Salas DCG3 preamp (line & headphone)

Hi Andrew,

The two violet wires are shield wires from the trafos going to the chassis
the electrostatic shield/screen wires should each be short and each be connected to the chassis where they come out of the transformer insulation. These sheild wires pass interference from the mains to the chassis. To do that at high frequencies they MUST BE LOW INDUCTANCE. They must be short ! Otherwise there is no point in wasting money specifying a screen if you use a high impedance connection to the Chassis.
safety earth, the one black wire I think you are referring to is actually green and it is the safety earth wire from the IEC socket, and yes they are connected to a common chassis bolt.
the green or green/yellow PE wire should be permanently and mechanically fixed to the chassis. Not shared with other connections, that may be dismantled at some later time. It is worth making this close to the IEC socket rather than trailing across the Chassis.
I'm not sure how to reduce the loop areas of the input sockets,
I am not talking about the long coaxial cable. I am referring to the connection at the input terminal. The core/Hot has been exposed when you stripped off the screen/shield. The exposed core is not protected from interference. It must be short, very short. The screen has been twisted to form what we colloquially call a pig-tail. That too should be short. Now look at the gap between the pigtail and the hot connection. That gap creates an area. The bigger the area the more interference that is picked up. You must make the loop area small. Insulate the core/hot with a bit of tape. Push the pigtail right up next to the tape. That reduces your loop area. Using the screwed on tag makes the loop area bigger. Instead you can solder the very short pigtail to the end of threaded collar around the hot pin. This minimises the loop area. Do this for every low level socket.
the selector switch will be mounted on the front of the case, so the input wires need to make it up to the switch and pot.

I'm not sure what you mean by the exposed core.
Hoprefully explained clearly above.
If by pigtails you mean the low voltage secondary wires leaving the trafos, I left them long for now to test the PSU, once everything else is wrapped up and functioning I'll trim them short.

Paul
 
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Yes - those links just fitted in the holes :) I had the wire in front of me when assembling the board :)

I had 8 pcs byv79-e in a bag which I had never used and I did not want to store them anymore :) Thats the reason for trying them here. If they are not usable in this config It is easy to change them to the specified ones in the group buy.

I like those links they look proportional in that board space reserved for Rz/J

They are fine ultrafast diodes with soft recovery too. They are a logical choice I would say.
 
George, how was your offset? I forgot to ask. As I am am interested in how the AD823 copes statistically for its spec tolerances in various builds.

Offset +-0.5mV maximum that I measured over several minutes.
Also rails voltage sag about 0.1V when I connected the amplifier.
Andrew, I know, inputs will be replaced with shielded wire next time I open the lid. I just got fed up stripping cables! Although there is no ill effect I can detect, even on FFT, at least in my environment.
Also will try a 10K pot, as I have a DACT one to spare. For the time I have a 50K Tocos.
 
Left is original from TME.
 

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