The Secret Society of Lathe Trolls

Is this pre-filter also included in your version of the SAB74B?


(From this reference: http://www.aqvox.de/download/Aqvox-RIAA-50kHz.pdf)

Aha! Maybe you can answer a quation I have about the SAB74B circuit!

On the original, Do you know the values of R29, C11, C12, and what sort of opamp is IC1?
I would LOVE to know!

If you look at the block diagram for the amp rack, what is labeled Amplifier System VG74, after the block that I marked with red text "RIAA For Recording", there is a box that represents filtering. High pass at 20Hz and Low pass at 17K. FYI, almost all cutters roll off around 16K or 17KHz. This is ...

Wonderful! It is odd. I've gone over the schematic several times. There are no notes pertaining to those capacitors anywhere on the document. This can mean two things. It was an error. It wouldn't be the first time things were mistakenly omitted on a Neumann schematic. Or, different models had diffe...

Hi Todd, that's excellent! Exaclty what I was looking for, many thanks! :D 8) :mrgreen: Could you perhaps fill in a couple of details? On the Modulation RIAA EQ schematic, does R38 (at the output) feed directly into the inverting input of another opamp? It looks like it ought to do something like th...

opcode66 wrote: I will go out of my way to find the right part of the schematic in question for you. It will take time. It will take effort. So, some patience may be required on your part. Ok?

That's very kind of you! I'm in no rush. Hope you don't feel like I've badgered you into it...

Brief VMS Cheat-sheet: VA - Pitch Box NG - Power Supply SV - Pitch Computer AS - Motor Control and Switching AM - Lathe Body SA - Suspension Box ZT - Chassis SU - Carriage Lever Switch So to that list you could also add 'SAL', which is the amp rack? And it is the only bit that I need to consider if...

You were asking for the RIAA EQ curve implementation SAL rack. So is SAL the same as VSM (as listed on the DVD)? Sorry, I'm not familiar with the various discrete parts that make up a lathe, and their names (am I even talking about it the right way, or is 'the lathe' one very specific part of the s...

opcode66 wrote:The schematics are available in a cd sold on ebay

http://m.ebay.com/itm/161352273238?nav=SEARCH

Well that covers one type of lathe. I cant believe they're the only schematics that exist, I mean, there were many lathe brands

The recording curve is an emphasis. It is the RIAA curve. Playback phono pre-amps have a de-emphasis. Most RIAA eq curves, be them emphasis or de-emphasis, are inaccurate to some extent. That is what I would like to examine- the accuracy of the emphasis circuits in some typical cutting amplifiers. ...

Hi everyone! I'm an electronic engineer, not a recording engineer, but this looks like the place to ask some specific questions about the electronics of cutting amplifiers. I may know nothing about lathes, but as an experienced analog engineer, maybe I can reciprocate by helping out with any electro...

Hi everyone! I'm new here, and I know very little about disc cutting. I'm an electronic engineer, not a recording engineer, but this looks liek the place to ask some specific questions: Recently I have become interested in RIAA equalization and the various arguments that exist, such as the "Neumann ...