Monday, April 20, 2009

audio: tube servicing

After several years of light use, one of my monstrous VTL MB-450 power amplifiers died. I replaced its KTK-2 fuse (ordered from Fuses Unlimited), and it worked fine for a few listening sessions, then it stopped, I replaced the fuse again and it died an hour later.

The right thing to do is ship all my amps back to VTL in beautiful downtown Chino for service, tube replacement, and rebiasing; they could simultaneously install the the coupling caps and the extended tube life upgrades that they have developed for this model. Total cost about $2,000; a worthwhile economic stimulus to support a small company with top-notch service, but it will have to wait for my OBAMPO (Obama bailout amp owners) stimulus money. Bea Lam at VTL thought the most likely explanation of these symptoms is a bad tube, so with trepidation, I did the wrong thing and tried to fix it it myself.

I watched the videos of guitar amp tube replacement (!) on ExpertVillage and eHow and carefully removed all the tubes. At first they all looked OK, I envisioned dangling wires and rattling noises like a broken bulb.
6550C tubes, broken Svetlana second from left, replacement SED tube
Looking more closely I spotted a silvery-brown discoloration on one tube (second from left). I ordered two replacement tubes from Magic Parts for $70. I received a matched pair labeled by Ruby of the winged C rename of the original Svetlana version of the 6550C variant of the original 1955 Tung-Sol 6550 design, all the way from beautiful downtown St. Petersburg Russia. (The tube on the right.)
VTL MB-450 with the top off and three valves removed
Reinsert tubes, adjust the bias on each one in that row of holes (risking death from the high voltages and massive currents), insert another fuse and the music is back!

The history and complexity of vacuum tubes is impressive: hot clouds of electrons, filaments, plates, platinum grids, etc. refined over a century. They demand careful mechanical and electrical engineering, are hand assembled, and even then every one has different electrical properties and benefits from careful selection and matching to its partners. I don't get obsessive and mystical about it (the VTL amplifiers simply sounded much better than solid state amplification), but many audiophiles and musicians do: in a guitar mag interview John Mayer confessed to spending evenings auditioning and matching tubes for his amps. Enjoy your equipment, but love your music collection more.


Sunday, December 28, 2008

audio: search for master tape holy grail continues

In thoughts on digitizing vinyl I talked about the futility of digitizing my vinyl records when what I really want is the best digital file possible.

There's a fascinating thread on the topic of better-than-CD digitized formats in the SMR higher-res forum. The engineer from Blue Coast Records wants to offer high-quality downloads, but like Pete Towsend in the EQ interview, concedes “we did a listening test and found that analog was the best medium and chose to record the Blue Coast Collection on 2", with a backup to DSD.” But a sounds-great-but-not-perfect digital file is much less compelling than the master tape. Figuring out that final format is I think the only hope for quality recorded music — why else bother going for better-than-CD sound when 95% of all music sales are crappy MP3s?

It's tragicomical that the biggest impetus for quality digital files is not artists and record companies trying to create sonic masterpieces, but people making bootlegs of live concerts. A How to make a DSD Disc guide seems focused on "Snow Patrol 2007-07-18 Phoenix AZ"

It's all somewhat irrelevant to me right now, the financiapocalypse means it's a stretch to replace the blown fuse on a VTL power amp, let alone buy a Squeezebox Transporter to play such digital files on my stereo, or some kind of HDMI gizmo so I can play the SACD release of Gaucho on my PS3 and hear it through my stereo.


Monday, June 2, 2008

audio: re-playing piano when recording

I've been following pro-audio DSD since I found out it's been anointed the ultimate archive format. There's the Sonoma DSD multi-track recorder, which apparently sounds fantastic for recording. So let me buy a two-channel playback version of that with the same Ed Meitner Digital-Audio converters, and sell me the studio masters!

