Audio, hi-fi and car audio - Digitising Vinyls (OT for uk.tech.digital-tv)

Regulars will recall that I've been digitising all my ACs, MDs, and
vinyls. I've almost completely finished this now, and as I've made
some discoveries which I at least found interesting, I'll put them on
record, before they are forgotten ...

First a reminder of the general situation ...

In various posts June 2011, Java Jive wrote:

I still have some audio recordings in the obsolete form of:

ACs: 'The Hitchhikers Guide To The Galaxy' first 2 radio series
About 60 MiniDisks.
About 125 LPs
About 5 x 45 rpms

Then there is the attendant hardwa

Denon HiFi (seperates) around DRA-275RD amp downstairs in lounge
Sanyo DC-007C Midi Tower (seperates) upstairs in bedroom/office.

DMD-1300 MD deck in the downstairs HiFi (may be faulty)
MDG-007 MD deck in the upstairs HiFi

Dual 601 turntable, aged, some rumble, no preamp,
Shure V15 Type III L-M cartridge
Shure VN35MR elliptical stylus
Phono inputs on Denon DRA-275RD downstairs.
NAD Phono Preamp.
Project TK38 turntable with inbuilt pre-amp, cartridge unknown
Moth vinyl washing machine

2 x Desktop P4s W2k (still), each with ...
SB Live with Digital IO dongle (SPDIF Coax & Optical In & Out)

Dell Latitude 610 laptop + docking station

USB Terratec Aureon 5.1 MKII (SPDIF Optical In & Out)

[...]

I record everything to LPCM wave files.

For some time, I've been thinking that it would be good to:

:-) Guard against irreplaceable but obsolescent kit going down
:-) Digitise these remaining vinyls before further deterioration
:-) Be able to play the vinyls without the associated hassle
:-) Lose this significant pile of junk, but keep the recordings.

I've had two major problems ...

Dust and gunge on the vinyls
Mains Hum

I've described how I deal with the dust/gunge problems here ...

http://www.macfh.co.uk/JavaJive/Audi...storation.html

... my plan being to record each vinyl, or at least each wanted track
thereof, twice:
1st Pass unwashed, via the Dual
2nd Pass washed, via the Project
... and ultimately keep only the best.

This didn't work out quite as expected, because I didn't like the
sound of the Project deck - I suspect it has a ceramic cartridge of
moderate quality, and therefore probably a pre-amp to match.
Consequently, I dismantled, rewired. and reassembled the Dual deck to
get rid of the hum. I ended up with quite severe tracking problems,
but was able to solve these well enough to get the job done to a level
of quality which I believe is about the best that could be hoped for
without expense on new and better equipment.

Despite having used it before (but perhaps my technique has improved),
I was totally unprepared, and therefore unexpectedly delighted, at the
almost complete restoration of most the vinyls by using the washer.

Here's a sample of the results (each file is a WAV of about 8MB) ...
Dual (before de-humming and vinyl washing):
http://www.macfh.co.uk/PrivTest/Cill...WifeBefore.wav
Project (after vinyl washing):
http://www.macfh.co.uk/PrivTest/Cill...ifeProject.wav
Dual (after de-humming and vinyl washing):
http://www.macfh.co.uk/PrivTest/Cill...sWifeAfter.wav

Note that:

:-) Many 'scratches' actually turned out to be grit or dust in the grooves and were completely removed by the washer.

:-( The Project has a rather boomy sound which lacks the top-end transients obtainable from the Dual.

:-) The rewiring of the Dual has COMPLETELY removed the hum.

Barring a handful of problem records with bad scratches, the results
obtained from the vast majority of them are far, far better than I
ever dared hope, let alone actually expected. Effectively, many of my
favourites sound 'as new', even before using software to remove those
minor blemishes that remain after washing.

Phew! I'm so relieved that it's now all but over.

I hope anyone who is still misguided enough to consider that vinyls
are superior to CDs will take note of all these problems (fuller
details appended), none of which occur with CD. It shouldn't be
necessary to say it, but such druids may care to note that when played
back through the same equipment, there is no audible difference
between the originals and the digital recordings.

WASHING VINYLS

For those interested who haven't seen one before, the washer consists
of a motorised turntable the size of a vinyl's centre label, the
central spindle of which is screw-threaded, and a velvet covered,
hollow arm, the top surface of which is perforated level with the
turntable, and which is connected to a vacuum pump. The motor and the
pump are controlled by seperate switches on the front. The procedure
for washing a vinyl is:

1) Attach it with Side 1 uppermost clamping it with a plastic nut
which screws onto the turntable spindle

2) Switch on the motor

3) Using a fine brush provided, wet the upper playing surface (not
the label) thoroughly with cleaning agent, which is a strong solution
of Isopropyl Alcohol (IPA).

4) Angle the brush into the grooves against the normal direction of
travel for a few revolutions, if necessary periodically moving the
brush across the entire radius of the playing surface.

5) Stop the motor

6) Turn the vinyl over

7) Start both the pump and the motor. The wet Side 1 is now
underneath, rubbing over the surface of the arm, which sucks off the
IPA and hopefully all the gunge from the grooves with it, leaving it
clean and dry.

8) During 7) for Side 1, you repeat 3) and 4) for Side 2, now on top.

9) Repeat 5) through 7) for Side 2.

