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 Заголовок сообщения: Реставрация STUDER С37
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Реставрация STUDER С37

THE TUBE IS MASTER
Restoration of Vintage recorders
A few years ago, I began to miss the nice sound of old vacuum tube mastering machines. The sound of our Studer A80 was quite acceptable, yet it seemed to lack the body and warmth of my old Ampex 300. So I dug a couple of my old Ampex 300 tape recorders out from under the pile of junk in the shop and began to fiddle around with them. These are remarkable machines, and for many decades were the workhorses in almost every recording studio and radio station. I cleaned one up, plugged it in, threaded a reel of tape and...Magic! What a sound.
Thus began an odyssey of transforming the 300 into a 1/2", 15/30ips machine, changing the speeds, rebuilding the electronics and having John French (JRF Magnetic Sciences) design and build a modern set of heads. I made some of the transports by hand, using some aluminum stock that matched the deck perfectly. The rest is history. This became our primary mastering machine at Sear Sound. Many albums were mastered on this machine, and one major label even went so far as to bring in a mixed album, record it onto the Ampex and the take the output from the playback head and re-record onto a Studer CDR CD recorder, just to add the sound of the Ampex machine on the album.
Just when we thought it was safe to go back into the water, I had the chance to pick up two Studer C-37 recorders. The blueprints are dated 1962, and I found that Gotham Audio (then Studer distributor) had sold six of these machines to RCA alone. Once the primary tape recorder in European studios, few C-37s were sold in the states, as Ampex controlled the market by then. I bought the two recorders instantly.
Each machine is a work of art. The electronics are all modular, which simplifies servicing. The transport hinges up and the front cabinet panel drops, providing total access for maintenance, including a convenient plate to put tools on. The deck has its own internal test meter and switch to measure various voltages throughout the recorder. A regular lightbulb is used as a variable resistor to set the proper startup torque to the motors (shades of my old Westrex film recorder that used the same idea). The wiring, harnesses and overall construction were typically Swiss. There are no VU meters on the machine, which is quite proper. When you align the machine, it should always be to the meters on the console.
The recorders were 1/4", 7.5/15 ips machines, so the first task was to change them into 15/30 ips machines, 1/2". After consulting a variety of knowledgeable people - including David Manley, who owns a slew of them - I got some of the parts that I needed. Then came the critical decisions.
I called Jeff Gilman at MDI Precision Motor Works in Hudson, Mass. He has a proprietary method of building up the capstan shaft size by using a ceramic sleeve. He also machined a series of roller guides for the 1/2" tape configuration. The machine nas no fixed guides - everything turns with the tape. Bill Titus did a lot of measurements for the tape path, and we added brass washer shims of different thicknesses to get all of the guides to the right height to match the head block.
The record and playback electronics were another problem. Beside the usual capacitor and tube replacements, the EQ had to be changed to conform to the various new head characterisitics and tape speeds. This is a "trial and error" situation. When you change the frequency curves to try to eliminate the "head bump" in the bass, the higher frequencies are then affected. After some experimentation, we found the right combination.
The final problems were the logic system and control switching. As machines of that vintage use relay logic, all the relays were cleaned up or replaced. Fortunately, the relays are standard "off the shelf" parts. Modern, microprocessor transport control is far superior, yet the relay system works fine, so we left it intact.
With the restoration completed, we ran wow and flutter tests. The machine came out better than the original manufacturer's specs (at 15ips, 0.04% weighted; and at 30ips 0.022% wow and flutter, 0.0175% weighted). Frequency response was what we expected, with the bass bump at 31Hz, starting at +.6 dB and staying within reason down to 15Hz.
The ultimate test for any piece of recording studio equipment is what the client will accept and will want to use in session. Sear Sound had the privilege of being selected to do the mixing for the Eric Clapton Crossroads II album, consisting of live and studio recordings that were recorded in the mid - 70s. (Jay Mark was the engineer and Bill Levenson produced with Kerry Rappaport for PolyGram Records).
The 2-inch masters for the '70s, mostly 16-track, had to be baked in a convection oven at 125 degrees for a couple of hours. They were then played on our Studer A80 16-track, 2-inch machine and recorded with timecode onto a beautiful new Studer A827, as well as a 48-track digital machine (rented from Toy Specialists). I don't like the sound of digital, but if I have to record digitally, this would be the machine of choice. It is built with the same care and attention to detail as the old C-37s. As Jay Mark decided to go 1/2", 15ips, Dolby SR, we set up our various 2-track machines. The moment of truth arrived. Which of our 1/2" machines would be best suited to the Clapton project? Using blind testing, it took about one minute for the choice to be made. The C-37 was the preferred machine to everyone. The sound had sparkle, clarity and "air" that other machines lacked.
The album was completed on the Studer C-37. The machine took a year of work, but it turned out well. At 30ips, the Ampex 300 has an "airier" sound, with more second-harmonic distortion, which many people find pleasing. The Studer is more accurate in terms of frequency response, but this is purely a matter of taste. No solid-state machine in our studio is comparable in sound to either of these machines.
I have always felt the deficiency of the sound of transistor equipment. Knowing this, I have always run a studio full of tube gear. Because of my 30 years' prejudice, I go to great lengths to be sure that this does not bleed over into the listening tests that we do. Neither I nor the visiting engineers know which machine or device they are listening to. They simply select button "A", "B", or "C". The differences are clear and apparent. As it often happens, the engineers' decision is the same as that of the producer and studio personnel. There is a clear and distinct difference, and in all the years of testing equipment, I can't recall any situation where vacuum tubes didn't sound superior to transistors.
--Walter Sear


