R/E/P Community
R/E/P => Klaus Heyne's Mic Lab => Topic started by: brightmillion on November 13, 2013, 06:10:25 AM
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Hi everyone,
My first post here, been lurking at all the posts in this forum, but since I don't know much about vintage mics, i don't have a lot to add.. but thank you all for the great info, i have learned a lot!! I am on the hunt for my first of the "big five" and thought I'd pick your brains.
I am looking at an M49 and am going to have it checked out in person by someone to verify, but I though I'd post a few pics to see if there is anything that stands out to you experts about this mic. Seller says it is all original including capsule and tube,so hopefully it is :) For all I know, those could be radioshack parts in there or macaroni noodles.. so thats why I'm asking those who know!
I assume, Klaus, you are far too busy to do a buyer inspection service, but can anyone recommend a tech to have this looked at? I have read here that James Gangwer is recommended for this type of thing?
(thanks in advance for any input!)
here we go::
(http://s22.postimg.org/50sncapvl/M49front.jpg)
(http://s17.postimg.org/qm47if0jj/M49back.jpg)
(http://s22.postimg.org/w05oyxr41/M49capsule.jpg)
(http://s15.postimg.org/kk1kv9r7f/M49inside1.jpg)
(http://s18.postimg.org/z06dm27rd/M49inside2.jpg)
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These are the only photos I have received so far, I don't have the mic in my hands...I have been communicating with seller (in the same town as me) but by email. I will ask for more close up photos, including the serial number plate.
On a quick look does it seem even worth checking in to? I really don't know the inside of a M49 at all and I don't want to waste anyone's time on this forum.
thank you
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I'll help you out, especially because you posted before my lengthy response. The exact information on the i.d. plate (exact microphone type and serial number, as printed on the plate) are very important here.
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I apologize if I have offended or seem just trying to make financial gain. I am more than willing to pay to have this mic authenticated and assume that I need to pay for this service. - (I did say this in my original post) - I am not just trying to get free info and run - I have actually sent you an email last week from your website inquiring about your services and asking if you are able to offer this service for hire. I assumed from what else I have read in this forum, you are far too busy to offer this sort of inspection service and I may not hear back, and I very much understand that.
My intention from the get go was to have this mic sent to a pro mic tech to have checked out- because, yes, I am new to vintage mics, I have no idea about these mics- but I do understand what knowledge is worth. I am assuming the cost of authentication to be part of the price paid for vintage equipment. I understand that the knowledge of a handful of people are literally what keeps vintage mics in existence and I very much respect that. I am willing to pay every penny of what a mic and a tech is worth, i'm not just trying to get a bargain or use the info I get on this forum as a way to negotiate with a seller. I literally do not know who to turn to as a newbie.
I just thought I'd post some pics here in case anyone was interested in taking a look. I do have a genuine interest in vintage mics and have read almost every post on this forum to try and learn. I am not a tech, nor will I any time soon feel comfortable to open up my own mics, I have just started my journey in vintage gear (I've been saving up for over 2 years to buy my first vintage mic) but I have a genuine respect for vintage gear, recording, and music in general. I am new here, and I may have misunderstood the protocol for posting/asking questions, and if I have overstepped my welcome asking for too much as a newbie, I understand. It was not my intention to illicit free professional advise that I should otherwise pay for, so I am sorry if it came off that way.
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OK, thank you, I will get that exact info and report back.
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The microphone pictured appears to be a genuine Neumann M49c of relative late production. I can not spot any modification, non-original parts, signs of soldering or other service activity. The one possible exception may be the capsule. It looks somewhat too pristine to be 40+ years old, but it does look to be a real Neumann K49.
As to the question raised by Klaus, I do wonder whether maintaining various specialty forums is not in itself a form of marketing, driven by an intent for eventual commercial gain. Anyone marketing themselves to be an expert authority should expect to be consulted for expert advise, opinion and recommendation...
