Doepfer

Hello Scott, 

Try to disconnect the Doepfer mains from earth. 

Jacco Ville
The Netherlands

HI

 

Thanks but that’s a very dangerous idea and not really a solution. There has to be some explanation of what’s going on and a much better, permanent solution. 

 

Scott

From: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com] 
Sent: Sunday, June 12, 2016 8:00 AM
To: Doepfer_a100@yahoogroups.com
Subject: [Doepfer_a100] Re: Loud ground loop hum

 

  

Hello Scott, 

Try to disconnect the Doepfer mains from earth. 

Jacco Ville
The Netherlands





[Non-text portions of this message have been removed]

Hello

1.) are the power supplies and the rack rails connected to ground?
2.) is your studios power distribution wired as star system? It must be 
based on a single wall outlet socket and then a central power "multiple" 
(I don't know the right english word for that, sorry). Or you must be 
very sure, that all wall outlet sockets are based on the same electric wire.

Florian


Am 12.06.2016 um 14:22 schrieb 'Scott Rogers' scott@scottfromcanada.com 
[Doepfer_a100]:

> HI
>
>
>
> Thanks but that’s a very dangerous idea and not really a solution. There has to be some explanation of what’s going on and a much better, permanent solution.
>
>
>
> Scott
>
>
>
>
>
>
>
>
>
> From: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
> Sent: Sunday, June 12, 2016 8:00 AM
> To: Doepfer_a100@yahoogroups.com
> Subject: [Doepfer_a100] Re: Loud ground loop hum
>
>
>
>
>
> Hello Scott,
>
> Try to disconnect the Doepfer mains from earth.
>
> Jacco Ville
> The Netherlands
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
> Posted by: "Scott Rogers" <scott@scottfromcanada.com>
> ------------------------------------
>
>
> ------------------------------------
>
> Yahoo Groups Links
>
>
>

Hi

 

1.      No the rails are not connected to ground. This is the way Doepfer built the box and I was not advised to change it.

1b. I do not know if the power supplies are connected to ground. They are covered metal boxes. I would have to rip them open to find out. There are ground wires in the power cables so I assume they are, however, my tech is telling me this is caused by a badly designed power supply so I can’t be sure. For info, I first bought a pre-assembled Doepfer Basis System 2 and then added 2 additional LC9 cases later.

 

2.      All power in the room comes from a reasonably good quality UPS that outputs a pure sine wave. There are over 20 synthesizers, a rack of effects and other synths, plus guitar pedals, other gear, 2 Genelec monitors, and a computer with 2 monitors, all powered from that one source. And as I said, there is no hum in the room except when I connect one of the Doepfer LC9 cases. When I patch something from a second LC9 the hum gets twice as loud.

 

3.      I suspect the power supplies will have to be modded to fix this so for now I have just purchased an Ebtech Hum Eliminator. I will put the audio output through this box for now and see if it removes most of the hum until I can find a more permanent solution. I have decided to do a little rearranging of modules since I had the main case apart anyway so I will report back in a couple of hours on how this works.

 

I’d still like to hear any other technical information or ideas that might help understand what is causing this, though!

 

Thanks

Scott

From: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com] 
Sent: Sunday, June 12, 2016 11:15 AM
To: Doepfer_a100@yahoogroups.com
Subject: Re: [Doepfer_a100] Re: Loud ground loop hum

 

  

Hello

1.) are the power supplies and the rack rails connected to ground?
2.) is your studios power distribution wired as star system? It must be 
based on a single wall outlet socket and then a central power "multiple" 
(I don't know the right english word for that, sorry). Or you must be 
very sure, that all wall outlet sockets are based on the same electric wire.

Florian

Am 12.06.2016 um 14:22 schrieb 'Scott Rogers' scott@scottfromcanada.com 
[Doepfer_a100]:
> HI
>
>
>
> Thanks but that’s a very dangerous idea and not really a solution. There has to be some explanation of what’s going on and a much better, permanent solution.
>
>
>
> Scott
>
>
>
>
>
>
>
>
>
> From: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
> Sent: Sunday, June 12, 2016 8:00 AM
> To: Doepfer_a100@yahoogroups.com
> Subject: [Doepfer_a100] Re: Loud ground loop hum
>
>
>
>
>
> Hello Scott,
>
> Try to disconnect the Doepfer mains from earth.
>
> Jacco Ville
> The Netherlands
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
> Posted by: "Scott Rogers" <scott@scottfromcanada.com>
> ------------------------------------
>
>
> ------------------------------------
>
> Yahoo Groups Links
>
>
>





[Non-text portions of this message have been removed]

Hi

 

Thanks for the info. I just bought an Ebtech Hum Eliminator which I hope will do the same thing for me. I’m just rearranging modules so I’ll reply with the results in a little while.

