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SOLVED Doepfer A-199 HUM (stops when I touch unit)
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Author SOLVED Doepfer A-199 HUM (stops when I touch unit)
outfit
The noise stops when I touch (ground) the spring reverb unit
The noise gets worse when i mess with the long cable it came with.
I am ordering a shorter cable next.
Anyone experience anything similar or advice for what to do next?
note: orientation of the unit made no difference.

Here is the research I have done so far:

I heard really loud hum when turning the Mix dial fully counter clockwise.
I did my research and learned about orientation of the reverb unit as well as picking up noise from the power supply.
Even when mounted in the best possible way:
http://www.accutronicsreverb.com/main/?skin=sub05_07.html
I still get noise.

I also took the reverb unit and put it right on top of the power supply to find out what that would sound like. I heard a loud hum but not the problem I have.

The only time this hum stops is when I touch (ground) the spring reverb unit.

I did read that buying a shorter cable can help:
http://www.muffwiggler.com/forum/viewtopic.php?p=1668770

Here is a picture of my unit:

According to the information here:
http://www.accutronicsreverb.com/main/?skin=sub05_07.html
It should be mounted with the orientation of my picture?
(just making sure I understand correctly)

My next step will be to buy a shorter cable. Playing around with the long cable did make the noise worse.

Any other advice?
Thanks
adaris
You might want to focus on the module rather than the reverb tank itself. Try moving the module around in your case, or if you have more than one case, try it in another case. It could be interacting with another module in some way, so moving the modules around it may also make a difference.
outfit
how come when I touch the reverb unit the noise stops?
it is crystal clear if i put my hand on the spring tank.
It is really strange.

I use a cardboard box case with the Doepfer A-100 kit.
The power supply to my case is two prong.
If that matters....

I have tried moving the module around a bit as well as unplugging the other modules. ( the hum kinda gets quieter when i touch the module itself but does not go away )

The only thing that has worked so far is touching the spring unit.
This is why I am convinced it is some kind of ground loop.

Trying another case would be great. That may take me a bit, i am saving up for one now.

Technically I found a fix, I just have to have one finger touching the reverb unit at all times, and there is no hum. :(

I will post back if the shorter cable works when I get it.
Also it will be the first module I try when I get a new case.
That will be great when I can test another case.
Thanks.
Pighood
Try rotating the tank at a different angle to the case in which the module resides.
sir stony
I'm pretty sure you mentioned the cause yourself: your power supply is two prong, which means your entire rack has no proper ground connection. The spring tank needs a grounding because of the sensitive nature of the electrics inside. Just get some alligator clips and make a ground connection to somewhere, usually the plumbing or a radiator are easily accessible and solid ground references.
ookrsia
The RCA cable that came with A-199 is a very basic one. The one that came with my A-199 was actually faulty and I had to use my own cable instead. In the end I ended up buying a shielded RCA cable and that did reduce the hum notably.

My reverb tank is not mounted anywhere, but I actually had to spend some time to find the right spot for it. The tank is super sensitive to interference. I ended up putting mine on a shelf that's far away from all electric equiptment.
lohacker
ookrsia wrote:
The RCA cable that came with A-199 is a very basic one. The one that came with my A-199 was actually faulty and I had to use my own cable instead. In the end I ended up buying a shielded RCA cable and that did reduce the hum notably.


This, mine had a lot of hum when I bought it and soon replaced the cable with a shielded one. But a strange side effect appeared, the original screaming feedback is more mild, in some patches is good but in other I prefer how it was before. The only thing I can think of is that the cable I'm using is very long (2m), I'd have to try with a shorter one one day.
R.U.Nuts
sir stony wrote:
I'm pretty sure you mentioned the cause yourself: your power supply is two prong, which means your entire rack has no proper ground connection. The spring tank needs a grounding because of the sensitive nature of the electrics inside. Just get some alligator clips and make a ground connection to somewhere, usually the plumbing or a radiator are easily accessible and solid ground references.