One of the recordings made with this gear is Glenn Gould live in concert, reprising his stunning 1955 recording of Bach's Goldberg Variations; Glenn Gould died in 1982. Another one is Art Tatum re-performing "Piano Starts Here"; Art Tatum died in 1956.

These recordings are of a player piano replaying a high-definition MIDI file created by software “listening” to the original poor-quality mono record. “Zenph® Studios is a software company that specializes in the algorithms and processes for understanding - and re-creating - precisely how musicians perform. ... We’re separating musicians’ performances from their original recording medium.”

OK, my mind is blown.

Years ago I went to a mechanical music museum in England. If you've only heard a cheesy player piano banging out ragtime, you have no idea how sophisticated some of the systems were. High-end player piano was the hi-fi of its day; wealthy people would install fancy pianos and monster pipe organs that played elaborate piano rolls that captured attack, pedals, and other nuances, "recorded" by famous pianists. I heard a roll of George Gershwin performing Rhapsody in Blue and the composer's take on his own composition was radically different from recordings I've heard. Zenph is creating new piano rolls by listening to old recordings.

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Saturday, March 29, 2008

audio: record scanning not a fantasy

It turns out my armchair fantasy of digitizing my records by visual scanning rather than dragging a stylus through the groove has been done by researchers, including project IRENE, the visualaudio project, and other attempts. Carl Haber at IRENE in a long interesting presentation (80MB! PDF) says
We study the use of new, optical measuring and image processing methods to create a digital representation of the complete record surface, on the computer, and then “play” it with a virtual needle.
He points out in another paper that a 10" side becomes a 300 MB processed image scanned in 2D (so an LP might be a few GB), and, just as I perceived, that “[the process] can archive images for future re-analysis with new algorithms.” Awesome, ship it!

Alas, the sound-to-noise ratio is poor. It's a vital technique for non-destructive archiving of sounds from rotting wax cylinders, cracked shellac transcriptions, and broken 78s, but doesn't come close to top-notch vinyl playback. The Swiss visualaudio researchers comment
Reaching the same quality as with a good 33rpm record played on a modern turntable probably is probably utopic.
Oh noooes, say it ain't so.

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Saturday, March 22, 2008

audio: thoughts on digitizing vinyl

I have quite a lot of vinyl records. I play them on a Rega Planar 3, a fairly high-end turntable.

I'm not dogmatic about analog vs. digital. My well-recorded CDs sound great, though the loudness war means many CDs are tiring to listen to. And many of my vinyl records sound fantastic, though some are warped or have irritating pops.

The thing about vinyl playback is the headroom for improvement is vast. Decent CD players sound very similar, but a better turntable solves real engineering problems and sounds much better than lesser turntables.

A big motivation to get a better turntable is to make better digital copies of my albums and singles. The digital library I cart around on music phones and PCs currently only has songs from my CDs

On that subject, I was struck by this review of a super-exotic Rockport Sirius III turntable:
I made two demo CD-Rs of various tracks using the Rockport, to A/B with the LPs in real time. Of course, the "live" LPs creamed the CD-R, which sounded slightly brighter and edgier but less immediate. Nonetheless, the CD-Rs did capture the Rockport's essence.

When I A/B'd the CD-R with the "live" LPs on the Yorke [a merely good turntable], the CD-R topped the LPs in overall presentation, dynamics, and especially solidity.
In other words, a digital recording from a super-exotic turntable sounds better than vinyl playback from a merely good turntable.

So, do I really want a $5,000 turntable? Not when there's someone with the same vinyl who plays it through a cartridge hand-made by the 90-year old sensei, mounted to a gazillion-dollar 1000 kg turntable hand-calibrated by its engineer, in an isolated underground vault, connected to the discontinued $25,000 Boulder phono preamp — I'll take his digital files instead of playing my own records!

The next issue is what kind of digital file to make. MP3 isn't enough, even FLAC lossless is only CD quality. I want future-proof. The consensus is zeroing in on DSD. The latest Absolute Sound has a review of the Korg DSD recorder capturing vinyl playback and makes the points of how close the DSD sounds to the original and how it's the best format for archival. Again, I want someone else's superb digitization of their vinyl. Her DSD archival file will be better than mine.

