[KenCalgary]

Hello folks, I'm new to electronics and while I've been reading online information and reading several books on the topic I'm still a little confused about some grounding issues (although not the safety ground requirement). I am putting together a line stage (Aikido) and phono stage (Tetra) preamplifier using John Broskie's PCB boards. I'm using an aluminum black-anodized enclosure and have sanded off the anodize wherever a ground point will possibly occur. Both the Aikido and Tetra boards "holds a star ground at its center."

My questions relate to grounding of the PCB board. At the moment I do not have jumper 7 connected (see below) and am using 1/2" metal standoffs (I can either use aluminum or brass) to hold the PCB above the chassis. The RCAs are isolated from the chassis.

Q1: Does the PCB board need to be grounded to the chassis?

Q2: Do metal standoffs ground the PCB to the chassis (even if the jumper is not in place)?

Q3: If the PCB board isn't grounded, what is likely to happen?

Quote from PCB board booklet: "Chassis Ground:  Jumper J7 connects the PCB’s ground to the chassis through the top leftmost mounting hole. If you wish to float the chassis or capacitor couple the chassis to ground, then either leave jumper J7 out or replace it with a small-valued capacitor (0.01 to 0.1μF). Warning: if rubber O-rings are used with PCB standoffs, then the ground connection to the chassis is not likely to be made..."

[sts9fan]

A1: No but you might want a switch to lift it.  Also is this an all DIY setup?  You will want at least one of the componets in the chain signal ground attached to earth ground.  If you have a comerical offering it is likely that the signal ground is connected to earth ground.  You can check with an ohm meter. 
A2: Possibly but those boards are diesel so maybe not.  I have switched to nylon ever since I had this issue with an amp.
A3: Could be dangerous, remove noise or could do nothing. 

I am sure others will add more detail and correct me if I am wrong. 

[KenCalgary]

With regard to Answer One: I was going to connect the grounds of the RCAs (except for the phono RCAs which have a different treatment) with a bare copper wire and then connect that wire to the earth ground using a resistor. Would this be suitable to connect the signal ground to earth?

[sts9fan]

You don't need to do that.  They will all be connected through the standoff if you have it connected.  Just connect all signal grounds to their correct location on the board.  If you want you could put the saftey ground lug under that standoff. 

[KenCalgary]

It is my understanding that the signal wires (left and right) from input RCAs are connected to a selector switch which then is connected to the volume control. The volume control positive and ground wires are then connected to the PCB board. There is no direct connection for RCA input ground wires on the PCB board. That is the reason I was going to connect them with a bare wire attached to earth. I have seen another alternative which is to twist the signal wire with its corresponding ground wire but only connect the signal wire to the selctor switch. I believe this is used to reduce RFI/EMI.

Am I wrong? I really am new to this and not sure exactly what is best.     

[sts9fan]

It is my understanding that the signal wires (left and right) from input RCAs are connected to a selector switch which then is connected to the volume control. The volume control positive and ground wires are then connected to the PCB board.

How are you getting a ground from the volume control?

[KenCalgary]

I'm using a stereo step attenuator which has tab connections for the signal wires; you then attach separate ground wires to the copper wire where the resistors are soldered. See attached photo.

[sts9fan]

Why not just attach all the signal grounds to the copper wire in ne spot?  What amp are you gonna use?
Kris

[KenCalgary]

Hi Kris, since it is a stereo attenuator there is a right and a left channel so each channel has a separate ground. I'm using a Parasound 2250 solid state amplifier at least for the near future (and as funds require). The tube preamp will be replacing a Parasound 2100 solid state preamp which I purchased - along with the amp - because I wanted to be able to connect my audio-visual receiver using the by-pass circuit in the Parasound. This enabled me to use my front speakers for the AV as well as music. I've since upgraded the speakers.

I've discovered that as I made improvements to my audio system I listen to music more than movies so am gradually moving away from the combination equipment.     

[sts9fan]

So my assesment is this.  Attach the gronds to the attenuator.  Put a switch on the jumper that will connect the signal ground to earth but allow you to lift it.  Connect the earth lug under the standoff that connects the signal ground to earth.  I bet your amp has the signal ground connected to earth so ***I*** would float the signal ground in the pre as long as you are using the amp.  Rememebr everything is still connected to earth through the grounds of the interconnects.  Just test the amp to see if this is correct.  Use your ohm meter to test resistence from the RCA ground to the safety pin on the power IEC or cable. 

Kris