New Pitch Computer

Post: # 13888Unread post **JayDC** Wed Mar 30, 2011 4:02 pm

subkontrabob wrote:funny, I just posted a link to a DIY solution, with optical feedback and a microcontroller (sorry, text is in german) in the backwards mastering thread:

http://www.rstaudio.de/TT1/tt1_de.html

I have seen this, and in english..

http://www.rstaudio.de/TT1/tt1_en.html

Post: # 13889Unread post **opcode66** Wed Mar 30, 2011 4:07 pm

Sometimes I think you post just for the attention. Nothing in what you said really relates.

There is one sensor. It shines light on a round strip on the bottom of the platter. The strip is in four sections. Two white, two black. If you had the lathe you are making comments about you would know this.

More accuracy would mean simply breaking the strip into more sections of black and white. However, I don't want to use a system based on a filament style light bulb. I would rather step into the modern age.

Please site a source for your statement. Optical rotary encoders are frequently used in robotics to tell the movement of armatures. Many industrial production lines use optical rotary encoders. It is a wheel with holes in it, with a led on one side and a photo sensor on the other. What in the world is going to wear out on it?

The flywheel moves with such minimal drag that it is barely noticeable. Besides the torque and mass of the rotating platter of a VMS will absolutely negate any minor amount of drag produced by rotary encoder.

Finally, I'm not looking to add scratching or digital dj capabilities to my system. I only use the tascam item as an example of a very accurate means to detect platter movement that is robust and proven. Yes, maybe not as good as vinyl itself when scratched, but that is not pertinent to this discussion. An optical rotary encoder would obviously be more accurate than the current quarter rotation sensing on the VMS. So, are you going to tell me how quarter turn sensors wouldn't be good for a digital dj system too?

By the way I dj as well and have for many years. I have 1200's, cdj's and time coded vinyl. I have used and played with almost every digital system there is for dj'ing. I've been writing dance music with real gear, not just a computer, for about 15 years. I know what's up too Jay.

Post: # 13892Unread post **gold** Wed Mar 30, 2011 4:22 pm

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

Post: # 13893Unread post **JayDC** Wed Mar 30, 2011 4:22 pm

umm.. so i have i.. and I had the hardware studio once, don't kick a guy coz he lost it all and has to start over.

maybe you should listen, instead of fighting, no one is trying to tell you what to do or how to do it, we just want you to do it the best way to ensure that people will want to use it.

You need to remove your personal feelings from the process, or none of us will be able to give you insight, weather it's good or bad.

You do have the goal to make this unit public right? not just for yourself.. who is going to buy it, we are. we are just trying to guide you, not force you to do it our way..

Whats the point of posting in a public forum, if your going to have a know it all attitude.. at least I can admit when I'm wrong, and learn from it, i have proved that here time and time again...

Not trying to start up bad vibes, but seriously, why even tell us about it, if you don't want our input or help, just to show off?

Post: # 13896Unread post **opcode66** Wed Mar 30, 2011 4:38 pm

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 doing.

Until someone gives me a solid verifiable answer (not opinion) as to why I shouldn't use an optical rotary encoder I will likely be going that direction.

Post: # 13897Unread post **JayDC** Wed Mar 30, 2011 4:43 pm

opcode66 wrote: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 doing.

Until someone gives me a solid verifiable answer (not opinion) as to why I shouldn't use an optical rotary encoder I will likely be going that direction.

the only down side I see is mechanical failure of the encoder..

My mackie d8b had encoders like that for the knobs, and after a few weeks of EQ sweeping, the encoders started to fail..

Post: # 13899Unread post **opcode66** Wed Mar 30, 2011 4:48 pm

JayDC wrote:the only down side I see is mechanical failure of the encoder..

My mackie d8b had encoders like that for the knobs, and after a few weeks of EQ sweeping, the encoders started to fail..

You are referring to a mechanical (metal contact) based rotary encoder. Not an optical rotary encoder. They are in no way related mechanically. The only similarity is that they both output graycode.

Post: # 13901Unread post **dietrich10** Wed Mar 30, 2011 4:54 pm

No plans to replace the Pitchbox ala Pitch98?

Post: # 13902Unread post **JayDC** Wed Mar 30, 2011 4:54 pm

opcode66 wrote:
JayDC wrote:the only down side I see is mechanical failure of the encoder..

My mackie d8b had encoders like that for the knobs, and after a few weeks of EQ sweeping, the encoders started to fail..
You are referring to a mechanical (metal contact) based rotary encoder. Not an optical rotary encoder. They are in no way related mechanically. The only similarity is that they both output graycode.

well if there are no actual contacts in the unit, then it should work well. I'm just weary of things like that, mainly since they don't make things like they used to, and most stuff made today is made to get worn out..

You seem smart enough to develop your own system, using tidbits of all these methods to come up with the best way..

The last thing you need is all your customers sending in their units to be repaired regularly.. although this could be away to achieve profitability..

Post: # 13904Unread post **gold** Wed Mar 30, 2011 5:08 pm

opcode66 wrote: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 doing.

Nope. The zuma doesn't get signals from the micro switches on the back.

Post: # 13906Unread post **opcode66** Wed Mar 30, 2011 5:17 pm

dietrich10 wrote:No plans to replace the Pitchbox ala Pitch98?

