Looking for schematics for the Big Briar 91A mod

Hi, I recently acquired a 91A theremin which I am quite happy with, but would very much

like to get the mod done on voice #2, which is supposed to allow for a tone close to that

of Clara Rockmore's theremin.

 

I was disappointed to find out that this Bob Moog's schematic is not readily available. I have a

good technician waiting to do the job if I can locate one somewhere. Does anyone have

or know of someone who might have it. Would much appreciate the help, thanks!

 

Adam

Montreal, Canada

Hi Adam,

this 91A mod was recently discussed on the Levnet mailing list and a Canadian 91A owner which has got this modification promised to send me high-res pictures from his audio circuit board, so that I could try to reverse-engineer it by comparing to my high-res pictures of an unmodified 91A board. But up to now I didn't yet receive the pics. As soon as I can advance on this subject, I'll post the news here.

Merci!

 

Hi Adam,

this 91A mod was recently discussed on the Levnet mailing list and a Canadian 91A owner which has got this modification promised to send me high-res pictures from his audio circuit board, so that I could try to reverse-engineer it by comparing to my high-res pictures of an unmodified 91A board. But up to now I didn't yet receive the pics. As soon as I can advance on this subject, I'll post the news here.

Thierry wrote: ".....a Canadian 91A owner which has got this modification promised to send me high-res pictures from his audio circuit board..."

 

Hmmmmmm.....I wonder who that could be?

 

Sorry guys, I have been rather busy lately and the whole thing just slipped my mind. I'll try to get around to it this week. 

 

The modification in question was supposed to emulate the sound of Clara Rockmore's instrument but I am sorry to say it doesn't even come close.

Sorry for my poor English grammar, it should read "... 91A owner who has ..."

Please accept my apologies!

Hello coalport,Thierry, haven't checked in for a while, still very interested in this mod and the schematics. Any progress on this? Adam

 

Hi Adam, when I purchased my 91A from Levnet founder Dave Ball, since he was living in Tennessee I had him ship the thing to Moog Music in Asheville N.C. so that the Rockmore sound modification could be made. The teks at Moog had quite a time trying to find Bob’s original specs. This was just a few months after Bob’s death in 2005. 

 

Although Bob promised to furnish SERIES 91 theremin owners with all the necessary diagrams and specifications so that repairs could be made to their instruments, this never happened. Now that Bob is gone, it will NEVER happen. 

 

 

I did take detailed pictures of my 91A circuit boards as I said I would, and I sent them to Thierry, but I do not know what he was able to deduce from them.

Hi, I recently acquired a 91A theremin which I am quite happy with, but would very much
like to get the mod done on voice #2, which is supposed to allow for a tone close to that
of Clara Rockmore's theremin.
 
I was disappointed to find out that this Bob Moog's schematic is not readily available. I have a
good technician waiting to do the job if I can locate one somewhere. Does anyone have
or know of someone who might have it. Would much appreciate the help, thanks!
 
Adam
Montreal, Canada

Greetings, enthusiasts of the theremin.
   I am quite interested in duplicating the 91A Big Briar. However, it is possible that I may succumb to the effects of aging before I succeed. But I have hope.
Here is my profoundly melancholic narrative...
My name is ROSS MARSHALL and I previously owned a B.B.91A, which I later sold after 10 years for double the original purchase price. I hope David Ball doesn't experience the same intense distress that I have felt in doing so. Subsequently, I discovered that no other theremin has such rapid responsiveness and linearity, as well as the necessary octaves. I have always found Clara's tube's "buzzing bumble bee" sound more appealing than the tone of the 91A. 
I have harbored remorse ever since. Here is my recent upload of my performance at the CIA club in the late 90's playing the 91A. I recently discovered a listing on eBay for a price of $10,000, but financially unable to purchase it...
     After misplacing my 91A, I subsequently considered obtaining the schematics. Moog's representatives failed to respond to my inquiry in the early 2000s. Since then, I have been pondering this matter.
Fortunate events occur: A decade ago, my brother and I encountered John Polstra, who resides on Lopez Island together with my brother. I live close on the mainland area! We went to the location, where I played his new tube theremin, and the man provided me with a duplicate!!! I currently possess a Polstra Tube theremin. Yet, the device exhibits sluggishness and lacks the quick response that I require, but it performs effectively, similar to Clara's device and sound like her bumble bees. 
    If anyone is interested in trading, I possess the schematics but you can get them from Polstra's web site. . However, I am of the opinion that Author Harrison's schematics are superior  because of using the older UX globe tubes. I have been experimenting with Clara's theremin design and making improvements, but I am not highly skilled in technical matters. However, Mr. Polstra appears to be a very skilled expert and is providing assistance.
Based on all the theremin posts and could provide some assistance in design. Mr. Polstra, with his professional expertise in electronics, could potentially contribute to the replication of MOOG's 91A IF if I had access to any and all available data and/or the schematics.
I kindly request permission and colaboration to acquire the high-resolution images of the aforementioned 91A. Polstra possesses the ability to efficiently deconstruct the boards and can easily understand their design. If others are engaged in this activity, we might collaborate in terms of designing and determining the necessary components.
     Please do not hesitate to contact me by any available means. I am serious and maybe wee can all succeed sooner.
I will soon upload images of my Polstra Tube Theremin and some videos playing on Youtube.
I can be contacted at: Please send what schematics and pictures you have to me- 
Ross S Marshall
4103 E. College Way, B110, Mt. Vernon, Wa. 98273
360-421-7195
CIA performance....
https://www.youtube.com/watch?v=1xBcVbARcYE

Hi Adam, when I purchased my 91A from Levnet founder Dave Ball, since he was living in Tennessee I had him ship the thing to Moog Music in Asheville N.C. so that the Rockmore sound modification could be made. The teks at Moog had quite a time trying to find Bob’s original specs. This was just a few months after Bob’s death in 2005. 
 
Although Bob promised to furnish SERIES 91 theremin owners with all the necessary diagrams and specifications so that repairs could be made to their instruments, this never happened. Now that Bob is gone, it will NEVER happen. 
 
 
I did take detailed pictures of my 91A circuit boards as I said I would, and I sent them to Thierry, but I do not know what he was able to deduce from them.

Mr. coalport, please reply on trading info on the 91A.
ROSS

PS. Question:
I am also looking for a technician qho has info maybe on advancing the RCA Clara's version for quicker volume response. What kind of extra circuit design could be added? Our recent experiments are not successful yet.
Please advise and contribute?
ROSS