Analog Tape Dr. AIX's POSTS — 15 September 2013

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I’ve been working with analog tape a lot over the past month. My Nagra and Ampex 440C 1/4″ machines have been put back into action after many idle years. The Ampex was parked upstairs for over 10 years until about a year ago. Following the RMAF show last fall, I decided I should dust it off, get it overhauled and sell it to an analog tape devotee. The machines are getting top dollar. It’s been parked just outside of my wife’s office since then. When she arrived the other day, she noticed that it had been moved and I’m sure she was hoping that I had finally junked it…but no, it was in the studio in active use as an editing platform. I knew there was a reason that I had kept it all these years. Yesterday was definitely a “living in the past” moment.

mwaldrep_editing_analog_tape

Figure 1 – Mark Waldrep (aka Dr. AIX) editing the master tape of Christian Jacob for a vinyl LP release.

So are other audio engineers, producers and the dedicated group of analog high-end users that prefer the sound of analog tape living in the past everyday? Well yes, in a way they are. And I can appreciate why after spending so much time listening to the sound of my recent piano recording of Christian Jacob. If pressed, would I choose the analog tape over the 96 kHz/24-bit HD PCM tracks of the same material…no way. But I do understand the appeal and the “color” or “timbral” modifications that analog tape imparts to a track. Is this why so many equipment designers and music sites use some form of the phrase, “sounds just like the analog master tape”?

Audiophiles should acknowledge that analog tape is simply one flavor among many different formats. It served the music industry very well for many decades and yes; it still has a place in this business. But it is not a high-resolution audio format knowing the limited dynamic range, moderate frequency response and other distortions that it suffers from. I use as my point of comparison the clarity, accuracy and transparency of HD PCM at 96 kHz/24-bits or better. This is a case of different strokes for different folks.

Yesterday, I lauded Cookie Marenco for the marvelous recordings that she produces. She prefers the sound of analog tape and DSD to PCM. She’s stated that when a group of audio professionals evaluated a recording made to analog tape, PCM and DSD, that the analog was chosen by 100% of them. I would have to get more information about that test because I’ve experienced just the opposite in a test we did at Snow Ghost Studios in Whitefish, Montana. Using state-of-the-art microphones, preamp, converters and recorders, Peter McGrath (a well-known recording engineer and representative for Wilson Speakers), myself and a group of about 6 other professionals rather quickly ruled out the playback from a new Studer A 820 24-track analog deck through an SSL Series 9000 console to VTL monoblock tube amplifiers to Wilson Alexandria speakers (total value of the signal chain…well over $500,000). The analog tape just didn’t have the sparkle and detail that the digital formats did. I wrote about the weekend at Snow Ghost some months ago.

As promised, here’s the analysis of the free “Jimmy and the Crows” track that Cookie recorded and which is available free of charge at the Blue Coast Records website. I downloaded the MP3, 96/24 WAV/FLAC (which are identical) and both versions of the DSD format in 2.8 and 5.6 MHz (which are also identical). The annotated spectragraph Figure 2 is below:

blue_coast_sample_spectra

Figure 2 – The spectragraph of “Jimmy and the Crows” from Blue Coast Records as recorded and produced by Cookie Marenco. (Click to enlarge)

We all know that analog tape has audible amounts of hiss associated with it. During the heyday of analog tape, people like Ray Dolby (who passed away last week) created systems for both professionals and consumers to minimize the amount of hiss we had to suffer through. For professionals it was Dolby A (and later Dolby SR) and for consumers it was Dolby B. Looking at the spectragraph, you can clearly see the hiss. And it is audible when listening to the track using both speakers and headphones. The plot on the right and the “purple haze” in the left hand graphics is the contribution of both the hiss AND high frequency noise associated with DSD or 1-bit encoding and the need to apply fancy noise shifting to the signal.

