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Buchla Music Easel keyboard tracking
MUFF WIGGLER Forum Index -> Buchla, EMS & Serge Goto page 1, 2  Next [all]
Author Buchla Music Easel keyboard tracking
sharema
Hi there,

i know it is in some way accepted that the Easel keyboard does not track well the pitch. But is it normal that in the higher frequencies this gets even worst and not even one octave is well tracked? Is the trim on the oscillators made to fine tune and correct this behaviour?

Thanks..
Citisyn
You may need to adjust the internal trimmers. Mine had similar tracking issues, but now it tracks pretty well over five octaves. A post toward the end of this thread describes the procedure: https://www.muffwiggler.com/forum/viewtopic.php?t=115374&highlight=
JamieH
As the above post, as I understand the tuning is slightly compromised for midi compliance, however I can get mine to be pretty good over 3-4 octaves, but I now like that it kind of does its own thing, it's got a its own character cool
abmusic
Same. I get about 4 octaves reliably. Have to usually do a little dialing in if there is any software stuff playing.
b4dw0lf
Mine also will track quite well but I have a few caveats.

The first few minutes from powering on the easel the tracking is all over the place. (I saw Todd Barton recommend not doing anything at all with the easel for the first 5 mins. This seems like very good advice).

Over the next 30 mins I find it reaches a stable zone where it will track pretty well almost to 5 octaves. This when adjusted correctly using the trimmers on the front panel.

I do find it continues to drift very slightly from here for the next 6 hours. after this point it seems rock solid. Just analog being analog

I did some testing and I am playing with this idea of putting a tempco like resistor on/above the surface mount ssm2212 (UA726 replacement(ish)). Adding some very light heat to the transistor package speeded up the time to good tracking and it did not deviate too much while the heat was constant. If no one else can replicate this mine might just be a little sensitive.

I don't feel changing the SSM chip for a real UA726 will not make that much difference but if anyone can prove different I am more than willing to entertain this.
synthi
b4dw0lf wrote:
Mine also will track quite well but I have a few caveats.

The first few minutes from powering on the easel the tracking is all over the place. (I saw Todd Barton recommend not doing anything at all with the easel for the first 5 mins. This seems like very good advice).

Over the next 30 mins I find it reaches a stable zone where it will track pretty well almost to 5 octaves. This when adjusted correctly using the trimmers on the front panel.

I do find it continues to drift very slightly from here for the next 6 hours. after this point it seems rock solid. Just analog being analog

I did some testing and I am playing with this idea of putting a tempco like resistor on/above the surface mount ssm2212 (UA726 replacement(ish)). Adding some very light heat to the transistor package speeded up the time to good tracking and it did not deviate too much while the heat was constant. If no one else can replicate this mine might just be a little sensitive.

I don't feel changing the SSM chip for a real UA726 will not make that much difference but if anyone can prove different I am more than willing to entertain this.


I had the same problem as you, the easel with the SSM take hours to estabilize pitch. I measured the drift and its more than a semitone(!!!) continuosly rising along a period of 2-3 hours at least, making it unusable for any musical work, also I was afraid of the continous trimming and the life of the trimmers. To make things worst, (try it), just switch the easel off and then on again within a few seconds and the pitch is still as at the beginig: all over the place, the scaling off, etc... and you must wait again during hours to stabilize. and I´m speking in a studio enviroment!!! a place with a more or less constant and controlled temperature!

I asked BEMI and they sent me replacement boards (mine original boards had the SSM "adapter" in place of the UA726). The new boards have the ssm soldered in and there seem to be som changes to help the oscillators. I was exciting when I received the new OSC boards, so finally I could work with my Easel. Changed the OSC cards and....Exact the same behaviour... waah

About that time I also received a couple of UA726s and since I had nothing to loose, I took my old (original) OSC cards witht he SSM adapter and replaced them with real UAs...and.... MAGIC!!
Now it work as it should. It takes 5 minutes to stabilize pitch at 100% but is in tune and scaling withing cents in about 30 seconds.
I told BEMI about this but never got a reply related to my questions. I had to spend almost 250USD for having my easel working at it should.
I`m tired of ttrying to comunicate with BEMI but in some tim will restart to ask for either UAs or old cards with real UAS in place, well and a new redesigned OSC board that actually work....

