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Old 14th February 2013, 05:39 PM   #1331
bcarso is offline bcarso  United States
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Quote:
Originally Posted by LuisMCP View Post
I have build a Sen I/V with a PCM1704 nos DAC.
I have two different power supplies, one for PCM1704 and other (floating) for Sen I/V.

DAC and Sen IV works fine, but there is a big hum noise.

I have experimented with and find:

1) Switching off the power don't remove hum !!
2) Disconnecting the DAC to Sen connections and noise don't changes.
3) Unplugging the USB does lower noise
4) Unplugging the power cord kills completely the noise.
Is the hum at the mains frequency precisely?
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Old 14th February 2013, 05:59 PM   #1332
LuisMCP is offline LuisMCP  Spain
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Quote:
Originally Posted by bcarso View Post
Is the hum at the mains frequency precisely?
Yes, 50 Hz

I have captured noise in a WAV file...
Attached Images
File Type: jpg hum.JPG (42.9 KB, 424 views)
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Old 14th February 2013, 09:12 PM   #1333
NicMac is offline NicMac  Italy
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Quote:
Originally Posted by LuisMCP View Post
I have two different power supplies, one for PCM1704 and other (floating) for Sen I/V.
Only one supply for the SEN? I don't know about the PCM1704, but I think you need two floating supplies just for the SEN with a SE DAC.

Last edited by NicMac; 14th February 2013 at 09:15 PM.
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Old 14th February 2013, 09:23 PM   #1334
LuisMCP is offline LuisMCP  Spain
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Quote:
Originally Posted by NicMac View Post
Only one supply for the SEN? I don't know about the PCM1704, but I think you need two floating supplies just for the SEN with a SE DAC.
A double PSU 0-18V and 0-18V...
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Old 15th February 2013, 12:26 AM   #1335
EUVL is offline EUVL  Europe
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Try two separate R-Core each one 18V for one channel of SEN.

But perhaps before you try that, buy 4x 9V batteries and enjoy the music first.
At least you would have more motivation to sort out your 50Hz problem.
And it is obvious where it comes from.

The rest has been discussed here often enough.


Patrick
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Old 15th February 2013, 06:53 AM   #1336
LuisMCP is offline LuisMCP  Spain
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Quote:
Originally Posted by EUVL View Post
Try two separate R-Core each one 18V for one channel of SEN.

But perhaps before you try that, buy 4x 9V batteries and enjoy the music first.
At least you would have more motivation to sort out your 50Hz problem.
And it is obvious where it comes from.

The rest has been discussed here often enough.


Patrick
I see.

It seems that Interwinding Capacitance in power transformer is a major issue here.

I would try with EI transformer, or perhaps a Faraday Shielded one.

Another solution could be a Common-Mode filtering in the 0-18V DC power-line

I never had suffered this problem before, nor have used a Floating PSU. I suppose that floating PSU of Sen IV is specially sensible to hum induction.. is it?

On the other hand, I meanwhile clarifying my ideas with your invaluable help and support

Regards,
Luis.
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Old 16th February 2013, 08:55 PM   #1337
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Hi Luis,

I've got a total of four R core transformers each one feeding a separate SEN channel via choke regulation, RCRC filters and then Salas Regulators. There is still some very low level hum getting through which is only noticable during low level (late night) listening which I am trying to get rid of.

Yesterday I fitted four 39mH 0.9 ohm common mode chokes just before the final 6800uF capacitor in the filtering. This had absolutely no effect on the (very low) level of mains hum which surprised me a little as the cut off frequency is 10Hz so I would have expected 100Hz to be attenuated by 40dB or so. However there was an unexpected and quite pronounced sound quality improvement to mid range and treble detail and imaging.

I am planning to try an isolation transformer in the feed to all 4 of the R Cores to see if that allows them to float free of the earth reference. I'll post here on its effect.

John
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Old 17th February 2013, 12:52 AM   #1338
bcarso is offline bcarso  United States
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Quote:
Originally Posted by John Luckins View Post
Hi Luis,

I've got a total of four R core transformers each one feeding a separate SEN channel via choke regulation, RCRC filters and then Salas Regulators. There is still some very low level hum getting through which is only noticable during low level (late night) listening which I am trying to get rid of.

Yesterday I fitted four 39mH 0.9 ohm common mode chokes just before the final 6800uF capacitor in the filtering. This had absolutely no effect on the (very low) level of mains hum which surprised me a little as the cut off frequency is 10Hz so I would have expected 100Hz to be attenuated by 40dB or so. However there was an unexpected and quite pronounced sound quality improvement to mid range and treble detail and imaging.

I am planning to try an isolation transformer in the feed to all 4 of the R Cores to see if that allows them to float free of the earth reference. I'll post here on its effect.

John
Another experiment that can be illuminating in disentangling electric field effects from magnetic ones: get a little E-I core transformer and energize its primary from your mains. Leave the secondaries open. Use it as a stimulus probe and move it about your circuit.
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Old 17th February 2013, 12:21 PM   #1339
LuisMCP is offline LuisMCP  Spain
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Quote:
Originally Posted by EUVL View Post
You switch the ZEN IV on and the charger off at the same time.
So when you are not playing, the charger is always on (at my home 24 hrs for days on).

Relays is low current. I use Omron G6S. 12V or 24V depending on your control circuit.


Patrick
Hi Patrick,

Why use a Relay instead a simple switch?
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Old 17th February 2013, 12:26 PM   #1340
LuisMCP is offline LuisMCP  Spain
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Quote:
Originally Posted by John Luckins View Post
Hi Luis,

I've got a total of four R core transformers each one feeding a separate SEN channel via choke regulation, RCRC filters and then Salas Regulators. There is still some very low level hum getting through which is only noticable during low level (late night) listening which I am trying to get rid of.

Yesterday I fitted four 39mH 0.9 ohm common mode chokes just before the final 6800uF capacitor in the filtering. This had absolutely no effect on the (very low) level of mains hum which surprised me a little as the cut off frequency is 10Hz so I would have expected 100Hz to be attenuated by 40dB or so. However there was an unexpected and quite pronounced sound quality improvement to mid range and treble detail and imaging.

I am planning to try an isolation transformer in the feed to all 4 of the R Cores to see if that allows them to float free of the earth reference. I'll post here on its effect.

John
Have you try to put the chokes in the output of your DC line, i.e. between PSU and Sen IV?
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