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Klaus Heyne's Mic Lab / Re: U67: Add More Top End?
« Last post by Brian Campbell on June 13, 2018, 11:05:05 am »
For example the initial U67u 00-00-00S. (Considering that 17 is the highest number for a capacitor in this model, the designation  as C17 may be an indication that is may have been an afterthought...):

Interesting to note in that schematic that the heater supply is +6.3V on pin 4 not -6.3V.

(Pardon me for bringing this thread up again but I find this mic fascinating)
Klaus Heyne's Mic Lab / Re: KM84 Low output suddenly
« Last post by BluegrassDan on June 12, 2018, 10:58:55 pm »
Thanks so much for the info. The voltage at the junction you specified is very low (close to 0).

I'll start with the caps and see how it goes. Thanks again.
Klaus Heyne's Mic Lab / Re: KM84 Low output suddenly
« Last post by uwe ret on June 12, 2018, 10:34:52 pm »
To check for proper operation of the FET measure the voltage at the drain (junction of R4, C4,C2 and S1). It should be close to 10V.
Very low voltage at this point, even near 0V could have various causes:
1.)      C4 = 1µF/25v Tantalum leaky or short circuit;
2.)     Zener diode GR1 = BZX45C24 leaky or short circuit,  (any 24V Zener with 0.5W  maximum power dissipation will do)
3.)     C5 or C8 = 5µF/25V Tantalum leaky or short circuit
I doubt the transformer may have been damaged, but if in doubt, measure for continuity between the red and black leads of the primary, and between the white and blue leads of the secondary.

A shorted FET (T1 = 2N3819) would result in a voltage of around 2V at this point.
Klaus Heyne's Mic Lab / KM84 Low output suddenly
« Last post by BluegrassDan on June 12, 2018, 09:33:23 pm »
Hey folks. I was playing at Bonaroo this weekend and using my KM84s. Everything was fine during mic check.

A bolt of lightning struck VERY close to us. Sounded like a rifle - flash and bang at the same time. One of the KM84s stopped working (the output is very low, although seemingly not distorted). No other equipment was damaged.

I got them home, swapped capsules, and determined the capsule is fine.

I'm not saying that the lightning caused the malfunction - could have been coincidence - but could something have been damaged due to high SPL? Could this cause the FET or one of the old tanatlum caps to fail? Is there a particular area I should zero in on?

Thanks in advance!
Recording The Rolling Stones “Brown Sugar” Sessions
Reconstructing the night that gave us rock songs for the ages
Jun. 15, 2012, by Bruce Borgerson

 - If you’ve seen the Rolling Stones Gimme Shelter movie, you might recall Jimmy Johnson’s brief speaking role.
He was the one coaching Keith Richards on the proper Alabama pronunciation of “Y’all come back, y’hear.”
For three nights in December of 1969, the Stones cut basic tracks and live vocals for three songs: “You Gotta Move,” “Wild Horses” and “Brown Sugar.”
The sessions took place at Muscle Shoals Sound Studios-the “burlap palace” at 3614 Jackson Highway—a nondescript former casket factory which the four rhythm section members had purchased earlier that same year.
Prior to venturing out on their own, the foursome (Johnson, bassist David Hood, keyboardist Barry Beckett and drummer Roger Hawkins) had been the core players at Rick Hall’s Fame Studios, where their rhythm tracks laid the foundation for soul hits by Aretha Franklin, Wilson Pickett, Etta James, Arthur Conley and others.
Since early in his Fame days, Jimmy Johnson had switched roles back and forth, playing fatback rhythm guitar on some sessions, engineering others. His early engineering credits included “Sweet Soul Music” and “When a Man Loves a Woman.”
But when the Rolling Stones arrived-with little advance notice-Johnson was confronted with something quite other than the relatively low-volume, laid-back soul and pop sessions that were his usual fare.
On one hand, you could say the fledgling Muscle Shoals studio was ill-equipped for the task. On the other hand, you might say maybe this turned out to be a good thing. Let recording history be the judge.
In this interview, Johnson reconstructs (as best can be expected after 35-plus years) the night that gave us a rock song for the ages.
Let’s try to set the scene for those sessions, starting with the console you used.
When we did the Stones sessions, we had a Universal Audio console with tube modules, the one with the big rotary knobs, knobs as big as your hand. We had ten inputs.
There was some fixed EQ on it, a fixed low end at 100 Hz, and you could go two clicks of boost at two and four dB, and you could roll back to minus three.
But that’s all it was. It also had an echo send on it. Back then, we were using a live chamber. It wasn’t until a year after that we got an EMT plate. Of course, we were uptown then!

