Hi,
I’m from France and I have exactly the same problem! In my home studio it works but sometimes on stage the parameters change by themselves.
As I play both bass an LP, I use a line selector. I have tried many things to fix the problem but no solution for the moment! DI, earth lift, changing the Schuko, using a Schuko with no earth… the only way to fix the issue is to find another power source.
As someone said it’s not very professional and when you go on stage for a big festival you cannot said : “hey the power you give me is not clean…” …50 other musicians were on stage before you and didn’t have the problem 
Hi,
Did anyone of the people who experience(d) this problem manage to solve it?
I am getting extremely frustrated by this issue! Currently, I simply cannot use the Little Phatty outside my home. (I live in the Netherlands.)
Since all my other equipment always worked perfectly fine in similar conditions, I cannot help blaming the Little Phatty for this… I am afraid that solving this issue will be impossible or that it will take a lot of time / money… 
I have also experienced this problem every time I perform live,
I use the standard UK Cable with the earth prong on it, and I’ve played in about 8 different venue’s, it still goes mad, With the knobs moving automatically and even getting stuck notes (No Midi) and the tuning dropping whenever it decides to.
The only place were my Little Phatty does work is at home in my studio and there it works like a treat with no problems at all. Its just an unreliable synth for live usage and performances. For live situations now I have to use the VST version to achieve the sounds. Which is a real shame because its a great synth when it Works perfectly.
I also have all the latest available updates installed as well might just mention.
I am sorry to hear that you cannot use the Little Phatty live, and have to use VSTs instead!
In another topic I have seen several solutions that may or may not work…, including:
-Don’t use the ‘pass thru’ setting for the knobs (I will try this as soon as I can)
-Use shielded instrument cables
-Use a passive DI box. (For me, an active DI box with ground lift did not work.)
-Use other devices, like power conditioners. Seems expensive and doesn’t work in most cases…
My current solution is using a Dave Smith Mopho Keyboard, which is largely analog as well and sounds good.
I have also seen and tried the “Pass Thru” setting and yet still the phatty has the issue unfortunately .
the same situation here with the DI box doesn’t solve anything for me,
Yes I have also been thinking about the Mopho as well! Yet all my other synthe’s work perfectly live including my 30 odd year old Pro one and Roland SH2. The Little Phatty is the only one that has let me down unfortunately…
hi,
Did you use a passive DI box? I read somewhere that this may make a difference. I’d also like to try the shielded cable option. If I remember correctly, the problem also occurs if I just plug an audio cable into the Phatty and then hold the audio cable at the other end. Don’t know what that signifies though 
I really hope it’s possible to solve this…
If not, the Mopho is a great little synth as an alternative. The bass sounds are probably not as ‘deep’, and the smaller size gives a less clean knob layout, but it’s really wonderful-sounding, has a lot of flexibility, a good form factor and weight, and a superior keyboard compared to the Moog.
Something like this would also be an option, but the experiment would cost about 50 euros…:
http://artproaudio.com/artcessories/audio_solutions/product/dti/
Yeah I only use passive, I have never tried an Active Box though, If that would make a difference to the way the Phatty Acts I have no idea, so I need to try that, but yeah I only use the Radial D2 Passive box, which is a fantastic DI box but it doesn’t solve the problem … I have yet to try an Active one.
Hmm, next to shielded cables, a passive DI box was more or less my last resort. Active DI box with ground lift didn’t work for me…
Next to the question on how to solve this, how can a product by a well-established company like Moog exhibit this kind of behavior for so many users?
contact techsupport at moogmusic dot com… they have a definite fix for any “dancing lights” / parameter drift you may be experiencing.
Thanks for the suggestion. I did this a day ago and just received a reply that there exists a grounding modification. Hopefully that will correct the error in the original Little Phatty.
Hi All.
I’m the OP. I went to the importer of moog in Denmark and had this fixed. At first he didn’t want to believe that this was even an issue, but when I showed him, he was pretty surprised.
After much thinking, he ended up having the grounding inside redone in a better way, and since the I’ve had absolutely no problems. So this is definitely a design flaw no matter what moog are saying in here, and it CAN and SHOULD be fixed.
One of my friends bought a patty too, and ended up having the exact same repair done, with same good results.
I’m glad for you that you had it solved! And it’s good to hear there’s actually a solution.
Very strange though that this is a design flaw in all (older?) Phattys and not more is known about it (I searched for hours on the internet for a solution).
One question: I hope to avoid long discussion with Moog about the costs of fixing this error, because I think it’s something that should have been correct in the first place… but how much did it cost you? 
An electrical engineer is currently looking at my Slim Phattys for this or a similar issue (my older Little Phatty Stage II is fine, but my two Slim Phattys have self-moving dials when plugged into power only). It looks promising that we have found the cause of my problem. I’ll post on the forums when I know more/have a solution to my Slim Phattys’ issue.
Regards,
David Smyth
NZ
Great, David, I hope it works out for you!
An EE?! Amazing the lengths a love for the Moog can send us to. Kudos for sticking with it. I definitely look forward to more info! 
If I wanted to get this grounding modification done, would I have to send it to the Moog factory or is there anywhere in the UK that will help me get this done, as I can’t live with this problem much longer! Im glad to hear there is a solution though! but yes I agree with pierrotlefou
“how can a product by a well-established company like Moog exhibit this kind of behavior for so many users?”
Sure you have to deal with a few more things when buying analog, but I have a few analog synthesizers that are 30 years old and never have suffered anything like this.
I’d imagine you could get your country’s Moog-contracted technician to install the ground mod. In my case (in New Zealand), the Moog-contracted Technician here was going to install the ground mod into my two Slim Phattys, but it turned out the SP’s already had the mod from the factory (I assume that since SP’s came out later than LP’s, they include the mod in SP’s when they’re built). So my Slim Phattys have the problem regardless of having the ground mod - but my situation is probably different to yours as it seems grounding is not the issue in my case (I’m still testing one of my SP’s with an Electrical Engineer).
Anyway email Moog Support about it - they informed me of the Moog-contracted technician (and their contact email address) in my country (in my case a repairman for my country’s Moog-distributor music store), and they offered to send the instructions to the technician if it was an unfamiliar mod. I emailed the technician to discuss the mod, and then I took my units to my local Moog-distributor music store who sent them to the technician for the mod installation.
I hope this helps!
Regards,
David Smyth
NZ
Cheers David! Just contacted Moog support and they gave me the details of a qualified engineer that has dealt and is familiar with Moog Products in the past, so hopefully I can get this all sorted out!
thanks once again!