This. I had the same issue with the same PSU. I just duckt taped a patch cable to the spring tank and the mounting rails of my rack. - Ghetto fix. hihi
Shledge
I'm surprised doepfer's PSU kit provided a two-prong cable, as it means... it doesn't have a ground.

You need to have it grounded. I would ditch the PSU entirely and get anything with a proper ground.
outfit
Is there anyway just to buy this part of the power supply:

That is 3 prong

Or directions somewhere how to hack it to make it 3 prong?
( I will look for that, I am not sure I want to spend too much money on my cardboard box case)
Is there something that will work with the bus boards that came with the doepfer diy case?

I will try grounding just the spring reverb unit to the rails. At least until I get another case that is built proper.

Thanks for all the help
Mungo
outfit wrote:
The noise stops when I touch (ground) the spring reverb unit
The noise gets worse when i mess with the long cable it came with.
I am ordering a shorter cable next.
Anyone experience anything similar or advice for what to do next?
You've got some good replies from people with the same problem:
lohacker wrote:
ookrsia wrote:
The RCA cable that came with A-199 is a very basic one. The one that came with my A-199 was actually faulty and I had to use my own cable instead. In the end I ended up buying a shielded RCA cable and that did reduce the hum notably.


This, mine had a lot of hum when I bought it and soon replaced the cable with a shielded one. But a strange side effect appeared, the original screaming feedback is more mild, in some patches is good but in other I prefer how it was before. The only thing I can think of is that the cable I'm using is very long (2m), I'd have to try with a shorter one one day.

R.U.Nuts wrote:
I had the same issue with the same PSU. I just duckt taped a patch cable to the spring tank and the mounting rails of my rack. - Ghetto fix. hihi

While doepfer talks about the magnetic interference from a power supply transformer and how to be careful where the reverb tank is installed, there is no mention of other sources of interference. The reverb tank uses small signals that are gained back up to modular levels, so are more sensitive to interference. They need much better shielding than "regular" cables or modules. The metal box around the springs is a shield that protects from electrical interference but it needs a way to direct that away from the springs. That can be as simple as running a wire back from the tank to a point elsewhere in the case to divert/direct the interference somewhere else.

outfit wrote:
Is there anyway just to buy this part of the power supply:
...
That is 3 prong

Or directions somewhere how to hack it to make it 3 prong?
( I will look for that, I am not sure I want to spend too much money on my cardboard box case)
Is there something that will work with the bus boards that came with the doepfer diy case?

I will try grounding just the spring reverb unit to the rails. At least until I get another case that is built proper.

Thanks for all the help
You don't need a mains earthed power supply to provide a connection for shielding, mobile phones have this sort of shielding inside them and work fine on batteries or their isolated chargers.

The ideal place to connect the spring tank shield to is the 0V of the spring reverb module. It should be doing this along the RCA cables but they may be poorly shielded themselves and running longer than needed. If shorter and better shielded RCA cables don't fix the problem, you'll just need to add your own shield/drain wire. Back to the modules 0V, busboard 0V, rails, any one should be fine.
outfit
Quote:
The ideal place to connect the spring tank shield to is the 0V of the spring reverb module. It should be doing this along the RCA cables but they may be poorly shielded themselves and running longer than needed.



Everything works great now, I tried two different shorter cables:

The grey ones worked best!

Here is the setup now:


It works great now. No noise!
Thanks everyone
It's peanut butter jelly time!
kay_k
Mungo wrote:

The ideal place to connect the spring tank shield to is the 0V of the spring reverb module. It should be doing this along the RCA cables but they may be poorly shielded themselves and running longer than needed. If shorter and better shielded RCA cables don't fix the problem, you'll just need to add your own shield/drain wire. Back to the modules 0V, busboard 0V, rails, any one should be fine.


so basically all one needs is one of those turntable RCA cables ?
https://images.app.goo.gl/EXJ1UhLanxnmVCZM9
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