 

Thanks!

Scott

From: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com] 
Sent: Sunday, June 12, 2016 11:01 AM
To: Doepfer_a100@yahoogroups.com
Subject: [Doepfer_a100] Re: Loud ground loop hum

 

  

Hi Scott,

 

I have had the same problem. I still don't know what caused it, but putting a Proel Active D.I, box between the Doepfer's output and my amplifier did the trick - the ground loop hum was gone.

Hope this helps.

 

Kind regards,

 

Ton





[Non-text portions of this message have been removed]

Ok, the Hum Eliminator worked. It’s nice and quiet now. Not the best solution, but certainly the easiest. 

 

I still have a big problem with all my envelope generators but I’ll start another thread for that.

 

I’m still interested in knowing what the original cause of the hum is (and a solution) if anyone knows.

 

Thanks!!

Scott

From: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com] 
Sent: Sunday, June 12, 2016 12:48 PM
To: Doepfer_a100@yahoogroups.com
Subject: RE: [Doepfer_a100] Re: Loud ground loop hum

 

  

Hi

Thanks for the info. I just bought an Ebtech Hum Eliminator which I hope will do the same thing for me. I’m just rearranging modules so I’ll reply with the results in a little while.

Thanks!

Scott

From: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com] 
Sent: Sunday, June 12, 2016 11:01 AM
To: Doepfer_a100@yahoogroups.com
Subject: [Doepfer_a100] Re: Loud ground loop hum

Hi Scott,

I have had the same problem. I still don't know what caused it, but putting a Proel Active D.I, box between the Doepfer's output and my amplifier did the trick - the ground loop hum was gone.

Hope this helps.

Kind regards,

Ton

[Non-text portions of this message have been removed]





[Non-text portions of this message have been removed]

Hi Scott

> I’m still interested in knowing what the original cause of the hum is (and a solution) if anyone knows.

Hum can be a very complex topic. To know the cause one would have to 
know all your equipment and all the cabling. That is not doable via the net.

25 years ago I did a lot of installations and the reconfigurations of 
professional recording studios. To find the cause for a hum, we usally 
unplugged everything(!) and then reconnected one cable by one, testing 
after each new cable. We used a scope for the monitoring (sometimes also 
a battery driven speaker for listening) and started always with the 
device which seemed to have introduced the hum.

Typically people have a low level basic hum, which they ignored for 
years, and then they add a device which makes this (former) low level 
hum very appearent. So assumingly the Doepfer rack is not the cause, but 
it is the piece which "puts the finger" on the weak spot.


In modern computerized studios there is one device which quite often is 
the cause for hum: the monitor of the computer. But this is only a blind 
guess. But it is often helpful to remove all connections to/from the 
computer (USB, Firewire, analog out from the headphoneout of the 
laptop...) from the interface and the analog audiogear.

Florian

The hum is probably caused by a ground loop. Due to safety reasons all metal parts of the A-100 cases are connected GND AND to earth
shield of the mains connector. If another component in your system (e.g. mixer, power amplifier ...) is connected in the same way a
ground loop is generated. The problem is that the safety reasons (all metal parts connected to earth shield) contradict to the audio
connection rules (not GND loops). Possible solutions are:

using special cables with GND connected only on one side
DI boxes
disconnecting earth shield (not recommended)

Best wishes
Dieter Doepfer

> I’m still interested in knowing what the original cause of the hum is (and a solution) if anyone knows.
>
> Thanks!!
>
> Scott

Hello Dieter

On 13.06.16 09:34 , yahoo@doepfer.de [Doepfer_a100] wrote:
> The hum is probably caused by a ground loop. Due to safety reasons all metal parts of the A-100 cases are connected GND AND to earth
> shield of the mains connector.

Scott wrote
"No the rails are not connected to ground. This is the way Doepfer built 
the box and I was not advised to change it."

These are LC9 cases. Are those cable in a different way?


Florian

Each of the 3.5mm sockets has a GND terminal and as soon as a connection is made to external equipment a GND loop may occur.

If the rails are connected to GND/Earth or not is not that important (though they are finally also connected to GND/Earth via the
front panels as soon as modules have been installed).

Best wishes
Dieter Doepfer

> Hello Dieter
>
> On 13.06.16 09:34 , yahoo@doepfer.de [Doepfer_a100] wrote:
> > The hum is probably caused by a ground loop. Due to safety reasons all metal parts of the A-100 cases are connected GND
> AND to earth
> > shield of the mains connector.
>
> Scott wrote
> "No the rails are not connected to ground. This is the way Doepfer built
> the box and I was not advised to change it."
>
> These are LC9 cases. Are those cable in a different way?
>
>
> Florian