RME Scaling Out Of Adjustment Again! ??

[glennfin]

My RME was just at the Moog factory a few months ago for a scaling adjustment, calibration, etc.
The oscillators were not tracking correctly. For example, if two oscillators are tuned in unison at middle C, then playing a C two octaves up, one oscillator would be "out" with the other one. This is a scaling adjustment issue.

Now several months later, the problem is back. My RME lives in a temp and humidity controlled studio, never moved, gigged, or otherwise abused in any way. This is very frustrating. I'm trying to record synth tracks and if I playing a part around middle C it's ok but as soon as I move up the keyboard 2 octaves, I can hear the oscillators beating against one another.

Is this a common bug-fault-issue with the RME?. I can't believe this would go out of adjustment after only a few months.

Maybe I should mount the scaling adjustment pots outside the RME so I can adjust them when it goes out....

Not fun....

[MC]

Maybe your power supply is bad. They can drift, which affects tuning downstream.

[glennfin]

Kinda doubt that. The DC voltages are regulated. If there was a power supply problem I'd imagine there would be other issues showing up as well. Wish I had a schematic.... Time to take another trip to Moog, not that I mind visiting Asheville but if this is going to happen every few months.........

Maybe your power supply is bad. They can drift, which affects tuning downstream.

[MC]

Kinda doubt that. The DC voltages are regulated. If there was a power supply problem I'd imagine there would be other issues showing up as well. Wish I had a schematic.... Time to take another trip to Moog, not that I mind visiting Asheville but if this is going to happen every few months.........

Maybe your power supply is bad. They can drift, which affects tuning downstream.

One faulty connector or solder joint is all it takes and they aren't regulated anymore. Have them monitor the power rails over a twenty minute period for drift as it warms up.

[glennfin]

As I mentioned, if this was a power supply problem, there would very likely be other issues. Anything's possible but this is a keyboard scaling adjustment issue and I highly doubt this has to do with voltage regulation per say. We can guess all day, but without a schematic to see how the volt-per-octave scaling is achived, it's just that.

I played around with it last night for a while, bringing up some presets, turning oscillators on and off at the mixer.
Oscillator 2 definately does not "track" oscillator 1 across the entire pitch range as it should.

I posted because I was hoping to get some feedback from other Voyager owners to see if this is a common issue.
Maybe someone from Moog can chime in on this?

Kinda doubt that. The DC voltages are regulated. If there was a power supply problem I'd imagine there would be other issues showing up as well. Wish I had a schematic.... Time to take another trip to Moog, not that I mind visiting Asheville but if this is going to happen every few months.........

Maybe your power supply is bad. They can drift, which affects tuning downstream.

One faulty connector or solder joint is all it takes and they aren't regulated anymore. Have them monitor the power rails over a twenty minute period for drift as it warms up.

[MC]

We can guess all day, but without a schematic to see how the volt-per-octave scaling is achived, it's just that.

And how did you conclude that I have not seen a schematic for the Voyager?

[glennfin]

I was refering to me not having a schematic for the voyager.

Do you have a schematic of the voyager? If so, can you explain how the volt-per-octave scaling is implemented?

It is my understanding that the voyager schematic is proprietary information and not available to users, but hey, I've been wrong at least once before.

We can guess all day, but without a schematic to see how the volt-per-octave scaling is achived, it's just that.

And how did you conclude that I have not seen a schematic for the Voyager?

[thealien666]

I suspect your "detuning" problem over time, might simply be caused by poor quality (or too sensitive) stretch tuning trimpots...

[glennfin]

I think you might be right about that.... perhaps a 10 turn pot upgrade/retrofit may be in order.

Of course, I am going to speak with Moog's service department before I do anything extreme like that.

Thanks!

I suspect your "detuning" problem over time, might simply be caused by poor quality (or too sensitive) stretch tuning trimpots...

[glennfin]

MC??

I was refering to me not having a schematic for the voyager.

Do you have a schematic of the voyager? If so, can you explain how the volt-per-octave scaling is implemented?

It is my understanding that the voyager schematic is proprietary information and not available to users, but hey, I've been wrong at least once before.

We can guess all day, but without a schematic to see how the volt-per-octave scaling is achived, it's just that.

And how did you conclude that I have not seen a schematic for the Voyager?

[MC]

I never said that I have the schematic in my possession. I only said I have seen it. I did some tech support for a brief period when Moog's folks were not available, so it was during that time that I had access to the schematics.

I have studied enough schematics of analog synths to know that the Voyager is not far removed from traditional designs. I've repaired enough of these things to know the common problems that cause a synth to go out of tune. I was rather insulted that you cast so much doubt in my suggestions so I'm not too anxious to provide further assistance. Good luck with moog tech support.