In the interest of full disclosure, I am currently still the Technical Director at Neumann|USA and Sennheiser Electronic Corp. with the intent to retire by the end of this year after over 50 years in the business (plus another 8 years before that of involvement as a hobby).
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Soapfoot and Uwe,
Thanks for your stimulating thoughts which I will respond to after work, tonight.
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I am not an expert, more like a vintage mic student, but 2 things are obvious. One, the mic was made between 1963 - 1974 because Neumann changed the red pilot light on the front of the M49 to a Neumann badge around 1962 and this mic has the badge so it must be 1962 or later (and it's the "c" version introduced around 1963). Neumann discontinued the M49 in 1974, so it can't be later than that. Secondly, the original K49 capsule has obviously been replaced by a new, but apparently genuine, Neumann K49 capsule. The correct AC-701k tube also seems to be present but I can't tell you if it's original or a replacement (not that it matters as all AC-701 tubes are new old stock as that tube was discontinued decades ago). Beyond that, I don't know enough to tell you what has been replaced and what is original.
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thanks for the input guys. I have received more photos and you guys called it, serial plate says M49c.
(http://s2.postimg.org/5acx7kuhl/photo_1.jpg)
(http://s22.postimg.org/bsn0tbldt/photo_3.jpg)
(http://s2.postimg.org/yfk9opz6h/photo_2.jpg)
(http://s23.postimg.org/nutw3ttsr/photo_4.jpg)
(http://s24.postimg.org/6dr5urn8l/photo_5.jpg)
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The reason why I was curious about the i.d. plate early on:
yours did not come with this mic originally (as far as I know, there is no M49 serial number that high*) plus, its rivet was hammered in unprofessionally deep into the bottom bell, and is not period-correct; plus, during the period the "c" model was made, the metal surface sheen was different-different grain from the media blast, so was the basket weave pattern and surface sheen.
Your i.d. plate is one of those late-design spare plates that were embossed with different stenciling than was originally used during production runs, and in your case under circumstances I cannot guess.
Also, housing parts, circular board and inner suspension were not properly attached- all of which indicates to me an after-the-fact job commissioned or done by a previous owner: an M49c amp mounted in an older M49 housing/head basket (see also the bright red sealing lacquer dots on the frame screws), then provided with new serial number way ahead of sequence.
Capsule looks curious: it indicates a 2013 production, but as recently as last month, Neumann K47/49 capsules I received, fresh from stock, were all still made in 2012. There is also that unusual letter "E" on the side….? Only a physical inspection could reveal whether this is an authentic Neumann K49 or a reskinned one, done in 2013 by a third-party provider.
* Someone once requested dating history of a similarly high M49c serial number in the archive section of the Neumann Pinboard, and Martin Schneider responded that there are no records, because the number was beyond production numbers for the model.
I will respond to the larger issue of free help I brought up later.
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From everything I see in the pictures provided, and my experiencethroughout several decades of my affiliation with Neumann, I am sorry, Klaus, but i am unable to agree with your comments about the type label design ('i.d. plate'), the way it is riveted, the stenciling, the housing parts, the circuit board, the suspension or the head basket. As mentioned in my earlier post, the capsule looks too pristine to be around 40 years old. But that too is OK, as it appears to be an original Neumann K49 capsule. If it required replacement before offering this specimen of a microphone for sale, it can only reflect very highly on the seller's integrity.
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Hello Uwe,
I respect and have always appreciated your expertise as Sennheiser's U.S. - technical director, and your long history in the company, which gives you a unique and valuable historic perspective. Needless to say also, that my electronic knowledge of electronics is minute, compare to yours. But I may have expertise in a slightly different field than yours: I may have seen, authenticated, and restored a few more vintage Neumanns than you have, and I may have developed an eye for even some of the smaller incongruities one encounters when looking at a mic as a whole, which simply comes from doing this a lot. And when you do one thing a lot, you normally get better at it.