 - Did you get the Universal modules new, or from another studio?
We bought all the modules new, and put it in our own little console frame. We had a cabinetmaker build us a console, the same as Rick did over at Fame, this was the same thing he had.
At the time, it was one of the best things you could get, depending on your budget, of course. Our budget wasn’t too big at the time.
And what kind of tape machines did you have?
We had a Scully eight track, a one-inch, and it was great. We had no noise reduction, though back then we cut a lot of stuff at 15ips. We just packed a lot of it on!
And the tape was very forgiving, so as a result it turned out well. We got a lot of saturation, and that kind of became part of the sound.
Back then…I don’t even remember any noise reduction at the time. I know there wasn’t any when we went up to Atlantic in ‘66. But there might have been some around that I didn’t know about.
Were you the only engineer on hand for the Stones sessions?
Yes, I did all those myself, along with my assistant, Larry Hamby. It was supposed to be Jimmy Miller, from what I understand, but he didn’t show up.
It was my intention to assist him when the whole thing started, because I heard they would be bringing their own people. As it was, he never made it down. So I became the unofficial-official engineer for all those sessions.
Did you cut all the basic tracks here?
They did some overdubbing later, of backgrounds, saxophone and acoustic guitar. But electric guitars, lead vocals, piano and even the percussion was done right there, Jagger did that. Mick Taylor was on those sessions, of course, and during “Wild Horses” Jim Dickinson showed up, from Memphis.
What happened is that their touring piano player, who was also their road manger, Ian Stewart, he played on “Brown Sugar” some, but during “Wild Horses” Jim Dickenson was out behind the where we put the guitar amps “Do you remember Paul Simon’s ‘Kodachrome’ where we went to double time and the tack piano comes in, the piano kind of goes crazy?
That was our tack piano, an old upright piano; we put tacks on the hammers so it sounded like a honky tonk. Anyway, Jim was back there just tiddling on it, playing along with what they had settled on as the groove, and Keith walked by and said, “Hey you need to play that!”
Let’s try to reconstruct how “Brown Sugar” was tracked. First, what mics did you have set up, starting with the drums?
We only had three mics on the drums. We ran a U47 up over the top up over the top, about nose high to the drummer. We had a high stand out in front, with the mic facing downward at the kit, from the bass drum in with a little boom that came over the snare.
So it gave a good overview of the whole kit, so you could play with a lot of dynamics and you could get an incredible sound. In fact, Charlie Watts wanted to buy that microphone! But of course, I wouldn’t sell it. He couldn’t get over the sound we were getting.
On the bass drum we used the E-V 666, a fantastic dynamic mic for the time. It was on a little stand looking to the backside of the drum. Then I had a hi-hat mic, which I think was another (E-V) RE-15, though it could have been a little (E-V) 635A, that remains in question.
The RE-15 was a better mic, had more response. We avoided using the 635A unless we had to. Actually, if not the RE-15 it might have been an SM57, more likely than the 635A.

