Digitizing vinyl

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Member
Joined 2002
Paid Member
Hi all
This thread is about to deal with digitizing the output of a vinyl playback cartridge, the ways of doing this, where in the signal chain, hardware and software issues and of course if there is merit to do it sound wise.

Which are the possible needs for applying digital RIAA equalization?
I can think of:
1. Transferring vinyl LPs to digital formats
2. Playing back Vinyl through a DAC within an DSP box, e.g. a MiniDSP kit

In both applications, RIAA can very well be implemented in analog but using a digital RIAA implementation may help in reducing the analog hardware needed, possibly reducing the complexity, noise and cost.

George
 
Member
Joined 2002
Paid Member
So let’s start by looking at the output of the cartridge

Moving coil and moving iron/magnet cartridges differ by at least 20dB on their electrical output and they require different electrical loading.
Maximum expected output depends on the cartridge and the track that it is reading.
Max modulation velocities have been surveyed and shown in SHURE V15 Trackability diagram (see att1).
Table 1 (att 2) is based on these maximum modulation velocities

Now, minimum noise level for vinyl is around –70dB rel 0dB @ 8cm/s [Burkhard Vogel “The Sound of Silence” 1st Ed, Fig 3.95] The Sound of Silence - Lowest-Noise RIAA Phono-Amps: | Burkhard Vogel | Springer

There is an opinion that we (they :D ) are able to hear sound signals which are buried in the noise.
If this is correct, we should target for a signal 20dB below the noise floor of vinyl.
We end for the minimum (lowest) music signal to be at –90dB rel 0dB @ 8cm/s.
This is equivalent to 0.00025cm/s and translates to different voltage level at the output of a cartridge. See Table 2 (att2)

This minimum signal will eventually enter an ADC and in order to be properly processed, it has to be of a level higher than the level of the Least Significant Bit (LSB) of the DAC.
If it is not of that level, it has to be amplified before it enters the DAC.(*)
What is the level of the LSB of a DAC then? See Table 3 (att 2)

Modern DACs claim an 24bit resolution. I don’t know if this is actually achieved and how common.(**)

(*) Please check if this is correct or not.
(**) I would love to have an answer to this by people who know what the reality is in praxis.

George
 

Attachments

  • Shure Trackability.JPG
    Shure Trackability.JPG
    138.7 KB · Views: 1,236
  • att2.PNG
    att2.PNG
    24 KB · Views: 1,229
I think you will need around 20 bits genuine resolution just to capture the input signal from the cartridge. That probably means a 24 bit ADC with a dynamic range of around 120dB - such devices may now exist, although most audio 24-bit ADCs seem to be more like 110dB. If the record is imperfect you may need some extra headroom to accomodate clicks. All this assumes that the dynamic range of the ADC is closely aligned to the dynamic range of the cartridge and vinyl, so you will either need more bits or a variable gain flat preamp.

Alternatively use an analogue RIAA preamp with a 16-bit ADC.
 
Member
Joined 2014
Paid Member
@DF96. You are trotting out the old mantra (which I used to believe in ). Based on the work Scott has done you really don't need silly headroom for the clicks, although it is an area that I think more investigation is needed in. Reading Scott's work has torpedoed a few of my preconceptions about this.
 
I didn't ask for "silly headroom", just enough headroom. I was thinking maybe one or two extra bits? Beyond that the cartridge would probably be floundering anyway. An analogue preamp would reduce clicks due to the RIAA HF rolloff.

It seems to me that to digitise vinyl you either need state-of-the-art digital technology, or a combination of 30-year-old analogue and digital technology. I think the latter is easier for DIY.
 
Last edited:
I didn't ask for "silly headroom", just enough headroom. I was thinking maybe one or two extra bits? Beyond that the cartridge would probably be floundering anyway. An analogue preamp would reduce clicks due to the RIAA HF rolloff.

It seems to me that to digitise vinyl you either need state-of-the-art digital technology, or a combination of 30-year-old analogue and digital technology. I think the latter is easier for DIY.

Any PC is SOTA enough for this problem. More info here: http://www.channld.com/aes123.pdf

From my measurements an LP provides 5 or 6 LSB's of dither at 24 bits. Choosing a pre-amp that recovers from overload perfectly might help but the information is lost anyway. I have found pop's that high are infrequent and if they simply flat top at max level it's none the worse for it.
 
scott wurcer said:
Any PC is SOTA enough for this problem. More info here: http://www.channld.com/aes123.pdf
My reading of that paper is that you may need 17-19 bits to get 16 bits worth of resolution, especially if you like Bob Marley's music. That is not too different from my wild guess of 20 bits.

As I said, IIRC the conclusion from an earlier thread was that analogue RIAA was better. Maybe someone could find the thread and then we can see why that conclusion was reached.
 
Over the years, I have digitized hundreds of my vinyl records. I've been using my old Nakamichi 410 preamp, which I found quite satisfactory when I didn't have CD or digital music, and I continue to find it so. My sound cards have been Turtle Beach Santa Cruz and Montego. I've found no reason to change those, and have been quite satisfied with the results.
Since my old turntable/cart died, I have been willing to entertain new there, though... B&O 4002 with Sonus Blue cart was quite good in the day.
 
Administrator
Joined 2004
Paid Member
Also Scott, we've discussed this before. What do you think is a good chip to use for linear gain boost of a phono cart output. What to use if you want to boost the signal going into an ADC.

I think that would be very relevant to this thread, so that people can try digital RIAA themselves. You recommended a SSM2019 or something like it, right? And perhaps a balanced input connection.
 
Also Scott, we've discussed this before. What do you think is a good chip to use for linear gain boost of a phono cart output. What to use if you want to boost the signal going into an ADC.

I think that would be very relevant to this thread, so that people can try digital RIAA themselves. You recommended a SSM2019 or something like it, right? And perhaps a balanced input connection.

Yes, or the THAT equivalent. They have a new diff-in diff-out version too.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.