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 Заголовок сообщения: Re: Реставрация STUDER С37
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Западный товарищ тоже заскучал по ламповому звуку.
Но всего пару слов сказал про электронику, всё больше по железу.
Мол, головки проблемно согласовать.
Так идеальных параметров и не требуется в ламповом звуке...


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Тим де Парвичини о С37 и не только...

An interview from Audio, January 1995

Tim de Paravicini, the Audio Interview: In Pursuit of Excellence
by Bruce Bartlett with Jenny Bartlett

Hidden away in a small company near Cambridge, England, is a man who upgrades analog tape recorders to near perfection. Tim de Paravicini modifies classic tape machines. He reworks them from the ground up, adding new tape heads, tweaking the transport, and replacing the electronics with his own custom tube designs. He also upgrades stereo microphones with special circuitry. And the results are worth it. His customers rave about the beautiful new sound, better than they can get with digital tape recorders.

An example of the de Paravicini sound is on A Meeting by the River, by Ry Cooder and Vishwa Bhatt. The experience of hearing this CD can be startling because of its presence, warmth, and purity. The recording won a Grammy for its engineering by Kavi Alexander of Water Lily Acoustics, an audiophile label. The electronics that contributed to this disc’s quality sound are the work of a man with a passion for audio purity that goes beyond digital quality. In fact, de Paravicini has contempt for digital sound as it now exists. He’s pushing the envelope far beyond what we ordinarily settle for in CD quality.

If you’re fascinated by the search for the ultimate in recording quality, de Paravicini’s story of modifications of recorders, consoles, and microphones will interest you, as will his provocative opinions on everything from digital sound to hi-fi "tweaks."

A man of many talents, de Paravicini is well known in esoteric audio circles as an extraordinary designer. While some of his circuit designs are tube and some transistor, all are original. He has been a consultant to Musical Fidelity and Lux Corporation in the design of many of their classic audio components.

Fourteen years ago, de Paravicini founded Esoteric Audio Research. The company makes vacuum-tube products for the high-end audio and pro-audio markets, such as power amplifiers, a microphone, a microphone amplifier, equalizers, and a compressor/limiter. With years of experience in disc cutting, de Paravicini has cut records for Water Lily Acoustics, Chesky Records, and Island Records. He also improved the performance of several recording lathes.

