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Re: Looking to Learn how to digitize Vinyls and Cassette Tapes...LOTS of questions!

Reply #25
So I talked to my co-worker yesterday (I believe, from what he was telling me, that he has worked with audio professionally for over a decade.) and he suggested I get a preamp instead and control the gain during recording from the preamp, rather than amplify the audio after recording (He told me audio will distort if you do that). My turntable is the LP120X, which allows you to change the preamp from the built in one. After doing a bit of research, I decided to buy this one...

https://www.whathifi.com/us/rega/fono-mini-a2d/review

So I'll be controlling the volume level from the unit and outputting via USB instead, recording until I can get the highest peaks to -1 dB (Although ApesBrain mentioned not going above -6 dB, any reason why?), then doing all the other basic remastering I mentioned earlier to fix any artifacts in the audio.

Thanks for all the help guys!

Re: Looking to Learn how to digitize Vinyls and Cassette Tapes...LOTS of questions!

Reply #26
Quote
No, you need a preamp stage between the turntable and the soundcard.  A variety of options are available, and they do make some difference to the quality you will obtain.  A cheap second hand amplifier is one decent possibility, but takes up some space.
The Audio Technica LP120 (like all USB turntables) has a preamp built-in.   It also has analog line-level analog/cartridge outputs.  (Most USB turntables do.)    Or it has a switch to use an external preamp.

Re: Looking to Learn how to digitize Vinyls and Cassette Tapes...LOTS of questions!

Reply #27
P.S.
If it was me* I'd probably buy the LP120 and use the USB connection.    It seems like a reasonably good turntable at a reasonable price, it's ready-to go with the built-in preamp and USB output, and it comes with a reasonably-good cartridge.    Then if I had a problem with the levels (such as clipping) when using USB I'd use the line-output.


* Like I said, I only very-occasionally digitize older records when I can't get digital versions.  I already have an older direct-drive turntable and an older receiver that somebody gave me.    (Plus, I have a preamp I built way back in the analog days.)      And, I have a couple of tower computers with regular soundcards and line-inputs.

Re: Looking to Learn how to digitize Vinyls and Cassette Tapes...LOTS of questions!

Reply #28
. .  .preamp. . . After doing a bit of research, I decided to buy this one...

https://www.whathifi.com/us/rega/fono-mini-a2d/review

So I'll be controlling the volume level from the unit and outputting via USB instead, recording until I can get the highest peaks to -1 dB (Although ApesBrain mentioned not going above -6 dB, any reason why?), then doing all the other basic remastering I mentioned earlier to fix any artifacts in the audio.

I think that Ragga preamp looks like an interesting choice that I hadn't come across before.  I once had a Pro-Ject preamp in a similar form factor which is great but I was not impressed by the sound, and to the extent I am asked for an opinion I would recommend against that make!

Moving on I see a couple of points. First of all I hate to give you conflicting advice, but I would strongly suggest you output analogue audio from the preamp via the RCA/phono outputs, assuming you have a decent soundcard like the Asus Xonar DX I mentioned earlier to go into.

The main reason for that is that hardware drivers can be a big issue and cause major headaches you may not discover for long periods depending on your workflow. 

In my view it is just more transparent and timely to confront those potential issues inside your computer which has some features intended to trap and alert you to that kind of problem, that although not foolproof are much better than having them located in what is literally a black box that doesn't talk!

This is also one of the main reasons pro audio equipment is so relatively expensive; users have significant hardware investments and can not afford downtime so demand rock solid driver support, which requires programming resources to ensure they don't glitch or fall over for example with new Windows updates.  In my view this is one very good reason to go with an Asus soundcard, since they have ample programming resources with a good understanding of low level hardware through their motherboard side.  Unlike say Ragga!

Regarding levels, you are getting a little confused.

The first issue is input levels into the soundcard, and you refer to a -6 dB target mentioned earlier.  This is appropriate for 16bit recording, but if you use 24bit as DVDDoug suggests you can and should use much lower input levels since the greater bit depth gives you better resolution resulting in no loss of sound fidelity even with peaks below <-25 dB (I personally aim for around -16 to -12 dB). 

This has various advantages, and the only cost is some disk space.  To use a little more of that I would suggest you capture audio at 96 kHz (combo is referred to as 24/96) and then make an archival copy of that.  BTW these are settings applied to the hardware via the driver and in software set up for 24/96, that you can then store in Audacity as 32bit 96kHz format with the conversion process from 24 -->32 bits handled automatically and transparently.

