Transferring
LPs to CDR: Some Advice
I am beginning
to get quite a few requests for my experiences in transferring LPs to
CDR, so I thought it best to write down my thoughts in one place. These
notes are an attempt to address the whole process at a reasonably deep
level. Some parts of it are bound to be of no interest to some readers;
I hope the sections are obvious enough that you can skip those parts which
don't apply to you.
Preliminaries
I am not a digital audio professional. Transferring LPs to CDR is my hobby,
born of the desire to preserve those parts of my LP collection which (i)
are unavailable on CD, or (ii) aren't essential enough to me to be worth
spending the money replacing them on CD.
My standards
are high. I have a stereo system which all but a small minority of audiophile
extremists would regard as "very high end". I'm not interested
in putting anything onto a CDR unless I can get fairly close to perfection.
The advice contained in these notes is empirical, and results from my
own personal experiences.
I work on
a PC, and can only offer advice in that arena. I have no knowledge whatsoever
of doing this kind of work on Macs or Unix machines.
At the end
of this document is a list of useful URLs.
Slightly
off-topic: why use a computer?: I got some email from someone who asked
me to add a short paragraph discussing alternative methods of archiving
LPs without using a computer, so I have done so at the end of these notes.
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Recording the LP to Hard Disk
Clean the LP
Before you start, you should do your best to clean the record as thoroughly
as possible; getting dust and gunge out of the grooves will eliminate
a fair amount of the lower level noise that would otherwise require a
very time-consuming job to remove at a later stage. Ideally use a vacuum
device; even better get them professionally cleaned by someone who has
access to a Keith Monks cleaning machine.
Playing
the LP
Use a good quality turntable to play the LP. The pickup cartridge should
be properly aligned and the stylus should be in good condition and clean.
A turntable
is a mechanical device which is vulnerable to airborne and floorborne
vibrations. Such vibrations can degrade the playback quality quite noticably.
Even the very best turntables can suffer in this respect. Therefore, while
recording the LP, keep sound levels as low as possible. Ideally you should
not use any kind of monitoring at all; don't worry about knowing when
the music starts and ends, just start recording from before placing the
stylus on the lead-in groove and continue recording right into the run-out
groove (trimming off these extra bits later is easy).
I will assume
that you will use a moving magnet or moving coil cartridge (all high quality
cartridges are one of these two types). The signal off such a cartridge
is both low in level (typically <5mV for moving magnet, <0.5mV for
moving coil) so must be boosted to about 100mV needed to drive line level
inputs, and is also RIAA equalised (applied when the LP is mastered to
get around mechanical limitations of the LP system) which must be reversed
so as to provide a flat frequency response for the line input. Both of
these necessary operations are achieved with a suitable preamp. If you
have a receiver or stereo amplifier with a "phono" input, that
input will perform this task, and the resulting line level output will
be available on the receiver/amplifier tape output. If you have higher
quality equipment such as separate preamp and poweramp, you'll know what
I'm talking about and I leave the choice of a quality phono stage up to
you.
Recording
to Hard Disk
Once you have a line level signal, it needs to be digitised and recorded
onto the computer's hard disk. Note that for a typical 40 minute LP, you'll
need about 500Mb of disk space, and depending on what PC editor(s) you
use, you might need another 500Mb for temporary files. Count on needing
about a gigabyte in total. There are two basic approaches depending on
the quality you require:
Use a "normal"
computer soundcard. You need a soundcard capable of 44.1kHz 16bit stereo.
All modern soundcards are able to do this. The (analogue) line level signal
should be fed into the line input of the soundcard, and the signal can
then be recorded straight to the hard disk.
Use an outboard analogue-to-digital convertor, and feed its (digital)
output into a soundcard capable of receiving digital signals. As with
using a "normal" soundcard, the analogue signal must be sampled
at 44.1kHz stereo. If you use an A/D convertor which is capable of more
than 16 bit resolution, you might wish to find a soundcard that can maintain
those bits (although you will of course have to convert to 16 bit before
actually burning a CDR). However, my own experience is that even the most
perfect of LP sources will be hard pressed to deliver a signal with more
than 12 bits resolution, so plain vanilla 16 bit is fine, and even truncation
without redithering won't harm the LP signal.