But, rather than arguing impressions, let's investigate the main point of contention (and the one that would affect the price of this mic the most): The probability that this M49 was delivered ex factory with that specific (high) serial number, and originally as an M49c. Please check with Neumann's historic delivery date list in Berlin (I am sure you have instant access), and report back what they say about this mic.
By the way, I am not claiming that the amp shown is not a genuine M49 'c' amp (all components on the printed circuit board and the lay-out are that of a genuine M49c), but the whole thing looks oddly re-assembled to me, as in: put together after the fact. The production records should support either your or my claim. I am eager to find out
Thanks,
KH
P.S.: If this is K49 is indeed from 2013 Neumann production, I am sure the seller still has Neumann's sales receipt and warranty documentation, which should ease the buyer's mind instantly. I would be suspicious, on the other hand, if that was not provided, and would then recommend a closer inspection of the capsule.
P.P.S. (addressed to the thread starter): Regardless of my gripe, you will end up with a free, expert authentication including major discovery work. Not bad?
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I appreciate all the info everyone.
Klaus, I am grateful for the free expert advice, thank you, and again, do not feel it is my "right" to get it for free just because this forum exists. I am more than willing to pay for this sort of service. Based on the small details that Klaus has detected, it remains the fact that there is some knowledge that can only be attained by constant effort and years of experience. And of course is valuable information, since after all, I am asking the question because the mic costs money. These seem to be details that even the best intentioned mic tech will less hands on experience might look at the schematics, verify that it is indeed correctly an M49c and send it on its way as "original". Which is what the seller is claiming that it was recently looked at by a known tech, and they verified that it was all original. Of course, just hearsay from my point of view since I don't have documents to prove this. But, still shows the incredible resource that folks who know this stuff are, especially Klaus.
I realize I am the one benefitting from this post directly and am grateful. I hope also, that the information gleaned will be a resource to teach others the finer points of being a mic detective.. that its not just about schematics, but also the small details of workmanship inconsistencies to reveal possibly post-factory work, rather than just the correct components being present. I'm sure if I compared photos of this mic and another M49c I would probably just assume it looks right on, given my no experience. But I have already learned to question all the details more closely.
To get off topic of this specific mic and back to the "bigger issue" of free advice.. I will talk a bit about my situation to see if you all have recommendations for me to proceed, which hopefully will shed light on a different perspective to this issue, opposed to most folks here who are already knowledgable of these mics and maybe already have one, two or a locker full of them. I understand the feeling of being used when the person asking is someone like me, who knows nothing and has nothing to add to this forum's worth. and seems to just be jumping in quick to get free advice and then disappear.
please excuse my rambling..
I am a young guy who has played music all my life and assisted in various studios with the "Big Five" and have experience first hand of the magic that they bring to recordings when compared to newer off the shelf mics. I don't currently own any vintage mics, and I am always disappointed with my own recordings missing this unexplainable "mojo" and have been saving for a long time to start a mic collection of my own. To use for myself, in my studio, and also just for the sake of I think its cool to have and preserve these pieces of history that many young people in our industry don't seem to care about. (laptop and USB mic, time to make a record right?) When I hear great classic recordings it just gets me, its the reason I make music in the first place like (probably) everyone else here. The first time I heard in person a vintage drum kit in a nice room recorded by a single C12 overhead through the neve console and I was hooked. how could one mic capture the magic of music so great..
ok, end of my backstory ramble (I guess as a newbie here I am trying to justify my place that I really am not just trying to get in the mic buying/selling gain to make a buck, that I really am passionate about mics, even though I know nothing about their insides.)
So, that all being said, I am on the market for a vintage mic, namely a M49. From all I have read around here, it is VERY possible that most mics being sold on the used market are not original either knowingly or not by the seller. So, I am very wary of what to purchase and my goal is to get the most original mic I can. not just to get a deal/ have bargaining power on a sorta original mic, but find a great one to be proud of.
I have always planned to have any mic I was going to buy inspected by a tech to authenticate, but, with the wide variety of mic specimens out there it seems I could literally keep buying mics, having them checkout out only to find none of them are even close.. since for someone of my (lack of) knowledge, I'm only going on the sellers word.
