The Secret Society of Lathe Trolls

The zuma gets start and stop signals as well as all the signals from the microswithces on the back of the lathe. Those in combination with the speed settings would allow one to approximate platter position. Since I don't have the source code for the Zuma chip I can only assume that is what they are...

The Zuma does not use any sensors to keep track of turntable position.

I think the confusion about the control signal source for the Neumann high frequency limiters stems from there being two models. The HK66 which came with the VG66 rack does indeed take it's control signal from the SI66 Circuit Breaker. This is post RIAA and would need an external RIAA encode circuit...

They are out of business. Confirmed via mastercraft. I don't think the reason it wasn't profitable was a lack of available work. I used to send them a lot of work. The records were good. The office...

Sure, it's all a matter of degree and it depends what the source of the DC offset is. It's a good idea to keep the DC offset on the SAL74 power amps tightly calibrated...

DC can damage cutting heads. It will also reduce headroom. Having DC current around a permanent magnet isn't a good idea.

Like I said in the above post I've seen dropped chip make that type of mark.

On first blush it looks like either the defect happened after it was cut or the defect was pretty deep on the lacquer since it penetrates the groove wall. It looks like a scuff. On the other hand it could be dropped chip that got stuck. Did you try blowing it off with nitrogen?

When I was starting out the same thing happened to me. I spent a few days chasing the pitch and depth system on my VMS62 Special. I finally gave up and called Al. He walked in, touched the slide, said "it's dry", put oil on it and left. I felt like an idiot. There are so many little things to keep t...

It should be a light film of oil on the carriage rail top and also underneath where the carriage meets the rail. I put a couple of drops right behind the carriage. Then slowly work the carriage back until the oil is sucked underneath. The object is to not have to remove any oil once the carriage is ...

Yes, stylus velocity and accelleration have to do with volume and peaks in volume. Velocity is the definition of level. Cm/sec FYI, for those cutters who have never used a test tone record. The 1K tone is measured at 7 cm/sec. This is the NAB standard reference level for 1k Hz stereo lateral. There...

opcode66 wrote:A groove at peak volume is about 7 mils.

Level is measured is cm/sec. This is very basic.

Very impressive. Could you tell us a little more about how it works and what you did?

Double post

The only advatages would be using modern chips and so I can offer modern conveniences with respect to flash updates and 24 bit audio processing. Okay, I'll spell it out. A 24 bit converter has a dynamic range of 144dB. On a great day vinyl has a dynamic range of about 65dB. In practical terms I'd s...

Your approach seems to be trying to build a better mouse trap before you know why the mousetrap was built the way it was, and if it needs improvement. I suggested early on in the thread that you try to reverse engineer the Zuma. This will not be easy and it will teach you a lot. I myself can't do th...

Are you saying that the stock computer only senses from -6db to 0db? If so, then I would take that to mean will I be more sensitive to much lower volumes than the VMS70 pitch computer? . What I said actually confuses two issues. Dynamic range and modulation offset. I would suggest researching how t...

opcode66 wrote: So, I can now read the intensity of audio at a discrete moment in time and store it. Soon I will be able to interpret audio at very high precision (24 bit).

Do you plan on programming the computer for 144dB of pitch and depth correction? The stock Neumann VMS70 system can do about 6dB.

The Zuma is a 6800 bus computer. To recreate it you would have to reverse engineer the EPROM on the CPU board. Only the input board was made by Zuma. The rest of it was off the shelf parts.

A direct plug in replacement for a Zuma would be very welcome. It's getting harder to keep them going. I would rather not rip the lathe apart to install another pitch and depth system. I think Zuma got it right by not disabling the stock system. If the Zuma goes down the stock system is only a dummy...