Nelson Pass said:
Yep...you were the primary 'other' of whom I was speaking. (My don't he speak purty when he has a mind to!) I recall one thread where you did the atypical thing and allowed yourself to be drawn into a protracted argument about what constitutes feedback. Your philosophy normally seems to lean towards avoiding conflict, but you stuck with that thread for quite some time. The problem with that is that it doesn't lend itself to sound bites. The overall theme is clear, but the pity quotes tend to get lost in the noise. A pity, really.
Grey
john curl said:
John, you're being grumpy again. There are plenty of great recordings made with Schoeps or Neumann mikes, you know that.
In fact I don't think a single RCA or Mercury LP was recorded with B&K.
Scott, I am not going to say that 50pf is too much capacitance for a mike. That would be unfair to commercial fidelity. I would also say that many good recordings have been made with Shure Unidyne 3 mikes, SM58's, etc. It is just that the BEST is usually a smaller capsule than 50pf implies. Just look at the curves. There was an AES paper given in Montreux Switzerland in 1986 by Herr Manger that gives the curves for many typical quality condenser mikes, like the ones you think OK. Check it out.
And some of those (the newer P48-only types) even contain one of the high-end audio angst items par excellence: a SMPS (*oh my God*) 😀 😀scott wurcer said:
john curl said:
John, please don't interpret what I'm saying as direct or implied criticism of your stance regarding feedback. As I said in my amplifier thread recently, this is a journey, not a destination. I have never been able to live with large amounts of feedback for long. Eventually, I learned that lower amounts of feedback tend to lead to better sound. With that in mind, it's natural to push towards the 0dB NFB level (setting aside arguments about degeneration for the time being) to see what happens. My initial impressions are very favorable, but it's early days yet and I'm a big proponent of long-term listening to decide what has staying power and what doesn't. It's easy to point to the low end as a weakness for low feedback amps and I fully intend to dump a truck load of NFB on my subs when I get the servo thing up and running. The question for me is what works best in the mids and treble.
In case anyone is wondering when I will deliver a "review" of the GR-25, don't stay up late at night. I don't review my own stuff. What I said above is as close as you'll ever see to a review. Face it, the ones who think I'm an idiot for building a 0dB amp would think I was deluded or lying or both after the review. Those who already thought low to no feedback amps were the logical end point of design would only see it as a confirmation of their beliefs. Either way...why bother?
Bob Cordell said:
Bob,
You and I appear to have some fundamental differences in our approaches to audio. That said, I didn't mean what I said as criticism of you as a person. Your feud--for want of a better term--with John seems to be deep-rooted and has clearly already lasted twenty-five years or more. From a bystander's point of view there's naturally a bit of curiosity as to exactly how this disagreement came about. You and John have mentioned these articles and letters a number of times and over time they've acquired an almost mythical quality. I mean, really, just what did these guys do to each other that the echoes are still being heard now, in 2008?
Then up pop the letters.
I read them and see little emotion in John's (if anything, it tends towards the dry and stuffy), a fair amount in yours, but given the amount of time that has passed and the fact that I'm not personally caught up in the Does TIM Exist Or Not wars, it's easier for me to view them dispassionately.
As such, my observation that your letter appeared to evidence more emotion was exactly that...an observation.
If I look back on that same time period and judge with hindsight and (hopefully) maturity (SHADDUP! NO LAUGHING ALLOWED!) the various things that I said and did...well...let's just say I would have done a few things differently, myself. I would never have married my first wife, for one thing. That's a biggie, and one with a lot more serious consequences than a mere spat over a distortion mechanism. For me, at least, and also for a few others who might rightfully feel they fell into the collateral damage category.