 - And Charlie brought all his own drums?
Yes, he brought all of this own kit.
What guitar was Keith playing?
It was a Gibson, but not a Les Paul. Do you know that model that was right under the Les Paul, the solid body double cutaway-what is that?
Oh yeah, the SG. I think it was an SG, and as I recall it was black. I remember it had those sharp horns on the cutaways. That’s what he played most of the time he was here.
And Mick Taylor?
Taylor, to my recollection, was playing a Strat. And guess what we came up with for Bill Wyman? Do you remember those Plexiglas body basses that were around then?
I checked with David Hood later and he says it was a Dan Armstrong. So to the best of our recollection, that’s what it was. He played through David’s Fender Bassman setup, the tube head and separate box.
And the guitar amps?
Keith played a Fender Twin, and so did Mick Taylor, and they brought those in with them. The loudness on those tracks really came from Keith. I had it put in that back booth and shut the door on it.
So Mick’s was out in the room?
Yeah, it was out, set where I normally played. If you looked from the control room it was on the left side, about the middle, facing toward the front. You see, we had all these wonderful baffles, covered with burlap, with that pink insulation underneath.
We would corner off the sound with a couple of baffles up against each other. It would just knock the directness off, it took a lot of top end off.
So you could balance it out, but not stop leaking altogether.
Exactly, you couldn’t really snuff the sound out. It wasn’t as evident in the other mics, but it was there.
How did you mic the guitars?
On the guitar amplifiers, let’s see there were two different ones, on Mick’s I had a Shure SM-57, and then on the other I was using.. I might have been using an RE-15 on Keith. But I had a real problem with Keith because he was running a Fender Twin amp wide open, I mean that sucker was getting it.
I had a real problem with distortion going on, but I happened to remember that my maintenance guy, about a month before that, had left me a 20dB pad that he had made, a homemade pad, so I just stuck it in between. So I dropped that level before it hit the front of the Universal Audio and it saved the day.
Otherwise, I would have been hosed. I still thank God for that. I would have just been screwed. So on Keith’s amp, ‘oh no, I remember what was on his amp, an RCA 77DX, because I was having to get that level down any way I could, it was a ribbon mic.
With the pad and that RCA, I made it, just barely. A lot of that had to do with how it sounded, and I was always real pleased with that guitar sound.

- I assume you close-miked the amps.
Yes, they were miked about two or three inches from the grille cloth, and with the Twins, we would get right in front of one of the two speakers. I’d make sure that both were working all right, and that one didn’t have a hole.
How about the piano mics?
On the piano I was using only one mic, not two, so I had to move it around to find the hot spot. I’m going to have to think on that one.
I think it was a U47, that was the other one, because three was all we had. And we used them all on every session. Jagger sang on a U47.
So the U47 on Jagger, that was a live vocal track? Or was it overdubbed?
I don’t think so, not unless he had to fix something in London. The only overdub I remember was the percussion that he did. He had mono earphones of course, and they were hearing what the board was hearing, they couldn’t get a separate mix.
Did you have a mic on the bass amp?
Yes, the bass guitar mic was an RCA 44. We didn’t have direct back in those days.
How much separation could you get in that studio?
Well, Keith’s guitar amp was in a booth, and Jagger was in the back of the room with baffles around him. There was some leakage going on, but you couldn’t tell because he was so close to the mic.
It was part of the sound. The drums did not have a booth, they were open, but with baffles. But there was a lot of leakage on the drums, cymbals and stuff, even though he didn’t play real hard.
Really? But there’s a lot of impact in the drums on that song, more than on most Stones tunes.
Yeah, it’s that mic and the way we set it. Even today, that would be a good way for a rock band to mic their drums, if they like some great live drumming sound. They would be surprised to find that sometimes less is more. I think it would blow them away.
And the sound of Keith’s guitar is so good, and I really attribute it to that RCA DX77 with the pad, going into that Universal Audio tube console which warmed it up, too. Pretty wild, huh.
Did you use any compression on those tracks?
None. At the time, I did not have a compressor in the building. It was a couple more years before we had compressors. The only outboard gear was that 20dB pad, that’s all I remember.
What about board EQ? Did you use much of that?
Mostly, on all sessions, I would use one click or two on the highs to air it out. It was set at around 3 or 4K, with two dB steps; you could go to two or four. We had 100Hz for the low end, and I guess around 3500 for the high.
I remember Barry Beckett saying he was sitting outside on the steps and could feel the building shaking.
Yeah, when they stated grooving around one in the morning, when I started the machines, it was an unbelievable thing; I have not experienced anything quite like that since.
If you compare Brown Sugar to other cuts done by Glyn Johns at about same time, most came out on Let It Bleed, you don’t get that kind of room sound. They have that clean separation, you don’t get the feeling of the whole room being pumped up by the music.
Right. You get the same thing from those old Motown records, cut at Hitsville USA in Detroit. When they moved to LA it all changed, they never had that wonderful sound again. I don’t understand how they could divorce it that way. But I love that sound, and the old Philly Studio, Sigma Sound and all the great records done by Gamble and Huff, God they were great!
Yeah, but up in Philly, they were probably saying, “How can we get that funky sound they have down there in Muscle Shoals?”
Oh, we didn’t even think about that. I suppose the grass is always greener somewhere else.

