Vinyl Transfer Distortion - Pre Emphasis??

[Gravity]

I have a client who is transferring a number of his large collection of old vinyl (around 1965 back to the 30's)

On almost all of the transfers there is a noticeable distortion on both high (caracas, strings, horns) and low (basses, drums) frequency content. This distortion seems only to be present when the recordings are made from the stereo inputs (when made in mono there's little to no noticeable distortion). It's important to note that other sources recorded through the same signal chain (minus the preamp obviously) do not exhibit the same problem, and that the monitoring chain sounds perfect. It's only on the recordings themselves, once it hits digital. The problem is noticeably exaggerated when the recordings are converted to MP3.

I've tried everything, from different phono preamps, to lowering the gain, to saying a few mantras and burning some incense... Nothing has worked... Not one thing. The best theory I can come up with is that the older records with thie various different pre-emphasis curves are screwing with the converters or preamps on the interface (onboard soundcard and an Apogee Duet are exhibiting the same issue...) Is there something that isn't noticeable in the analog domain but might be manifesting itself in the digital realm? But then it doesnt explain why the change between mono and stereo...

I'm stumped. No amount of research is getting me anywhere and I don't know enough about old vinyl to know for sure what's going on here.


Anyone got any ideas? I'm at the end of my rope!

[vineyardgray]

Why not get your hands on a "new" piece of vinyl and test your theory? Waltz down to the record shop (, remember when we used to go to the record shop?) and pick yourself up a virgin. (Vinyl that is).

MR

[David Kulka]

There is no compatibility problem between phono preamps and converters. It should just work. RIAA playback EQ reduces high frequencies during playback, and really I doubt that the de-emphasis (not pre-emphasis, that happened in the mastering room and was surely done correctly) has anything to do with this.

I assume that this distortion is heard when the phono preamp is monitored directly. Are you able to bypass all the digital stuff and monitor your preamp directly to verify this? Maybe with headphones, if nothing else?

All 33 1/3 RPM LP's and all 45's are RIAA with the same EQ. 78's have many kinds of EQ (there were like 12 different standards!) so if you are transferring 78's, then it's a whole other story and you will need to do some research on special preamp setups. 78's need a different stylus, too.

1930's stuff will be 78's, 1960's will not.

There might be issues with the cartridge, the tracking force, anti-skating, etc. Maybe this is a bad example of tracing distortion (not tracking the groove properly) and the noise problem tends to cancel in mono. With stereo turntables, vertical modulation of the groove (or out of phase energy between the two channels) will cancel in mono. If the turntable sounds ok by itself, maybe oscillation or RF is finding its way into your rig and messing with the converter, as you suggested.

But maybe the real problem is: wrong turntable. To transfer both 78's and RIAA with decent quality, you'll probably need 2 different systems. More info about your discs would help, and maybe a sound file?

[Ken Paul]

Have you tried more than 1 cartrige/stylus combination?

-kp

[Gravity]

My only thought about pre v.s. de emphasis was that the RIAA curve wasn't as aggressive a roll off on the de-emphasis side.

But these are great suggestions that I hadn't thought of at ALL... This is why I come here :-) I should clarify that the CLIENT is doing the transfers on his own, and I don't have access to his rig. I'm just doing some research for him. I have (mostly) eliminated the most obvious 1D10T errors so far... but right now its a matter of asking him to try something, and having him report back with the audio files. A long process to be sure.

[Les]

Hi,

I used to design phono cartridges. It could be a lot of things, but if the records are mono you need to sum L+R to get rid of any vertical modulation.

I don't know if you're still working on this, but if I coulld hear a sound clip
I might be able to find the cause.

also, what cartridge/stylus/turntable are you using?

Les

[Hane]

Originally Posted by Les

Hi,

I used to design phono cartridges. It could be a lot of things, but if the records are mono you need to sum L+R to get rid of any vertical modulation.

I don't know if you're still working on this, but if I coulld hear a sound clip
I might be able to find the cause.

also, what cartridge/stylus/turntable are you using?

Les

Since you used to design cartridges, is there any advantage to using a mono cartridge to play mono records over using a stereo cartridge to play mono records and summing the L+R signals electronically?

[Les]

Hane, I don't see any particular advantage of using a mono cartridge. It's
likely to be old, with low vertical compliance and poor quality.

The technology we used in the late seventies/early eighties resulted in some crazy good cartridges...some could track 100+ cm/sec recorded
velocities at a fraction of a gram. They could also do 50kHz if it matters.
The modern styli give the possibility of tracking unworn parts of the
groove at least on lps. And summing L and R will very effectively knock out the vertical stuff.

Les

[Hane]

Originally Posted by Les

Hane, I don't see any particular advantage of using a mono cartridge. It's
likely to be old, with low vertical compliance and poor quality.

The technology we used in the late seventies/early eighties resulted in some crazy good cartridges...some could track 100+ cm/sec recorded
velocities at a fraction of a gram. They could also do 50kHz if it matters.
The modern styli give the possibility of tracking unworn parts of the
groove at least on lps. And summing L and R will very effectively knock out the vertical stuff.