The MP3 at 320 kbps actually sounds very, very good. The high frequency noise is gone but there are no ultrasonic components to the sound. I would guess that most casual listeners would not be able to tell the MP3 file from a CD resolution version or the high-resolution PCM and even the DSD files.

The analog tape converted to 96 kHz/24-bit PCM sounds the best and is the most accurate representation of the original. The sound is warm and smooth throughout the audio band and only hints at the hiss compared to the DSD files. If I had my Nagra slung over my shoulder and Cookie would make me a copy of the analog master, I’d prefer to listen that way. The reasonable alternative to my mind is the accuracy of a HD PCM transfer…and that’s what you get with the 96 kHz/24-bit FLAC or WAV. There is absolutely no difference between the FLAC version and the uncompressed WAV file. During a realtime decoding of the FLAC file, it might suffer on an underpowered machine, but to say that a FLAC file “sounds” different than a WAV file of the same source is simply untrue.

So let’s take a look at the DSD versions. Cookie told me that she records the output of her analog mixing desk to a Korg MR 2000 DSD recorder capable of 2.8 or 5.6 MHz 1-bit recording. In the plots on the spectragraph, the two versions are identical. There is no benefit from using the 5.6 MHz sampling rate over the 2.8 MHz standard. In fact, when I first did the analysis, the lines were exactly the same and I wasn’t sure whether I had actually completed the scan. Only when I added .5 dB to the DSD 128 file, was I able to see the spectra of both versions.

The DSD versions don’t have to work very hard. There’s not much in the way of ultrasonics in the analog original file (they top out at around 30 kHz) and of course, there’s the hiss. In reality having any recording scheme extending beyond 30 kHz is unnecessary in the case of an analog tape source. The DSD files are rolled off at 42 kHz (a PCM file at 96 kHz would extend to 48 kHz). And then there’s the additional HF noise caused by the DSD encoding. Who would reasonably want that?

Cookie is a staunch supporter of higher prices for DSD and in general for her “premium quality” productions. In fact, I may try converting some of my HD PCM recordings to DSD and elevate the pricing. I’m already considering issuing limited releases on 2-0 track analog tape. The philosophy of “give the consumers what they want” might just be a better way to go.

However, I’ve based my reputation on a different way of operating. I prefer to “give consumers the very best that I can offer at a reasonable price”. I didn’t get into high-end audio to get rich. I started AIX Records and iTrax.com to show what was possible with no compromise audio production techniques AND new high-definition audio standards.

So the ultimate question still stands. Is anything that goes through an analog tape production step capable of high-resolution audio specifications? The answer is clearly no. As wonderful as Cookie’s recordings are, they are not high-resolution…but they are very high-quality standard resolution recordings.

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About Author

Dr. AIX

Mark Waldrep, aka Dr. AIX, has been producing and engineering music for over 40 years. He learned electronics as a teenager from his HAM radio father while learning to play the guitar. Mark received the first doctorate in music composition from UCLA in 1986 for a "binaural" electronic music composition. Other advanced degrees include an MS in computer science, an MFA/MA in music, BM in music and a BA in art. As an engineer and producer, Mark has worked on projects for the Rolling Stones, 311, Tool, KISS, Blink 182, Blues Traveler, Britney Spears, the San Francisco Symphony, The Dover Quartet, Willie Nelson, Paul Williams, The Allman Brothers, Bad Company and many more. Dr. Waldrep has been an innovator when it comes to multimedia and music. He created the first enhanced CDs in the 90s, the first DVD-Videos released in the U.S., the first web-connected DVD, the first DVD-Audio title, the first music Blu-ray disc and the first 3D Music Album. Additionally, he launched the first High Definition Music Download site in 2007 called iTrax.com. A frequency speaker at audio events, author of numerous articles, Dr. Waldrep is currently writing a book on the production and reproduction of high-end music called, "High-End Audio: A Practical Guide to Production and Playback". The book should be completed in the fall of 2013.

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