New Article…

Jimmy Johnson wasn't scheduled to record the Rolling Stones during sessions the British bad-boys booked at Sheffield's Muscle Shoals Sound Studio for early December 1969.
A studio co-owner, Muscle Shoals Rhythm Section session guitarist on Aretha Franklin hits and recording engineer on such smashes as Percy's Sledge's "When a Man Loves a Woman," Johnson was just going to assist with The Stones tracks. Jimmy Miller, a percussion-oriented New Yorker who'd helmed The Stones' darkly brilliant previous two albums, "Beggars Banquet" and "Let It Bleed," was again set to produce. 
"All of a sudden 12 hours before the session I found out I've gotta do it," Johnson recalls now. "Because Jimmy didn't make it. He didn't make the flight. Oh, boy." During the eventual sessions, which went down Dec. 2 - 4, 1969, Johnson captured two Stones originals and bona fide all-time classics, the hip-shaking "Brown Sugar" and pastoral ballad "Wild Horses," as well as one of the band's best deep-cuts, a cover of Fred McDowell's transient blues number "You Gotta Move." The troika ended up on The Stones' landmark, druggy 1971 album "Sticky Fingers."
"We had to get those songs cut within about five hours (each)," Johnson says. The 1969 Stones sessions, held about a year after Muscle Shoals Sound opened, typically began around 6 p.m. "The songs were not even finished written, two of them, 'Brown Sugar' and 'Wild Horses,' they wrote them as we were doing them."
While in the Shoals, The Stones crashed at the Holiday Inn in downtown Florence. Footage of the group, which at that time consisted of Mick Jagger, Keith Richards, Billy Wyman, Charlie Watts and Mick Taylor, outside the Holiday Inn can be seen in the music documentary films "Gimme Shelter" and "Muscle Shoals." These days, a Hampton Inn & Suites is located on those grounds, at 505 S. Court Street. And 4:30 p.m. Friday a historical marker, produced by the Alabama Tourism Department, commemorating The Stones' Muscle Shoals Sound sessions will be unveiled at the Hampton Inn. And in case you were wondering, the marker will look similar to those black, rectangular plaques in front of antebellum homes and whatnot - and not in the shape of the iconic Rolling Stones lips logo.
Johnson checked in from Sheffield via phone for this interview.
Jimmy, you're on record as not being a Stones fan before recording them but that opinion changed after working with the band. Why?
We'd always heard a ton of different things because of their PR. When they were working they were drinking a little but they were not drunk and there were not any drugs to speak of - there might have been a little smoke. But nothing to excess because they were so business-like and really dedicated in the studio. I would say for about two to four hours they were looking for the tempo and the guitar riff and that was Keith's deal. Just watching them put it together was pretty amazing because it would be so loose in the beginning your eyes would kind of roll a little bit, if you know what I mean, but buddy when they got down to it and by the time I started doing takes ...
And there was nobody there to say, "You better start rolling tape." But that was one good thing about being a session player: I knew when the optimum cut was coming. The first time I ever heard them say something to me, it was, "Was that (take) it?"  and I'd either say, "Let's do one more" or "Come on in and listen, that's it." If I asked them to do another one there was no problem getting another take. When they'd come in and listen they'd all be happy with it and leave for the night.
How many takes did you cut for each of those three Stones tunes recorded at Muscle Shoals Sound?
I don't think I went over five or six. I found out what their engineer/producer does: They put it together on the floor themselves and it's kind of a joint venture between Keith and Mick.
Were you told why The Stones picked Muscle Shoals Sound to record?
They always said they liked the records we cut and in the ("Muscle Shoals") movie Keith says they'd always wanted to come here if they could, and it was pretty shocking when we heard they were coming.  I was real impressed with how they put their records together and how good they were, and I immediately became their fan by the time they left. Believe me.
Bobby Keys, who played the sax solo on "Brown Sugar" and was a Stones sideman for decades, died earlier this week. What do you remember about working with him on "Brown Sugar"?
He didn't make the trip. He was just doing concerts with them and he didn't normally record with them until they finished their parts and then he'd come in and overdub his part, and that's what happened on this one. They overdubbed him (for "Brown Sugar"), to my knowledge in England. He had been friends with them since the beginning.
Before The Stones cut at your studio, who was the best-known artist to work there?
The first hit we did didn't come around until after we'd been there about eight months. Which is normal. We were booked every day but you build a backlog of it because you don't release records as soon as you cut them. There's a lot of work with album covers and that kind of thing. So it was usually about a year after you finished the tracking and cutting of the album and in this case, it was two years. "Take a Letter, Maria" was the first hit we cut there. Basically, it was a million seller. As a matter of fact, the interesting part of that was we got it on the very first take. That's a very magic cut, if you listen to it. [Laughs.]
Every make it to the Florence Holiday Inn rooms The Stones were staying at?
I never did. At the same time the Atlantic (Records) attorneys and The Stones' attorneys were all meeting at the Holiday Inn to work out a distribution deal for The Stones records.
Back in the late-60s, The Stones were probably some pretty far-out looking cats for North Alabama. Did you ever hear any reaction from friends outside the industry about seeing them around town?
Well, the big thing was very few people knew they were in town, and I think a lot of the people that did see them didn't recognize them. And that kind of got to them a little bit.
Klaus Heyne's Mic Lab / Re: Golden Age Premier GA-47
« Last post by klaus on June 11, 2018, 02:57:37 pm »
With time, the marketplace usually determines the true value and staying power of any new microphone launched.

