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Old 6th November 2012, 07:49 PM   #7631
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You can use one pre-regulator for two Paradise boards though if you have enough current. Andrejs had that arangement in his system at Krefeld without hum problems.
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Old 6th November 2012, 08:19 PM   #7632
RCruz is offline RCruz  Switzerland
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Yes I know that.... I am actually using only one pre-regulator feeding the two boards and have been using that setup in other situations (my power amp for instance) but would like to profit from some better crosstalk isolation. The trouble is I am actualy working on a very tight budget and can not get another TX in the near future so I found this idea in the ESP pages.... Power Supply for Power Amplifiers
What bothers me more is that I can not identify the extra GND loop when going from one single prereg to two preregs in parallel using the same TX.
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Old 7th November 2012, 09:35 AM   #7633
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Just to make it clear I am using a single TX with single prereg without any hum.

I removed some components so you can view easily what I mean.... the two pics below represent the single prereg that I am using now (perfect) and the new layout I would like to try.

Please let me know if you see an aditional GND Loop in the double prallel prereg sketch
Attached Images
File Type: png SINGLE PREREG HUM FREE.png (24.9 KB, 260 views)
File Type: png DOUBLE PREREG.png (28.7 KB, 236 views)
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Old 7th November 2012, 09:44 AM   #7634
FdW is offline FdW  Netherlands
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Quote:
Originally Posted by RCruz View Post
Just to make it clear I am using a single TX with single prereg without any hum.

I removed some components so you can view easily what I mean.... the two pics below represent the single prereg that I am using now (perfect) and the new layout I would like to try.

Please let me know if you see an aditional GND Loop in the double prallel prereg sketch
If there is no hum in the first then I see no reason for hum in the second. Beyond that, check the player for the Q1, Q2 and Q3 connections.
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Old 7th November 2012, 08:15 PM   #7635
FdW is offline FdW  Netherlands
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Quote:
Originally Posted by RCruz View Post
Just one more question Frans, in your double mono schematic (two tx) I see you do not connect both grounds (left and right) together.

Also you do not make any reference to the output connections, so I admit we can leave both channels running completely independent without any common reference between them. What if there is a slight voltage difference between both channels grounds... does it procuce a current flowing in the output interconnects ? (I assume both output negatives will be joined inside the following preamp / power amp).
That’s right (spotted) and it is wrong (drawn). Check this out here is an updated (again) drawing In this new arrangement for 2 TX's the circuit/signal-ground is only connected (left to right) in the attached amplifier, no loops possible any ware. Your concern about voltage differences is cared for by the RX, RXL and RXR resistors.

Wow this is difficult to get right... but we will succeed
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File Type: png GroundLoopABCD.PNG (124.8 KB, 282 views)

Last edited by FdW; 7th November 2012 at 08:26 PM.
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Old 7th November 2012, 08:28 PM   #7636
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Quote:
Originally Posted by RCruz View Post
Regarding TT connections, IMO Q2 and Q3 are not common because in good setups, the four wires comming out of the cart are always isolated from each other.

Connection Q1 to C is normal if C is the tonearm tubing, but C does never connect to any wire comming out of the cart.

That is why a single TX + prereg works.
But no harm in checking I will leave the notes about it in the drawing.
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Old 7th November 2012, 08:42 PM   #7637
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Now it looks cool.... wonderfull idea those 10 ohm resistors to take care of gnd voltage fluctuations... I am really glad you cared to hep me in this subject.

Now about chassis grounding and TT ground connection.... My best results where obtained by connecting the chassis directly to mains earth and connect the circuit gnd to the chassis via the DDCR.

So A2, E2 and G should be all connected together forming a star but isolated from the chassis. The TT arm GND wire should then be connected to this star gnd and not to the chassis.

Please take your time to review this because these are my findings... not a rule
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Last edited by RCruz; 7th November 2012 at 08:55 PM.
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Old 7th November 2012, 08:49 PM   #7638
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This is an interesting discussion, thanks.
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Old 7th November 2012, 08:56 PM   #7639
RCruz is offline RCruz  Switzerland
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Please reread #7649 after my last edit
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Old 7th November 2012, 09:00 PM   #7640
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I connect my metall chassis Spiral Grove SG1 also to mains earth. That way i get dead silent results.
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