Les

Grado, Ortofon,Shure, Dynavector and Lyra do make modern mono cartridges, so i doubt that they'll suffer the problems you mentioned. The logic according to some people for using a mono cartridge is, the difference signal rejection occurs at the point of conversion from mechanical vibrations at the cantilever to the coil; which is aligned to read only the sum signals.

The five companies mentioned wouldn't put mono cartridges on to the market if there wasn't a demand for them. I was considering buying a mono cartridge since my mono records vastly outnumbers my stereo ones; then again i could be going down a blind alley.

[Les]

Hane,
For sure if enough people want it, it will be made! If I still designed cartridges I would be delighted if folks bought both a stereo and mono
unit. And.... I might just start making them again! That's one reason I peruse these forums.

I worked at Shure, btw.

I would be perfectly happy with a stereo cart for mono recordings because:

1) You can use a variable summer to optimize azimuth angle, and get exact vertical cancellation even if recording angles were a little off.

2) The most research dollars were spent on the stereo cartridges, and
they had superb performance. We sweated bullets to make cartridges like
the V15 VMR and the ML140HE (one of mine) the best we possibly could.
Yes, i'm biased, haha.

3) summing after the pre improves s/n by 3 db!

Sadly The beryllium cantelevers used in the above had to be discontinued due to difficulty in getting materials. And the stylus assembly is really the
heart of a cartridge.

I can't even recommend the ML140HE I designed because even NOS will have hardened bearings by this time. The Beryllium made these have such high performance. It has the highest speed of sound of any metal. To replace a stylus I have to renew the bearing and diamond on an old one.

I could even tell you how to build a summer if you're handy with
tronics. Heck, what am I saying?? I could just build you a beryllium
mono cartridge if you really want one!

Les

[Hane]

Originally Posted by Les

Hane,
For sure if enough people want it, it will be made! If I still designed cartridges I would be delighted if folks bought both a stereo and mono
unit. And.... I might just start making them again! That's one reason I peruse these forums.

I worked at Shure, btw.

I would be perfectly happy with a stereo cart for mono recordings because:

1) You can use a variable summer to optimize azimuth angle, and get exact vertical cancellation even if recording angles were a little off.

2) The most research dollars were spent on the stereo cartridges, and
they had superb performance. We sweated bullets to make cartridges like
the V15 VMR and the ML140HE (one of mine) the best we possibly could.
Yes, i'm biased, haha.

3) summing after the pre improves s/n by 3 db!

Sadly The beryllium cantelevers used in the above had to be discontinued due to difficulty in getting materials. And the stylus assembly is really the
heart of a cartridge.

I can't even recommend the ML140HE I designed because even NOS will have hardened bearings by this time. The Beryllium made these have such high performance. It has the highest speed of sound of any metal. To replace a stylus I have to renew the bearing and diamond on an old one.

I could even tell you how to build a summer if you're handy with
tronics. Heck, what am I saying?? I could just build you a beryllium
mono cartridge if you really want one!

Les

So you worked for Shure, that’s interesting. The V15 VMR was a highly rated cartridge; Thanks for the explanation on why that model was stopped. Were the mono cartridge coils aligned to detect summed signals only or were coils aligned for stereo and the two channels just summed together internally?

Does the summing circuit work on similar principle to this software or have I got the wrong idea completely? I’d be interested in the summing circuit. Is it possible to post up a circuit diagram?

A mono V15 VMR! Err… how much? Though as they say, "If you need to know the price....."

[Les]

I think the only current Shure mono one is the m78. I didn't have anything
to do with that one, so I don't know about the field configuration. I play my 78s on a victrola!

That VST might do the job if you have a software host for it. I Have several similar to it in my studio DAW. Or do it with hardware. I'll try to scare something up.

As far as making mono cartridges, well... it wouldn't be a V15V....it would be better! I do use beryllium for acoustics projects in my lab because it's the very best metal for microphones, speakers, and of course cartridges. Hard to come by and potentially very toxic in the manufacturing process, but safe in the product. I guess some of the supply difficulties have to do with it being used in some key nuclear weapons components. Boron has fairly good properties as well, but you also have to have the proper geometry to take advantage of it, which is generally problematic. Beryllium wins hands down.

Anyway if you would really like a beryllium mono cart...pm me and we'll talk. I don't want to hijack the thread.

Les

[drtechno]

RIAA Equalisation didn't get popular till the fifties
if you have 78 laquar disk, it is probably AES curve (flat)
there was several record equalisation curves around until the RIAA eq became the standard.there were over 100 combinations of turnover and rolloff frequencies in use, the popular ones being Columbia-78, Decca-U.S., European (various), Victor-78 (various), Associated, BBC, NAB, Orthacoustic, World, Columbia LP, FFRR-78, microgroove, and AES.

That is why the equalization type was printed on the lable till the mid 60's on all records printed comercially.

you might wanna try hooking the phonograph to two microphone channels (pins 2&3) without phantom power on and ground the turntable on pin 1 of one of the mic channels on the board. play with equalisation till it sounds good. If you have an aphex aural exiter, mix some of that in and you'll be pleased.

[TOFT]

Have you tried a different needle?
Perhaps your needle is fine with mono, but not with stereo?
Or am I asking a very stupid question?