A service such as what you all are giving me for free here seems to be a possible service that is needed for people like me - and I mean PAID service. sort of a "pre-inspection" service. Where the buyer (me) would send as many photos and info as possible to the tech, and for a fee they can at least spot/recommend whether its even a tree worth barking up. I know a personal inspection is needed still in the end, but it seems Klaus, you can spot most things even in photos. To tell someone like me, who says, I want an all original M49, "yes" or "no" not worth even going through the buying/inspection process.
in my hunt for a great mic, I'd gladly pay for this service. even if i had to pay the fee a number of times each time I found new mic before I even moved forward on getting one inspected in person.
What is a guy in my position to do? And I'm not saying that in a pity kind of way, I mean, literally what do you all recommend for someone with little knowledge to go about purchasing a mic? Do you guys know reputable and knowledgable mic brokers that would really know what they are selling that would warrant the premium in price.. there seems to be a much greater availability of mics through the general used market.
ok, sorry for the long winded post, I'm just excited about getting a mic and really don't know where to turn for this sort of guidance.
Klaus, would you consider offering such an email photo inspection service? It obviously takes your time to look at this post and respond, and I'm willing to pay for that knowledge, I just don't know how to go about doing it.
but, I'm sure you can think of a million reasons not to get into such a game..!
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I do not want to continue to dominate this discussion as I have so far. But you are in parts of your post addressing me directly.
1. I have for many years offered pre-inspection services- in person or remotely. Please contact me privately, if interested. Though I am booked for any months in advance, I maybe able to help you over the phone with some tips. Unfortunately, I am not aware of anyone else doing this in the U.S., but hope that readers here can point out trustworthy alternatives.
2. I may disagree with you a bit on the absolute necessity to only buy 100% stock-original vintage mics.
As you so eloquently explained, you work in a professional studio environment, and can detect with confidence when a mic's sound hits your soul. For all you know, the M49 offered to you, and which you pictured in this thread, may be such a mic- even if some items may not be 100% period-correct. If you are willing to go strictly by sound, and don't mind deviating from perfect appearance and adherence to originality, by all means, go for it! After all, no one will ever see the mic which you made beautiful music with.
What I would try to avoid though, is to pay a financial premium for any mic that may not deserve it, because the next, better-educated buyer after you will likely not pay it, leaving you with a financial loss in a market that usually does not incur losses. That's where a pre-purchase check-out would come in handy.
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Thank again Klaus, I appreciate the insight on choosing a mic, and that sound and feel is what to go on first and then base price on "market value"
I am thinking that this mic will be a good piece for capturing great sounds at the "right price". I appreciate everyone's helps with identifying that at least whats inside the mic on first look appears to be what "should" be in an M49c, even if the mic wasn't originally off the factory line as a "c" (or at least that's how I understood everyone's speculation)
As far as the details of this mic go- I have asked the seller about the capsule, since there was some speculation about it, here's what I found out: the capsule is not the original and has indeed been replaced only 3 months ago with a genuine Neumann K49 capsule. Seller has receipt to verify. THe original was toast and they opted for a new one as opposed to a reskinning job. So,it seems it could be a 2013 capsule in there..
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If the recent K870/K67 capsule I installed in one of our three U67s is any indication, then the 2013 capsule could be very good indeed. I bet Klaus will have the first-hand experience to know for sure.
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Neumann does maintain an interesting forum specific to their products, and with many interesting threads regarding vintage Neumann products. On their forum home page is an interesting link for inquiries about manufacturing dates for microphones produced before 1990. Through that contact you could find out that this specimen was one of the last five M49c produced in Berlin and delivered to Japan in March of 1974. I also got confirmation that the capsule has been replaced with an original Neumann K49 of very recent (2013) production, and with the standard protective top bumper removed in the interest of authenticity. (It is not required under the large head basket of the M49.) The wire from the capsule's center electrode should be rerouted, as it is currently touching the the rubber stand-off, possibly leading to handling noises. The pictures further suggest the plastic base of the head assembly should be more clear and transparent and might benefit from careful cleaning. According to the factory experts, all other parts, including the housing, basket, type label and their assembly look completely original for the confirmed 1974 pedigree.
