Neumann BSB 74 Acceleration Limiter

[mossboss]

Here is the low down on this much misunderstood devise for all who care Some of the maths behind it as an explanation as well
It was circulated back on 24th of the 6th 1974 followed by another supplement at some later date as depicted here
There was a lot of questions raised at the time of the first circular regarding the various option available on this so the second page was circulated some time later
This was well before my direct involvement on the VMS's
I was told the background to the story by an old timer who is no longer with us unfortunately
So here it is and apologies for the delay Technical issues uploading this




and the second page



Ok Now Guys don't shoot the messenger please, further esoteric questions on the ins and outs on this directed to me would be out of order
Further and once again
I answered Concrete man's question as a simple number as that is what he asked for
My answer was based on this very paper as well as my very own experience and set up on owned VMS lathes
By the way we have yet to cook a head after about over 800 sides this year alone so far
Counting past cuts it would be getting to quite a few 1000's
Nothing wrong with Neumann's engineering either
It works
It ain't broke don't fix it
Further
The last paragraph has to be taken seriously
I would be very reluctant to disconnect the two channels
Some of the CD mastered crap that is submitted today with a few tweaks for an extra charge saying it is also mastered for Vinyl ready for cutting by some who call themselves Mastering Engineers leaves a lot to be desired
So care is called for unless you want to spend a day cleaning it up so as to be cut-able
Else one risks cutting a side with bad channel correlation or a differential in channel levels that may just give you a jumping stylus on play back
A worst case scenario do the head in but there is protection there regardless
Than it becomes a case why risk it
Not hard to do either two of the above
Than the boards are full of questions why is the stylus jumping when everything was A OK or why did my cutting head smoked?

Cheers

[Nickou]

Yes , the manual is a good reference , in fact the only one ...
cheers

[concretecowboy71]

Moss Man!

Sweet information. Thanks for taking the time to do that. It includes all the info I was personally looking for. And I am sure it holds info that those who understand the math may be able to mine for even more insight.

[mossboss]

Concrete man
Its all good mate
Happy to help any way I can
Take the things there as a given in this case there is little if anything to be improved
Its all quite simple really
Want a .6 mil radious?
You have to limit acceleration
How?
Limit current
To what level?
The example gives you the criteria the current setting and a plain enough explanation
Nothing more needs to be done there
No arguments or comments here so the light may have come on than
A good thing to
By the way I have started the process so as to have all of the VMS manuals bulletins and various other bits and bobs collected over the years scanned and put on a stick which will be available some time this year
Its a job and a half as some of the pages are A2 in size and some are A4 but folded over as many as 4 to 5 times Mostly A4 though some of them Typed on a typewriter Phew, early word processors? Ha Ha
Once it is done it will be available to any one as it seems that there are people out there without resource to them
There will be a cost as I am paying someone to do it
It will be kept as low as possible so the more copies people want the less the cost
It will include all the schematics operation manuals setting it up alligning the head Calibrating the chanels feedback adjustments Bulletins and notes etc etc etc
The whole shooting box and dice including the SP 72 SAL 74 B and VMS 66/70 bits, Sx 45 head, Sx 68 head as well as the SX44 to much to mention here
It may also save a lot of posts here that can be easily gotten from a reference to the manuals
Once the cost's associated with the excersise it will be made available here for members (as a down load) of this forum after a certain amount of posts I suppose or some formula that warrants it
The one offered on ebay is as useful as Tits on a bull
Cheers

[opcode66]

I'll buy a copy!

[concretecowboy71]

I would buy a copy also.

I have a few bulletins, including one about half-speed mastering. It is pretty funny actually. Who ever wrote it, was not really a fan.

I also have one for replacing the half-nut, that would be a god send for anybody that does not have it.

[greybeard]

mossy, count me in among the paying guests. I am happy you are not spending personal time on this, but that you are overseeing the quality.

I can tell you that the jpg files you sent behaved very strangely when i made them into a pdf document: the width was 3x the height. O.K. I converted to tiff files. Then Adobe made it into two properly proportioned pages, but they are negative! Something odd is definitely going on. I shall probably have to make negative tiffs.

[opcode66]

I've scanned and compiled a number of docs into pdf files. I would be happy to help if need be. Sounds like Mossy has it under control though.

@concrete - that would be a good resource to have. One problem though. Where does one get a replacement halfnut at this time?

[concretecowboy71]

As far as the half nut is concerned, A good machinist should be able to make a drawing from an old one and then make one out of the proper material (nylon?? Is that correct?).

I am lucky to know two guys that are skilled machinists and like the challenge of new parts. If I could score a half-nut somewhere, we could all pitch in an have spares made.

