Noise reduction (in Adobe Audition)

[Greg Miller]

Originally Posted by Bob Hart

I have an old AWA gram <snip> The waveform off it is exceptionally weird with the peaks on one side of the centreline about twice as deep as their opposites.

You mean with any program material on any disc? If so, that sounds extremely wrong to me. It would almost make me think there's a Class A amplification stage somewhere that is biased wrong, and is not operating in the linear part of the transfer curve.

Originally Posted by Bob Hart

I ended up creating a filter I called de-RIAA and then created other filters for each of the equalisation charts I could find for the various record labels of the times.

There's another NR/editing package called Diamond Cut Audio. I believe they're just released v.8, I was a beta tester for v.5 and v.6 a few years ago. As I recall, they have reverse RIAA curves, curves to convert RIAA to some of the other standardized curves, etc.

In fact, the guys developed the software originally so they could clean up some old phono recordings (maybe cylinders; my memory is unclear about that). Then they started to market it. I think they presently sell some of the actual audio recordings, as well as the software.

They actually have a lot of interesting NR tools, some of which Cool Edit didn't have IIRC. Additionally, some of the tools can work in "pass-through" mode, live and in real time. So, for example, if you're broadcasting a live phone call, you can run it through Diamond Cut and clean it up digitally as live audio, on the fly.

I used the program quite a lot for cleaning up some terrible old cassette tapes. But eventually I came back to Cool Edit, because I had learned on that program and could work much faster with their GUI. Still, Diamond Cut has its place, especially for NR, and it's a lot less expensive than Audition.

-- Disclaimer: Although I was a beta tester several years ago, I have no business affiliation with the company.

[Bob Hart]

The AWA was the first generation of their transistor reproducers and amps, all discreet components and no ICs. Prior to that it was valves ( called tubes in the US ). I think they were still learning the solid state ting then or maybe something has gone off over the years.

[Greg Miller]

Do you see this same flaw (asymmetrical peaks) on both channels, and on all phono records?

[Bob Hart]

The waveform is munted in both channels. The old stereogram also used a BSR crystal ( ceramic ) pickup.

Apparently dynamics are best but I personally prefer the "brighter" sound off the ceramic pickups for the older recordings which seems to break through the surface noise a little better. But that is just me. sound is a very subjective thing.

I have also damaged my hearing by being too close to too many angle-grinders and spoiled my hearing through working with HF radio over a period of time which "conditions" one to ignore and filter through noise and static. This is the exact opposite of what an audio engineer is about.

I have an Ortofon pickup with a 78 stylus on an electronic turntable ( which I must get back from the person I loaned it to. )

[Greg Miller]

My gosh, were there stereophonic ceramic pickups? It's hard for me to remember what technology (or lack thereof) existed 50 years ago. I guess I do recall such a thing, but only in the inexpensive "home quality" phonos, never in anything intended for broadcast or studio use.

However, one reason I asked about "both channels" was because I was pondering whether it's a problem with electronics or with the pickup. It's possible that there is a mechanical problem with the cartridge that is actually causing the stylus to mistrack in such a way that its output (i.e. the input to the preamp) is not symmetrical.

If you're using a pickup that old, and a ceramic one at that, it is probably well past its useful lifetime. Something in the suspension has most likely dried out, and is no longer keeping the stylus (or, actually, the cantilever arm) properly supported and centered.

I hasten to add that playing records with a bad pickup -- which IMHO includes any ceramic pickup -- will greatly accelerate groove wear, not to say damage. I always thought of ceramic pickups as "record eaters" since they require much higher tracking force, which is hell on those very fragile vinyl grooves. Of course if you're playing ratty old shellac discs, perhaps they can better survive the abuse.

[Bob Hart]

Ceramic or crystal. I may have got it wrong. Basically there are two flat strips agitated by a rubber carrier which supports the stylus. I presume the two very fine centres in each of the strips is the crystal material.

The audio off the dynamic pickups was better for fidelity.

The old shellac-on-bakelite disks suffered from stylus wear as readily as any other. Steel needles would not have been very friendly. In Carnarvon Western Australia, when I was a kid there were still one or two people using mesquite thorns for record needles. They were good for two plays.

[Greg Miller]

IIRC, ceramic and crystal were the same basic design, just a different piezoelectric material used.

True, the old discs were subject to wear, especially with the acoustic (i.e. non-electric) reproducers. But in that case we're talking a tracking force of several ounces, not a few grams. Surely a '60s era ceramic pickup tracking at ~5 to 10 grams would cause a lot less wear than an acoustic pickup tracking at 10 ounces.

And yes, I have an old crank-up victrola that uses interchangeable steel or cactus stylii. (Actually it's an Edison disc player with an alternate lateral playback head. The head for Edison discs was for vertically modulated grooves, and had a fixed diamond stylus.) There were a few different dimensions of steel stylii, for different playback loudness levels! Some day I should lower the stylus onto a good digital scale, and see just how much tracking force those things exerted... it would undoubtedly be scary.

[Bob Hart]

Regarding cylinder/roll recordings, there was a guy in Canada I think who was recording from old Edison cylinders using modern stereo pickups but reversing the poles on one channel so that the combination of both channels then detected vertical inputs. His tracking arm was incredibly long but light and balanced so that the arc of movement along the cylinder was as straight as need to be.

[Paul R Johnson]

My gosh, were there stereophonic ceramic pickups? It's hard for me to remember what technology (or lack thereof) existed 50 years ago

Not even fifty years ago! The crystal/ceramic pickups were still fitted in budget end equipment in the 70s and wary 80s. Garard SP25 and the BSRs with turnover cartridges were very common, and moving magnet cartridges were firmly in the hi-fi end of the product range throughout that time. Hi-fi shops were selling styli for these in the early 90s! Today, technology is obsolete before the guarantee runs out - back then, asking for a new cartridge for twenty year old product was common! I seem to remember selling little in-line pads so old ceramic cartridges could be connected to new amps that didn't have a ceramic input any longer!

[Greg Miller]

Aargh, you're right, and that brings back terrible memories. We used to call BSR by a name that seemed appropriate, given the [lack of] quality. I will say only that the "B" stood for "Bull" and you can ponder over the rest.

Aside from the difference in gain, IIRC the input for a ceramic cartridge needed different EQ from a magnetic input. One type had output proportional to stylus velocity, the other had output proportional to stylus amplitude. So the "converter" you recall should have had some EQ compensation built in, not just a simple resistive pad.