Need help entering the Digital world.

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GeeVee

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Joined 2007
#1
Hi all
I have been hanging around DIYAUDIO for many years, and have never delved outside the analogue section of this great site.

Anyway, it is now 2015, and I am getting dragged kicking and screaming into the digital world.

I have done as much research as I can, but I still am not comfortable that I fully understand what is required, and the best way to implement what I am trying to achieve.

I am sure that many may find my questions humorous!!
Anyway, here goes:

I have a vast collection of vinyl, many of them audiophile recordings, and a substantial collection of ½ in R to R of live band recordings. (Many of them using Nakamichi Hi Com and DBX Noise reduction)
All equipment for vinyl playback and R to R playback etc is ready to go.
Essentially, I would like to transfer all of these recordings to a computer / hard disk, at the highest possible resolution, without getting silly. (I hear 24 bit, 192 kHz is the way to go)

I have looked at several DAC’s with USB and fire wire interfaces, but can’t understand how you select the bit size and sampling rate, as most are just boxes with no controls.

Now the questions:

1.How do you alter the sampling rate / bit depth. Is this done through software? If so are there generic ones out there?

2.USB 2 or Fire wire?

3.What is the best format for high quality? I hear .WAV and .FLAC are the way to go

4.Any suggestions on commercial DAC’s, which are reasonably priced?

5.Any suggestions on kits (I have no probs at all in electronics construction)

6.Any of those being sold on EBay any good?

Once again, sorry to have to ask stupid questions, but at least here I am certain that I will get good advice

Kind Regards
George
 
#7
AlanL said:
Yes, you need adc. I have one of these that would work https://www.steinberg.net/en/products/audio_interfaces/ur_serie/modelle/ur28m.html. There's probably better for your purposes.

Basic info on these devices: Audio Interface Buying Guide

I'd imagine there are soundcards that would work, but maybe not @ 192k.
Click to expand...
Hi AlanL.
Thanks for your reply.
As you can see, digital is very new to me.
I am trying to get the best transfers possible, as many of my R to R recordings which were done at 30 ips on my Studer 820 are just incredible to listen to. Just not very practical

Thanks.
 
#10
GeeVee said:
I am trying to get the best transfers possible, as many of my R to R recordings which were done at 30 ips on my Studer 820 are just incredible to listen to.
Click to expand...

No matter how good they are, there won't be any content beyond 24 kHz or so (apart from interference/pilot tones that you really don't want to record), so a 48 kHz sample rate would be enough, but you might want to use 96k to be sure. Definitely no point in 192k (also makes your choice in ADC's easier). You also won't have a SNR better than maybe 72 dB, equivalent to 12 bits, so 16 bits is more than enough, but if you use 24 bits to record, and normalize to 16 bits after recording, you have more head room in case you don't get the gain right.

Remember that unlike with analog, you never, ever want to reach clipping (full scale) going into the ADC. You are OK normalizing it to just below full scale once it is in digital form.
 
#12
#14
I have no other DAC use experience in which I can compare the TC Impact. I have heard from others with more experience with other DACs that they think it is super solid in that capacity, IE not the best, but no slouch.

As an ADC it is great, very versatile. I use it everyday either through my headphones or through my stereo. I am enjoying my music and that is the main point!

Down the road I might look at a dedicated DAC for play only, but who knows.
 
#15
Julf said:
No matter how good they are, there won't be any content beyond 24 kHz or so (apart from interference/pilot tones that you really don't want to record), so a 48 kHz sample rate would be enough, but you might want to use 96k to be sure. Definitely no point in 192k (also makes your choice in ADC's easier). You also won't have a SNR better than maybe 72 dB, equivalent to 12 bits, so 16 bits is more than enough, but if you use 24 bits to record, and normalize to 16 bits after recording, you have more head room in case you don't get the gain right.

Remember that unlike with analog, you never, ever want to reach clipping (full scale) going into the ADC. You are OK normalizing it to just below full scale once it is in digital form.
Click to expand...

