Building a symmetrical psu B1 buffer

[woodturner-fran]

If you have hum then realistically its a ground loop. The fact that when you disconnect the LS ground and still have music means that the ground part of the signal is still getting to the LS.

Think of 2 separate "grounds". One is the signal ground. the other is the safety ground or "earth". This earth is connected to the chassis and the ground pin of the IEC. The signal ground and earth are only connected at one junction, and separated by either a CL60 or 2 diodes (cheapy 1n4007 are AOK) wired 69 style, and then with a ~10R 5W resistor and 0.001-0.01uF >250V cap in parallel.

If you can configure it that way then you will have zero hum. But you must make sure signal ground doesn't contact the chassis anywhere.

Fran

[Malka07]

Thanks for your help Woodturner-Fran...Ive been trying hard to think where the signal grounds could be in contact with the chassis...is it posible that the metal standoff's im using for the boards are somehow causing this? coz apart from that i really cant think of anything else

Is there anything i could check with my Mutimeter Continuity function?

Alon

[AndrewT]

The signal lines coming in from the RCAs are not screened and not twisted.

This is one of the biggest problems with two channel amplifiers. How does one connect the source to the power amp and maintain an interference free connection from source to power amplifier through a pair of spaced apart RCAs?
Those two loops that are visible would be excellent aerials for transformer hum and EMI.

But the buzz is also a clue. It may be a PSU grounding error. Where is your main Audio Star Ground?

[Marra]

Does anyone know of a supplier other than Selectronique for R core transformers. I was going to order 2 because they seem to be the transformer of choice for the DCB1 but selectronique want payment by bank transfer which means an extra 30% on the bill! Thanks in advance.
Marra

[ClaveFremen]

Originally Posted by Marra

Does anyone know of a supplier other than Selectronique for R core transformers. I was going to order 2 because they seem to be the transformer of choice for the DCB1 but selectronique want payment by bank transfer which means an extra 30% on the bill! Thanks in advance.
Marra

I've buyed from Selectronic with Credit Card, I don't remember if via PayPal but I'm sure of it...

[Malka07]

Originally Posted by AndrewT

The signal lines coming in from the RCAs are not screened and not twisted.

This is one of the biggest problems with two channel amplifiers. How does one connect the source to the power amp and maintain an interference free connection from source to power amplifier through a pair of spaced apart RCAs?
Those two loops that are visible would be excellent aerials for transformer hum and EMI.

But the buzz is also a clue. It may be a PSU grounding error. Where is your main Audio Star Ground?

Hi Andrew, thanks for your help. The signal lines are a twisted pair, the only ones that ar'nt are the dcb1 output to output rca's as the wire are very short.

I have attached a labeled picture of my build, hopefully it will be more clearer as to whats happening with my build.



I also found out that on my optivol board, all the signal grounds are connected to each other...Input L/R and Output L/R all connected together.
Is this maybe why when i disconnected the Input grounds(doing this got rid of a loud hum, when chassis ground is connected) i still got sound, because the output grounds are still connected and they are connected to the input grounds on the board??? Have a look at the attached pic...



Also i dont have a main audio star ground?? i thought that this would be done on the boards...how would i do this??

Thanks for your help.

Alon

[regiregi22]

Originally Posted by Malka07

I wasn't expecting an improvement in SQ, i only did it because (1) I had a spare Shunt Reg and (2) I read somewhere that a clean power supply can help keep a fan quiet...so i thought id give it a go...

I would try to change a the fan for a better one. That is a really improvement, audible for any person, even if they don't know anything of HIFI they will be able to discern a clearly decrease in enviromental noise around the equipment.
And a very important thing, run it below 12v. 9v is ok but you can go lower. This bring the most important improvement in noise. Try it with a pot to control it.

Connect the CL-60 between the earth ground that comes from the IEC and the central ground of the DCB1 power supply, that's between the two big filter capacitors. The connect the ground from the IEC to the chassis. The rest of the audio input or output or Optivol grounds should be disconnected and isolated from the chassis. This point is very important.
Check with the DMM in continuity mode if there is a short between the RCA connectors and the chassis. It should have nearly the same resistance than measuring the CL-60 alone.
Yoour main star gorund should be between both big capacitors of the DCB1

Regards,
Regi

[Marra]

Originally Posted by ClaveFremen

I've buyed from Selectronic with Credit Card, I don't remember if via PayPal but I'm sure of it...

Thanks for that. I emailed them because I don't sepak or read french and they got back to me saying payment to be by bank transfer. I've sent them another mail so hopefully they'll let me pay by paypal.

[Tea-Bag]

Alon, what kinda 220R's you got? They look like Z-foils. Yum.

[AndrewT]

Originally Posted by AndrewT

But the buzz is also a clue. It may be a PSU grounding error. Where is your main Audio Star Ground?

Originally Posted by regiregi22

..............Your main star ground should be between both big capacitors of the DCB1

no.
That puts the charging currents in with the audio currents.
The main star audio ground MUST NOT be between the the main smoothing caps.
The Main Audio Star Ground can be after a short link from the main smoothing cap Zero Volts. Even 1mm of short link would do the job properly. MyRefC v1.3 uses the length of the plated through hole on the PCB as this separating link. It's just like Sugden have used, 1.6mm long and perfect separation.