This mic will have to prove its value against the competition in its price class. Any shortcomings will be publicized by early users and spokespeople for the competition.
Klaus Heyne's Mic Lab / Golden Age Premier GA-47
« Last post by RuudNL on June 11, 2018, 12:15:38 pm »
I found this picture of a Golden Age Premier GA-47 microphone.
Except from the (outside) looks, there isn't very much that reminds me of a U47...
Advertised as a 'top class' microphone, I have serious doubts about the construction.
IMHO it looks like a (bad) DIY microphone.
Very long wires from the capsule to the tube, all components are 'floating' in the air, only soldered to the base of the transformer it seems. As they say: 'this was done because point-to-point wiring sounds much better than a PCB'.
Personally I think it is just cheaper, without the expenses for a PCB.
I would never buy this microphone!  (+/- $1500)
Klaus Heyne's Mic Lab / Are Tube Microphones Less Reliable?
« Last post by klaus on June 08, 2018, 01:20:07 pm »
Are Tube Microphones Less Reliable?

If my life depended on the answer to this question, then, yes, tube mics are significantly less reliable than solid-state mics.

Start up a tube mic 100 times, and at least one time it will fail. A 1% failure rate is frustratingly unacceptable in a commercial recording environment, especially when you cannot easily predict and prevent when that moment will come.

After observing tube mic failures for more than three decades, I am still baffled by their utter unpredictability, which complicates prevention.

