ZA-21 Light

[opcode66]

I have come across an original ZA-21 BM light fixture. The bulb tones on my multimeter, so it seems to be intact. Can anyone tell me what sort of voltage it needs. I just have two bare wire ends...

[opcode66]

BUMP

I just need to know how much voltage to give this light. It is a The Buchman-Meyer Calibration light. ZA-21 in the Neumann literature. I can't find anything that tells me what the bulb is rated for. There are no markings that I can see. One can only assume it runs on AC. Just need to know how much.

[Radardoug]

Put it on a variable power supply, and turn it up slowly till it reaches the required brightness. Its not rocket science.

[opcode66]

No thanks. I would rather find out the original specification first. Then source a proper transformer.

The bulb is very specialized. It is simply too valuable to risk...

Finally, it wants AC. Not DC. Most variable power supplies are DC. I think you mean a Variac.

[Radardoug]

A filament bulb will run on AC or DC. It doesn't mind.
You could use a variac. Or you could use a d.c. supply as suggested.
I have seen articles from you that suggest you are experienced with electronics.

[opcode66]

1. This bulb is one of a kind. I searched for 3 years for one.

2. I am unwilling to risk running anything but the original specification through it.

3. You have the natural given right to believe anything you want.

4. I am careful as hell when it comes to Neumann gear.

5. I have the devices I've made, video of those devices working, tons of posts that indicate I know what I'm talking about, inventions that are near completion that will be released to the community, I've assisted other cutters with my knowledge. I have absolutley nothing to prove to anyone.

[Radardoug]

By the way, looking in the VMS66 manual the microscope light is specc'ed at 6 volt 15 watt. Maybe the same one?
However the power supply diagram shows the microscope lamp supply as 9 volts a.c.
So even Neumann don't know!

[opcode66]

This is the very special bulb. You can see there are patterns in the glass of the bulb that I searched over 3 years to find. Not going to easily find another working one. Therefore my care as its custodian. Not the same as the scope bulb which I have an entire bag full of.

[opcode66]

The Buchman-Meyer light is the only way to actually measure modulation (i.e. volume) on disc. Volume on disc is truly measured in cm/s. It is a measurement of the velocity of stylus as it is plays the grooves. If we were cutting sine waves, the velocity is the highest at the zero point of the wave. At the top of the wave and bottom is when the velocity goes to zero and movement reverses direction. You can use a Buchman-Meyer light to measure the modulation levels of the various frequencies on the disk. The light causes patters to easily be seen and therefore measured. So, the patterns on the glass of the bulb, its brightness, the throw distance and the angle at which you have the light casting on the disc are all important factors to get right. Therefore, getting the power correct (instead of guessing as Radardoug suggested) is a good idea.

[audadvnc]

This bulb is for viewing the "Christmas tree" modulation pattern I take it?

[dubcutter89]

I'm no owner of the za21 but afaik it is just a spot light (but I'm not able to tell this from the shape of a light bulb)

@opcode

if you really want to save that bulb, why not just try to insert another one (standard bajonet connector?) with known ratings and give it a try?
or maybe you can compare it by size/ohm rating of filament to some known bulbs in your drawer...

Lukas

[Stevie342000]

I figured out what the light is but would have liked more clarity on it. Yep I get I must be careful bit too (but why this preciousness, it's just a thing, an object, at some point it will fail and where will your precious obsessiveness be then?). I get the caution too but not previous part of attachment of such importance, to an object. The factor that is not know is the working volts? It could be 60V or 110V or 240V. It will only give you the results you are looking for with the light pattern on an AC supply, yep got that figured.

I get the I wish to acquire the knowledge too, so what do we have a ZA21 is a light bulb that tones? All light bulbs will tone on an AC volts supply at the frequency of that supply.

What do we know about Buchmann-Meyer light patterns. I know little, I get it in principle (I learn most effectively by seeing or doing not just reading), but how do you physically measure that you are cutting at X or Y Hertz (cycles) at Z inches (Centimeters) per second. I get the up to crossover point in RIAA curve it acts as constant amplitude and above crossover it acts as constant velocity (or is it the other way round, never remember that, I don't need to I just need to know it does that). I suppose I could go read it up in Sound recording by Oliver Read but for me it serves no purpose or as yet it has no identified purpose. I don't see how you physically measure with the light and then translate that into the information required or what the information that can be gained by cutting light patterns is.