Second is the issue of the level you amplify your final audio file to and you mention -1 dB, whereas DVDdoug earlier discussed 0 dB.

The main practical basis for leaving some headroom in your final lossless file (eg 16bit/44.1kHz FLAC) is that the acoustic models used by converters to lossy formats like MP3 will alter the resulting waveform, and as such the process may produce peaks greater than the original.  Without any headroom these could exceed 0 dB generating what is known as clipping or digital distortion which is to be avoided at all costs unless you are working with 32bit files.

I personally use -0.3 dB as my target currently, which has been gradually creeping up over the years based on experience.

However, I should say the way I implement that is via what is known as a hard limiter that uses an element of compression to knock down peaks exceeding the limit, as opposed to the way the Audacity amplify function works which is to calculate the uniform multiplier applied to all data.

Finally on audio processing and going back to the workflow you posted earlier, as the first Audacity stage I would strongly urge you to apply what is known as a high pass (HP) filter, to remove any inaudible subsonic frequencies not already filtered out by the preamp.

It sounds counter-intuitive, but the effect of removing this low level stuff is to actually tighten up the the audible frequencies and the resulting sound particularly the definition of the lows/bass is much better.

Unfortunately there are a number of filter designs to achieve this and I am not sure what is currently available through Audacity.  FWIW, I personally use something known as a Butterworth design which I consider the best sounding, but again there are many possible implementations and this is an area where trial and error and your own ears should determine selection.

Regardless the key parameters of all HP filters are the cut off frequency and slope, which represent first the frequency at which half the dB level has been knocked down, and secondly the rate at which the attenuation occurs (the implication of the cut-off is that the filter starts working above the headline frequency).

However, the main objective is to eliminate any hump in your raw unprocessed frequency spectrum that usually appears around 10-16 Hz.  Try to look at a frequency spectrum plot to identify the problem area on your specific system, then experiment with different cut offs (and slopes) in the 16-24 Hz area to make sure you eliminate it in what you find to be the most musically pleasing way. 

Different records mastered by different engineers pressed on different plant may also benefit from different filter parameters and one size doesn't necessarily fit all, so try to use your ears and be wary generally of entirely mechanical processes.  Speaking of which it is a good idea to have some decent monitors set up correctly!

And if you have kept an archival copy of the raw capture and find a far superior way of post-processing in future, it is no problem to go back and make changes.

Re: Looking to Learn how to digitize Vinyls and Cassette Tapes...LOTS of questions!

Reply #29
One thing nobody has mentioned...

One of the most important aspects of getting a good vinyl transfer is to make sure the record is clean. The kind of surface noise caused by general dust and muck in the grooves is the most difficult to deal with in software. (Clicks and pops are relatively easy to remove in comparison).

The best way to clean records is with a vacuum device such as Keith Monks, VPI, Nitty-Gritty or Moth. But these are expensive. If you decide to try without a vacuum, be sure to rinse thoroughly with DISTILLED water.

Re: Looking to Learn how to digitize Vinyls and Cassette Tapes...LOTS of questions!

Reply #30
Quote
Moving on I see a couple of points. First of all I hate to give you conflicting advice, but I would strongly suggest you output analogue audio from the preamp via the RCA/phono outputs, assuming you have a decent soundcard like the Asus Xonar DX I mentioned earlier to go into.

So you are suggesting instead of this...

1. Play vinyl on LP120X
2. Process through preamp
3. Output through USB

I should do this...

1. Play vinyl on LP120X
2. Process through preamp
3. Output through RCA to Asus Xonar DX sound card

Quote
In my view it is just more transparent and timely to confront those potential issues inside your computer which has some features intended to trap and alert you to that kind of problem, that although not foolproof are much better than having them located in what is literally a black box that doesn't talk!

Whilst I understand what drivers are and how they work, I'm not exactly sure I understand what you are saying here.

Quote
The first issue is input levels into the soundcard, and you refer to a -6 dB target mentioned earlier.  This is appropriate for 16bit recording, but if you use 24bit as DVDDoug suggests you can and should use much lower input levels since the greater bit depth gives you better resolution resulting in no loss of sound fidelity even with peaks below <-25 dB (I personally aim for around -16 to -12 dB).