Here are some of the reasons why tube mics fail:

An example of how and why tubes fail can be found here: (http://repforums.prosoundweb.com/index.php/topic,1150.0.html). Other microphone tubes are not far off from these observations, where a good 10% of failures are beyond anyone’s ability to predict or prevent, even with extensive pre-testing and lengthy burn-ins.

Tubes fail most often, not because a filament wire breaks, or vacuum is lost, but because at impurities swirling around from electrode to electrode become audible- the tube develops discharge sounds that will never go away.

Why does that occur in some tubes after 10 years, and in others after 10 minutes? I have no satisfying explanation.
My best theory why and when tubes fail resembles my theory why we fall off the ladder and break a leg: instability during transition. Rarely does anything happen when things are stationary, but when stepping on or off the ladder, instability of position and movement change conditions under ones feet.

The same goes for tubes: every time I turn on the power supply, it stresses the system, even if only slightly.  That moment of instability can push a fault that’s been building to the surface.

Contacts. Contacts. Contacts.
Contact surfaces of electricity-carrying metals are inherently in a stressed state: electro-chemical reactions cause surface deterioration through current transfer, even across silver or gold plated surfaces.

Deterioration accelerates when mating with dissimilar types of plating. That’s why you try to avoid mating silver-plated XLR pins with a gold-plated ones.
But even across the same type of plating, oxidation continues until its resistive effect blocks the contact and shows up as noise or catastrophic failure. You get it on plug-in mic heads, tube sockets, output connectors, and, especially insidious, because hard to detect, on badly soldered connections od components and traces.

Because heat and heat cycling are an added accelerator of thermal and component instability, tube mics are more affected. Heat and heat cycling (mic on, then off, then on...) of metal surfaces speed up material transformation and contact deterioration through repeated expansion and contraction.

In sum:  when the properties of electricity-carrying components change enough through temperature effects, they become unstable.

An average mono tube mic with variable pattern has more than 40 soldered cable connections between mic and mic pre, and quite a bit more in a stereo mic.

Unless each of these wire connections was perfectly executed, using best soldering and cable routing practices, chances are one of these wire connections will fail, especially once physical stress from abuse is added. The first to fail are usually shield terminations, due to their unwieldy stranding that is often just mechanically clamped down under the connector’s stain relief.

Power Supply.
They work the hardest: AC rectifying, voltage filtering, dropping and dividing... most of these processes are stressed by high currents, voltages and heat - components dry out, resulting in voltage increases with addition

The instability caused by heat is exacerbated by a lack of periodic maintenance- probably the single most significant contributor to tube mic failures.

To minimize chances of sudden failures, here are three preventative measures every tube mic owner should undertake:

1. Have a qualified technician check supply voltages at least once a year, and immediately when tubes are changed. Have the voltages measured INSIDE the mic, not inside the power supply (voltage drop in cable). and adjusted to no more than the median values recommended by the mic (not tube!) manufacturer. Burn in a new tube for at least three days continuous operation. Have the voltages of new tubes re-checked after 24hr continuous operation, and rechecked periodically thereafter.

2. Use a plastic bag over the mic before and after every session. Keep the bag on the mic when stored (http://repforums.prosoundweb.com/index.php/topic,1146.0.html)

3. Operate the tube mic system properly:

Before the session: Connect the mic cable to the power supply and microphone BEFORE you plug in the AC cable, only then turn on power supply.

After the session: Turn off the power supply, THEN disconnect the AC cable from the power supply, then the cable from the mic

Klaus Heyne's Mic Lab / Re: Schoeps m221b transformer
« Last post by Recording Engineer on June 08, 2018, 03:01:30 am »
What are those impedances and the ratio anyhow?
Klaus Heyne's Mic Lab / Re: Schoeps m221b transformer
« Last post by afterlifestudios on June 08, 2018, 01:47:30 am »
Update:  I wrote to Schoeps and got this reply within just a few hours...
Hello John

Earlier M221 had the A925, later models the A700. In case of a defect transformer it was replaced by the A700 for older models as well.  Their in-out ratio was the same, their impedance as well. So their diference had no influence on sound or other parameters.

Kind regards,

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