Is it not just simple to measure each component part i.e. power amp correct its response so that it's flat, cut a disc then compensate for the cutter head, I can do that, I got that figured but light patterns seems like a lot of effort to me for what is just a hobby for me. I don't need it, I would however like to know how it works and why?

Ah a light has just dawned, that bulb has a grid pattern etched on its outside or inside right, so when you cast a beam of light at the correct angle as shown in Read book you can physically measure the discs right. There must be a reference chart that you then refer to or a formulae which will tell you what dB you are out by. Sorry apologies ducking now, right heads up, if you could get an (scanned) image in some way of that grid on the bulb could you not then replicate it i.e. transfers. So you get that pattern when using a regular bulb. I do not think the bulb is that important which I think is the point Radardoug was making what is important is the grid pattern it casts and or maybe the frequency it is operating at, so you can measure the results.

Personally I still think it's easier to cut disc at required equalisation 78, RIAA, NAB or whatever you fancy from your old fashioned method like me or from you lap top or digital source on a previously equalised or compensated system and then measure the output from that known frequency at a known level on an equalised or compensated playback system. This would then tell you what further compensation you needed on the recording side.

[opcode66]

I've located the answer independently. Drum roll......

6 Volts 15 Watts

Very low power.

--------------------------------

I don't really have the time to try to clone this bulb. Nor the want. There are other projects that I will be offering soon as products. Those require my free time.

This has nothing to do with calibration of my cutterhead. Of course, I follow the Neumann calibration procedure and use a NAB test tone record with properly calibrated VU meters and a properly adjusted playback cartridge. I want to use the light for other purposes. I want to accurately be able to measure modulation on disc. But, not to calibrate my SX head. When shown on the disc, a sort of christmas tree like pattern emerges and can be measured. It is terribly handy for analysis. I am gathering a variety of tools and materials necessary to do certain work. This is one of them.

When you say "All light bulbs will tone on an AC volts supply at the frequency of that supply." you are not understanding what I was saying. I set my multimeter to the connection testing mode where it gives off a tone when the probes are connected. The tone indicates closed connection. You can use this to test fuses. You can also use this to test light bulb filaments. I got a tone when connecting the leads to the two terminals of the socket style bulb. Thereby indicating that the filament was good. It was not blown (not an open connection).

[Stevie342000]

Well that is good news, that is a very low voltage low watt bulb indeed.

It may be worth gathering the data i.e. what the mesh size is that is cast (I am assuming this is what happens) lest that should not be visible or information you would be able to gather when this bulb bits the dust. It will eventually it may not last that long. Perhaps a clear laminate sheet would suffice made up to the same grid size.

Where did you find the information? It was buried somewhere in the User manual for the Neumann?

I may not have been clear what I was referring to was with reference point to all frequencies from say 20 Hz to 15 plus kHz at 0dB. You can add compensation to ensure the record or playback chain as flat as possible to 0dB from end to end. But the Buchmann-Meyer technique refers to the level for a known frequency which gives you the level of the cut in cm/s.

Yes I got the buzzer from your multimeter indicating that it was not short circuit. I/we will await news of your other projects they maybe of interest to me but are probably outside of my requirements.

I am glad you found the information and shared it with us all, I do not have a Neumann but do find them fascinating. They are nothing if not ticklish (complicated) machines but when set they perform for awhile but need constant attention? I have no experience of Neumann but know they are the best.

But out of preference I would prefer a Scully both suffer from nerves brought on by age but not so much to go wrong with a Scully built to run for years and years and years. Neumann's tend to have electronics in them which are obsolete or many of the transistors or some of the i.c.s are. Which is the reson d'etre I stick with tube/valve electronics. You can do most things with tubes that you can do with solid state and it keeps the room warm as well, which eases cutting

Perhaps you could come up with a post on how you use Buchmann-Meyer light beams and actually measure the cutting level in cm/s. That I would be interested in seeing and it would be of use to many others I am sure. It's the how you translate the light beams into cutting level that I do not get right now. Is there a chart to reference to in relationship to how many wiggles you get per cm at a known frequency that has been cut? I know your busy but that would be

I know what the pattern looks like commonly referred to as a Christmas tree pattern.

[Stevie342000]

Well decided to do a little research on Buchmann-Meyer light patterns and found this http://www.collinsaudio.com/Prosound_Workshop/BBC_%20LP_Light_Pattern.pdf

Should have known the BBC would have it covered, I forgot I saw it recently. Well off I must go read said report.