Congratulations on this exceptional find, and many good recordings!
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Thanks, Uwe. Nice bookend, to the thread, and to the M49 model, too!
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Thanks Uwe, for the detailed history of my mic! I really appreciate your research and knowing the details from the factory made me a confident buyer. The mic is now in my happy hands and I am excited to get recording! Having a history of this particular mic makes it that much more fun to own and a great story for studio comers, whether they want to hear it or not..!
I am going to burn in the tube for 48 hrs to see if there are any strange happenins with the tube and then check out the power supply to see if I should get it adjusted. I'll upload some pics of the power supply (i think its original). I'll post back with my findings and first recording impressions!
I'm going to then look into the "cardioid only" mode per Klaus' recommendation since I doubt I'll use it for anything but cardioid.
Thanks again for everyone's input and help :)
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Intersting. So, by in 1974 they had stopped using the Bosch output cap in C5, and started using what looks like a wet tantalum cap, with a .69µF value?
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Say what? 0.69 mfd? Where do you see that?
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First page, picture below the one showing the type label... But not to worry, it is indeed an original aluminum electrolytic (not tantalum, as they were not be available for the necessary voltage rating).
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The "10.69" below the "1µF" is the manufacturing date of the cap: October 1969.
Besides, there is no standard cap available that as a .69mfd value.
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Oh. Duh. That makes much more sense. Something tells me that cap doesn't sound so good!
On that note, are the output caps in U67s electrolytic or tantalum?
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They are polarized electrolytics- Siemens mostly.
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Oh. Duh. That makes much more sense. Something tells me that cap doesn't sound so good!
On that note, are the output caps in U67s electrolytic or tantalum?
J.J. - what do you mean by "Something tells me that cap doesn't sound so good!" ?
because of the date or type?
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I have never heard an electrolytic cap that has sounded close to as good as either a paper and tar Siemens cap or a film cap, when in the transformer coupling position. And yeah, you could guess that a 44 year old electrolytic cap probably isn't in the best shape, either!
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J.J. can you provide a technically correct and logical explanation why one type of capacitor in an audio circuit should sound different (inferior) to another? Can you supply credible proofs (data, measurements, graphs) to support such emotional opinions?
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I'll pipe in.
Cyril Bateman's excellent (though a few decades old) tests and measurements (complete with a thorough methodology that you can replicate yourself) expound on the subject at length.
http://www.scribd.com/doc/2610442/capacitor-sound
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Uwe has asked one of the Eternal Questions...
I'm also interested in the "sonic" differences between capacitors.
"Capacitors have unwanted inductance, resistance, and dielectric absorption. Different materials and manufacturing techniques produce varying amounts of these unwanted parasitics that affect a component's performance."
One parameter that may relate to sonic differences is dielectric absorbtion:
"Briefly, dielectric absorption has been revealed as a major source of distortion in audio circuits. Film dielectric type capacitors, particularly polystyrene, have very low dielectric absorption and for this reason are preferred in audio circuits."
Another effect that I think may affect sonic performance is the amount of "smearing" between voltage and current caused by the dielectric phase angle:
"When a capacitor is used as a series element in a signal path, its forward transfer coefficient is measured as a function of the dielectric phase angle, (theta). This angle is the difference in phase between the applied sinusoidal voltage and its current component."
http://www.reliablecapacitors.com/consider.htm
The link above also tries to explain the theory behind the use of "bypass" caps.
Of course, the best test is listening...
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... I was hoping to look beyond the marketing hype for multicap components ...
