mounting RCA and speaker terminals on chassis

[jaimango]

These forums have been great for learning a lot about the topic of DIY audio, thanks everyone! This is my first post however, as I have not been able to find out about this simple question:

We are currently building a little chipamp from BrianGT. When mounting the RCA jacks and speaker terminals, do we have to make sure that they aren't actually touching the chassis somewhere? Or is it ok to have the signal ground touching the metal chassis? If they do have to be mounted without touching, what is the best way to do so? We are working with drilled aluminium panels here.

I know this may seem like quite a simple question, but I am quite new to this and I actually haven't been able to find out.

Thanks in advance.

 

[Nordic]

Signal grounds should be isolated from chassis or you'll get lots of hum.

 

[Vikash]

Welcome jaimango.

The jacks will come with two insulating washers (coloured plastic) which go either side of the panel and prevent the jacks touching the panel. The drilled holes should therfore be sufficiently sized.

 

[jaimango]

Thanks for all of your help, I'm happy to say no hums here.

In the end, the connectors I purchased didn't have any insulating washers; however I bought a multi-pack of plastic washers on ebay, and fit them to the back panel.

The threads on the connectors wouldn't fit (as the panel was 3mm Alu) but since it was so soft I just routed some washer sized holes through 1-2 mm and now it all fits together nicely.

 

[Conrad Hoffman]

For power amps I've successfully mounted the RCAs in the chassis, reasonably close together, with the chassis ground point right between them. The output connectors should never ground to the chassis. It won't work with phono preamps, but it might be possible with line stages. Not preferable, but possible.

 

[AndrewT]

mounted the RCAs in the chassis, reasonably close together, with the chassis ground point right between them.

that seems like a practical work around.
Presumably the aluminium (not steel) needs to be clean and corrosion free.
Is the Safety Earth elsewhere?

 

[jaudio]

Welcome jaimango.

The jacks will come with two insulating washers (coloured plastic)

Where can I buy just the washers?

 

[AndrewT]

Hi,
the two washers need at least one with a step to prevent the RCA coming into contact with the chassis.
The washers need to suit the physical dimensions of the RCA socket thread and length. The hole in the chassis needs to match the washer step and not the thread diameter.
You might be able to use plain washers and an insulating sleeve, but this would be a once only fiddle that may perform just as well.

 

[jb74]

plastic washers

http://mouser.com/

search for part # 561-SW25 (plastic shoulder washers I have used)

The online catalog page where that part is found will show
other washers as well

 

[jaudio]

Re: plastic washers

http://mouser.com/

search for part # 561-SW25 (plastic shoulder washers I have used)

The online catalog page where that part is found will show
other washers as well

Thanks

 

[jaimango]

I got my washers via ebay - here in the UK I did a search and wound up getting:

Nylon Washers. M5 M6 M8... 50 Mixed Pack.

I think you'll find it's always nice to have a few nylon washers of different sizes, especially if you are doing more work with the chassis,as they can really come in handy.

 

[artfuldodger]

This is a link to Mike Labuda's amp in the completed amps section of chipamp.com where he grounded the RCA inputs.
http://www.briangt.com/gallery/nigc-mlabuda/GainClone_005