I'm confused. I thought the end goal was to get as close to 0 dB as possible, ensuring maximum volume, whilst still not losing detail via clipping by going above 0 dB.

Quote
This has various advantages, and the only cost is some disk space.  To use a little more of that I would suggest you capture audio at 96 kHz (combo is referred to as 24/96) and then make an archival copy of that.

I believe the preamp only supports 16/96, although maybe that is only if you are using the USB port and the audio is being converted to digital via the preamp.

Quote
Second is the issue of the level you amplify your final audio file to and you mention -1 dB, whereas DVDdoug earlier discussed 0 dB.

My co-worker mentioned that this is a bad idea because it causes distortion and that I should be amplifying the audio via the preamp, which is why I wanted to use the USB port of the preamp, as apparently the gain knob doesn't work with the analog out.

Quote
Finally on audio processing and going back to the workflow you posted earlier, as the first Audacity stage I would strongly urge you to apply what is known as a high pass (HP) filter, to remove any inaudible subsonic frequencies not already filtered out by the preamp.

You mean step 8 here?

https://manual.audacityteam.org/man/sample_workflow_for_lp_digitization.html

Here is the problem...although I really like high quality audio I'm....fairly ignorant of how it all works to put it mildly. For example, in this step it says "with a setting of 24 dB per octave roll-off, and a cutoff frequency of 20 - 30 Hz". I have no idea what an "Octave roll-off" is, reading the "High Pass Filter" page didn't help at all, and reading the definition of "roll-off" didn't clarify anything either. I'm also not sure exactly what to use for the frequency and would probably just go 25 Hz since that is in the middle of the range suggested.

Speaking of my workflow, should I always be doing DC correction, even if the waveform appears to be centered on 0 dB? It wouldn't hurt anything if it already was, right?

Quote
And if you have kept an archival copy of the raw capture and find a far superior way of post-processing in future, it is no problem to go back and make changes.

Oh, don't worry, I will definitely be keeping a master copy that is created immediately after recording.

Re: Looking to Learn how to digitize Vinyls and Cassette Tapes...LOTS of questions!

Reply #31
So you are suggesting. . .I should do this...

1. Play vinyl on LP120X
2. Process through preamp
3. Output through RCA to Asus Xonar DX sound card
Correct, for several reason, including the fact I am pretty sure you will get better driver support with something like the Asus card, that may be pushed out via Windows update. Regardless you may want to check the card manufacturer's website regularly to see if there are driver updates.

But if your usb output from the preamp is limited to 16 bits I would personally also see that as a deal breaker, and look to capture in 24 bit.

This is linked to the issue of levels, and I'll try to explain again.  While the goal is get the final version of the file as close to 0 dB as possible to maximise loudness, there are different requirements for the initial capture which basically involve getting the best definition without suffering digital clipping.

There is some legitimate disagreement about this, but for argument sake let's say @ 16 bits you need to peak at -6 dB to fully capture the resolution (dynamic range) of your vinyl, with the wind behind on a sunny day, etc.

But as mentioned @ 24 bit resolution you can peak at significantly lower levels and still capture all the detail needed to digitally amplify the signal without any loss of quality when post processing "inside the box" say in Audacity.

This distinction is important for real world applications, because if you are aiming to peak at -6 dB @ 16bit resolution you have a relatively small margin of error to avoid clipping at signal levels that exceed 0 dB. 

For example you may not have leveled your input perfectly and find that you're actually peaking closer to -4 to -3 dB when playing main sections of tracks rather than just short sections at the beginning when spot checking levels before capture (otherwise you would have to play the record twice to precisely measure your peak to calibrate off).  That could then lead to clipping if there is suddenly a much louder section or say if there is a pop or a scratch, and you would then have compromised audio that should be re-ripped at lower levels.

With input levels set much lower @ 24 bits you have a bullet proof margin of error, and these types of risks are eliminated and you will get reliable results and crucially almost certainly save a lot of time ultimately from avoiding mistakes.

On the HP filter it is confusing, and scanning the Audacity guide i see I have used different terminology which hasn't helped.

As I suggested try to use the frequency plot function in Audacity to examine how much subsonic content your system is generating by zooming in and looking for a hump in the low frequencies between 10-16 Hz.  If there is anything there try to get rid of it, and smooth out the left side of the curve by adjusting the parameters.