Considering the signal and power levels encountered in most condenser microphones I still question applicability of the cited effects. I yet have to find mainstream manufacturers' coupling or bypass capacitors with measurable (or truly audible) influence on low level audio signals. Aware of opening a likely Pandora's Box, I propose that any such influence is more probably due to questionable component values rather than improper specific types in the first place. Conceding possible affects on reliability, stability and longevity, this may be a justification for custom modifications and 'improvements' on the original circuits. Otherwise allow me to file this topic along the the audibility of certain interconnect cable materials, connectors and mains cables in audio systems...
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Uwe, the only thing I am qualified to give in this discussion is my ears. In trying many transformer coupling caps in mics, I have never heard an electrolytic that I thought sounded as good as a quality film cap, or even a good PIO. They feel harsh to me, and lack the type of harmonic character I find pleasing. I am trying to avoid using the type of esoteric terms such as "warm" or what not.
As usually happens, I talk to technically qualified folks about my observations, and they explain to me why I am hearing a difference.
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Discussing subjective impressions of sound can quickly lead to trench warfare and loss of respect for differing positions (my experience).
Let's not do that here, but let's assume that positions we disagree with were honestly, thoroughly, and intelligently formed. The scientific process demands nothing less.
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Mr. Sattler--
Did you read Cyril Bateman's complete paper and experiments, linked above?
If so, I'd love to hear about any flaws you perceive with the methodology.
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Doug Self and Richard Marsh have done a bit of research into the audible effects of different capacitor formulations, there are AES articles about it as well.
Where measurble differences show up they are far beyond the 20 hz~20k hz audio bandwidth. In the audio band, even the best test gear (Audio Precision) will not show measurable differences, you will need a network analyzer for that.
However, most do and will hear differences between mylar and polyprop/polystyrene film caps. I found it best to compare them in a circuit that will allow direct coupling, no caps. Then you can listen for cap differences and the losses against no capacitor. Most find the no cap option to offer the best fidelity.
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Jim,
have you been unable to measure harmonic distortion in the audio band in coupling applications? Or are you talking more about "frequency response" as opposed to distortion products?
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I can measure THD and IMD several ways, but none show the effects of a passive capacitor unless it has a filtration effect in the audio band. The active component errors (transistors, opamps, valves) all wash out any passive component measurements.
That's not to say you won't hear differences, most do. That just tells you the human ear is capable of detecting some small differences the best audio test rigs cannot.
This is why test gear is best for finding errors, not for telling you when it sounds best.
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The human ear is capable of detecting some small differences the best audio test rigs cannot.
This is why test gear is best for finding errors, not for telling you when it sounds best.
AMEN!
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I think that way about measurements in audio in general. They help us understand and explain that which we perceive, and we're best off when we do not rely on them to tell us what we are and aren't allowed to perceive.
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For instance, metal film resistors measure better than carbon. However, even as bad as carbon comp resistors measure in terms of noise and distortion, I find they are such an essential part of the sound of some circuits, which just don't sound as nice with metal film. Moog synths are a huge example of this.
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For instance, metal film resistors measure better than carbon. However, even as bad as carbon comp resistors measure in terms of noise and distortion, I find they are such an essential part of the sound of some circuits, which just don't sound as nice with metal film. Moog synths are a huge example of this.
Fender guitar amps are another.
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That's one reason old moog stuff drifts so much. The carbon composition resistor values change with heat. Same in Fender amps where the heat is more extreme.
Also consider when 1960's guitar amps were built, carbon composition resistors were the norm as metal film resistors were very expensive back then. Now only a couple of companies still make the carbons, Allen Bradley stopped some years ago and they made the best.
It also comes down to personal choice: I have replaced all my resistors in my 1960's era Fender amps with Dale CMF metal film resistors. I get a smoother overdrive and clearer tops. Carbon composition resistors have a built in "aural exciter" function, they spit in the top end. I found that to sound harsh in recording gear.
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You final point also brings up another philosophical issue: Are different tonalities of differing component materials closer to, or further away from, audio fidelity, and does that matter?
