Cartridge output question

[tima]

Pardon my ignorance...
Suppose I have a MC cartridge spec'd by the manufacturer to have an output of 0.5 millivolts.
Is that peak output or what is it? Put slightly different: does a cartridge's output voltage vary across a record?

 

[kodomo]

It is the output value taken for stylus tracking at a particular rate (50 mm/sec). As all (afaik) companies use the same reference, you can have an idea of different cartridges outputs in relation to each other and as you already know it is to determine the amount of gain you would need.

 

[tima]

It is the output value taken for stylus tracking at a particular rate (50 mm/sec). As all (afaik) companies use the same reference, you can have an idea of different cartridges outputs in relation to each other and as you already know it is to determine the amount of gain you would need.

Thank you Okan. That makes sense - the spec'd output is output at a standard velocity of travel. Okay, two follow-on questions if I may:

The linear travel velocity of the stylus changes as it moves from outer groove to inner groove. Does the output voltage change as the stylus moves from outer to inner groove?

Does/can the output voltage change based on groove modulations, at any point on the record?

 

[shakti]

Does/can the output voltage change based on groove modulations,

To my understanding this voltage change is the base for the dynamic of a record.

no groove modulation => no voltage => no music

 

[tima]

To my understanding this voltage change is the base for the dynamic of a record.

no groove modulation => no voltage => no music

Thank you. That is what I suspected. Can I put this as: the stylus traveling the grooves modulates amplitude?

 

[shakti]

Thank you. That is what I suspected. Can I put this as: the stylus traveling the grooves modulates amplitude?

yes, it is that simple.

 

[kodomo]

Thank you Okan. That makes sense - the spec'd output is output at a standard velocity of travel. Okay, two follow-on questions if I may:

The linear travel velocity of the stylus changes as it moves from outer groove to inner groove. Does the output voltage change as the stylus moves from outer to inner groove?

Does/can the output voltage change based on groove modulations, at any point on the record?

It is not just 50mm/sec but tracking a 1khz tone horizontally. I did not put that part so you missed it. Unless there is modulation on the record, there is no output as Shakti says. So normalyy the output values should be written like Output voltage @ 1kHz, 50mm/s horizontal direction

 

[zerostargeneral]

Stylus-groove relations in the phonograph playback process: Ingenta Connect

www.ingentaconnect.com

 

[zerostargeneral]

E-library page - AES

AES E-Library ← Back to search

www.aes.org

 

[zerostargeneral]

Cookie Absent

 

[tima]

Thank you dear general for these references !

 

[mtemur]

Pardon my ignorance...
Suppose I have a MC cartridge spec'd by the manufacturer to have an output of 0.5 millivolts.
Is that peak output or what is it? Put slightly different: does a cartridge's output voltage vary across a record?

It is the output value taken for stylus tracking at a particular rate (50 mm/sec). As all (afaik) companies use the same reference, you can have an idea of different cartridges outputs in relation to each other and as you already know it is to determine the amount of gain you would need.

Normally output voltage of a cartridge refers to measured voltage using CBS test record’s dedicated track at 5cm/sec (45rpm). Some manufacturers use 3.54cm/sec (33.3rpm) ex. ZYX, Benz Micro etc.

MC cartridges produce voltage depending on how fast and how far the stylus moves. There are other approaches that use displacement.

The linear travel velocity of the stylus changes as it moves from outer groove to inner groove. Does the output voltage change as the stylus moves from outer to inner groove?

If both groove shapes are exactly the same then yes. but in order to get consistent output throughout the record inner grooves are more modulated. that’s why inner grooves look more zig-zag shaped compared to more linear looking outer grooves. And that’s why it is harder to accurately read inner grooves. Hence “inner groove distortion”

Does/can the output voltage change based on groove modulations, at any point on the record.

Yes, always.

 

[Neil.Antin]

@tima,

Look at Figure 37 of the book. It shows the wavelength simplistically as the groove modulation wavelength (ridge to ridge distance) to reproduce various frequencies between the outer and inner-most grooves for 12-inch, 33.333 rpm and 45 rpm records. At the highest frequency the values can be as small as 10 microns for a 33.333 rpm record at the inner groove.

Look at Figure 39. 1000 Hz is the zero-crossing point (0-dB) of the RIAA curve. The peak 'stylus' velocity is limited to the record tangential velocity which for a record at 33.333 rpm is 51 cm/sec at the outer groove and 20 cm/sec at the inner groove. Figure 39 also shows the peak amplitude (stylus displacement) and this is generally limited to 50um. Additionally, the peak amplitude is also limited by the stylus shape.

XI.4.5.a The maximum amplitude is generally associated with how wide the groove can be before cutting into the groove next to it. Recalling Figure 37, as the frequency increases and as the stylus tracks closer to the inner groove, the stylus has less time to travel from rest to the modulation peak amplitude and therefore higher (peak) velocities occur. The practical limit of peak velocity occurs when the peak velocity of the modulation equals the linear (tangential) velocity of the groove (the speed at which the record passes the stylus). Exceed peak velocity and the “…groove swings become so sharp that the stylus tends to ride up over them instead of traveling around them. (30)”

XI.4.5.b Groove modulations produce sine-waves and these have curves with a radius defined by the square of the linear (tangential) velocity divided by the stylus acceleration (paragraph XI.4.2) The (tip) radius of the stylus is tracing these curves. At higher frequencies, the radius of the sine-wave curve decrease. If the radius of the sine-wave curves becomes less than the stylus tip radius, the stylus will be unable to trace the modulations and “…the stylus loses its ability to follow the modulations accurately and tends to "gloss over them (30)” leading to loss of signal output and distortion. A conical stylus that can have a tip radius of 0.0018-cm (not shown Figure 39) has difficulty in tracking high frequency peak velocities and amplitudes

The cartridge output is proportional to the stylus velocity. So, a cartridge that is specified at 0.5mv at 5cm/sec could output as much as 5mv at the highest peak velocity for 33.333 that can be achieved at the outer groove. This peak output can overload a preamp that does not have a lot of headroom. Note that 45 rpm has higher allowable peak velocities - i.e. greater dynamic range/signal-to--noise.

The challenge for classical music is that the end-of-program crescendo occurs near the inside groove where the maximum peak velocity is the least and this requires the recording engineers and the cutters to do some heroic work to reproduce. It helps that the RIAA recording curve is attenuated (signal reduced) at the lower frequencies (<1000 Hz) where the peak amplitudes generally occur.

 

[tima]

@Neil.Antin

Thank you Neil - excellent. I forgot you had all this information covered in Chapter XI of your publication: Precision Aqueous Cleaning of Vinyl Records-2nd Edition

If those few reading this thread are curious about why Neil's observations are included in a paper on record cleaning, he writes:

"Why are we concerned with these groove and stylus details? While the recording industry is often focused on the maximum peak velocity that can be recorded, from a precision clean perspective the opposite is of interest; and understanding the very small modulations and large accelerations involved provides insight to how small amounts of contamination can have an impact." (XI.4.6)