Using a "normal" soundcard is certainly a much cheaper option,
but the inside of a PC is a very hostile environment for analogue signals.
Some soundcards are better than others in their rejection of this noise
pollution. Ensoniq and Turtle Beach are two highly regarded and affordable
makes. The ultimate in quality for "normal" soundcards probably
remains the Digital Audio Labs CardD+, but this is about $600. In general,
Soundblasters perform poorly (with the possible exception of the AWE 64
Gold, which some people tell me has quite good sound quality; I've not
used one of these, but can report that my experience with an AWE 64 Value
was not good). Most cheap unbranded Soundblaster compatibles have simply
dreadful sound quality.
As for soundcards
which can receive a digital signal, there are a host of options. The cheapest
one known to work well is a "digital-only" version of the DAL
CardD at about $300, but this only supports COAX SPDIF. Two other highly
regarded cards are the Zefiro ZA2 and AdB MultiWave Pro, both of which
support COAX and optical SPDIF and professional AES/EBU standards; these
two cards are about $450. Turtle Beach has just released the Montego A3D
which can take an SPDIF daughter board; street price for the combination
should be well under $200. I don't know anything else about this card
or its SPDIF capabilities.
Humming
Along with the Music
It's quite possible that when you hook up the line level output from the
LP playback system to the input of your PC's soundcard, a hum will result.
This is due to problems with the ground connections on various parts of
the whole setup (usually the PC's ground and the stereo system's ground
are at different voltages).
Trying to
rectify this kind of hum can be problematic, but a few things to try are:
Plug all
mains electrical items (ie. all stereo components and the PC) into the
same mains outlet, using multiway adapters as necessary. (The power consumption
of all these kind of devices is so low that this will not overload the
outlet). This forces all the components to share a common ground, which
might fix the problem.
If sharing the same outlet doesn't help, you'll have to start disconnecting
the ground connections from some components. Start with the turntable
itself. If this doesn't work, check to see if the turntable's connection
to the preamp/amp/receiver has a separate ground wire and try the effect
of attaching/removing it from the preamp/amp/receiver's grounding post.
If you still have no luck, try disconnecting the preamp/amp/receiver's
ground (both with and without the turntable ground re-connected). However,
beware of any dire warnings in the manufacturer's manual about this: in
many cases it will be safe, but some components might not have insulated
cases.
Rod Smith tells me that cable TV connections can sometimes cause a ground
loop if they are fed into the stereo system. In this case, the simplest
solution is to disconnect the cable TV output from the stereo system while
recording into the computer.
If all this fails, then I'm at a loss as to what you might try, short
of removing all grounds from all components, bundling them all together
and strapping them to a copper pipe buried in the (real) ground!
Setting Record Levels
Whether you choose to go with a "normal" soundcard or external
A/D convertor, it is important to set the input levels accordingly. The
aim here is to get peaks as close to 0dB as possible without exceeding
that level. This is for two reasons:
It uses the
maximum resolution available with the 16 bits. Having said this, since
an LP signal manages about 12 bits resolution at best, you could in theory
afford to leave a huge headroom (eg. peak around -12dB or even less) without
losing resolution.
(Less obvious but probably more important) If you record at a low level
and burn a CDR, you will end up with a CD that plays too quietly in comparison
to your other (commercial) CDs. While it is possible to bring the level
up using the "normalisation" feature of many WAV file editors,
such normalisation is never perfect (the arithmetic that is performed
results in rounding errors), and so it is better to avoid this if at all
possible.
As a guide, I tend to pick what I think is the loudest part of the LP,
and set record levels to register about -3dB for that part, which leaves
a little headroom in reserve.
Unlike recording
to analogue tape (where pushing the signal level well past the nominal
maximum level can sometimes be a valid approach) it is absolutely crucial
that you never exceed the 0dB level. If you do, the result is digital
clipping; an extremely unpleasant-sounding type of distortion.
Track
Splitting
When recording an LP to hard disk, don't be tempted to try and split the
tracks at this stage. You will want to retain the correct timing of inter-track
gaps on the final CD, and it is much easier to split the tracks and retain
the correct length gap using a PC editor later. (Indeed, you may use a
CDR burning package that doesn't need the tracks to be in separate files
anyway).