I'm not going to try to coax you two into something hokey like a group hug, thinking it will cure all ills. What you two decide is up to you. I, like some others apparently, find it difficult to read enough conflict into those two letters to justify the burden you carry in the here and now. That's not criticism either; just an observation. I'm sure anyone who looked in on my first marriage would find it difficult to understand the slow building of momentum that led to the inevitable crash at the end. Sometimes these things grow by imperceptible degrees and those on the outside can't quite grasp the depth of feeling of those directly involved.
In another twenty or thirty years we'll dredge up these words and see how we feel about them...
Grey
john curl said:
Following B&K microphone has 50pF capsule capacitance
MICROPHONE SYSTEM FOR EXTREMELY
LOW SOUND LEVELS*
by
Erling Frederiksen
ABSTRACT
This article shows how the thermal noise of microphone cartridges, caused by Brownian
movements of the diaphragm, can be minimized, and how low inherent noise levels of
preamplifiers are obtainable by optimization and the use of modern components.
In an experimental system, third octave and A-weighted noise levels have been reduced by 16 dB
relative to conventional systems. This analysis has resulted in the development of a new low
noise Condenser Microphone Type 4179 and a matching low noise Preamplifier Type 2660
Do you know Erling? I do, and I own one of the mike capsules that he designed that has high capacitance. I got the capsule 40 years ago, and made my own electronics around it. It measures pretty good, on axis. Where do you think the fundamental resonance is located? Even though it is an omni mike, what is the OFF-AXIS response?
I have worked with almost every mike type over the decades. B&K 1/2" mikes were first introduced by George Quellet of Stellavox, Suisse; the Grateful Dead Wall of sound, Mark Levinson, Crystal Clear Recordings, and many others. Of course, some prefer the characteristics of Sennheiser, AKG, Neuman, and Shoeps. Specific performers often have a favorite mike with characteristics that match their voice.
I have worked with almost every mike type over the decades. B&K 1/2" mikes were first introduced by George Quellet of Stellavox, Suisse; the Grateful Dead Wall of sound, Mark Levinson, Crystal Clear Recordings, and many others. Of course, some prefer the characteristics of Sennheiser, AKG, Neuman, and Shoeps. Specific performers often have a favorite mike with characteristics that match their voice.
john curl said:
That's interesting the article and mike are only 20 years old. B&K makes instruments with 200V excitation. Their recording spin off (DPA) is more recent.
scott wurcer said:
🙄
Vacuous and infantile accusations against the hearing abilities of others are a natural consequence of having run out of half-baked arguments to support such an untenable and unsubstantiated position.
Nobody uses a 1'' mike for recording, UNLESS it is for extra low noise. I met Erling in 1974 when we discussed modifying the 1/2'' mikes that we were purchasing for lower noise. He was first to warn me about delta C / C distortion. Have you checked that out yet?
On my part, I lowered the noise floor on the standard mike by about 10dB and I have the measurements made by B&K to prove it. Of course, all 1/2'' mikes were made after the fact, to my modifications. (we had to pay for the mods, anyway)
In checking, I have a older 1" mike with perhaps 60pf of capacitance from B&K, well known to, if not designed by Erling himself.
On my part, I lowered the noise floor on the standard mike by about 10dB and I have the measurements made by B&K to prove it. Of course, all 1/2'' mikes were made after the fact, to my modifications. (we had to pay for the mods, anyway)
In checking, I have a older 1" mike with perhaps 60pf of capacitance from B&K, well known to, if not designed by Erling himself.
Hello
J' apporte ma pierre à l' édifice
or
I bring my stone to the building. ( I don't know the real translation )
I've simulated a complementary differiental use by Graham Maynard and Destroyer X ( and surely designed by Dr Self ) 😎
To respect the usage, I put the schematic, the spectral and time graph too.
On the simulation, they're harmonics around 1,9 kHz and 3,9 kHz. They're wrong ( S*** HAPPENS ).
Distortion calculated are :
H3 : 0,4 %
H5 : 0,3 %
H7 : 0,2 %
H9 : 0,063 %
D ~ 0,963 %
Input voltage is 0,1V / 1kHz.
