Doepfer

Hello all . 

I am having serious humming problem in my modular system . 
I tried and still trying dozens of combinations and possibilities but in the end i couldn't succeed and wanted to ask some assist . 

I am using 4 x Doepfer A-100G6 housing . 

All connected to same power source and phase . 

I am using cwejman mx4s mixer connected to Cwejman AI2 than to Soundcraft Ghost which is my main mixing console . 

So far what i tried ; 

- connecting all the studio equipment on same power source (as a standart rule) : no change
- connecting ground points of 4 doepfer racks together : no change 
- connecting a part of chassis from ghost mixer to grounding point of doepfer cases : no change
- power regulator : no change 
- connecting same racks to my friends studio : no change 
- connecting power cables with reverse polar : no change 
- using DI box between Cwejman AI2 and Ghost mixing console : no change
- emptying racks completely and trying modules single by single : no change 
- connecting cwejman mx4s mixer to one empty case and connecting cwejman ai2 to the other case , or connecting them both in the same case : no change 

And as you can imagine i am a bit desperate at the moment , because i tried all the possibilities, and also suggestions from different people. 

I will be very happy if someone has an idea out of the things which i tried so far . 

thanks a lot

Hi

 > I am having serious humming problem in my modular system .


Did you monitor the Doepfer rig standalone (without any connection to 
the outside world but the powerconnectors - no MIDI!!!) and insert a 
headphone in a VCA out - it will be not extremely loud, but will be 
enough for checking. Is the hum also there without any connection to the 
outside?


If no: There is only one serious method for tracing a hum. Disconnect 
everything in your studio, and reconnect one cable after the other and 
check after each cable, whether the hum is added. And if i say 
"everything" I mean everything. All power cables, all audio, speaker, 
lan, midi, usb whatever cable. You start with no cable connected at all. 
Then you start from the beginning:

Poweramp to poweroutlet and speakers to Amp -> switch on -> check
Mixer to power and to Poweramp -> check -> switch Mixer on -> check
Reverb to power -> check -> switch Reverb on -> check
Efx-Send to reverb in -> check
reverb left out to fx return left -> check
reverb right out to fx return right -> check
and so on...

In my studio this took a whole day, but it was worth the effort.


BTW: To my experience today to most likely source for humming are USB 
midi or audio interfaces which are supplied by USB instead of a separate 
own powersupply.

Florian

Hello Florian 

First of all thanks for taking time and answering me ! 

Today i did exactly what you wrote here. I took all the audio and electricity cables out . 

My experience with modular system follows ; 

Lets say;

-you have a module in case A 
-you have same module also in case B 
- And you have your outputs going to your mixing console from case C 

When you connect the module in case A to case C , there is a hum . 
When you connect same module but from case B to case C , there is no hum . 

And sometimes if a module is making hum from Case A , when the time you connect another module from Case B somehow killing the hum coming from Case A . 

Another example ;

lets say you have Cwejman MX4S mixer in Case A 
And on Case C you have Cwejman AI 

When you connect them each other , there is no hum , but when take something from Case B to MX4S where it is connected to case A , with this chain , output from Case C is also starting to make hum . 

Seems like modules each other are able to kill the hum , but also modules each other are also creating the hum . 

If Cwejman MX4S mixer is on high volume, but no signal inside , this is reducing the hum coming out from AI2 . 
But when you start to volume down the channels of MX4S , hum is getting higher again . 


As summary , hum is getting high and low also if you start to play the volumes of the devices . 

Is it normal ? 
In this case , grounding 4 Doepfer cases are sense ? 
If yes , what is the proper method to do it ?  I have exactly the same yellow green grounding cable . What i tried was , connecting grounding points of the 2 racks together . 
But is that enough ? 

As an example of grounding each other ;

Case A > Case B > Case C > Case D 

After this point do i have to turn back from Case D to Case A too ? 


Well, these are my experiments . 






--- In Doepfer_a100@yahoogroups.com, Florian Anwander <fanwander@...> wrote:

>
> Hi
> 
>  > I am having serious humming problem in my modular system .
> 
> 
> Did you monitor the Doepfer rig standalone (without any connection to 
> the outside world but the powerconnectors - no MIDI!!!) and insert a 
> headphone in a VCA out - it will be not extremely loud, but will be 
> enough for checking. Is the hum also there without any connection to the 
> outside?
> 
> 
> If no: There is only one serious method for tracing a hum. Disconnect 
> everything in your studio, and reconnect one cable after the other and 
> check after each cable, whether the hum is added. And if i say 
> "everything" I mean everything. All power cables, all audio, speaker, 
> lan, midi, usb whatever cable. You start with no cable connected at all. 
> Then you start from the beginning:
> 
> Poweramp to poweroutlet and speakers to Amp -> switch on -> check
> Mixer to power and to Poweramp -> check -> switch Mixer on -> check
> Reverb to power -> check -> switch Reverb on -> check
> Efx-Send to reverb in -> check
> reverb left out to fx return left -> check
> reverb right out to fx return right -> check
> and so on...
> 
> In my studio this took a whole day, but it was worth the effort.
> 
> 
> BTW: To my experience today to most likely source for humming are USB 
> midi or audio interfaces which are supplied by USB instead of a separate 
> own powersupply.
> 
> Florian
>

Hello,

you did not truely answer the central question:

does the hum exist, if you do not connect the Doepfersystem to any 
mixer, but use a VCA-out or A138-Mixerout with an headphone?

If yes: the fault is in the Doepfer system.

If no: the fault is in the groundwiring of your power connections.


Florian

timbre1096 schrieb:
> Is it normal ? 
no

> In this case , grounding 4 Doepfer cases are sense ? 
> If yes , what is the proper method to do it ?  I have exactly the same yellow green grounding cable . What i tried was , connecting grounding points of the 2 racks together . 
> But is that enough ? 
The Doepfer system  needs no additional ground, but it definitely 
requires that all connected devices (A100 racks, external mixer, 
poweramp, effects) share one common power ground. The power connector of 
all A-100 racks MUST be three prong connectors and the multi power 
socket bar must use all three lines.

Florian