Although de Paravicini will upgrade any tape machine, his favorite is the legendary Studer C37. "It’s a good, reliable workhorse," he says. According to him, the C37 blows away everything else, even an Ampex MR70. The C37’s tube circuitry is simple, with no microprocessors to get in the way. Even before the upgrade, the C37’s specs are notable. The frequency response is rated as 20 Hz to 15 kHz, +1, -2 dB, and S/N is 75 dB (rms, weighted) at 15 ips. After de Paravicini’s modifications, the response is 7 Hz to 35 kHz, +/- 1 dB, and S/N is 90 dB!

One happy user of a de Paravicini tape deck is Chris Rice, owner of Altarus Records, a classical label. Rice had de Paravicini modify three Studer C37s - two 1-inch and one half-inch. "The heads were custom made to Tim’s specifications," says Rice. "The mechanical modifications he did himself. He stripped the electronics out and rebuilt his own circuitry into the existing modules, doing hundreds of modifications. He uses his own EQ curve. He also provides an AC mains regenerating power supply because the machines are not quartz locked; they depend on mains frequency. By doubling the capstan diameter, Tim doubled the tape speed from 7 1/2/15 ips to 15/30 ips."

According to Rice, "The new machines are incredibly stable mechanically. They sound fabulous, very quiet and more dynamic. They’re very clean and have no grungy noises. With the new Ampex 499 tape, the modulation noise is down so low, you can almost forget about it. It gives you quite a lot of leeway in your recording level. You don’t have to worry about compression because these tapes will happily go up to 9 dB over. The tape saturates way before the electronics overload."

Rice notes that his analog decks sound better to him than digital, even without any noise reduction. "They give a more accurate representation of what’s coming down the line. That has to be my final criterion: How closely can I capture what’s coming in from the microphones?"

Another satisfied user is Sam Rivers, a producer of jazz records. He sent de Paravicini two broken-down Studer A-80s to modify into a 1-inch and half-inch model. Vince Clark of Erasure also has one of de Paravicini's machines.

Kavi Alexander, the engineer with Water Lily Acoustics, won his Grammy for engineering a Ry Cooder album with a de Paravicini recorder; it was a 1-inch, two-track Studer C37. Alexander used a Blumlein stereo pair of custom microphones, which was built with rectangular mike capsules by Milab and with tube electronics by de Paravicini.

When I interviewed Tim de Paravicini, I was struck by his strong, original opinions about audio.

In some circles you have the reputation of a hi-fi tweak.

I'm not. I'm too academic to get into that. The hi-fi fraternity is bizarre, full of dangerous amateurs. I try to steer clear and do genuinely innovative work - something that's worthwhile.

What caused you to start modifying recorders?

I was dissatisfied with their performance, If "line out" doesn't sound like "line in," that's not good enough.

What’s the main advantage of your 1-inch analog recorder over digital recorders?

The sound quality. My analog recorder has four times the sampling frequency! The bias frequency is 160 kHz. The magnetic-particle flow past a playback head is equivalent to a 24-hit word, which is amazing resolution.

Analog recorders can sound wonderful, but DATs are so portable and convenient.

Oh, God, I hate DATs. Stopping and starting with those things is a pain in the ass. With an open-reel tape, you can pause it and go instantly; it's human; it's tactile. Whereas DATs stop, fit, fart, and think about what they're going to do - they're just not friendly. And unlike DAT tape, analog 1-inch tape archives beautifully. Some tapes made in 1955 are earthshakingly good. They still sound fresh. But talk to anybody with U-Matic tapes or DATs, and see how well they store. Run a DAT through a machine 20 times, and you're struggling.

If analog tape sounds so much better than digital, what improvements should be made in A/D, D/A converters?

First of all, the frequency response should extend from 3 Hz to 50 kHz, because we experience those frequency limits. We are able to detect audio up to 50 kHz. We don't hear it, but we experience it in other ways. I can give you tinnitus very quickly if I run an ultrasonic cleaner at 45 kHz. You are aware that it's on, and your ears ring when it's shut off. On the low end, we detect mechanical vibrations down to 3 Hz. When a marching band walks past you, you feel the drums in your stomach and bones. And that's all part of the sound.

