Ground loop problem with (self-adjusting knobs)

[pierrotlefou]

Hi,

I have searched this forum for the 'self-adjusting knobs' problem, caused by a ground loop, of the Little Phatty, but haven't found a definitive solution yet.

When connecting the LP with a PA speaker, the knobs start to change settings by themselves. As I have read elsewhere on this forum, this is caused by a ground loop. And indeed, it doesn't happen when the PA speaker and LP are plugged into the same multiple socket. However, if both are plugged into different sockets (I have tried all combinations of grounded and non-grounded), then the problem occurs. I have tried to place an active (battery powered) DI box with ground lift between the two devices, but that also didn't help. (I live in The Netherlands.)

At home, I can make sure that both devices are plugged into the same multiple socket, but on stage, connected the LP to a PA speaker (often through a mixer), this is not under my control. So the problem is that I simply use my Moog synth on stage without having a back-up synth, which seems ridiculous. (Fortunately, my Mopho Keyboard never exhibits this problem - neither has any other synth or stage piano I have used in the past.)

Does anyone have a solution that will fix the problem?

[e3p0]

I'm not sure if some DI with transformers on the input would help. Furman or similar power conditioners too? I don't know, I am just brain storming.

Does anybody with a Voyager ever see this issue, or is it just us "lucky" Phatty owners?
-e

Good Luck!
Post results.

[pierrotlefou]

Thanks!
Anyone on this forum who has used a (Furman) power conditioner, and can tell a little bit about his/her experience?

[David Smyth]

Thanks!
Anyone on this forum who has used a (Furman) power conditioner, and can tell a little bit about his/her experience?

I can. I tested out a Furman P-1400 AR E Voltage Regulator/Power Conditioner for my two Slim Phattys' self-adjusting knob problem. It didn't help for me (although my Slim Phattys have the problem if only plugged in to power - i.e. it is not a ground loop caused by connecting to other gear). But seeing as your problem sounds like a ground loop, I don't know if my unsuccessful testing of one Furman model rules it or any other model out for your situation.

Other points (regarding the Furman P-1400 AR E model):
- It's a nice design and easy-to-use unit.
- It has plenty of IEC power outlets for powering multiple devices.
- It's going to add a bit of weight if you're moving gear around.
- It's quite an expensive unit (it was alot of money to spend even if it did work for me).

I tested the 230v/240v version of the Furman here in New Zealand along with a few other devices such as a computer UPS, an Isolation Transformer and Surge Protection.
No devices have solved my two Slim Phattys' self-adjusting knob problem at this point.

Check my other posts if you want more details of my struggle.

Regards,
David Smyth
NZ

[cliffman]

I have used the Ebtech HumX for various ground loop issues, haven't tried it with LP. I do not know if they make a non-US version.
http://www.ebtechaudio.com/humxdes.html

[pierrotlefou]

Thanks!
Anyone on this forum who has used a (Furman) power conditioner, and can tell a little bit about his/her experience?

I can. I tested out a Furman P-1400 AR E Voltage Regulator/Power Conditioner for my two Slim Phattys' self-adjusting knob problem. It didn't help for me (although my Slim Phattys have the problem if only plugged in to power - i.e. it is not a ground loop caused by connecting to other gear). But seeing as your problem sounds like a ground loop, I don't know if my unsuccessful testing of one Furman model rules it or any other model out for your situation.

Other points (regarding the Furman P-1400 AR E model):
- It's a nice design and easy-to-use unit.
- It has plenty of IEC power outlets for powering multiple devices.
- It's going to add a bit of weight if you're moving gear around.
- It's quite an expensive unit (it was alot of money to spend even if it did work for me).

I tested the 230v/240v version of the Furman here in New Zealand along with a few other devices such as a computer UPS, an Isolation Transformer and Surge Protection.
No devices have solved my two Slim Phattys' self-adjusting knob problem at this point.

Check my other posts if you want more details of my struggle.

Regards,
David Smyth
NZ

Thanks for the reply.
The problem with these 'difficult' issues is that you may end up spending half the price of your Phatty, and still have no solution!
I will re-read your threads. Do you have a solution currently? (Or sold your Phatty...?)

[Voltor07]

I'd contact Amos at Moog if I were you. He might offer a working solution.

[David Smyth]

Thanks for the reply.
The problem with these 'difficult' issues is that you may end up spending half the price of your Phatty, and still have no solution!
I will re-read your threads. Do you have a solution currently? (Or sold your Phatty...?)

I'm currently having my Slim Phattys looked at by an electrical engineer. At this stage it looks promising (may have found the cause of the problem)! I will update when I know more/have a solution.

I'm not sure if this will necessarily apply to ground loop problems when connected to other devices (it could well do), but testing out some things so far shows some good results for my specific problem (lights moving around when connected to power only).

I will keep in touch.

Regards,
David Smyth
NZ

[petrveliky]

The only workaround I discovered is to plug my LP into an amp instead of a PA speaker. I have a Roland KC550 and when I bring that to gigs it works fine. Only at the gigs where I packed light and left the KC550 at home did the LP have the dancing knobs problem. I tried it with a few different gigs and luckily the second and third time I was able to use another band's bass amp, which worked perfectly. But from now on I just bring my Roland KC550 to every concert, use that as a monitor, and XLR-out to the soundboard. Hasn't failed yet.

I'm in the US btw.

[gruvsyco]

I'm having these problems and it's getting very frustrating. None of my other hardware seems to be having issues. My Little Phatty starts wiggin out either with the audio jack or usb (usb is much worse though). If additional hardware is needed (power conditioners, DIs, transformers) this really should be advertised with the product.

[David Smyth]

I have posted an update to the modding/testing here:

http://forum.moogmusic.com/viewtopic.ph ... 26#p102526

Regards,
David Smyth
NZ