Most of my problems with the Easel and BEMI are in the thread: "Is BEMI ignoring me?" here:
https://www.muffwiggler.com/forum/viewtopic.php?t=149024&postdays=0&po storder=asc&start=0

I spoke with some people here and also some techs and reading the specs for the SSM (on paper) should work, so there are two theories: BEMI is using counterfeit/rejects SSM ICs, or the SSMs don´t work in that circuit without a true redesign, not only a drop-in replacement.

So if your Easel have the old OSC cards with that SSM adapter you are really lucky. throw away the SSM adapter card (no need to desolder, its fitted in the transistor header!!!) put a couple of real UAs and your life will change...
Good luck! Rockin' Banana!
I
ttown23
As the person who sold the 2x UA726 chips to synthi, I am very happy to hear that these worked out!

I have taken a look at the hi-res images of the "SSM adapter board" that BEMI is putting into the newer Easel. My suspicion, though I have not confirmed this by obtaining and testing one of these adapter boards, is that the implementation of the SSM2212 chip in that adapter board. Specifically, it seems that a TEMPCO was left out.

More information on this topic can be found here:

https://www.muffwiggler.com/forum/viewtopic.php?t=160337&postdays=0&po storder=asc&start=25&sid=3b4f8a526f13644bddcd1634b50c9b8c
analoglsd
ttown23 wrote:

I have taken a look at the hi-res images of the "SSM adapter board" that BEMI is putting into the newer Easel. My suspicion, though I have not confirmed this by obtaining and testing one of these adapter boards, is that the implementation of the SSM2212 chip in that adapter board. Specifically, it seems that a TEMPCO was left out.


Mine has the SSM adapter board and no TEMPCO resistor and is extremely sensitive to temperature changes.

synthi wrote:

I asked BEMI and they sent me replacement boards (mine original boards had the SSM "adapter" in place of the UA726). The new boards have the ssm soldered in and there seem to be som changes to help the oscillators. I was exciting when I received the new OSC boards, so finally I could work with my Easel. Changed the OSC cards and....Exact the same behaviour... waah


Mine exhibits the same behavior that yours did before you installed the UA726. When they sent you the new OSC boards, did they just have the TEMPCO resistor installed?
sharema
Hi all, thanks for all the relplies. I see the topic took a path i am not very comfortable with: putting my hands inside the easel..

To sumarise:
1. I read about trims in the BACK of the 208 and from what i understood i have to move them to make my first attempt to correct the tracking, but now my question is: what is the role of the trims in FRONT of the easel?
2. Going on on the discussion, people started speaking about changing components of the easel! But from what i understand this is necessary not for the tracking itself but to have a stable pitch faster, correct?
vgermuse
sharema wrote:
...but now my question is: what is the role of the trims in FRONT of the easel?


These trim pots scale the over all tuning.
Here's a recent video on how to tune the easel with those trim pots


Posted in this thread:
https://www.muffwiggler.com/forum/viewtopic.php?t=162124
synthi
Quote:


Mine has the SSM adapter board and no TEMPCO resistor and is extremely sensitive to temperature changes.


Mine exhibits the same behavior that yours did before you installed the UA726. When they sent you the new OSC boards, did they just have the TEMPCO resistor installed?


Is not enought to put a tempco in the unused holes in the adapter board, it will do nothing. The circuit must be redesigned to make use of a tempco. The SSM+tempco is not a direct replacement, the UA is stabilizied with an "oven" that keep it warm and at an stable temperature. The tempco is a resistor that changes its resistance with temperaturwe variations. You see those are different methods, not interchangeable...
For your second questions, the replacement OSC boards that BEMI sent exhibit the exact same behaviour than the old ones. The new ones don´t have tempcos, is not a circuit redesign. AFAIK just the SSM is soldered and they add a trimmer to the board (that was hot glued to the PCB in the "old" cards) meh
synthi
sharema wrote:
Hi all, thanks for all the relplies. I see the topic took a path i am not very comfortable with: putting my hands inside the easel..