Ten years ago in Stereophile, I said that digital was never going to work well in the chosen format. Digital should use a 400 kHz sampling rate and 24-bit words. Then it will satisfy the hearing mechanism and won't have a digital sound. Digital has a "sound" purely because it is based on lousy mathematics. The manufacturers presuppose too simplistic a view of our hearing mechanism.

But manufacturers don't want to change - it's the lowest-common-denominator syndrome. It's like 525-line television, which allows you only X amount of resolution. With digital, you've fixed your resolution parameters, where analog never had that problem.

I still do work on the vinyl record; it still can be advanced. The number of vinyl molecules passing the needle every second is equivalent to half a gigahertz. So there ain't a lot wrong with it, fundamentally. You can carry on improving it without losing compatibility. It's like good old 35-mm films - you carry on improving films, but there's nothing to stop you from shoving them through the same old projectors!

I've been pioneering work on a CD player that runs at 88k, but it only works with CDs that were cut at 88k.

When storage density increases enough, we won't have the excuse for using only 44.1k.

Right. The manufacturers should have said, "Let's go gung ho and create a real system that works right." A 12-inch LaserDisc would have given you an hour's worth of music to the highest standard. Manufacturers try to pretend that what's good enough for Joe Doe at $5 is the state of the art.

Getting back to your recorder mods, what transport modifications do you make?

Whatever makes the system more stable. Actually, wow and flutter is more limited by the tape than the transport. Tape is a mechanically compliant item, and 1-inch tape has much more tape stability and strength than quarter-inch. Yes, the wider tape costs more, but it's a small part of the total project cost.

How did you first learn about tape-head design?

I stripped a lot of machines on the market, worked out my own mathematics, and read papers by Jay McKnight, from Ampex, and so on. I ask the tape-head manufacturers, like Saki, to build heads to my specific requirements. I emphasize bass performance and the fineness of the laminations.

Do you recommend using Dolby SR with your machines?

No. It's unnecessary, and it doesn’t work well under dynamic piano conditions. It doesn't encode a control signal, so it can only approximate. The noise floor in my system is limited only by the microphone. You can't hear its tape hiss - just microphone hiss.

You use vacuum tubes in many of your designs. Some people have said that tubes have euphonic even-order harmonic distortion. Do you rely on this tube nonlinearity to achieve the sound of your mods, or do you always run the tubes in their linear region?

I do not rely on tube nonlinearity. I don't want a sound in my machines. What comes out must sound the same as what went in.

The "warmth" in a lot of tube electronics is due to their dismal top end, the bad transformers they use, and the loading down of their high-impedance outputs. Because of the output transformer and the feedback used, many tube circuits have a partial bass instability that gives a bloated bass. Any warmth in the tube sound is a defect, but listeners don't want to know that.

I don't have to use tubes in my designs; I only do it for marketing reasons. I've got an exact equivalent in solid state. I can make either type do the same job, and I have no preference. People can't pick which is which. And electrons have no memory of where they've been! The end result is what counts.

Most transistor-circuit architecture was different from tube-circuit architecture, and that's what people were hearing, more than the device itself. The main advantage of tubes is that an average tube has more gain than an average transistor. Second, tubes don't have the enormous storage times of transistors, so they are very fast. Tubes go to 100 MHz without trying.

Moving on to microphones, your mikes use rectangular diaphragms, tube electronics, and huge transformers. Why?

A circular diaphragm has one dominant resonant mode. But a rectangular diaphragm does not have the same resonant mode in both axes, so it tends to have a flatter response. Also, a rectangular diaphragm has less off-axis coloration in the horizontal plane than does a circular diaphragm of the same area.

My mikes are transformer-coupled, triode designs. The electronics have a frequency response of 5 Hz to 35 kHz (-1 dB).

I use transformers in my microphones because they can do the job better than anything else. There's no advantage in transformerless circuits because a lot of them can't drive long lines. As long as I know that the electronics of my microphone go from 3 Hz to 100 kHz at the end of 1,000 meters of cable, I'm all right.

