Doepfer

After achieving some very promising results with a NOS Type 8 8BB3C1B and my A-199 I have become interested in the challenge of installing a massive 17" 9AB3C1B reverb tank within my A100PMS12 and wish to ask for thoughts on adequate shielding. The toroidal transformers are emitting more pulse into my reverb tank than I thought would be possible, have spent a tedious hour with the whole thing under power, carefully sliding the tank around inside looking for neutral positions. I can tell you all that when the A-199 return signal isn't having to fight electromagnetic interference, it sounds bloody marvellous and clean. Add a compressor and you're in BBC radiophonic heaven. I omitted the RCA connectors and have hard soldered Belden shielded wire from A-199 PCB to reverb tank input and output transducers. Belden wire shield connected to ground on A-199 pcb. Have located the mu-metal product 3M Ultraperm 80, however I don't know if the rejection and permeability are correct for blocking PMS12 transformer hum just a few cm away. Cheers!

at the Gräfelfing facility are there any pieces of mu-metal within easy reach to simply check if a few millimeters of this substance will be sufficient to reject EM interference being emitted by run-of-the-mill 120V Doepfer power supply 2, toroidal transformer, 1200mA inside a-100 pms12? It is an expensive material to purchase, if there is no hope of this working would like to know in advance. Thanks!

29.07.2015, 17:03, "XCVII supraleiter@yandex.com [Doepfer_a100]" <Doepfer_a100@yahoogroups.com>:

> After achieving some very promising results with a NOS Type 8 8BB3C1B and my A-199 I have become interested in the challenge of installing a massive 17" 9AB3C1B reverb tank within my A100PMS12 and wish to ask for thoughts on adequate shielding. The toroidal transformers are emitting more pulse into my reverb tank than I thought would be possible, have spent a tedious hour with the whole thing under power, carefully sliding the tank around inside looking for neutral positions. I can tell you all that when the A-199 return signal isn't having to fight electromagnetic interference, it sounds bloody marvellous and clean. Add a compressor and you're in BBC radiophonic heaven. I omitted the RCA connectors and have hard soldered Belden shielded wire from A-199 PCB to reverb tank input and output transducers. Belden wire shield connected to ground on A-199 pcb. Have located the mu-metal product 3M Ultraperm 80, however I don't know if the rejection and permeability are correct for blocking PMS12 transformer hum just a few cm away. Cheers!
>
>

> at the Gräfelfing facility are there any pieces of mu-metal within easy reach to simply check if a few millimeters of
> this substance will be sufficient to reject EM interference being emitted by run-of-the-mill 120V Doepfer power supply 2,
> toroidal transformer, 1200mA inside a-100 pms12? It is an expensive material to purchase, if there is no hope of this
> working would like to know in advance. Thanks!

I'm sorry - we have no mu-metal here.

Best wishes
Dieter Doepfer

Finally got the opportunity to experiment with a 314mm x196mm x 0.2mm sheet of 3M Ultraperm 80 MuMetal in my A-100 PMS12. 

Having practically no formal knowledge of engineering or physics or means to measure the emissions, it came down to patching a basic sparse LPG bongo striking occasionally and CAREFULLY sliding the tank around inside the case under power listening on headphones. I took a grinding wheel and reduced the sides of a large Accutronics 17" reverb tank and hard-soldered shielded wire directly from the A-199 into the transducers in order to get it to fit. Very cramped, but will fit. Listen posterity, in my experience there is nowhere within the PMS12 to place either a 17" (type 09) or 9" (type 08) tank that will provide high quality results. It may be possible to relocate one of the power supplies. It may be possible to spend great sum of money on thicker shielding material. While the 3M mu-metal sheet does clearly reduce the inductive noise somewhat it's nowhere near what would be studio acceptable. The A-199 needs to be redesigned with a hint from Springray, external connections. When the tank is far enough away from the transformers the sound is totally beautiful. Considering building a shielded external box for tank and using XLR connection. The type 08 tank performed better than type 09 on A-199.

04.08.2015, 08:53, "yahoo@doepfer.de [Doepfer_a100]" <Doepfer_a100@yahoogroups.com>:

>>  at the Gräfelfing facility are there any pieces of mu-metal within easy reach to simply check if a few millimeters of
>>  this substance will be sufficient to reject EM interference being emitted by run-of-the-mill 120V Doepfer power supply 2,
>>  toroidal transformer, 1200mA inside a-100 pms12? It is an expensive material to purchase, if there is no hope of this
>>  working would like to know in advance. Thanks!
>
> I'm sorry - we have no mu-metal here.
>
> Best wishes
> Dieter Doepfer
>
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On 01.11.15 08:01 , XCVII supraleiter@yandex.com [Doepfer_a100] wrote:
> Considering building a shielded external box for tank and using XLR connection.
Why do you try to remove the symptom instead of healing the cause? 
Remove the transformer from the powersupply pcb, build an external box 
for the transformer and feed the low-volt-AC via an socket into the 
doepfer case. This would be much easier.

This is the solution, I choose on my Wurlitzer 200, where the 
transformer causes hum in the pickups. The MU-shield for the  Wurlitzer 
pickup row would cost around $150. The housing for the transformer and 
the connectors costs $20.

Florian

Herr Florian, because one may wish to omit or arbitrarily audition various different reverb tanks in the casual future, the idea of externalmounting a power supply trafo is akin to an insulin pump and/or colostomy bag (less gvts hanging out at the gig).

01.11.2015, 17:51, "Florian Anwander fanwander@mnet-online.de [Doepfer_a100]" <Doepfer_a100@yahoogroups.com>:

> On 01.11.15 08:01 , XCVII supraleiter@yandex.com [Doepfer_a100] wrote:
>> Considering building a shielded external box for tank and using XLR connection.
> Why do you try to remove the symptom instead of healing the cause?
> Remove the transformer from the powersupply pcb, build an external box
> for the transformer and feed the low-volt-AC via an socket into the
> doepfer case. This would be much easier.
>
> This is the solution, I choose on my Wurlitzer 200, where the
> transformer causes hum in the pickups. The MU-shield for the Wurlitzer
> pickup row would cost around $150. The housing for the transformer and
> the connectors costs $20.
>
> Florian
>
>