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Old 13th August 2012, 09:32 PM   #6731
RCruz is offline RCruz  Switzerland
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Quote:
Originally Posted by Stefanoo View Post
What I like the best is battery powered followed by a well designed shunt.

I tried battery alone, battery with some RC filter, but didn't sound as good.
Now that is a very good idea... off course you need a very large baterie because the shunt is allways working at full steam.

Sometime ago we discussed the idea that a shunt would isolate whatever is happening before it so a "normal" tx + rectifier + smoothing would be enough.

My experiments told me that even a change in TX is quite noticeable.
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Old 13th August 2012, 09:35 PM   #6732
Salas is offline Salas  Greece
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Quote:
Originally Posted by Stefanoo View Post
was that a comment to my post?
No, we just cross posted. It was something I forgot to mention. What comes last imposes its output characteristics for the PSU chain can refer to your PSU configuration preferences post also nontheless. *I was talking RC cells not battery ones.
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Old 13th August 2012, 09:42 PM   #6733
Salas is offline Salas  Greece
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Quote:
Originally Posted by RCruz View Post
Now that is a very good idea... off course you need a very large baterie because the shunt is allways working at full steam.

Sometime ago we discussed the idea that a shunt would isolate whatever is happening before it so a "normal" tx + rectifier + smoothing would be enough.

My experiments told me that even a change in TX is quite noticeable.
The CCS can filter well ripple and rectification noise up to a frequency but don't expect theoretical performance to hold much high as the loop paths and physical layout are nasty enough in any build bar RF engineered instrumentation, especially when low signal is involved. That is why people still seem to pick up various Tx and filter caps, or common mode chokes seem smoothing out, etc. Most important function is that the CCS does not shake the outside nodes with signal demand. It also sets high bias for the output parallel circuit.
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Old 13th August 2012, 09:45 PM   #6734
RCruz is offline RCruz  Switzerland
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Most important function is that the CCS does not shake the outside nodes with signal demand. It also sets high bias for the output parallel circuit.
Would you please explain that a little further Salas ?
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Old 13th August 2012, 10:06 PM   #6735
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That is what the Constant Current Source does, it supplies a constant current. Many argue that a constant current draw makes life easy for the transformer-diode-cap combination
that proceeds it.
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Old 13th August 2012, 10:15 PM   #6736
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Also theoretical, the high output impedance of the CCS could suppress distortion in the shunt. Yes, PSUs have distortion too. This mechanism is the same then driving a dynamic loudspeaker from a high output impedance amp. Distortion from varying input impedance are suppressed because the variation in the impedance is small compared to the high output impedance of the CCS.
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Old 13th August 2012, 10:20 PM   #6737
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Here is some information why distortion goes down with current drive :http://www.essex.ac.uk/csee/research...nt%20drive.pdf

Of cause a shunt is not a loudspeaker and i am not a great shunt designer but this mechanism COULD be at work.
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Old 13th August 2012, 10:47 PM   #6738
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Quote:
Originally Posted by RCruz View Post
Now that is a very good idea... off course you need a very large baterie because the shunt is allways working at full steam.

Sometime ago we discussed the idea that a shunt would isolate whatever is happening before it so a "normal" tx + rectifier + smoothing would be enough.

My experiments told me that even a change in TX is quite noticeable.
yes you need a little larger battery. It is also important to keep battery cells equally charged.
That is where a sophisticated power battery management system comes into play.
I would like to start this project out. I have been planning on working on this for my other projects, but I didn't have time till now.
It is a matter of choosing the right micro and the right interface and writing some code.
If there in interest in this I can start it out if people are interested with powering the phono up with batteries, which is a big plus from a hum standpoint!
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Old 13th August 2012, 11:14 PM   #6739
Salas is offline Salas  Greece
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Would you please explain that a little further Salas ?
As JG said. Plus you can arrange plenty extra current (with a heat penalty) to lower the parallel output circuit's impedance.
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Old 13th August 2012, 11:35 PM   #6740
Salas is offline Salas  Greece
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Quote:
Originally Posted by Stefanoo View Post
powering the phono up with batteries, which is a big plus from a hum standpoint!
The floating battery gives freedom from ground loop possibilities but its not an unsolvable issue with electronic PSUs also. I have shown this in another thread recently, its the FFT of a no PSRR JFET 20dB MC pre-pre (one high mS part only) driven by 5 Ohm Zo voltage divider. 5mV signal output, 0dB=1V. No 100Hz ripple or harmonics, 50Hz hum well suppressed for a 2m long single ended measurement loop. The PC was mains supplied. Although a battery can be a quick and sure way to avoid the hum headaches, it takes a major maintenance and control effort to really do it nicely. Gonna end up with Arduino like stuff if SOTA.
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