TONE HISTORY

Recording engineers and producers (many today are also guitarists) are just as crazy about tone. They're always searching out gear that will impart that classic tone and character to their recordings. While guitarists talk about maple neck Stratocasters and compare Marshall to Fenders , engineers talk about classic tube Neumann and AKG mics or the earlier ribbon mics from RCA.
Their debates often center around "tubes verses transistors" (sound familiar ?). Vocalists are just as particular about the mic they record with , and they certainly perform better when they're happy with their tone!
Rock's early recordings were made with a fraction of the tools (or the time) we use today. Bands would polish their act in the clubs , sign a contract and immediately hit the studio. A few weeks later , their first album was on the way to the stores! Elvis , Roy Orbison , even the first Beatles albums were made in weeks , and not months or years like some of the albums produced today.
The studios were always booked solid.Engineers kept the same few mics constantly set up , a certain mic for vocals , another one for drums , yet another for the guitar amp or piano...whatever sound the best.
Everybody just played (and sang) togheter live (in real time!) until they got a keeper. Then on to the next 3 tunes before lunch , they had to finish the album by the weekend. This assembly line system , born from necessity , heavily contributed to the classic , yet diverse tone signatures of records made at Capital , Motown or Sun Records. The same tube mics were used over and over once the engineer got the tone he was looking for. They didn't use much EQ or effects , but instead would change the mic placement to correct a problem or improve tone.
Bill Porter , a living legend in Tone History , has graciously contributed many details about his early recording sessions. Bill has engineered over 7000 sessions that have produced 579 hits on the charts , 49 top ten , and 11 number one records!
His credits include Elvis (Now or Never,Lonesome tonight,Good Luck Charm,Stuck on You),Roy Orbison (Only the Lonely,Crying,It's Over),the Everly Brothers (Kathy's Clown,Louise,Till I kissed her, Ebony Eyes). The common tonal thread through all of Bill's creations was vacuum tube mics , which he still uses daily to record.
When we speak about vacuum tube mics , we specifically refer to tube type condensor mics as opposed to the modern condensor mics which use semi-conductors. A condenser mic has a built in amplifier in close proximity with the capsule to amplify the signal from the capsule as early in the audio chain as possible. Condenser mics are more sensitive microphones with more detail as compared to conventional dynamic type stage mics.
The first condenser mic was patented by engineers at Bells Labs in 1919.
They were made for research and motion pictures. However , no significant condenser mic was produced for commercial purposes by U.S. companies partly because the bandwidth of broadcast radio , the primary user of mics , was limited to 5 KHz. The RCA ribbon mics were king of the commercial market in the states and so few quality tube type condenser mics were developed. Germany was a different story , however. German radio was state owned and the Germans wanted the best audio possible. The Neumann company developed many high quality condenser mics from the early 30's thru to the mid 50's. These Neumann and AKG tube mics , and a few from Sony (particularly the C37 tube condenser mic) were the mics that helped create the tone of the early Rock recordings , still very desirable today.
The early Neumann and AKG condenser mics used tubes for their condenser amplifier circuits , they had no choice. The introduction of the transistor brought the end to many (if not all) tube audio products and condenser mics were no exeption. The improved noise and distortion specs of semi conductors initially interested engineers who had been fighting noise battles for years in broadcast and recording. In the mid sixties , Neumann , AKG and the other condenser microphone companies experimented with some Nuvistors (sub minture tubes) , then completely converted their condenser mic product lines over to use transistors.
The new technology looked good at first , measurements showed that the transistor mics are superior because they have lower noise and less distortion while requiring virtually no maintenance (the electronics,that is). However , a musician , producer , or an audio engineer is more concerned about tone. Great recordings are more about tone and less about noise and / or distortion , yesterday and today.
The primary two companies responsible for the premier tube condenser mics were Neumann (Germany) and AKG (Austria) , however both mics were also sold under the Telefunken name. We've all listened to these mics over the years without even knowing it , and I think you might find it interesting to know which models go with which recordings. What follows is a brief overview of these classic tube mics from this perspective.