Record the vinyl straightaway, without putting it back in its sleeve.
In fact, really, one should use a new inner sleeve, but these days my
budget doesn't extend to spending any more money on obsolete
technology.

MAINS HUM

The page linked above also mentions mains hum in passing, but a fuller discussion
follows ...

I found that however I connected up the Dual, I got a big hum. I
tried all the following combinations severally and together, all
without making much of a difference:
Earthing the metal of the deck via the mains lead, and not
Earthing via the earth terminal of the amp, and not
Using the seperate preamp, and the phono inputs on the amp

Finally, in desperation, I took the turntable out of its box, and
discovered that the grounds of the cartridge connections were
connected to the metal of the deck. I cut these connections and
rewired them so that the metal of the deck is earthed via the mains
lead, and separately the grounds of the cartridge, like the signals,
come straight out of the back to the outputs. This is a HUGE
improvement: there is no build-up of static, and it's effectively
hum-free until I start the motor. With the motor running, there is
some residual hum, which I'd like to get rid of, but at least the
result is listenable.

When I tried the new arrangement with the NAD pre-amp, there was just
a little more hum, so I've been using the HiFi phono inputs.
When I tried it additionally connecting the metalwork to the earth
connection on the amp either there was either no difference or it was
worse, I can't now remember which, only that no benefit was obtained.

My conclusion from all of this is that a vinyl record-deck should be
wired as follows, but I'd be interested to see if others agree ...

If the deck is driven from mains voltages, then its metalwork should
be earthed via the earth in a three-core mains lead connected to the
earth in a 3-pin plug. In this case, the metalwork of the arm should
be insulated from the deck and a seperate earth point provided to
connect the arm to the amp earth.

Whether or not the deck is driven by mains voltages, the cartridge
should be connected to the outputs via screened cable over the
entire distance. The problem is that screened cables are stiffer than
the tiny wiring commonly used in an arm, and their stiffness might
affect the tracking if the job's not carefully done.

I did once wire up an old Garrard deck like this, as an experiment. My
recollection is that it was hum-free. I got the shielded cabling from
RS or Maplin's [...]. It was
two cores, about the same thickness as you'd find in a pick-up arm,
with a common braiding outside, then a thin outer insulation. It was
quite flexible, I do not recall ever noticing tracking problems with
it.

The above was exactly how I removed the hum from the Dual.
This was the cable used:
http://www.maplin.co.uk/2-core-overa...ped-screen-127

As you can hear on the samples above, effectively this did completely
remove the hum. I can just about hear something at about the same
level as the white noise when the volume on the amp is turned up full,
but if I were to actually play anything at that volume, it would
probably demolish the house.

However, the difference between the ways that the Garrard and the Dual
bring the cable out of the pick-up arm allowed this to work quite well
with the Garrard, but gave me quite severe tracking problems with the
Dual.

With the Garrard, the arm mounting was tubular in construction, so
that the cables came out through the centre of the bearings. By
leaving a generous loop hanging underneath the deck before the cable
was brought back up and fastened to the underside of the deck, the
leverage exerted by the stylus over the full length of the pick-up arm
was sufficiently greater than any resistance to being twisted exerted
by the cable, so the arm tracked sufficiently well.

However, with the Dual, the bearings are not such that the cable can
be brought out through them, but rather it escapes by a tortuous
route, finally jumping off a plate underneath the arm mounting. That
this is as much as a couple of centimetres in effective radius and the
lack of any suitable points to fix the non-moving end of the cable at
the optimum distance away meant that there had to be a significant
loop of cable being pulled to one side or the other as the arm tracks,
and the large radius coupled with the weight of the cable in the loop
meant that the cable caused tracking problems. After a great deal of
trial and error, I found that it was necessary to attach the cable
when the arm was positioned approximately in the middle of its full
sweep.

Then, if I set the turntable running about 15mins or so before
beginning recording so that the cable got nice and warm, then the arm
would usually track over the entire span of an LP. If by chance it
didn't, which was rare, and usually on the first LP of the day, I
would set the Bias Compensation to max for the first three tracks or
so, then lift up the arm, set the compensation to zero, and put down
the arm again for the remainder of the side. I had occasional other
problems. For example, there was a Dubliners' LP which was a tight
fit on the central spindle, so effectively while it was on the
turntable it was conical in shape, and, particularly on the last track
or so, the stylus was always trying to fall out of the groove down the
slope, leading to bad distortion. After some ineffectual random trial
and error, I logically worked out the actual cause, pushed the centre
of the LP down flat on the TT, and the problem was instantly solved.

However, bad scratches were still very much more likely to make the
stylus jump to a neighbouring groove than hitherto. I have about 6
such vinyls for which I'm probably going to have to accept the poorer
quality of the Project. For some reason or other 45s were more prone
to tracking problems than LPs, the worst of all being the 'floppy'
records that magazines such as 'Private Eye' (every Christmas) and
'Guitar Player' used to supply with particular issues. I had to
resign myself to using the Project for those - not a problem for the
PE ones as quality was not an issue, but disappointing for the GP one
that I have.

So I've effectively rendered the Dual's second-hand value to zero,
but, as I bought it in about 1972/3, I reckon I've got my money's
worth out of it.

I really think that those manufacturers who are still making
turntables should consider using the above wiring scheme in every
model. I'm sure the tracking problems should be solvable at the
design stage.
--
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