Faulty LP

Ddr · Post by **Ddr** » Tue Feb 10, 2009 4:47 am

any more news on the subject.
i'm in the UK too, had this exact problem a few years ago. i love the sound but couldn't deal with it and Turnkey at the time just exchanged it instead of finding a solution. so i exchanged 3 different MLP before giving up.
i then wrote to Amon who wrote a lenghly email of things that could have been the cause, earthed power issues, cables etc etc... i bought another MLP, moved to a different studio, and still the problem persists.
any ideas?
Ddr

kabubi · Post by **kabubi** » Thu Feb 12, 2009 7:44 am

Hi everyone,

i own a LP se I (silver back) updated to OSII
i have the same issue using some of audio cables (dunno exactly which type). When i plug it (for example) into an audio interface the issue appear. if i replace the jack with another cable, it disappear.

Voltor07 · Post by **Voltor07** » Thu Feb 12, 2009 8:59 am

kabubi, it sounds like a case of bad cable. If there's a short in one of the cables, you'll have a grounding issue. I'd throw away the offending cable or label it "not for use with LP".

kabubi · Post by **kabubi** » Fri Feb 13, 2009 7:39 am

Voltor07 wrote:kabubi, it sounds like a case of bad cable. If there's a short in one of the cables, you'll have a grounding issue. I'd throw away the offending cable or label it "not for use with LP".

yes Voltor, that's exactly what i've done

Amos · Post by **Amos** » Fri Feb 13, 2009 11:14 am

just an update to say, still working on this... I've been talking this week with head engineer Cyril Lance. We have a few speculations but no solid theory yet.

Is anyone in the USA having this problem? Or only outside the US?

Anyone with this LP problem, please let me know the Volts/Hz of your country's power grid. Let's see if there are any common factors there.

It's definitely the case that poor/no ground on the power cable can cause this.
It's definitely the case that stray voltage on the audio cable can cause this - "stray voltage" can be due to a short/bad ground on the audio cable, OR due to a power problem with your mixer or powered speaker that puts AC or floating ground on the audio cable.

however, in a case where you know beyond a shadow of doubt that the connection to ground is perfect on the AC power side, and you have no other cables plugged into the Phatty, and you still get this same problem... then there may be an unknown factor at work. That is what we are trying to determine now.

please read this message carefully and try to rule out all of the above, and then report back and let me know. Thanks!

-Amos

kabubi · Post by **kabubi** » Fri Feb 13, 2009 11:36 am

well, i live in italy where we got 220 v / 50 HZ

i noticed that i can induct the issue using a 9" power cable (the jack used to connect an amp head to a cabinet)

when i connect it to LP's audio output the problem appear, until i unplug the jack.

sometimes it does also happen when i plug a standard cable between LP and an audio interface (mine is a m-audio ozone).

hope this will help

alamilla · Post by **alamilla** » Sun Feb 15, 2009 8:51 am

I live in the UK where it's 220V 50/60Hz
I've tried using it in different rooms and even different houses so I am confident it's not the power supply or a grounding problem
I don't use audio cables other than headphones (the problem persists regardless of whether or not the headphones or an audio cable is plugged in or not)
what intrigues me is that the parameter value drifting only occurs in the Oscillator section, nowhere else

the problem has meant I haven't been able to use LP live because it's now unreliable

scaremi · Post by **scaremi** » Sun Feb 15, 2009 10:07 am

Hello everybody,
I'm from Italy where it's 220V 50 Hz.
It's the same for me, I don't use audio cable but only headphone or not and the parameter value drifting only occurs in the oscillator section.
I hope moog stuff will find a quick solution.
Regards
Emidio

alamilla wrote:I live in the UK where it's 220V 50/60Hz
I've tried using it in different rooms and even different houses so I am confident it's not the power supply or a grounding problem
I don't use audio cables other than headphones (the problem persists regardless of whether or not the headphones or an audio cable is plugged in or not)
what intrigues me is that the parameter value drifting only occurs in the Oscillator section, nowhere else

the problem has meant I haven't been able to use LP live because it's now unreliable

Tangsonghe · Post by **Tangsonghe** » Sun Feb 15, 2009 1:10 pm

Hiya, I was in touch with Amos about this last year
and although Amos was very helpful (thanks Amos!),
I detected no earthing issues with my unit -cabling
etc and sometimes even have the problem when I
was using nothing but headphones. My experience is
that the problem is intermittant (though persistant).

I am pretty sure that the problem emerged for me after
upgrading the OS but this might be another false association.
Amos, were there changes in the way the latest OS scans the
knobs for voltage changes in 'Track' mode? It looks to me
that fluctuating voltages are being interpreted as knob changes,
which triggers 'TRACK' mode to erroneously move the value
closer to the knob value until they coincide and real analogue
part of RAC kicks in. I think that's why the Moog guys go for earthing problems as the most likely cause.

I have since reluctantly changed my unit's settings to pass-thru
which largely circumvents the problem (unless the knob position
is close to the initial position, then you see a little flicker).

Amos · Post by **Amos** » Mon Feb 16, 2009 11:52 am

one possibility is that we can change the firmware to make the pots a little less sensitive to tiny changes of voltage when the pot is at rest. We call this a "box check" - as in, there is a "box" of a certain size around the current pot voltage, and if the voltage strays outside the box, we decide that the pot is moving. As long as the voltage stays inside the box, then we decide the pot is at rest. If you have a very quiet system where there is not a lot of background noise, you can make this box quite small. This means that you only need to move the pot a tiny bit before it goes "live" and RAC is turned on, the LEDs are updated, etc. Once the pot is "live" and in motion, then it doesn't matter what size box you were using to detect when it was at rest.

The only effect you'd get from increasing the size of the box check. is that you would have to move the pot slightly farther at first before it would "pick up" and go live. So, there might be a slight value jump at first.

I will see if we can get a version of the firmware with a larger box check for some of you who are having this problem to try. I will let you know when/if this option becomes available. We'll also continue to investigate the hardware/electrical angle.

Kind regards,

Amos

EricK · Post by **EricK** » Mon Feb 16, 2009 3:37 pm

THats the same principle thats on the Voyager right? Just a little bit of give and take before the digital brain registers the change?

By the way, on mine there is really no tiny amount that you can move the pot without the synth reckognizing it.

Eric

Tangsonghe · Post by **Tangsonghe** » Mon Feb 16, 2009 8:59 pm

Hiya EricK, I guess the principle is broadly the same, but achieving
the parameter change from the initial digitally generated patch CV settings
with pots rather than encoders is a bigger challenge!

Amos, a hearty thanks to you and your colleagues!

alamilla · Post by **alamilla** » Mon Apr 13, 2009 6:38 am

any updates?

my LP still has this problem
is there a dealer or store in the UK I can get to look at it for a potential repair?