There was a discussion over at Twisted Pears Legato I/V thread concerning the EUVL F5X. That I/V has no DC between +/- balanced outputs but does have common mode DC via ground and +/-. Vitalica, who has an EUVL F5X prototype, reported that they would not work together without a capacitor to remove the common mode DC.
So, I am wondering if after biasing via grounded X, can one remove the input ground reference (R100/102) as well as R21/22, and will this allow common mode DC on the input?
I don't think I want to advocate floating my power amp ground in order to cope with a IV converter which has a design problem (namely common mode DC).
In my design philosophy, I would choose to solve the problem where it arises, namely at the IV circuit.
A coupling cap is the easiest solution, but there are also many IV circuits that does not have a common mode DC and sound better.
Suggest you talk to NicMac by PM. He will have a few stories to tell about various IV's he tried with the 9018.
Patrick
In my design philosophy, I would choose to solve the problem where it arises, namely at the IV circuit.
A coupling cap is the easiest solution, but there are also many IV circuits that does not have a common mode DC and sound better.
Suggest you talk to NicMac by PM. He will have a few stories to tell about various IV's he tried with the 9018.
Patrick
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Star Point Grounding
The diagram of the PSU in http://www.diyaudio.com/forums/pass-labs/183362-f5x-euvl-approach-71.html#post2959552 does not show any path connecting from the star grounds of the main amplifier boards and chassis ground. The only connection is through the input cable shield to whatever signal source is driving the F5X. Does this mean that the amplifiers totally float if no source is connected?
The diagram of the PSU in http://www.diyaudio.com/forums/pass-labs/183362-f5x-euvl-approach-71.html#post2959552 does not show any path connecting from the star grounds of the main amplifier boards and chassis ground. The only connection is through the input cable shield to whatever signal source is driving the F5X. Does this mean that the amplifiers totally float if no source is connected?
Not allowed.
All mains powered equipment should have all exposed conductive parts connected to chassis.
The Chassis must be permanently connected to the Protective Earth. This last connection must be low impedance (short thick wire) to ensure the chassis voltage cannot reach lethal voltage during a mains fault condition. That main's fault current can approach and even exceed kA.
All mains powered equipment should have all exposed conductive parts connected to chassis.
The Chassis must be permanently connected to the Protective Earth. This last connection must be low impedance (short thick wire) to ensure the chassis voltage cannot reach lethal voltage during a mains fault condition. That main's fault current can approach and even exceed kA.
The F5X power supply schematic shows power-line ground (Protective Earth) connected to the chassis.
My question was about the star grounds associated with the 15 volt power supplies and amplifier boards. These appear to connect only to the input connector shield, which if unconnected would allow the amplifiers to float. Maybe that is ok. An alternative might be to connect the star grounds to chassis via back-to-back diodes.
I need to be careful what I post here.
The chassis should be earthed. So should be the shield in the Tx. As Andrew said.
For my own use, I do float the star ground of both channels.
In my own audio chain, the only place where the left and right channel Gnd's are connected is at the player.
The rest of the chain is all floating.
But I do use back-to-back diodes + 1R resistor + cap (see Fig. 4 of the following link) to tie both star grounds to the chassis.
Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
Patrick
The chassis should be earthed. So should be the shield in the Tx. As Andrew said.
For my own use, I do float the star ground of both channels.
In my own audio chain, the only place where the left and right channel Gnd's are connected is at the player.
The rest of the chain is all floating.
But I do use back-to-back diodes + 1R resistor + cap (see Fig. 4 of the following link) to tie both star grounds to the chassis.
Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
Patrick
No need to be careful.
If you recommend something potentially dangerous, I'm sure someone will recognise it and shout to the heavens how wrong that is.
But, from your description it sounds like you have incorporated a Disconnecting Network into your Safety Earth connection.
I tested a version of the DN and reported the results some years ago.
If you recommend something potentially dangerous, I'm sure someone will recognise it and shout to the heavens how wrong that is.
But, from your description it sounds like you have incorporated a Disconnecting Network into your Safety Earth connection.
I tested a version of the DN and reported the results some years ago.
Thanks Patrick. That was the answer I was looking for. It is similar to Nelson's grounding.
Am I correct to assume that the "back-to-back diodes + 1R resistor + cap" is done separately for each channel?
Davide,
I presume you bought the 35mm diameter caps because if our mistake.
We'll find a special solution for you (and anyone else in the same situation) so that you can still use them.
You may have to solder the wires instead of terminal blocks.
But that would be a minor imperfection.
When I am ready I shall post the solution here.
I hope some time next week.
Patrick
I presume you bought the 35mm diameter caps because if our mistake.
We'll find a special solution for you (and anyone else in the same situation) so that you can still use them.
You may have to solder the wires instead of terminal blocks.
But that would be a minor imperfection.
When I am ready I shall post the solution here.
I hope some time next week.
Patrick