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Cleaning
up the Recording
Once the signal is on hard disk, the hard work begins.
Trimming
Out Unwanted Sections and Fading In & Out
These are essential steps, and can be done easily using a wide variety
of WAV file editors. Two affordable shareware editors that I strongly
recommend are GoldWave and CoolEdit96. Try to get the start of the WAV
file as close to the beginning of the music as possible, leaving perhaps
a quarter second in reserve. Once you've trimmed this excess at the start,
edit the first few samples to make sure they are zero on both channels
and then fade in the next few samples (making sure you get to full volume
by the time the music starts); all this messing about is to get a nice
clean start to the CDR without a click. The same procedure is required
at the end of the LP, although here you should aim for a longer, gradual
fade out. I like to add a little extra silence at the end; this is because
some CD players make quite a bit of mechanical noise at the end of a CD
(eg. relays switching, laser sleds parking, etc), and I prefer this not
to happen the instant the music finishes.
Removing
Clicks, Pops and Noise
Even the best LP will have some minor clicks that you'll want to remove.
Some very old records might have so much tape hiss you'd like to reduce
that, too.
I'll deal
with removing constant noise first, as this is easiest to deal with. CoolEdit96
has a fine broadband noise reduction mechanism: you select a region that
is only noise, and CoolEdit samples it; you then select the region to
be noise-reduced, and CoolEdit subtracts the noise spectrum from the selected
region. This works well, but for tape hiss can cut out quite a bit of
the high frequency programme content. You might instead try playing around
with GoldWave's parametric EQ, using fairly steep notch filters; this
can sometimes work well.
Finally, I will mention another package called DCart. This has a fairly
good dynamic noise limiter, which varies the amount of hiss reduction
based on the amount of high frequency signal that is present. When there
is a lot of high frequency energy, the amount of hiss reduction is small;
this takes advantage of the fact that the high frequencies that are present
mask the hiss. When there is little high frequency content, the amount
of hiss reduction is high, and the loss of what little high frequencies
there are isn't very noticable. This approach can work remarkably well,
especially on "busy" music, although it pumps badly on some
kinds of signal (eg. solo piano).
Removing
clicks and pops without adversely affecting the music is really difficult.
There are a number of packages on the market which claim to do so automatically,
and their number seems to be growing on an almost daily basis. I have
tried the following: DCart, DART Pro, CoolEdit Pro (a more expensive version
of CoolEdit96), Sound Laundry, Spin Doctor (bundled with Adaptec Easy
CD Creator Deluxe), WaveRepair (written by me, so take what I say about
it with a suitable dose of suspicion :-). They all suffer from the same
basic problem: they sometimes work very well, and other times they actually
make things worse. You can try fiddling with the parameters, but this
rarely results in any significant improvement. Some of them (DART Pro,
and especially CoolEdit Pro) have so many configuration parameters that
it's well-nigh impossible to try them all out, especially since they perform
their processing so slowly. Sound Laundry and WaveRepair are better in
this respect because they operate in real time and you can adjust the
parameters while listening to their effect. The bottom line is that there
is as yet no automatic way to remove all the clicks and pops without also
losing too much of the music. I perform this step manually in most cases,
by listening to the waveform, homing in on the clicks, and redrawing the
wave shape with the mouse. When doing this, it is best to monitor on headphones
as they are far more revealing of clicks and pops than loudspeakers. In
order to manually redraw a waveform, both GoldWave and CoolEdit96 have
the ability to zoom in to individual samples and move them. However, their
interfaces for this operation are clumsy, and WaveRepair is a much better
tool for this task.
Another type
of vinyl artifact you might want to remove is distortion due to damage
caused by previous mistracking. Manually redrawing waveforms certainly
doesn't get you very far with this. I have found that this kind of distortion
can sometimes be removed quite well by the packages mentioned above (Spin
Doctor, CoolEdit Pro, et al). I have also on occasions been able to reduce
mistracking damage using parametric EQ with a very deep notch filter at
a fairly high frequency (eg. around 15kHz). This dulls the frequency balance,
so a compensatory lift somewhere around 4kHz is needed to restore some
of the lost "sparkle"; it's not perfect but it can be an improvement.