Some transformerless mikes have pathetic headroom. Disgusting. We're besotted with this phantom-power philosophy. Most of the mikes draw only I damn milliamp at 48 volts, max. That's 48 mW of energy; it doesn't give you a lot of headroom. I want a mike that can shove 3 volts, +12 dBm, down a line, 20 to 20k, boom! Why so much voltage? Suppose you take a capacitor mike that produces 10-mV output with 74-dB SPL input. At 144 dB SPL, the mike will put out over 3 volts.

You've said that we experience sound down to 3 Hz, and that reproduction down to this frequency is essential. Do studio consoles go down that far?

No. The average console has all these cumulatively rubbish electronics in it. If you cascade 10 amplifiers, each with a response down 1 dB from 20 Hz to 20 kHz, you end up with a cumulative 10 dB down from 20 Hz to 20 kHz. So you must minimize all degradation. Since I use a lot of transformers in my stuff, each transformer must be very wideband.

Unfortunately, the average manufacturer looks at only one piece of equipment, in isolation. They quote a tape machine as having a response of 50 Hz to 15 kHz, +/- 1 dB, and say that's fine. Yes, in isolation. But not as a cumulative system. Tony Faulkner uses a mixing console of mine, full of tubes and transformers, but it's vastly flatter than most of the mixing consoles on the market.

What's your overall design philosophy?

Audio devices should not have a sound of their own; they should be virtually a black box. The results prove themselves in recordings using my products. They do the job.

Whatever the device is, I look at it and say, can that device be logically improved? Forget about cost. Companies like Neumann charge a lot of money, but I say, could they make that product a little better and charge a little more for it? Try to make things better, whether it's outrageous or not. Somebody will want it and will pay for it.

Any last words?

I try to provoke people. I'm sick and tired of the me-too factor, the lemming factor. Just because everybody else wants to jump off a cliff doesn't mean I have to.

Many audio companies tend to rest on their laurels and don't bother to take the next step forward. They should leap ahead instead of staying on the back burner. They have the potential to be stunning.

Discography

The two recordings below, among the finest-sounding available, were made with de Paravicini’s modified tape machines and microphones.

Ry Cooder/Vishwa Bhatt: A Meeting by the River, Water Lily Acoustics WLA-CS-29-CD. Kavi Alexander, producer. (Available from May Audio Marketing, P.O. Box 1048, Champlain, NY 12919; 800/422-7525). This beautiful blend of Western and Eastern acoustic music was Stereophile’s Recording of the Month, and was reviewed in April 1993. In my opinion, the highs are especially sweet and gentle. The sound just flows effortlessly into your ears. The only hiss you hear, which is slight, is that of the microphones.

Ustad Ali Akbar Khan, Indian Architexture. Water Lily Acoustics WLA-ES-20. Kavi Alexander and Sallie Reynolds, co-producers. (Available as a double LP from Finch & Marsh, 2457 Cascade Trail, Cool, CA 95614; 916/885-2279.)

The following four recordings, again with excellent sonics, were mastered by de Paravicini and John Dent at The Exchange on a custom-built, all-tube cutting system designed by de Paravicini.

Ravel, Daphnis et Chloe, Boston Symphony Orchestra, Charles Munch. Chesky RC15.

The Power of the Orchestra/Mussorsky, Royal Philharmonic Orchestra, Rene Liebowitz. Chesky RC30.

Clark Terry, Portraits. Chesky JR-2.

Ana Caram, Rio After Dark. Chesky JR-28.


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Начали во здравие - аналог, лампы, магнитофоны.
И вдруг - райкудеровские сидюки зазвучали лучше?!
Простительно только для 95 года.
А дальше - больше: оказывается лампы у него только в рекламных целях...


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С37 в версии Тима:


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Вадим Шлемский писал(а):
С37 в версии Тима:

Есть подозрение, что обратные связи вредны для звука не только в питании,
например, в стабилизаторах с катодными повторителями,
но и в механике, например, в системах отслеживания скорости, вроде прямых приводов в вертушках.
Полагаю, правильнее стабилизировать натяг ленты не измеряя его напрямую,
с последующей быстрой установкой тормозящего напряжения,
а измеряя среднюю скорость вращения катушки. Интересно, как в этих монстрах сделано...
Дедовский качественный лентоприжим в этом смысле предпочтительнее.


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