Stepped attenuator ground wiring

[PassionForSound]

Hi all,

I've just added a Dale resistor stepped attenuator to my SEX. Reading some comments over on the Crack thread at Head-fi there's discussion of shorting the earth. Currently I have the earths of the left channel shorted (in and out connected) and the right channel earths shorted (in and out). The left and right channel earths are currently not connected. Should they be?

Here are some average pics I took after installation. Hopefully they show enough.

 

[mcandmar]

Nope that doesn't apply to the S.E.X. amp, the Left and Right channel are kept separated all the way until the headphone socket.  I'll post up a picture of the attenuator wiring when i get home from work..

 

[Grainger49]

Oooo, I like the  looks of the attenuator.  The really odd thing is I want to build one.  I get a kick out of that kind of project.

 

[mcandmar]

Hopefully this will help as its the complete unit with input & output wiring. The section closest to the chassis was the right channel on mine, red wire from the input RCA connects to the upper most terminal, output red wire to tube connects to the lower, and the black wires from both the Input and Output connect to the ground ring at the very bottom.

The left hand channel is a mirror image, ground ring at the very top, then the output, then the input as you work down towards the chassis plate.  Note none of the channels are connected to each other, they are totally independent.

Only other thing to watch is the shield for both the input and output wiring should be joined together, but should not make contact with anything else. It should terminate to the chassis at the middle position of the tube socket standoff.

@Grainger: This is the DIY kit version i bought http://www.ebay.com/itm/DIY-kit-Dale-23-Step-Attenuator-for-Volume-Control-100k-/280321499342?pt=US_Amplifier_Parts_Components&hash=item414476a0ce believe me by the time you have all 96 resistors fed into place and soldered it wont seem like such a good idea anymore.

 

[Grainger49]

I think I would enjoy it as a half hour at a time sipping a brown liquid.  At the half hour mark I won't want to solder or measure resistors.  So to the next evening.

I'm looking at two mono 23 step attenuators for my FP 2.  Thanks for the link!

 

[mcandmar]

You will get a good few nights entertainment out of it so.  Rebuilding the gold point took me a few evenings to disassemble, clean, resistor match and reassemble.

 

[Grainger49]

I think I took 10 nights to assemble my Eros.  I kind of went nuts color coding the heat shrink on the STP for the signals.  I ran the jumpers for all the circuit boards flat against the PCB, they looked tidier.  It was a labor of love.

 

[mcandmar]

Oh don't worry i suffer from a bit of OCD too, all the resistor colour codes have to be orientated the same way so you can read them from left to right, it has to match the orientation of the labeling on the PCB, all components have to sit flush.  The attached pic says it all really, all the "DALE" marking and resistance codes had to be the same, and i had to ensure they were all perfectly centered between the two PCB's. That's after resistance matching them between left and right channels of course..its fun being me.

 

[JamieMcC]

Wow Mark nice job looks superb keep up the ocd! 

 

[PassionForSound]

Thanks everyone for your help. I couldn't see any signs of the earths being joined in the SEX so thought I had it right (and it was working well), but thought it best to double-check.

 

[Paul Joppa]

The input grounds in the SEX go to T12 and T22. At the top of page 23 in the current (v.2.1) manual you can see the short bare wire that connects T12 to the chassis at T13, and the long black wire that connects T22 to T13. T13 is the one and only, single-point chassis ground for both channels.