[thealien666]

I understand that the schematics for current Moog products are proprietary. But it's frustrating to have to continually guess what part of a Voyager could have a problem. Most of the problems are often simple things that could be easily fixed, without having to send units for repair at considerable risk and cost, if only electronic hobbyists and technically trained people, like some of us, could have access to schematics, or at least parts of them...

Heck, simply the retuning/calibrating procedure of a Voyager is a "big secret" (not so much anymore, no thanks to Moog Music). As if someone should have his Moog guitar sent to a tech every time it needs to be tuned ? The very nature of an analog synth using VCOs, even a modern one, implies that it will need to be retuned or re-calibrated at some point, but yet no "tuning acces holes" are provided on recent Moog synths. Contrary to all models before that. Moreover, the Voyager still uses some sensitive single turn trimpots for its stretch tuning and scaling.

Finally, despite Bob's best efforts, the temperature compensation circuitry on a Voyager isn't very efficient, which doesn't help tuning/scaling issues. Not much better than 30 years old designs.

Sorry for the rambling, but sometimes you want to help others, but you can't do much because you lack information that should be made accessible, in some way.

[glennfin]

No need to feel "insulted" because someone disagrees with your suggestion. I'm not going to repeat what I've already said about the slim chance of a power supply issue affecting just the scaling on one oscillator, and as long as we're qualifying our experience, I've been employed full time in electronics manufacturing, design and repair for over 36 years both as a technician and an engineer. In addition to that, I have many hours of experience working on analog synth circuits (ARP, Moog, PAIA, CAT, etc...) I've also designed and built from scratch, analog synth modules/circuits in addition to analog processing for musical instruments. To suggest something non-specific like a power supply problem for the issue I posted is akin to taking your car to a mechanic and having him tell you "yep, looks like a problem with your engine"

Feel free not to "provide further assistance"

I never said that I have the schematic in my possession. I only said I have seen it. I did some tech support for a brief period when Moog's folks were not available, so it was during that time that I had access to the schematics.

I have studied enough schematics of analog synths to know that the Voyager is not far removed from traditional designs. I've repaired enough of these things to know the common problems that cause a synth to go out of tune. I was rather insulted that you cast so much doubt in my suggestions so I'm not too anxious to provide further assistance. Good luck with moog tech support.

[glennfin]

Hi Alien,

Thanks for the reply. I agree 100% with everything you've said, especially the "no tuning acces holes" and "sensitive single turn trimpots for its stretch tuning and scaling"

To give some credit to Moog service, they did provide me with the scaling adjustment procedure after I explained my level of experience. Unfortunately, the no external access to internal adjustments is a problem. I really don't want to yank the RME out of the studio, march it down to the bench, take it apart and re-adjust the scaling every couple of months.

I'm going to look into some sort of solution like the possibility of remoting the scaling trimpots (or 10 turn full size quality pots) to a rear mounted daughter board with access holes. That way I can quickly make the adjustments in the studio with just a frequency counter, etc...

I understand that the schematics for current Moog products are proprietary. But it's frustrating to have to continually guess what part of a Voyager could have a problem. Most of the problems are often simple things that could be easily fixed, without having to send units for repair at considerable risk and cost, if only electronic hobbyists and technically trained people, like some of us, could have access to schematics, or at least parts of them...

Heck, simply the retuning/calibrating procedure of a Voyager is a "big secret" (not so much anymore, no thanks to Moog Music). As if someone should have his Moog guitar sent to a tech every time it needs to be tuned ? The very nature of an analog synth using VCOs, even a modern one, implies that it will need to be retuned or re-calibrated at some point, but yet no "tuning acces holes" are provided on recent Moog synths. Contrary to all models before that. Moreover, the Voyager still uses some sensitive single turn trimpots for its stretch tuning and scaling.

Finally, despite Bob's best efforts, the temperature compensation circuitry on a Voyager isn't very efficient, which doesn't help tuning/scaling issues. Not much better than 30 years old designs.

Sorry for the rambling, but sometimes you want to help others, but you can't do much because you lack information that should be made accessible, in some way.

[MC]

No need to feel "insulted" because someone disagrees with your suggestion. I'm not going to repeat what I've already said about the slim chance of a power supply issue affecting just the scaling on one oscillator, and as long as we're qualifying our experience, I've been employed full time in electronics manufacturing, design and repair for over 36 years both as a technician and an engineer. In addition to that, I have many hours of experience working on analog synth circuits (ARP, Moog, PAIA, CAT, etc...) I've also designed and built from scratch, analog synth modules/circuits in addition to analog processing for musical instruments. To suggest something non-specific like a power supply problem for the issue I posted is akin to taking your car to a mechanic and having him tell you "yep, looks like a problem with your engine"

Feel free not to "provide further assistance"

Oh, you're just in time.

I'm leaving for an extended vacation, with no access to email or internet. In my absence, you seem qualified enough to provide technical assistance to forum members, as I have for years. So glad to have an expert come along!