Flat Phono Preamp Based on John's P10 and 2SK389

[mediatechnology]

I think I should probably stick with the "less is more" philosophy for the flat transfer path and simply keep the 6 dB/octave DC-blocking filter.

My intention was to deal with warp/rumble in DSP.
I think I can add a HPF to the RIAA text definition file.

For playback there are two 6 dB/octave poles in the monitor path.
The first is in the flat preamp path to strip off DC using a film cap.
The second is the post-RIAA gain stage which strips DC of the RIAA output.
The inserts we added would be a good place to insert a rumble/warp filter.

[ricardo]

The question is if this filter impulse response makes it more difficult to de-click cleanly.

A HPF should not delay the HF energy in clicks and pops, but if there is any DC or LF content in those transient perturbations, that can get smeared.

I don't know how the click and pop removers deal with LF.

There's a number of conflicting issues.

Old analogue de-clickers simply blanked out the signal to 0V. If there was 'DC', then the 'hole' would be also be a (albeit smaller) click. So there is an argument for 'some' LF filtering before de-clicking so there's less periods of significant 'DC'.

But a sharp (12dB/8ve or more) would 'ring' longer when triggered by a click and may lead to longer periods with 'DC'.

Perhaps 6db/8ve IEC (the shortest & nicest 'ring') before de-click .. and a 12dB/8ve section after, the two forming a Butterworth 18dB/8ve filter.

And don't forget the pickup arm/cartridge is another peaking 12dB/8ve LF filter usually with a dB or MUCH more, boost at 20Hz.

The better analogue de-clickers used a sample/hold. Today, I believe the digital ones interpolate .. which makes the choice of LF filtering point much less critical I think.

I recall seeing some phono preamp designs back in the day that incorporated multi=pole HPF into the popular single stage NI op amp RIAA feedback. (As I recall additional Rs and Cs in parallel with the EQ components). I was never comfortable with the LF phase and amplitude response, preferring the simple well damped IEC pole.

I've designed such a preamp and put myself in the camp that says it 'sounds' better.

Must see if I can dig it up. It was done before I wrote my Linear Circuit Analysis programme so frequency response was via loadsa very painful algebra.

As really a speaker & DBLT man, I've no doubt, judicious subsonic filtering especially on vinyl gives better sound, more tuneful bass bla bla.

[JR.]

http://www.decodedmagazine.com/the-eip- ... hing-them/



If my records looked that pretty I wouldn't have ticks and pops...

JR

[mediatechnology]

This virgin audio information is then reproduced without digitization maintaining true analog sound as close as possible to when the master tape was recorded. The Laser Turntable even allows you to play records that have been severely warped or damaged over years of wear and tear.”

So it's analog. Interesting.
I thought the same thing: What a pretty record.

I've no doubt, judicious subsonic filtering especially on vinyl gives better sound, more tuneful bass bla bla.

I agree. I found (by accident) that simply steering the warp from Side to Mid made a big difference in listenability.
The warp "information" was still there, but it was less noticeable.

[emrr]

I think there was a similar laser turntable in the late 1980's. Similar price!

[Gold]

From what I understand the laser turntables are not an unqualified success. I haven't used one but I've been told that they produce strange artifacts when they don't track properly. Worse than a good old cartridge.

[ricardo]

I found (by accident) that simply steering the warp from Side to Mid made a big difference in listenability.

You gonna explain to us mere mortals what dis magic trick is?

[Speedskater]

Some Laser Turntable history:

http://en.wikipedia.org/wiki/Laser_turntable

[emrr]

OK, I remember the mid-80s press releases about vaporware.

[JR.]

I'd call these (laser players) more like science fair projects for audiophools with too much money.

By the time these were being developed, sundry versions of digital media were under development.

Vinyl was good for it's heyday (no offense vinyl guys)...really good, but time goes on and superior technology prevails.

Arguably we are past the point where consumers are willing to pay more for even more sound performance, because they can't hear enough benefit to justify the extra cost. While there will always be a niche market willing to pay almost anything for the promise of some etherial sonic nirvana. The idea of a laser record turntable sounds pretty cool... Making this work better than mechanical playback on the majority of discs out there, is a very difficult task.

This is surely attractive for archival (non-destructive) playback of historical recordings, but that market for that is too small to support much R&D.

JR

PS: I don't recall much about applying M-S to vinyl... There were stereo image modifiers playing with sound stage back in the day, and phase encoded (SQ, QS, whatever) quad channel systems. IIRC separation in typical cartridges was challenged (maybe 20 dB on a good day). I pushed a lot of L-R through surround sound rear delay systems but that ambience channel was HP and LP filtered. For companding tape noise reduction I used a dynamic HPF to attenuate low bass when it was not accompanied by significant program energy.