I believe only fools will "upgrade" musical instrument components in the belief that more of the essence of the instrument will come out- say, put a film & foil tone cap in a '59 Les Paul- But we all know (do we?) that the essence of any musical instrument is the totality of its contributing sound-shaping components. And that essence is inviolate and 100% subjective- anyone can do what their acoustic taste buds dictate, and with impunity.
But... microphones? Isn't there a widely-held belief that a microphone's function shall be to stay "neutral" so that what it picks up and transmits stays intact?
Which brings me to my oft-repeated position on this: a microphone is a terribly primitive approximation to our hearing. It lacks many of the complex, interactive parameters that contribute to our oral impression of the world. Therefore, a microphone at its best creates the (artificial) approximation to human hearing with features an electrical engineer might find appalling: highly non-liner frequency response, attraction to certain kinds of compression and harmonic distortion, while being repulsed by other kinds…
In the end, the best microphone (me thinks) is the one that best retains the connection to the musical event or emotional attraction to the voice. This can be, and often is, a microphone with inferior measurements (U47, ELA M251…) and, to the contrary, it rarely is a microphone with superior measurements (B&K, some Neumann TLM and Digital models).
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Audio is objective, psycho-acoustics are subjective. Measurements can certainly verify how well any given piece of equipment will perform. However, it can not predict whether you will like it or not. Individual preferences and dislikes can not be quantified and manipulated in some mathematical equations. For listening tests alone, don't underestimate the power of suggestion and wishful thinking (auto-suggestion).
With the capabilities of contemporary test equipment, I'll go as far as turning around the prevailing opinion, and postulate that we can measure and quantify everything we hear, but we can not hear everything we are able to measure...
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Count me in as one of the fools that has redone the electronics of his Les Paul to hear more of the essence of the instrument. It has a custom preamp/buffer and a switch to cut out the tone circuits entirely. The tops are more open and clear with the cabling and it's passive low pass filter effect running 20 feet to an amplifier.
I don't use Bumble Bee wax impregnated tone caps, a pure waste of money, any WIMA polyprop will do just fine for a treble cut.
I spent several years testing everything I could with the Audio Precision rig I have. I found out quickly that stuff we hear is not measured. I also found out some stuff we hear is measured. Then you find out stuff you don't hear is measured.
Dirty Harry said it best: "you got to know your limitations". Ears and test gear both have limitations, I found using both to work through stuff is the best overall solution to audio niceness.
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one of my favorite quotes from the venerable H.H. Scott:
"If it sounds good and measures bad, it's good. If it sounds bad and measures good, you've measured the wrong thing."
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... if you can not measure it, you may have to use a different instrument or test procedure ...
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... if you can not measure it, you may have to use a different instrument or test procedure ...
What is going to work better than an Audio Precison test rig? I have that and it will not measure small audible differences in many cases. A perfect example is cables. Many hear differences with those but the AP will not detect their differences. Use an Agilent or HP network anayzer and you will start to see those differences at a much higher than an audio bandwidth. Ray Kimber has that $50,000 piece in his lab used to design his spectacular cables.
If there were tests or proceedures (a collection of tests with pre-programmed perameters) that would measure every sonic difference heard by the end user, I would already own it. Part of the problem is that the test stimulus used by audio analyzers are fixed waveforms, sine or square. Music is full of violent, radical waveforms not at all like the oscillator outputs of the best analyzers.
Until actual music waveforms can be used as the test stimulus, we will only find the best way to measure simple waveforms, not musical waveforms. There is going to be some stuff missed.
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Until actual music waveforms can be used as the test stimulus, we will only find the best way to measure simple waveforms, not musical waveforms. There is going to be some stuff missed.
AMEN. (Starting to feel like the Church of Klaus here…)
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AMEN. (Starting to feel like the Church of Klaus here…)
Klaustianity?
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klausology ;D
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so do the electrolytic caps (such as the one {output cap in C5??} in question in the photo that started this "cap sound difference" debate) wear out over time? sorry if this is a dumb question.. I know replacing the caps in my fender amps really get things sounding good again, but I'm sure thats a completely different reasoning compared to mics.