I think you are underestimating the Studer A820. Unlike digital stuff, it has no built-in brick wall filter, so you can expect some output octaves above 20 kHz, especially at high tape speeds. The bias frequency is 153.6 kHz (according to some website), so if you don't want to record the bias, just keep the sample rate well below 300 kHz.
 
#16
marce said:
Another thought, is there software available that would help clean up any nasties such as clicks , tape hiss etc. with the minimal involvement ?
Click to expand...
Yes, there's plenty of such software (though the best, or sometimes even good, results require more than minimal involvement). The best thing to do for LPs is to reduce clicks and noise BEFORE digitizing, by using something like a Nitty Gritty (the minimum) or Keith Monks (luxury) record cleaning machine, or look elsewhere on DIYaudio for the ultrasonic cleaning thread.

You also want to keep copies of your original digitized files regardless of what filtering and processing you do to make your "listening" files, as you might later decide that the processing removes something you wanted to hear. Fortunately, disk storage is cheap thesedays, even for 24-bit/192k. You'll want to do backups, as well.
MarcelvdG said:
I think you are underestimating the Studer A820. Unlike digital stuff, it has no built-in brick wall filter, so you can expect some output octaves above 20 kHz, especially at high tape speeds. The bias frequency is 153.6 kHz (according to some website), so if you don't want to record the bias, just keep the sample rate well below 300 kHz.
Click to expand...
More importantly, you want to keep the anti-aliasing filter cutoff frequency below the bias frequency.
 
#17
MarcelvdG said:
I think you are underestimating the Studer A820. Unlike digital stuff, it has no built-in brick wall filter, so you can expect some output octaves above 20 kHz, especially at high tape speeds. The bias frequency is 153.6 kHz (according to some website), so if you don't want to record the bias, just keep the sample rate well below 300 kHz.
Click to expand...

Hi Marcelvdg.
You are 100% correct in your statement - Bias set at 153.6kHz. (some other recorders have bias' up to 450 KHz)

I think a lot of people underestimate what a mastering quality R to R is capable of, when using high quality tape at 30 ips.

It has been likened to containing information level equivalent of 24 bit / 400 kHz

Even such notable as Tim de Paravicini of EAR has stated in interviews that his modified Studer machines area capable of this resolution.

Anyway, I digress.

I am enjoying the input by all to date, and have been undertaking as much on line research as possible

Regards

George
VK5ZG
 
#18
benb said:
More importantly, you want to keep the anti-aliasing filter cutoff frequency below the bias frequency.
Click to expand...

I agree, but as the stop band of the anti-aliasing filter usually starts close to half the sample rate, that's equivalent to using a sample rate somewhat below 300 kHz. For example, with a half-band filter that has a transition band from 0.45 to 0.55 fs, stay below 279.27 kHz sample rate. You may have to go lower when you have a "smooth" filter that extends way above fs/2 (which doesn't make any sense to me anyway, but that's another discussion).

(By the way, the late Michael Gerzon once proposed to use the bias frequency to digitally correct for wow and flutter, but I don't think anyone has implemented this in commercially available software.)
 
#20
MarcelvdG said:
I think you are underestimating the Studer A820. Unlike digital stuff, it has no built-in brick wall filter, so you can expect some output octaves above 20 kHz, especially at high tape speeds.
Click to expand...

Not much.

Here is a comparison of the Studer A820 at 15 ips (light green, -2 dB @ 20 kHz) and 30 ips (dark green, -2 dB @ 32 kHz), compared to the Apogee PSX-100 digital system at various sample rates. As we can see, 48k (black) covers the 15 ips case, and 96k (red) more than covers the 30 ips case.

As to number of bits needed, the Studer has a A-weighted SNR of 77 dB, equivalent to 13 bits.


237765d1306904133-ampex-studer-frequency-responses-30ips-882k-96khi-freq.jpg
 
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