Moog Model 10 Tuning and Warm Up Time

[PaulLawler]

Hi Guys,

I bought the Model 10 last week and have to say it's wonderful in every way, but it's taking approx 4-5 hours warm up time to give me a good 4 octaves stable tuning. I can't get one octave in tune before it warms up properly.

I'm using it with Logic Pro and the Kenton Pro-2000mk2. During the warm up period I can correct the tuning a bit with the Kenton's scaling controls, but once it's warm I set that back to zero.

The only way I can make it stay in tune after this is to not use the Fixed Control Voltage, I leave it set at 1 and then change octaves on the oscillators.

Obviously it sounds glorious once its in tune but it's making it difficult to use in my work, I'm having to have a timer switch it on at 5am

Is this normal behaviour, or have I missed some calibration instruction ?

[noddyspuncture]

Probably normal... my 901's drift quite a lot, some of them more than others though. Their sound makes it totally worthwhile sticking with them and not upgrading to the 921's.

I modified mine adding a front panel control in the place of the lower of the three inputs sockets on the 901a so I can basically recalibrate 'on the fly' and compensate for any scale drift.

I gig mine and have even managed to compensate during playing.

[PaulLawler]

They seem ok once they’re warm, maybe the odd bit of overall tuning now and then, just a shame they take so long to become useable.

[AlakaLazlo]

My vintage 2P has 2 sets of 1x901a/3x901b. Takes about an hour to settle in before they stabilize. I bought the system from Sound Arts in the 70s and they added a low tracking pot to the back of each of the 901bs. I get about 5 solid octaves. My Cirklon also has assignable scaling per CVIO out, and using that, I can get 6ish octaves. The range switches on the 901as are pretty much useless as they change the scaling just a bit which throws the tracking off.

[PaulLawler]

Does a tracking pot alter the sound in any way if it's correcting tuning ?

[ummagumma]

curious if anyone has improved the range switch circuits on the 901a's, to make them more accurate?

[PaulLawler]

I managed to create a good in tune tracking via the Kenton Pro of around 3 octaves, this is in the first warm up hour so a huge relief in that sense.
EDIT: I'm having to create a new scaling preset per hour, I guess it is slowly expanding it's range.

[ummagumma]

may be a dumb question, but do you have it located for example: ogainst an outside wall, in winter? or near a baseboard heater/some other place in your house where temp is not stable?

[PaulLawler]

It is around 10 inches from an outside wall and it is pretty cold outside currently. My studio is heated though, not overnight of course. I'm pretty sure none of that is helping, I've just not had anything that behaved like this before so wanted to make sure there wasn't an issue or fault that could be looked into first, or even something I could do more, like some kind of calibration ...but then again would that even work as it's pretty much a moving target for the first half of the day.

[ummagumma]

I wonder if you took the back off, it would stabilize faster?

speculating here: but if the space is unheated overnight, it has time to get cold inside the case

then when you turn the heat on during the day, because the model 10 is sealed inside a box, it takes a long time for the room temp to reach the inside of the case & stabilize the oscillators

[PaulLawler]

I'm going to try one of those survival heat blankets tonight see if it helps. But in your opinion does this not seem normal for 901s then with you suggesting removing the back ? I have contacted Moog a couple of times but got no answer yet. The store does have another in stock if it's a fault.

[ummagumma]

well to be honest I do not have one, so I am only guessing

but based on what I have read about temp instability of early oscillators, I would guess your problem is related to the environment?

maybe leave the heat on overnight & see if it helps?

or possibly the store could let you try the other one & see if it behaves the same, in your space?

[AlakaLazlo]

I was thinking about this earlier today. It is very possible that some of your tuning issues are due to temperature fluctuations.

In 79, I was crazy enough to use the IIP on stage at the Troubadour in LA. Every time a spotlight was on me, it also hit the Moog and the tuning when to s*&t. Last time I used it live...

I have the backs off both my vintage P Cabinets. (Never actually had them...) They are about 6 inches from a wall, but that wall has been covered in acoustic foam (which is a great insulator). With the backs off, there is no heat buildup. Once the room heats up in the morning, the temp is pretty stable throughout the day. My system stabilizes pretty well in about an hour and stays that way until I shut it off.

[Rarecomponentadsr]

I made natty little thermal jackets out of thick packing foam for the relevant transistors in the 901a/b ‘s
Seems to help and worth it for the sound of the 901b’s.
Takes an hour and costs nothing.

[ummagumma]

are the oscillators more stable when warm, or cool? or it doesn't matter, as long as the temp is constant?

thinking of a small HVAC unit with a thermostat.....you could build a little beer fridge inside one of those cabs!