(This still locks in the playback of the vinyl record on a particular turntable, cartridge, arm, and digitizer. What about future improvements to vinyl reproduction? So my most radical thought is to capture the record and read it in software. It should be possible to make a detailed scan of the record surface itself. Then software can reconstruct the audio waveform without the primitive mechanical operation of dragging a diamond along an undulating spiral valley. As long as the initial scan is high enough resolution, software can do a better job knowing what kind of cutting head made the vinyl, how vinyl deforms when stamped, where best to read the undulations in the walls. I have no idea if a 100 square inch microscopic 2½-D scan is remotely practical.)

Returning to reality, if the record companies were smart (OK, that's still unreality), then they would meet the demand for very high quality digital copies. From a rant
My concern is that we get every possible historical recording archived to DSD as soon as possible, AND that the artists (both performance and recording) can and should make DSD the authoring medium of choice, REGARDLESS of what happens to it subsequently.
Definitely! The DSD file becomes the fabled "master tape" that is the source for every released version of the music. But unlike a reel-to-reel tape, the music's owner can sell me the master DSD file, charging me more than a $0.99 MP3.

Here's Pete Townsend of the Who on DSD, from a great interview about recording music:
Genex DSD [was] what my Mastering Supervisor Jon Astley preferred. I preferred the sound of analog tape (1/2", Dolby SR at 15 ips) but they sounded so close it was almost impossible to tell the difference. ... It’s hard to tell whether going to tape would have produced better sound on CD. A CD is pretty difficult thing to get to sound “warm” (whatever that means, such a hard word to define in audio terms).
So the ultimate sound would be to play Pete Townsend's analog master tape. But even an analog fan like Pete Townsend says the original DSD file sounds fantastic, then gets mucked up when you turn it into a CD. So sell us that master file! 2L is one label offering this, as a test: a DXD file, as well as several lesser formats.

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Thursday, June 21, 2007

Joni Mitchell triggers hi-fi porn

I got the Shadows and Light DVD, a nice extended concert. I don't want to believe Jaco Pastorius is dead! Then listened to Blue on vinyl, so incredibly alive, raw, perfect. It's a drug, I want more sonic pleasure, or the echo of someone else's orgasm. I know it's wrong and I'll go blind but:
Even by Court and Spark, also engineered by Henry Lewy, the sound flattens. Or maybe it's my equipment.

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Wednesday, May 16, 2007

music: why so much sounds so bad

This short video tells you all you need to know.

More on the loudness wars here and here

I want the numbers from the last link on every CD review. Average sound level as percentage of loudest, and instances of clipping.

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Monday, January 29, 2007

stereo on

speakers in living roomSound in the new house! Yes, these are large panel speakers; for scale, that's a 70-inch plasma TV between them :-) . I finally bolted them to Mye Sound stands, and the Rega turntable is now on a wall shelf, but otherwise it's my old hi-fi in new location.

It still has a way to go: there's a lot of buzzing from electrical interference, and the sound stage seems hollow in the center (though wide as heck between the speakers). But records that up until now I've only heard on cheap systems are transporting, the detail revealed on Ys is amazing and you hear the sound around the notes that's completely absent in most audio playback. Optimizing the speaker location will take a long time; tweakers on the aptly-named Planar Speaker Asylum say a change of 1 degree or an inch makes a big change in sound. And I may yet spring for the RPG Bicubic Diffusor acoustic panels on the ceiling that Richard Bird of Rives Audio recommended (which cost about 4 times more than the speakers!).

Two friends have the same Magnepan MG 3.6 speakers, and they're also putting time and money into improving the sound. I see the appeal of the easy setup of a big box speaker like the Wilson Audio, but those cost tens of thousands of dollars and the soundstage and treble aren't any better.

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