The only other thing I have found is that the research was done pre AES and the papers were filed with Acoustical Society of America. Which can be found here "A New Optical Method of Measurement For Phonograph Recordings" G. Buchmann and E. Meyer
Acoust. Soc. Am. J. 12(2) :303-306 (1940)

The other thing I found is Al Grundy had Buchmann-Meyer light beam kit. This link maybe of use as well http://www.stereophile.com/features/cut_and_thrust_riaa_lp_equalization/index.html and I found it all on http://prorecordingworkshop.lefora.com/topic/14377755/LP-Calibration#.U3ExgnbN6Sp

Hope it helps now I am off for that reading all 53 pages of it.

[Stevie342000]

The BBC paper was interesting, it explains how it works and why you do the measurements. Not the sort of thing I am interested in or most people would be. It's an industry standisation tool, which looks bulky and expensive. In the form of an optical tool it's neat but not that neat.

Assume there is a scaled down version, the pictures, figures and illustrations were top notch. I had seen it before and had meant to have gone back to it but forgot about it.

I have other fish to fry other than Buchmann-Meyer light patterns to determine cutting level in cm/s and accuracy to 1dB plus or minus at a known radius and frequency.

I thought Buchmann-Meyer was real old school and it was super-ceded but by what escapes me for now.

[opcode66]

But out of preference I would prefer a Scully both suffer from nerves brought on by age but not so much to go wrong with a Scully built to run for years and years and years. Neumann's tend to have electronics in them which are obsolete or many of the transistors or some of the i.c.s are. Which is the reson d'etre I stick with tube/valve electronics. You can do most things with tubes that you can do with solid state and it keeps the room warm as well, which eases cutting

By the time I am done with all the mods in the pipeliine, there won't be much left of the original electronics functioning in my lathe. So, I am upgrading the electronics piece by piece.

Perhaps you could come up with a post on how you use Buchmann-Meyer light beams and actually measure the cutting level in cm/s. That I would be interested in seeing and it would be of use to many others I am sure. It's the how you translate the light beams into cutting level that I do not get right now.

As with most of my work, I make videos and post them here as the work is completed. That will continue for sure. I PM'd you regarding the reasons why I'm interested in this measurement tool.

[Stevie342000]

Yes I got the pm just replied to it.

Would I be right to assume that there are a lot of electronics in the Neumann lathes that unobtanium due to obsolescence in the actual solid state circuitry used?

Agreed videos are the way to go, I found some of the detail in the BBC papers a bit long winded but got enough of it to understand but understood so much more when I saw the pictures.

All for the KISS method there is a lot to be said for it. In fact it is my preferred method why complicate what is not complicated got much better at keeping it simple stupid over the years. Getting a research based science degree helped a lot. Of course the older adage of that is that there is more than one way to skin a cat but when you analyse it it's still a skinned cat no matter what method you used to get there.

I can see from your PM that you got a lot on your plate, it's well thought out and you are well on your way to achieving what you set out to do. I look forward to seeing the results on the forum.

Personally about to realise my ambition in cutting my own discs a pipe dream nearly 30 years in the making. Got a few bits of electronics to build but should cutting discs (a little bit later than I had planned) in about 6 months if not sooner. Done a few test cuts got good results a Sugden is much simpler than a Neumann or Scully the principles are still the same just that we are back to that cat again.

Well go to run, it's getting late here.

[opcode66]

A lot of the electronics are very basic circuits. At least in the lathe itself (ZT70 Lathe Cabinet). The amp rack is a different story. Some of the capacitors are getting tricky to find. Like the enormous ones in the power supply for the audio rack. They screw in. There are a number of modern day equivalents for all of the transistors that are used. The inductors are also seemingly off the shelf. Not hard to replace. Standard resistor values as well. Though some of them are marked on the diagram 2% so you have to be sure those are replaced with quality low error parts.

Bulbs are getting more scarce as well. They used a lot of obscure sorts of bulbs like bayonet style, etc. But, my plan for those is once I can no longer find a replacement, I will simply break out the glass and filament and replace with a board that is surface mounted LED with surface mounted resistor that will go into the same metal connector as the original bulb. That will make the equivalent of nearly any indicator lamp. But, for now, I have a stock or replacements for all: bulbs, cables, transistors, fuses, and belts. I have also been accumulated other spare parts for the AM lathe body itself. Mostly for cloning.

[opcode66]

The ZA-21 Buchman-Meyer Light

I put it next to a Shure cartridge on a technics headshell to give an idea of size.

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