To sumarise:
1. I read about trims in the BACK of the 208 and from what i understood i have to move them to make my first attempt to correct the tracking, but now my question is: what is the role of the trims in FRONT of the easel?
2. Going on on the discussion, people started speaking about changing components of the easel! But from what i understand this is necessary not for the tracking itself but to have a stable pitch faster, correct?


You use the internal trimmers for:
A/ for setting the oscs initial frequency (ie, you play C note but when perfectly tuned the "fine" knob is not centered, you can correct that
B/ Hi freq compensation- the OSCS will be out of tune in the upper registers, with this trim you can make both oscs be "untuned togueter" hmmm..... Mr. Green yes out of tune but with no beating between them.

the scaling is done with the front panel trimmer.

The changed components (UA726) makes the easel work as it should. the early easels from BEMI had UA726 (the same as the original easels) and they work fine; then they began to use a cheaper part and without any kind of temperature compensation that makes the easel oscs unusable for any musical work. A musical instrument that takes hours to stabilize pitch (!!!) and just switching on/off will beging the process from the begining is useless. I can´t imagine how can be this issue in a live enviroment, or just with a intermitent light near the easel.
Is not just a question of "how fast". As a reference I have my EMS synthi AKS next to the easel, a 1973 model with the original oscillators (no tempcos) and it takes "only" 10-15 minutes to completely stablize and comparing with the easel (with the SSM ics) the Synthi is rock solid tunewise.
synthi
ttown23 wrote:
As the person who sold the 2x UA726 chips to synthi, I am very happy to hear that these worked out!

I have taken a look at the hi-res images of the "SSM adapter board" that BEMI is putting into the newer Easel. My suspicion, though I have not confirmed this by obtaining and testing one of these adapter boards, is that the implementation of the SSM2212 chip in that adapter board. Specifically, it seems that a TEMPCO was left out.


Thanks!!!! Yes your UAs made my Easel enjoyable, a true instrument, as it should be!!!! Mr. Green

Also as I pointed, yes the pads acrosss the SSM iC in the adapter board calls for a tempco but is not enought just putting a tempco there: the osc circuit must be redesigned so the resistance variations with the temperature in the tempco is actually compensating the pitch...
synthi
vgermuse wrote:

These trim pots scale the over all tuning.
Here's a recent video on how to tune the easel with those trim pots


Thanks Todd for all your help to the easel users, but also for your wonderful sounds and music smile

I`m pretty sure you have an early BEMI easel with the UA726s in the oscillators. Did you tried one of the newer Easels with SSM ics in a musical context yet? have you compared or checked those tunning issues?

Thanks!
Drillionaire
synthi wrote:
Also as I pointed, yes the pads acrosss the SSM iC in the adapter board calls for a tempco but is not enought just putting a tempco there: the osc circuit must be redesigned so the resistance variations with the temperature in the tempco is actually compensating the pitch...

The pads for a resistor on the SSM2212 adapter PCBs were for a potential heater resistor that was never implemented.

As for a tempco, as far as I know, the latest 6B and 7B cards are being built with a tempco that makes the tuning stable within ~±15 cents over temperature fluctuations (even being a centimeter or so away from the SSM2212 on the PCB).
The resistors that are replaced are R92 and R112 on cards 6B and 7B respectively.
They're both 330 ohm resistors and should be replaced with 330 ohm tempcos with a coefficient of 3300ppm/ºC.
I believe these are what are being used: http://www.mouser.com/ProductDetail/Panasonic/ERA-S33J331V/?qs=sGAEpiM ZZMu61qfTUdNhG30u3hgzjZBwmtJAmp3KPU8%3d
vgermuse
synthi wrote:
vgermuse wrote:

These trim pots scale the over all tuning.
Here's a recent video on how to tune the easel with those trim pots


Thanks Todd for all your help to the easel users, but also for your wonderful sounds and music smile

I`m pretty sure you have an early BEMI easel with the UA726s in the oscillators. Did you tried one of the newer Easels with SSM ics in a musical context yet? have you compared or checked those tunning issues?

Thanks!