THE NEUMANN U 47:

Introduced in 1948 , this mic was the peak of quality for that time. It had a 28 mm gold sputtered PVC diaphragm in a dual membrane design.
The polar patterns were selectable between omni directional or cardioid.
Later Neumann would introduce the U48 which is allowed for the cardioid pattern.The preamp was simple , using a 30's era radio pentode (VF14) wired as a triode with cathode feedback for gain coupled to an output transformer to interface with the other equipment.
The VF14 tube was very microphonic and prone to high noise so special selection was necessary.
(note : some late production versions U47s were made a RCA Nuvistor, which was a sub miniture vacuum tube originally developed for the Miniuteman missle program , these new tubes were retrofitted into a design made for the VF14 with poor results since the two tubes were entirely different in performance.
The U47 mic set new standards of audio excellence,and it's price reflected it's excellent performance.
A U47 sold for $ 390 in 1953 when the top of the line RCA ribbon mic , the 77A , sold for $ 135 !
However , once a studio finally got one,they wound up using it on the premier vocalist or instrumentalist they were recording , and the RCA ribbon mics were delegated to background vocals or horn sections.
Incidently , ribbon mics are still highly favorde for recording horns and many other applications. Since The U47 was usually the best sounding mic in any of the top studios around the country , it was the mic responsible for the vast majority of classic recordings from the 50's , 60's. The solid state mics had there impact as engineers would always try a new mic , but many engineers kept right on using the U47 until today it is unquestionable the most famous of the classic tube mics. It is especially a favorite with male vocalists , and it's famous for it's big warm tone.
It had relatively large proximity effect (this is the relationship of distance to bass response , moving closer to the mic increases bass response. So a vocalist can really work the mic for different tonal effects , making it a very responsive mic. It's definitely not a "flat" mic (most of these older mics were not), and has a characteristic pek around 8 KHz that many engineers like.
In use:Bill Porter used it exclusively on the above mentioned hits of Elvis Presley , the Everly Brothers , and most of the Roy Orbison hits. This mic has never fallen out of favor , and is the '58 Flametop Les Paul of clasic tube mics. Need more convincing? Take another listen to the Beatles Rubber Soul album. Virtually every track used the U47 mic....vocals , drums , guitars , amps and of course that tambourine!

The Neumann M49:

This was the top of the line Neumann and was even more expensive than the U47. The M49 was the wolds first electronically variable multi pattern (it offered 5 patterns!), remote controlled condenser mic. It didn't resemble any of the other Neumann mics because it was developed by IRT , a special research laboratory set up by the post war German government. However it was manufactured at Neumann , and since it was so advanced , and expensive , far fewer were produced and so they are more rare than U47's. They've got a great sound , similar to the U47/U48 as it used the same capsule. However the electronics were different and Neumann chose a special low moise Telefunken triode , the MSC2 which was similar to interchangable with the AC701k. Obviously , it had a great big warm sound,and a particular favorite of female vocalists.
The M50 was a variation on the M49,using the same housing but another diaphragm. The M50 had a 12mm omni capsule inside a 40mm plastic sphere for high frequency directionality.

The Neumann KM53 , KM54 and KM56:

These mics were developed for the early television industry as they required a smaller mic but still with good quality and low moise. The KM stands for "Klein Mikrofon" , or small mic. They developed a smaller capsule , using an incredibly thin nickel material as the membrane of the capsule. The KM53 was a omni directional polar pattern,the KM54 was cardioid pattern only, while the KM56 used a dual diaphragm version of the KM54 capsule to create 3 selectable polar patterns. Later , Neumann made a stereo version , the SM-2 , by using 2 KM56 capsules that could be rotated 270 degrees with respect to the other. In M-S stereo recording , one capsule was set to figure 8 , the other to cardioid pattern and a remote pattern controller allowed the engineer to directly to alter the width of the stereo image,extremely hip idea directly from George Neumann. Neumann patented this idea,adding to the 400 or so patents he had by then,and later licenced it to AKG who took of their C-12 capsules and built the stereo C-24 discussed later in this chapter.
In the recording world , these didn't have the big sound (or the big capsules) of the U47 or M'49 , but the sound quality was high and the frequency response was very true to life. The amplifier used a section used a newly developed triode especially for condenser mics,the Telefunken AC701k. These tubes are no longer manufactured today , however they can be found. It should be mentioned that in general , tubes in these old tube mics lasted years,and seldom actually outright failed. However , most engineers feel uncomfortable without a spare tube on hand , just in case.
More Neumann Notes and Notables:
The real tube mic freaks will be very disapointed if I fail to mantion a few other models of Neumann tube mics which have their place in Tone History. Neumann put his design emphasis on the capsule , and not the electronics,hense the unknowing loss of all those great tube mics as he switched to transistors (just like CBS Fender amps!). Therefore , the differences between the various Neumann mics are determined mostly by the capsule design , and many models used the same capsule in different housings. Basically , there are two families of Neumann large capsules in the old mics,the solid backplate type which is used in the M7 , U47 , M49 , and the two-piece backplate type which is in the U67 , M269 , SM69 , U87 , and other newer models. The more recent two-piece backplate version was developed to try to get some more high frequesncy response and improve the proximity effect. These are fans of both types of designs as they definately sound different. The U67 also has EQ in the electronics to try and calm things down. Neumann also made a stereo mic which used two of the U67 capsules all housed in the shell with two AC701k tubes , the model SM2.
It should ne boted that the early Neumann capsules used a 8mm PVC material to make the diaphragm. Later , with the introduction of the U67 , Neumann switched to a newly developed DuPont plastic film called Mylar. The early PVC material lost flexibility over time which caused a loss of low frequency. For this reason , eventually most these old PVC type diaphragm capsules crack and need rebuilding , something to keep in mind when shopping for an old Neumann. Some Neumann caspules also used ultra thin Nickle type diaphrams such as the KM series capsules.