Huh? You know that's the plan D. The current tangent of discussion is centering around clocking platter rotation and knowing it's position. I was suggesting an alternate to the photostrobe employed by the vms. Or at the very least a modification to it to provide more than qaurter turn data.

Post: # 13908Unread post **opcode66** Wed Mar 30, 2011 5:59 pm

gold wrote:Nope. The zuma doesn't get signals from the micro switches on the back.

I stand corrected. For some reason I thought it did. The Zuma gets the following signals from the lathe: 33/45/16/22 status, stop status, start status, base pitch, LL, LV, V, Right Preview H/L and Left Preview H/L. Additionally, there is an input for quartz crystal stabilized TT's.

So, the Zuma's estimate of disc position must be arbitrary. That is to say a calculated estimate and is not based on signal input from the lathe at all. But, that is not necessarily the only way to do things.

Post: # 13909Unread post **dietrich10** Wed Mar 30, 2011 6:03 pm

opcode66 wrote:
dietrich10 wrote:No plans to replace the Pitchbox ala Pitch98?
Huh? You know that's the plan D. The current tangent of discussion is centering around clocking platter rotation and knowing it's position. I was suggesting an alternate to the photostrobe employed by the vms. Or at the very least a modification to it to provide more than qaurter turn data.

I have not completely followed your path of thought yet. I was thinking you were just making a modern zuma that hooks into all that is on a vms as is.

Post: # 13910Unread post **opcode66** Wed Mar 30, 2011 6:09 pm

dietrich10 wrote:I have not completely followed your path of thought yet. I was thinking you were just making a modern zuma that hooks into all that is on a vms as is.

Hmm, I think I mussunderstood what you were saying. Can I make a replacement for the actual drive motor? No, that is not the plan. Can I put the functions of the command buttons on the control box into what I'm doing, for sure!

Post: # 13920Unread post **TotalSonic** Wed Mar 30, 2011 8:00 pm

Opcode -
Best of luck in getting something running! Very cool project you are doing and my best wishes to you at having it go smoothly.

Best regards,
Steve Berson

Post: # 13928Unread post **Nickou** Thu Mar 31, 2011 6:24 am

There is a lot of ideas , some of them very good, for this project of new pitch controller.
It is nice to imagine the perfect interface , to speak about tacho metters etc ...
or synchronization between the lathe and the computer , and it is true than those retails are important .

to make a new pitch controller , the first question is : what is the task of a pitch controller in vinyl cutting ?
the answer is : the task of a pitch controller is helping the operator to make the best use of the space he has on a lacquer to record his program of music.

second question : which information this controller needs to operate ?
answer : the controller needs to know the music program , and the related space used on the lacquer to cut this program

third question : how the controller can know the space needed by the music and how the controller can use this information to make the best use of the available space on the lacquer ?

the answer is : Very good question ! : you re project is there !

fourth question : do I have to do first the interface and later the pitch controler in itself ?

answer :if you want , but it will be imposible to realy think about it before you find all the answers to question 3

to begin to answer to question 3 , a good question is : how I can know the space I need cut cut a sine at 1 kHz and a speed 7 cm per second ( just an example ...), from that and some mathematics with the very big help of Joseph Fourier , you will be able to begin to compute all those infos

all the real job is there,
when this job is done , you can begin to realize a prototype in the real word , and later adding all the user parameter and building a nice interface

I think it is not good to begin a project by its end

Post: # 13931Unread post **opcode66** Thu Mar 31, 2011 10:41 am

@Nickou - I have all the equations necessary to calculate the pitch value required to maintain minimum land between grooves based on peak analysis. Yes, that is not the way an VMS80 or Zuma works. But, that is step one. Once that works, then I will modify the routines to nestle the grooves based on maintaining a minimum distance between the actual waves at any point in time.

I would not be talking about creating such a system without having gathered the appropriate sources for such calculations. I am not beginning a project by its end. I am simply not discussing every detail here on the board. So few people on the board would be able to help me with such calculations. Why even bring them up here?

Do you really think I would be sitting here designing something around nothing. I wouldn't make the body of a car with no engine. This is not the first project I've ever worked on...

Post: # 13939Unread post **opcode66** Thu Mar 31, 2011 11:51 am

Here is the block diagram of the design I have previously described. This would be Version 1. Version 2 would not need preview audio and would use ASIO sound device to play audio out to the lathe.

I suppose I will have to start posting equations next lest I be accused of being a fake.

Post: # 13943Unread post **gold** Thu Mar 31, 2011 1:36 pm

What about depth control?

Post: # 13945Unread post **opcode66** Thu Mar 31, 2011 2:03 pm

Was thinking this would be an option in the software much like base pitch. So, another line to the lathe from the USB Device controlled by commands from the computer for depth as well. I will add another line to the block diagram. This needs to be a varied current and not a varied voltage. So, I will be using a DAC that does both.

Also, to be clear, the USB Device will contain the circuitry for one PS66 with four switchable pathways for speed control (since each would requre different values for about 19 components). Each pathway will be switchable for diameter. The swithcing is controlled by the USB Device via commands from the computer.

My vision is for the computer to save almost all of the possible cutting parameters to a file.