Thanks synthi for all your great contributions too!
I'm on vacation and away from the Easel will check it upon my return.
It's been through many permutations, new cards etc over the past few
years. I'll have to look at the cards to answer your question. Best wishes and thanks w00t
Minimoog56
Thanks Drillionaire!
synthi
Drillionaire wrote:
synthi wrote:
Also as I pointed, yes the pads acrosss the SSM iC in the adapter board calls for a tempco but is not enought just putting a tempco there: the osc circuit must be redesigned so the resistance variations with the temperature in the tempco is actually compensating the pitch...

The pads for a resistor on the SSM2212 adapter PCBs were for a potential heater resistor that was never implemented.

Thanks a lot for sharing your knowledge drillionaire smile, yes I know the pads in the adapter goes to voltage points thats why say a tempco there will do nothing. At one point in my desesperation because the tunning problems I was thinking in using a kind of little low voltage lamp there to maintain the ssm hot....

Drillionaire wrote:
As for a tempco, as far as I know, the latest 6B and 7B cards are being built with a tempco that makes the tuning stable within ~±15 cents over temperature fluctuations (even being a centimeter or so away from the SSM2212 on the PCB).
The resistors that are replaced are R92 and R112 on cards 6B and 7B respectively.
They're both 330 ohm resistors and should be replaced with 330 ohm tempcos with a coefficient of 3300ppm/ºC.
I believe these are what are being used: http://www.mouser.com/ProductDetail/Panasonic/ERA-S33J331V/?qs=sGAEpiM ZZMu61qfTUdNhG30u3hgzjZBwmtJAmp3KPU8%3d


Do you know what revision is using the tempcos? The new osc cards I received have the ssms soldered. Don´t know if they have tempcos installed or not but the tunning issues are the same as with the old cards with the adapters. The only cure for mine is using UA726s... I can post a pic for the "new" boards I got.

Thanks again!
jurekprzezdziecki
synthi wrote:
b4dw0lf wrote:
Mine also will track quite well but I have a few caveats.

The first few minutes from powering on the easel the tracking is all over the place. (I saw Todd Barton recommend not doing anything at all with the easel for the first 5 mins. This seems like very good advice).

Over the next 30 mins I find it reaches a stable zone where it will track pretty well almost to 5 octaves. This when adjusted correctly using the trimmers on the front panel.

I do find it continues to drift very slightly from here for the next 6 hours. after this point it seems rock solid. Just analog being analog

I did some testing and I am playing with this idea of putting a tempco like resistor on/above the surface mount ssm2212 (UA726 replacement(ish)). Adding some very light heat to the transistor package speeded up the time to good tracking and it did not deviate too much while the heat was constant. If no one else can replicate this mine might just be a little sensitive.

I don't feel changing the SSM chip for a real UA726 will not make that much difference but if anyone can prove different I am more than willing to entertain this.


I had the same problem as you, the easel with the SSM take hours to estabilize pitch. I measured the drift and its more than a semitone(!!!) continuosly rising along a period of 2-3 hours at least, making it unusable for any musical work, also I was afraid of the continous trimming and the life of the trimmers. To make things worst, (try it), just switch the easel off and then on again within a few seconds and the pitch is still as at the beginig: all over the place, the scaling off, etc... and you must wait again during hours to stabilize. and I´m speking in a studio enviroment!!! a place with a more or less constant and controlled temperature!

I asked BEMI and they sent me replacement boards (mine original boards had the SSM "adapter" in place of the UA726). The new boards have the ssm soldered in and there seem to be som changes to help the oscillators. I was exciting when I received the new OSC boards, so finally I could work with my Easel. Changed the OSC cards and....Exact the same behaviour... waah

About that time I also received a couple of UA726s and since I had nothing to loose, I took my old (original) OSC cards witht he SSM adapter and replaced them with real UAs...and.... MAGIC!!
Now it work as it should. It takes 5 minutes to stabilize pitch at 100% but is in tune and scaling withing cents in about 30 seconds.
I told BEMI about this but never got a reply related to my questions. I had to spend almost 250USD for having my easel working at it should.
I`m tired of ttrying to comunicate with BEMI but in some tim will restart to ask for either UAs or old cards with real UAS in place, well and a new redesigned OSC board that actually work....

