Enhancing audio data from moving magnet turntable?

[Klаus]

Hi there!

When using a moving magnet cartridge turntable for playback on your stereo set you usually need a device called phono pre amp. My question here: Is it possible to do with Audition what that phono pre amp device would do to the turntable’s original audio output?

Thanks –

Klaus

[SteveG_AudioMasters_ · Accepted solution]

Simple answer - no.

But let's expand on that a bit, so you know why, because it's a two part answer, the second part of which Audition could potentially cope with, if it wasn't for the over-riding problems of the first part...

The initial problem is that the signal from the cartridge is at a very low level, and applying that to a normal sound-card input would just have it lost completely in noise; these inputs are designed to work with inputs at least two orders of magnitude higher in terms of signal strength. Not only that, but they have completely the wrong impedance for any sort of phono cartridge, so even if you could get a usable signal, it wouldn't sound very good because the cartridge resonance wouldn't be correctly damped. Phono preamps are designed to deal with this; they have much lower noise, and are designed for low-level signals.

The second thing they do is provide EQ for the cartridge. This is in a standardised form based on a RIAA curve, and if you had an un-EQ'ed output from a preamp, Audition could technically manage this, although you won't find a preset, because nobody in their right mind would ever want to do this; it would be far from ideal. The reason for this is that the other thing that happens in the preamp is that the EQ is integrated in the design of it, and the noise performance is optimised for it. The nature of the EQ is that the bass gets a hefty boost, and if you just used an ordinary but sensitive preamp, you'd end up with a noise performance you really didn't like very much afterwards.

So this is why phono preamps exist - because they are the only correct way to achieve the results, I'm afraid. No getting round it at all...

So when you said "When using a moving magnet cartridge turntable for playback on your stereo set you usually need a device called phono pre amp" the word 'usually' is, I'm afraid, incorrect - it is always if you want to be able to listen to the results!

[Klаus]

Very clear and plausible reply, Steve, thanks a lot!

[ryclark]

However if the turntable is already connected to a stereo amp (which is what you imply) then the preamplification and EQ will have already been done in the amp. If so the easy way is if the amp is decent enough to have a recording output available, originally meant to connect to an external cassette deck recorder, which you can probably connect directly to your PC's audio interface and get reasonable results.

[Klаus]

Well, I’d actually like to disconnect the turntable from the stereo set and to move it over to my desktop area to connect it to my computer. I now believe I do have to buy some little stand alone phono pre amp for this.

[SteveG_AudioMasters_]

Klаus  wrote

Well, I’d actually like to disconnect the turntable from the stereo set and to move it over to my desktop area to connect it to my computer. I now believe I do have to buy some little stand alone phono pre amp for this.

That is absolutely correct. There are lots of them on the market, with a price range that is barely plausible...

[Klаus]

The turntable is a 40+ years old Sony PS-X60 with an (I believe) AT95E cartridge, so I won’t have to spend a fortune on a level matching pre amp ...

[SteveG_AudioMasters_]

The sort of thing you probably should be looking at is something like this: Pro-Ject Audio Systems Phono Box E It doesn't cost a fortune, and apparently works pretty well.

[ryclark]

Also you can get Phono Preamps with built in USB connection to your PC thus bypassing any built in soundcard connection if you don't already have a good external USB audio interface.

[Klаus]

Phono Box E came in yesterday, works quite nicely.

[SteveG_AudioMasters_]

Sounds like a result to me...

[Klаus]

Yap. The only thing I might miss one day is an on/off switch.

Just now I am recording one side of an old lp full of test signals, in order to generate some sort of adjustment profile from it. To compensate any left/right level differences, at least.

[SteveG_AudioMasters_]

Klаus  wrote

To compensate any left/right level differences, at least.

With a lot of older pressings, they weren't that accurately set up in the first place! On my system, some albums have anything up to 3dB variation between the channels - and that's without altering a thing. What I've found to be the most accurate and satisfying solution is to use Audition's phase scope (not the meter, the actual polar display) - you'll soon see what needs correcting if you use that. Another thing that's often useful to do is to convert the signals to Mid-Side stereo for click suppression, and declick each channel separately. You'll generally get far more clicks occurring near groove edges, so generally the Side channel reveals more of them. When you're done, just convert back to normal stereo again. This is a bit sneaky, I must admit - but it's an absolutely lossless process, so why not? Oh and yes this works just as well with mono records, except that often you can just lose the Side signal (the stereo difference information) altogether, and just use the Mid for the output.

[Klаus]

Well, it’s the left/right differences my system is producing what I’m aiming at. This view (from Cool Edit, that is) shows slight differences for signals that should be of equal level.

Thanks for your declicking advices. As I am not yet familiar enough with Audition I may find them pretty useful a bit later

[ryclark]

0.7 of a dB is nothing for a stereo record pickup. As well as mismatches in the windings of the pickup itself offsets of that sort can be caused by mechanical misalignment of the cartridge roll axis or the disc itself either due to wear. Also remember, as Steve, says to check the phase angle of the output since yaw misalignment can cause phase shifts.

[Klаus]

I agree. I did an overall comparison, based on all the left/right signals of the recording, and there seems to be a deviation of about 0.7%. So I tend to consider my system to be quite well chanel-balanced 🙂

Regarding phase angle and yaw misalignment: Is there any tutorial or video to explain about all that to a newbie like me?

[SteveG_AudioMasters_]

It's all to do with cartridge and arm alignment. Any tutorial covering that will give you the basic idea of how this works. Generally there isn't a lot you can do about the arm - the offset and overhang are generally fixed by the manufacturer - but the alignment of the cartridge in the headshell needs to be carefully adjusted for best results. Generally yaw would only be a problem if the cartridge wasn't mounted square on - in other words twisted on its horizontal axis with regards to the grooves. It also needs to be axially level (when you look from the front - often called azimuth). There are some other things that need attending to as well, and yes a guide would be a good idea, I think... try this one: A Beginner’s Guide to Cartridge Setup — Audiophilia