[mossboss]

Hi Guys
My man has already photocopied the manuals with a photocopier on steroids which we have in Melbourne Its about $150K odds worth
He spend quite a bit of time cleaning up some of the copied pages so it looks OK the manuals are pretty dry and yellowing
The next step is to now scan this new photocopy than put the lot on a stick Actually there woud be two or 3 files there so as to print out the diff paper sizes
No point in printing it out and offer hard copy To heavy to ship out
He was not impressed when I suggested to him He did say its a pain but easier now with the new paper as it can feed through the scanner
Argh well It has to be done
Half Nut's
Not a big deal for a machinist at all
Nylon was the material in actual fact Nylon 6
((diversion useless info ) Its called Nylon as it was developed by two teams One in NYork the other in LONdon))
Their where machined out of two pieces stuck/glued together
Now days very thin industrial double sided sticky tape will do the trick
After machining and thread cutting they where separated so you got two nuts one did not have to mill the piece down to get one of the halfs
Any macinist with a reasonable thread cutting lathe can do them
The space/gap was as small as possible As a guess a bit of paper glued there would do the job Part them of throw the lot in a bucket of water for a while so the paper got soft than split them up
Cheers

Cheers

[mossboss]

GreyBeard
These two pages where first copied Than scanned and cleaned up so they look reasonable
In other words they where edited in something, Photoshop I think,
He is a pro printer so he knows what hes doing
I think I know what you mean but as I had trouble up loading them here
Not sure what he done I wasnt there did not ask but I got him to upload them I could not get it to work
I struggled for a couple of days he did with a few strokes
Horses for courses I suppose
Cheers

[greybeard]

Hi Mossy,

the things you may have to do to yellowing and creased paper to make a cleaned-up version -- I have tried the lot. Sometimes channel separation and working on the grey of the three that has the greatest contrast will get you there quicker. The point is, if you do it all the time you get the hang of it and are efficient, if you only do it rarely, then it is quite cumbersome. You have to save a lot of files and devise ways to let the file name tell you which parameters you adjusted. Now, the real trick is to end up with a one-bit (black/white) image that is still clear. That takes up so little space compared to a raw scan of the same resolution, about 10%. I once downloaded a document from a slow .edu website: 50 MB. I took each page, straightened the skewed pages, adjusted gamma and reduced bit depth. In the end I had a nice 5 MB document. I sent it to the .edu person who had written it and made the original scan, to use as a replacement, but the old 10-minute version is still there. Oh, well, when I use the document I use my own, and I look at it with the old Dulux phrase in mind: "I did this". The important thing for me is that the 1-bit version prints in black and white from pdf, but just a bit more gives me halftone printing with a not very good screen resolution.

There are people out there who scan yellowing pages of old journals, and then OCR convert the text to a modern font very similar to the original, interspersed with original scanned images. This makes for a hybrid document that is generally easier to read, but some of the original feel drains away at the same time, IMHO. So, please do not go as far with the scanned versions.

[mossboss]

Grizo
I hear you Instruction out already Hey its a matter of authenticity as well after all
Cheers

[mossboss]

I would buy a copy also.

I have a few bulletins, including one about half-speed mastering. It is pretty funny actually. Who ever wrote it, was not really a fan.

I also have one for replacing the half-nut, that would be a god send for anybody that does not have it.

Argh The half speed mastering
Neumann never went along with this idea In actual fact they resisted it for a long time
The reason behind the resistance was the fact that some "pushing" its always possible or even there on any cut
In simple terms the stylus pushes the material away rather than cutting it as it suppose to
Half speed accentuates this effect so it was resisted for a long time until the point was reached that they yielded
As a bit of useless background
Half speed come about by some one cutting with the standard 16 2/3 rpm for a 33 1/3 cut with the tape down from 15 to 7.5 inches
I was told that this started the trend or demand for half speed cuts as it certainly sounded different No idea who it was or what was cut But it was a deliberate act on the cutters part not an experiment
Cheers

[opcode66]

The most significant points in the half speed cutting bulleting:

“We know of no technical reason which would move us to recommend this process to anyone.”

“those which tend to emboss or “push” the lacquer – appear to be increased at half speed.”

“We furthermore believe that the loss of one octave at the bottom of the range is significant enough to cast doubt on the feasibility of this technique.”

The other interesting part is at the end. They show you the eq curve you need to apply in order to use the RIAA built into the amp rack while cutting at half speed. No mod to the RIAA in the amp or pitch computer are necessary as long as you build the equivalent passive eq circuits and feed your preview and program signals throught them.

[JayDC]

lol.. i think know what this really does now.. I'd toss it out of the chain..

it's all in how you look at the word "acceleration"..


peas..

[mossboss]

Hey when you spend your $30-40 k for your system you can do that
On my systems if any one suggests or attempts to get it off the chain they get thrown out
Guess what they never get another look in
Cheers

[opcode66]

I like to have head protection. And, they are made very well. You can tune the Reduction knobs to zero in on just the right amount of reduciton so it isn't noticeable but is still kicking in when the highs are sustained. The signal is split and recombined. The lows are not touched. If you jack the reduction it sound horribly muffled and wouldn't be what you want to cut to disc. But, after adjustment it really works well.

[JayDC]

Hey when you spend your $30-40 k for your system you can do that
On my systems if any one suggests or attempts to get it off the chain they get thrown out
Guess what they never get another look in
Cheers

lol.. it was just a suggestion.. please don't kill me.. hahaha

I personally think a scully/westrex or a lyrec/ortofon combination is a better alternative. Wish you could use a presto/presto combination, but a there was never a stereo presto head.. I just want to feel the love on vinyl, not get everyone all crazy..

[mossboss]

Todd
100% correct Keep it there and you would never have a stylus jumping out of the groove
Unless of course the signal is out of phase which can sometimes sneak through just at the boarder
Better Still, head will always be SAFE
Cheers