I can do other measurement with other value if needed.
For the simulation, I use Isis v7.2 SP6 and its own model. I can provide all files.
Regards,
Max
J' apporte ma pierre à l' édifice
or
I bring my stone to the building. ( I don't know the real translation )
I've simulated a complementary differiental use by Graham Maynard and Destroyer X ( and surely designed by Dr Self ) 😎
To respect the usage, I put the schematic, the spectral and time graph too.
On the simulation, they're harmonics around 1,9 kHz and 3,9 kHz. They're wrong ( S*** HAPPENS ).
Distortion calculated are :
H3 : 0,4 %
H5 : 0,3 %
H7 : 0,2 %
H9 : 0,063 %
D ~ 0,963 %
Input voltage is 0,1V / 1kHz.
I can do other measurement with other value if needed.
For the simulation, I use Isis v7.2 SP6 and its own model. I can provide all files.
Regards,
Max
Attachments
)
john curl said:
John, you have heard of Georg Neumann? I don't think he would like what you're saying about his U-47. Didn't he also design the best record cutting lathes in the world? And yes I do know how capacitive transducers work.
Let's drop this and get back to circuits. I posted that capacitive feedback circuit because it's a complete paradigm shift from resistors. You can make a low gain feedback circuit without the noise of the gain resistors. That mike preamp works (I actually built it). Conceivably you could use the 270pF cartridge termination as the input and 27pF as the feedback and make a 20dB head amp with ONLY the input noise of your FET. I want to bring one to the burning amp festival.
Again, Neumann makes good commercial fidelity mikes. I used the KM-84, years ago. Built electronics around the Neumann capsules, but among the commercial mikes, the U67 is very good, the U87 is OK. They are indeed 1" mikes, and they are fairly quiet as a consequence.
Let's look at their frequency response: U87 "In cardioid the response is held within 2dB from 200Hz to 14 kHz, above which it falls very steeply. At 50Hz, however, quite a noticeable bass loss of 5 dB is apparent. The frequency response curve remains almost identical up to 60 degrees off axis, but at 90 degrees falls very sharply above 10 kHz, but has a 4.5 dB resonant peak at 9 kHz. ..." Angus McKenzie 'Comparison Studio Microphones' 'Studio Sound' pp. 643-647.
Let's look at their frequency response: U87 "In cardioid the response is held within 2dB from 200Hz to 14 kHz, above which it falls very steeply. At 50Hz, however, quite a noticeable bass loss of 5 dB is apparent. The frequency response curve remains almost identical up to 60 degrees off axis, but at 90 degrees falls very sharply above 10 kHz, but has a 4.5 dB resonant peak at 9 kHz. ..." Angus McKenzie 'Comparison Studio Microphones' 'Studio Sound' pp. 643-647.
By the way, Scott, where did you find that 5G resistor? Do you know why the resistor is 5G or more?
PMA, the 1/4" B&K is one of the best mikes to measure tweeters, BUT it is VERY noisy, so is not used normally in recording.
john curl said:
The U 47 is well-known for its clear sound, with a distinct emphasis in its upper-midrange frequency response. It has been used in countless famous recordings. The Beatles' producer Sir George Martin used the U 47 extensively in the group's recordings and claimed it was his favorite microphone.
Yes John, I also understand the noise issues of capacitive transducers. DigiKey stocks the Ohmite ones, real 5G, checked it on my Keithley 610C. I have also tried "leakage" biasing with some smoke detector FET's I had in my junk box, got >25G equivalent, but I'm not sure people are ready for that. Though a little 'birdy' sent me a schematic that shows the commecial guys are already doing this.
Now, do you know who got them to use 5G resistors, 35 years ago? PS The highest that I can find is 2.38 x 10 (11th) at the moment. I would be afraid to touch it, as it would probably drop dramatically in value. It has been in my possession since 1973. Haven't found a use for it, yet.
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