A 24dB roll off is fairly aggressive, and I would generally stay below 18dB and experiment with cut offs in the 18-25 Hz range.  But try to play with some settings then look at the new frequency plots and listen out for the change; the interesting result is that - up to a point - the more you cut the louder the bass is perceived.

On the DC correction I can't help you.  It is not something I use, and unless you can actually hear some sort of hum I would be inclined to skip that stage, and it's not a tool available in the audio editor I use anyway.  That said this is partly a reflection of my mistrust of black boxes, and the Audacity team certainly know what they're doing so it is extremely unlikely they would implement anything that could damage your audio.

Re: Looking to Learn how to digitize Vinyls and Cassette Tapes...LOTS of questions!

Reply #32
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But if your usb output from the preamp is limited to 16 bits I would personally also see that as a deal breaker, and look to capture in 24 bit.

Understood. Did a bit more research on preamps that can capture at 24/192 and I found this...

https://www.amazon.com/dp/B07QR6Z1JB/?coliid=I1RHFLWX0BJYUO&colid=3H2NSLACZ6GEG&ref_=lv_ov_lig_dp_it&th=1

So I might purchase that and a used Xonar D2X to output to, since it'll also double as a nice sound upgrade for my speakers.

Re: Looking to Learn how to digitize Vinyls and Cassette Tapes...LOTS of questions!

Reply #33
Understood. Did a bit more research on preamps that can capture at 24/192 and I found this...

https://www.amazon.com/dp/B07QR6Z1JB/?coliid=I1RHFLWX0BJYUO&colid=3H2NSLACZ6GEG&ref_=lv_ov_lig_dp_it&th=1

So I might purchase that and a used Xonar D2X to output to, since it'll also double as a nice sound upgrade for my speakers.
Ah, that's not going to work, because the preamps in the Focusrite are specifically designed for microphone/instrument input, as opposed to phono/turntable input which requires specific equalisation of the signal.

However, I must admit I appear to have made a wrong assumption about your turntable, with which I was unfamiliar; looking at the specs, it seems that the analogue output can be switched between a conventional phono out signal that requires preamplification, and one to which that has already been applied internally (presumably by the same means that serve USB/sound card processing).

If that is the case, you do not in fact need a separate external preamp, and can just take this signal straight from the turntable into the sound card.

i suspect you may obtain - perhaps only marginally - better results from the separate Ragga preamp, which is a great name in turntables generally, but you may as well try the minimalist approach first and see if you are satisfied with the results before spending any extra money.

But you should still go for a separate soundcard due to the other advantages already discussed.

Re: Looking to Learn how to digitize Vinyls and Cassette Tapes...LOTS of questions!

Reply #34
Just so I am understanding this correctly, the time when the audio is turned from analog to digital is when the frequency and bit depth is determined correct? Also, if I were to apply gain from the sound card's control panel, would that be before the audio is digitized, and therefore allows me to control the dB of the peaks correct? That is honestly the biggest reason why I wanted a separate preamp. The turntable itself doesn't have a gain knob and I want to make sure I'm getting the volume of the audio at the proper level.

 

Re: Looking to Learn how to digitize Vinyls and Cassette Tapes...LOTS of questions!

Reply #35
Just so I am understanding this correctly, the time when the audio is turned from analog to digital is when the frequency and bit depth is determined correct?
Right (strictly speaking set).

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Also, if I were to apply gain from the sound card's control panel, would that be before the audio is digitized, and therefore allows me to control the dB of the peaks correct?
I am not able to generalise on the first part of that, but you can certainly alter the gain of the digital signal via the driver and do so transparently which is the important bit.

Quote
That is honestly the biggest reason why I wanted a separate preamp. The turntable itself doesn't have a gain knob and I want to make sure I'm getting the volume of the audio at the proper level.
If your concern is with ripping/digitising the vinyl then as I have tried to explain this should not be an issue at all with 24 bit capture. There will be plenty of gain as long as you are peaking around -20 dB.  More likely you should be preparing to attenuate levels!

If your concern is with listening to records loud while capturing that is a different issue, and you might need to look at alternatives.  However, when you are ripping vinyl you really don't want the whole house shaking as this can produce unwanted artifacts from vibration.  FWIW I invariably rip with just headphones to eliminate any potential effects from this.

 
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