The AKG C12 and C24:

Introduced in 1954 , it was the AKG answer to the Neumann U47 mics. The C-12 and C-24 are mono (C12) and stereo (C24) version yet use the same capsule design. The C24 allowed or stereo recording from a single point source. The C24's dual capsules could be rotated to acvhieve various perspectives for stereo recording. These AKG C12 capsules were quite complex and very time consuming to manufacture,which made them quite expensive!
The single capsule had 5 seperate air chambers suspenden between the 2 very thin (6-8 microns) gold sputtered membranes,using a total of 47 hand assembled parts (compared to 8 parts in the Neumann U47 capsule).
The assembly was so delicate that it took years to train an employee to produce a consistent quality capsule,an even then it took many hours to build one acceptable capsule. The opposing diaphragms were variably charged with polarized voltages by the power supply to change between the optional polar patterns. The amplifier section used a dual triode 6072 (a specially selected 12AY7 and similar to the 12AT7 we chose for our Model One and Two tube mics)
However , what really sets these AKG mics apart from the Neumann tube mics is their crystalline top end. They have the sizzle , and they cut thru a track without being overbearing or loud. The C12 and C24 bring out the silver edge to a bright voice , without the harshness associated with some transistor condenser mics of today. Telefunken marketed a very close version of the CV12/C24 series calling their models the M-250 and M-251. These Telefunken versions are vertually identical to the AKG, and are in great demand by knowlable engineers. AKG ultimately replaced the C12 with the 414 solid state condenser , and later redesigned the capsule to instead use injection molded plastic and many fewer parts. This greatly reduced production costs. While the 414 has been a commercial success as one of the best selling condenser mics,it is very different sounding than the C12 , and studio engineers who can afford to chose , will opt for the C12 every time over the 414.
Recently , AKG has reissued a version of the C12 , calling it simply "The Tube" and while it is a great sounding tube mic,the general consensus is that it doesn't measure up to the original C12,probably because AKG chose to use the cheaper 414 capsule rather than trying to recreate the original complex C12 capsule.
It is perhaps the second most recorded vocal mic of the last 50 years , just behind the U47. Warm , yet bright , it is the sound of Phil Collins , Mick Jagger.....

The AKG C60:

This was AKG's answer to the small condenser mics offered by Neumann , and again developed for use in television where size was a consideration. Naturally it has to have a smaller capsule , one with a .50" diaphram and mounted at the end of this mic shell which offered good off-axis and transient response because the barrel of the mic didn't interfere with the sound waves. The capsules were available in omni or cardioid patterns and could be interchanged easily. The AKG C12 and Neumann U47 were side address mics , with the capsule directed out from the side of the barrel as opposed to from the top as with the C60. One down side to these smaller capsule mics was that the had less output ans therefore were a little noisier. However , they didn't exhibit the same proximity effects as with the larger diaphram mics. Much like speakers,smaller diaphram capsules didn't get as fat a sound as the larger ones , just less surface area.
The amplifier used a 701k like the Neumann KM series , and had an unusual design that placed the output transformer inside of the power supply instead of the mic barrel like all other condenser mics.
In use:Bill Porter had left Capital and moved to Monument Records before he had an opportunity to use the new C60. He instantly liked it and used it to record Roy Orbison's "Pretty Woman" and "It's Over". The C60 sound is once again best described as warm and bright , although perhaps not as warm or fat sounding as the larger capsule mics. AKG's were in generally known for their high frequency detail , while Neumann's for their warmth and realism in the vocal range.

