Attenuator pad question

[AndrewT]

the "grounding" resistors are not really that.
They connect Signal Hot to Signal Cold, i.e. from Hot pin to Cold barrel of the input socket. keep this loop very small and compact. It acts like an aerial picking up interference and the bigger the loop the bigger the interference. That was the advantage of locating the attenuator inside the metal barrel of the plug. The screening effect of the metal barrel attenuated the interference.
Now that you are inside the amp, the biggest interference are the mains current loops.

 

[mimmo]

Hi Andrew,

Thanks for your input.

I think I understand the basics of how attenuator pads work in general. So, you suggest that I should stick with attenuators soldered directly inside rca plugs?

But should I be aware other issues than possible interference if all of the ground resistors are connected tied together via audio ground.

Thank you for your time on this!
M

 

[DF96]

After trying few integrated and pre+power amp combos I have come to a conclusion that my problem really is related to having excess gain.

I told you this in post 4.

If I would like to solder attenuator pads directly to the rca sockets inside the amp should I expect problems as all of the audio grounds are tied together? Or can I simply make individual pads on each input sockets and just connect all of the grounding resistors to audio ground?

Each RCA socket must have something already connected to the outer tag. Use this as the ground for the attenuator pad on that RCA. No need to connect separate grounds, or separate connected grounds. Just use what is already there.

 

[mimmo]

^
Yes, I am aware that you partially mentioned the possible problem with overall gain. And it has also been knocking at the back of my head as well. I just wanted think out loud that after trying various combinations the excess gain is really the issue here. Sorry if not being clear enough.

And I appreciate your instructions regarding the pads inside amp. As I have the resistors around I guess it doesn't hurt to try it as I can always go back to previous. In the worst case I just move the Hypex to my studio and use it there...
We'll see.

Thanks again for figuring things out!
M

 

[AndrewT]

Is your Hypex fitted with a balanced impedance input?
If so, then you need to maintain that balanced impedance for the connection to the input.

 

[mimmo]

Hi Andrew,

I am not using balanced input.
I followed this when wiring the inputs (Dropbox image link):

https://www.dropbox.com/s/u87e7wbaxf4g9qv/Screenshot_20161208-150426.png?dl=0

 

[AndrewT]

attach your info.
How have you disabled the balanced impedance input?

 

[mimmo]

Hi Andrew,

I am not sure if I am following, I try to..

I haven´t altered the balanced impedance input otherwise than my wiring.
As I mentioned I have followed the wiring guide from Hypex. So, this is how I have done it (but audio ground not connected to chassis):

An externally hosted image should be here but it was not working when we last tested it.

Should I be aware of something else needed?

Thanks for your patience!
Mikko

 

[AndrewT]

I suggest you change the socket to XLR, or mini XLR.
Preserve the balanced impedance as far back towards the source as you can.
Connect pin1 direct to Chassis. Then connect the screen to chassis, either via pin 1, or via an ultra low impedance connection.

There is a very easy and very cheap way to convert an unbalanced source to a balanced impedance source.
Jensen ap note 003 shows it. And B.Putzeys uses it for the output of his balanced volume control.