Most of my problems with the Easel and BEMI are in the thread: "Is BEMI ignoring me?" here:
https://www.muffwiggler.com/forum/viewtopic.php?t=149024&postdays=0&po storder=asc&start=0

I spoke with some people here and also some techs and reading the specs for the SSM (on paper) should work, so there are two theories: BEMI is using counterfeit/rejects SSM ICs, or the SSMs don´t work in that circuit without a true redesign, not only a drop-in replacement.

So if your Easel have the old OSC cards with that SSM adapter you are really lucky. throw away the SSM adapter card (no need to desolder, its fitted in the transistor header!!!) put a couple of real UAs and your life will change...
Good luck! Rockin' Banana!
I


i have got the same problem. mod osc is unstable all the time. no warm up helps. the drift sounds like random pitch modulation. it makes mod osc useless - i use it only for modulation for principle. the problem is frustrating i must say and it needs to be fixed. anyone recommends a solution in europe?

my easel is late 2015.

thanks jurek
Drillionaire
synthi wrote:
Do you know what revision is using the tempcos? The new osc cards I received have the ssms soldered. Don´t know if they have tempcos installed or not but the tunning issues are the same as with the old cards with the adapters. The only cure for mine is using UA726s... I can post a pic for the "new" boards I got.


The tempcos are green and smaller than all the other resistors on the 6B and 7B cards. There are some rev4 cards that had the tempcos installed by hand. I believe there are newer cards marked "rev4/5" that have the tempcos installed by the pick and place machines like all the other surface mount components.

I might be able to get a picture of the rev4 cards with the tempcos installed in the next few days.
10 Miles High
Hi fellow wigglers,

I have Roman's 208r here (absolutely loving it) and I am just unable to tune the modulation OSC. Complex OSC tunes fine, but with the Mod OSC the trim pot just doesnt go as far as I would need it to be to narrow the tracking enough. The screw just won't let me narrow the tracking, every octave on the keyboard spreads wider then it should.

Roman himself seems to be quite busy now (and far away also), but maybe someone out here can give me a hint. Would it be feasible to exchange the trimming pot or maybe I could put a resistor after it (to narrow the tracking).

But which value (replacement pot or additional resistor) would be right? I am totally lost on this.

help

10 Mh
jurekprzezdziecki
So my issue was resolved. The problem was a faulty potentiometer of fine tuning. Terminals pots was broken and not contacted what was caused the faulty current flow and as a result of jumping pitch. Unfortunately, all potentiometers used in the instrument are very bad quality. Two volume ones was scratchy as well. Basically all the potentiometers have been replaced and the problem disappeared. So I'm happy again. I must mention that the professional inspection of the instrument was done by polish engineer Roman Sowa, to whom I am grateful and I recommend it wholeheartedly if you have a similar problem, or need professional service in Europe.

http://www.midi-hardware.com

Jurek
synthi
Drillionaire wrote:
synthi wrote:
Do you know what revision is using the tempcos? The new osc cards I received have the ssms soldered. Don´t know if they have tempcos installed or not but the tunning issues are the same as with the old cards with the adapters. The only cure for mine is using UA726s... I can post a pic for the "new" boards I got.


The tempcos are green and smaller than all the other resistors on the 6B and 7B cards. There are some rev4 cards that had the tempcos installed by hand. I believe there are newer cards marked "rev4/5" that have the tempcos installed by the pick and place machines like all the other surface mount components.

I might be able to get a picture of the rev4 cards with the tempcos installed in the next few days.


My replacement cards don´t have tempcos... they are rev.4 boards. I have some tempcos on hand (big ones, 1K and 2 K I think, could I use them insteead of the 330ohms???
Tnanks!!!
CliffordMilk
I have an early BEMI Easel and want to swap the socketed UA726 replacements for the real thing. Could anyone please help me get the UA726 orientation right? I’m really not sure which pins correspond to which sockets.
papz
Is a component shape showing the µA726 tab position not drawn on the PCB ?
The tab is pin 10.

Replacing the expo converter will most likely need a recalibration of the oscillators.
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