The Other Tube Mics:
Another German company , SHOEPS , made several really good tube condenser mics. The most notable is their model MK221 which had a front mounted 21mm diameter capsule,and is a studio favorite for acosutic guitars. Sony also made a real beautifull sounding mic , their C37,which had a large diaphragm and offered vaiable patterns of cardioid and omni. It has become mre highly regarded after it went out of production,like so many other tube audio products. Perhaps,this was one reason Sony has gone back to making tube mics!
It would be inaccurate to suggest that ALL the classic recordings were made on tube mics. The ribbon mics,which predate condenser mics,were in constant use in many studios from earliest Rock recordings and are still used today! Therefore , the Honorable Mention award in the classic recording mic category goes to these mics. Here's a brief overview of these classic mics,which of course enjoyed the benefits of those early tube mic preamps to get their unique tonal character.

Ribbon mics:

The RCA ribbon mics , which were not condenser type technology (no electronics) but another technology,were the only other significant mic in this Tone History. Their diaphragms were made of thin metal film strechted between two rather large magnets,this looked like a metallic ribbon hence the name. The technical name was "Velocity microphone", and this is usually what appears on the name plate.They had a lock on the U.S. broadcast market and were often used for early rock recording , mostly because of their wide availability and relatively low cost as compared to the high priced German and Austrian tube condenser mics.
Their advantage was that they had a great sound , with very low distortion.On the down side,they had a low output,which meant more amplification was necessary from the tube mixing console,they were also fragile. A strong vocalist could actually blow out the ribbon diaphram , but this was not so much a problem in broadcast as it was with Rock'n Roll.
These ribbon mics were the ones mostly seen and heard on the old radio and TV shows like the Grand Old Opry and later on early Dick Clark's American Bandstand shows. Sinatra is often pictured singing into a RCA 44 ribbon mic. Since ribbon mics were much lower output,and therefore relied on the tube mic preamps for much of their gain,tubes were again a part of the tone puzzle associated with ribbon mics.
OK,so now that you know more about these great sounding classic recording mics....what can you do about it. If you were reading this 30 or 40 years ago,you could have bought any of these mics for peanuts. Today,any of these above mentioned mics could start around $ 3,000 and a mint condition , prime sounding example could sell as high as $ 10,000.
Many companies like AKG and Neumann have released new versions of their classics,and these are excellent sounding tube mics with their own distinctive tonal character. Vacuum Tube Logic (USA), Microtech Gefel (formerly the East German Neumann company) , Sony (Japan) and of course Groove Tubes Audio all offer new versions of vacuum tube mics and/or tube mic preamps which go direct to tape or DAT. In the meantime also other companies which I can not all mention here are offering releases of their classic mics.
One contribing factor to this high cost of tube condenser mics is that all tube mics require the use of special power supplies to provide the filament and plate voltages for the tube which is contained in the barrel of the mic. Additionally , special multipin cables and connectors are also required to connect the power supply to the mic. Standard XLR connectors are located in the power supply,and the signal level is usually standard balanced mic level.

CONCLUSION

There is one sure fact after all is said about tube recording , and that is that now , more than ever,it is here to stay. Tube mics help warm up the tone of modern digital recording format which most listeners agree sounds sterile and cold by comparison to analog tape recorders. Tube mics are responsive , they make singers stretch , the same way a great sounding tube guitar amp can help us play better. You can reach with a tube mic and it goes with you , just like a good amp does. Tube mics and ohter audio gear has a "normalizing" effect , for lack of a better word.
The headphone monitoring systems commonly used today employ standard transistor amplifiers. I think transistor amps contribute to the common problem of listing fatigue. Of course,all the early recording sessions used tube amps to drive the multipul sets of headphones. these early headphones amps were usually a high quality tube amp like McIntosh in the U.S. studios,or Quad amps in the European studios.
As I am only a collector of these great microphones with a very big curiosity on how they work , I wrote this article to inform everybody who is doing recording work or is related with classic microphones. I found many information out of an article who was already written in the late seventies by Dick Rosmini , Steven Paul , and Bill Porter.
I hope someday you and I get the chance to explore recording with some tube gear and then see (hear) for yourself what many engineers are talking about! ....One tonal moment is worth a thousand words,and the role of tubes in "Tone History" could fill an encyclopedia. Unfortunately , I don't have Gigabytes of webspace available....

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