Normalisation
and Equalisation (EQ)
These are optional steps that may sometimes be appropriate. If for whatever
reason you recorded at too low a level (peaking at less than, say, -8dB),
then normalisation is probably worth doing. As for EQ, some LPs do suffer
from high frequency dullness, and it's worth giving the top end a little
boost. The most I've ever put on is about +6dB from 5kHz upwards; this
is usually only necessary on reissue LPs that were probably pressed from
"high-mileage" stampers. In general, it's best not to fiddle
too much with the balance chosen by the people who originally made the
LP. As with trimming and fading, these steps are straightforward using
GoldWave and CoolEdit96; both have quite nice EQ facilities, although
I have found that GoldWave seems to run faster when performing EQ.
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Preparing
Tracks for Burning
Splitting Tracks into Separate WAV Files
Depending on your choice of CDR burning software, you may need to split
the individual tracks into separate WAV files. This can be done with a
wide variety of WAV file editors (including GoldWave and CoolEdit), but
the best one for this purpose is probably CDWAV, which can be found on
Mike Richter's Files for CDR page. On the other hand, you may have a CDR
burning package that will place track (and maybe index) marks within a
single WAV file. In this case, you will need to prepare a suitable definition
of where those marks should be. I myself use GoldenHawk's CDRWin for CDR
burning, which does allow multiple tracks within a single WAV file. Because
of this, I added a feature to WaveRepair whereby you can graphically place
track and index marks in the waveform and get WaveRepair to write out
a CDRWin cue sheet. CDWAV can also create CDRWin cue sheets.
Stripping
Out Headers and Trailers, Padding Blocks
I've never come across one, but have heard rumours that some CDR burning
software fails to ignore the WAV header, which must be stripped from WAV
files before burning. More likely is that an incorrect WAV header might
not be noticed by the CDR burning package, which thinks it is audio data
and puts it on the CDR. Some WAV file editors place housekeeping information
at the end of the WAV file, and this too may need to be stripped depending
on the burning software you use. Finally, if the music data in a WAV file
is not a multiple of 2352 bytes (the block size on a CD), then the last
block might be left as garbage, resulting in a small click on playback;
other burning software will fill the last block with zeros, so be sure
that the last sample in your WAV file is zero to avoid a click at the
transition. There is a utility called StripWave which can help here, and
can be found on Mike Richter's Useful Addresses for CDR page.
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Burning
the CDR
This is pretty straightforward. Just make sure you don't do anything that
might interrupt the data flow to the burner. Things like screen savers,
auto-answer modems, email servers and the like should be switched off
for the duration of a CDR burn.
I usually
burn CDRs from DOS, with no TSRs installed. Call me paranoid, but as far
as I'm concerned burning a CDR is a realtime operation, and DOS is the
only (vaguely) realtime operating system available for the PC. (Luckily,
there is a DOS version of the burning software I choose to use). That
said, I am aware that the vast majority of CDRs are burned under Win95
or NT without any problems, so if that's the way you want to work don't
let me deflect you.
IDE hard
disks are perfectly capable of delivering the data rate required to burn
a CDR, even if you burn at 4x speed. Take no notice of those who say you
have to have SCSI disks (not that I have anything against SCSI). Likewise
with so-called "A/V" disks; these are unnecessary for this kind
of work (they are really for heavy-duty multitrack and video work). Some
people will claim you need to defragment your hard disk before burning,
but modern disks have such low seek times that I don't bother with this
any more, and I've not had a coaster yet. You may hear horror stories
about "thermal recalibration" interrupting the data flow. This
is largely a thing of the past (having been superceded by "embedded
servo") so you probably don't need to worry about this. I'm not aware
of any current production hard disks that still use thermal recalibration.
Track-at-once
burning can be used, and with the variable gap capabilities of some hardware
and software can be made to approach disc-at-once results, but frankly
all this fiddling about is just skirting around the basic issue, which
is that audio discs are best made in disc-at-once mode, period. So don't
buy a writer that doesn't support disc-at-once, ok?
Regarding
CDR burning software: for audio CD creation, I very strongly recommend
CDRWin (and its DOS version, called DAO). CDRWin does one thing very well:
it writes CDRs in disc-at-once mode, and allows you to lay out the tracks
and indexes exactly how you want. Unlike other packages, it doesn't make
any decisions for you. I like to stay in control.
