on my amp - will that help?

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JoachimStrobel

JoachimStrobel

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Seems like a ADC coupled to a Dac via Toslink would be another idiotic expensive solution.
 
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JoachimStrobel

JoachimStrobel

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Hello,

a while ago I posted that I will use the Ohlbacher 8 for achieving galvanic separation and wondered if it will impact the audio quality.
I have two of these devices in usage. One sits between a NAD T778 and a Parasound HCA1200 driving two centre speaker and one conditions a Parasound HCA1000 which drives the Height2 speakers.
While computing the DIRAC filters, I measured both loudspeaker pairs with and without the galvanic separator. The display is not good as I use Dirac Live for that and Powerpoint to overlay the two sweeps.

Nevertheless, one can see that for the centre (Canton RCL, no control box), below 100hz one losses 3-5 db with the Oehlbacher device. Dirac takes care of that. For the Height2, which are small Dali Fazon Satellites, I loose 1-3 dB below 100 hz which less important as they cross into the subwoofer/Mains at 60 hz.
 

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sergeauckland

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So,
I tried everything: no phono, plugs close, reversed, disconnect stuff….
I finally admitted defeat and used this Oehlbacher galvanic separator. No more hiss, all perfect. I just do not understand how the thing will not change the sound. I hear nothing, it sounds good.
A decent transformer is transparent, so won't change the sound other than to remove the ground loop. What distinguishes an expensive transformer from a cheaper one is that an expensive one will handle a higher voltage level at a lower frequency. As your transformer is handling line-level signals of the order of 1-2v, your cheaper transformer should go down to 20Hz without adding any detectable amount of distortion, whilst a Jensen or Sowter transformer will handle 5-10x that voltage level at 20Hz. Also, a Jensen or Sowter will do that into 600 ohms, whilst yours will have been designed on the assumption it works into a high impedance, so providing a benign load.

Good transformers are expensive, but if you don't need 10v out at 20Hz into 600 ohms, then a smaller and cheaper transformer will do fine.

EDIT:- Having just seen your answer about the level difference, yes an expensive transformer should have an insertion loss of around 1dB. Smaller and cheaper transformers will have a higher insertion loss, 3dB is normal. I'm surprised it's as much as 5dB.

S.
 

Mr. Widget

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Hello,

a while ago I posted that I will use the Ohlbacher 8 for achieving galvanic separation and wondered if it will impact the audio quality.
I have two of these devices in usage. One sits between a NAD T778 and a Parasound HCA1200 driving two centre speaker and one conditions a Parasound HCA1000 which drives the Height2 speakers.
While computing the DIRAC filters, I measured both loudspeaker pairs with and without the galvanic separator. The display is not good as I use Dirac Live for that and Powerpoint to overlay the two sweeps.

Nevertheless, one can see that for the centre (Canton RCL, no control box), below 100hz one losses 3-5 db with the Oehlbacher device. Dirac takes care of that. For the Height2, which are small Dali Fazon Satellites, I loose 1-3 dB below 100 hz which less important as they cross into the subwoofer/Mains at 60 hz.
While you can "fix" the frequency response with DSP, it is always better not to if you can avoid using the added filters. This is why I suggested the Jesen transformers. Yes they cost more, but they will not have the negative side effects.
 
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JoachimStrobel

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I totally agree that a more expensive transformer is better, while I like to mention that the ones I use are 60€ each and hence not a bargain either. However, I believe that the problem is the design of the Parasound amps that are fine pieces but I always struggled with them. So my plan is to either have them properly serviced (they are 25 years old) or replace them with 500€/piece new amps (of course returning those if they do not improve the situation)
 

Mr. Widget

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I totally agree that a more expensive transformer is better, while I like to mention that the ones I use are 60€ each and hence not a bargain either. However, I believe that the problem is the design of the Parasound amps that are fine pieces but I always struggled with them. So my plan is to either have them properly serviced (they are 25 years old) or replace them with 500€/piece new amps (of course returning those if they do not improve the situation)
Can you borrow different amps or return the new amps if making the change doesn't solve your issue? I agree that it is possibly the best solution, but it would be unfortunate if after spending a lot of money on new equipment you still had the same ground loop problems.
 
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JoachimStrobel

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Can you borrow different amps or return the new amps if making the change doesn't solve your issue? I agree that it is possibly the best solution, but it would be unfortunate if after spending a lot of money on new equipment you still had the same ground loop problems.
I try to borrow or do an Amazon thing.
 
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