Maybe this question belongs in the other recent thread about what makes an "all original" mic,, but, can you guys clarify for me if there are components in vintage mics that are "regular maintenance" type parts, like the car example of changing spark plugs.? Are there components that over time do lose sound quality and should (must) be replaced, or is it always a matter of when things start to sound off then something has failed, but otherwise don't touch anything until it's broke?
for example if someone found a brand new, never used old stock u47 in a closet, would it sound as good today as it did when it was manufactured? or would even an unused specimen benefit from some new (but authentic/correct) parts replaced?
I realize there is plenty of debate about changing things and if it helps or hurt tone compared to the original design, but i'm speaking in purely making a vintage mic sound the same as it did when manufactured (whether that is the best or not opinion wise) - and i guess i'm asking as a newbie to having a couple vintage mics, what should I expect for maintenance with my new friends (mics)? - do they need regular tune ups?
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Wet electrolytic caps do dry out over time, they loose mfd's as a result. Usually you detect a high pass function when they dry out.
As far as audio quality is concerned, el caps are probably the worst passive component you can shove quality audio through. They absorb and filter electrons, the source of sound.
This is why many use a quality film cap alone or as a bypass to allow those electrons to pass through that would be absorbed by the electrolytic cap.
An audio system without the use of blocking caps sets the bar much higher, you can get spoiled by that sound. Still, some don't like that, "too much music". Many are conditioned to "recorded sound" and want their work to sound similar. No problem, most commercial gear will get you that sound. The open sonic effects of a direct coupled audio path are much harder to find.
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When bypassing an electrolytic with a film cap of a smaller value, isn't it true that the (typically) higher ESR of the electrolytic will let higher frequencies (cutoff determined by film cap's value) take the "path of least resistance" around the (presumably) lower-ESR film cap?
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If that theory of electrons taking the "path of least resistance" in a dual-cap paralleled arrangement can ever be proven to be true, it then would need to be examined how perfect the electrons' behavior is. For example, if some electrons at a certain frequency cross over get confused which path to take, what happens?
From my personal experience, I have reversed my opinion stemming from my original impression that bypassing coupling caps in microphones does any good (for a decade I religiously bypassed my f+f caps with styrenes of 10000pf or less, depending on circuit), and now believe that it does more harm than good: It smears the midrange (always more important to our ears than any high end benefits). Instead, I selected even better and more expensive f+f caps than were available 20 years ago.
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Ask any RF or power supply designer about bypass caps, they will explain it better than I. There is a reason all your audio gear uses a larger el cap combined with a small cap as a bypass in it's power supply, there are limits to what an electrolytic cap can pass or filter, they have internal resistance (ESR) that rises with increasing frequency, an effect the better film caps avoid. Their dialectric absorbtion rates are also very high compared to film caps.
Switch mode power supplies must use small caps to aborb and filter switching transients and artifacts. Bob Dobkin, head of Linear Technology has done papers on this subject. They specify certain types and even brands of film capacitors to assure their switching mode power supply chips perform up to spec.
As I mentioned before, these audio types of 'tests' and evaluations must be done using an el cap, a film cap and then no cap in a circuit to fully understand the sonic effects of capacitors on your audio. Most have never done those three comparisons so they may not have the background to make any assertions one way or another.
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Jim,
Your examples of using bypass caps are from different applications than small signal, close to zero current, coupling caps in condenser mics. I am not questioning their use in power supplies, especially with polarized electrolytics.
I agree with you that only comparative tests can decide whether bypass caps in the coupling position of microphones are appropriate or not. I found their sonic contribution to be negative when combined with very good film and foil caps. So I now remove the bypass caps from mics previously modified by me when I did not know any better, and I upgrade the f+f caps while I am at it.
The before-and-after effect is clear to my ears, every time I undertake this change.
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But what about in signal applications where the use of an electrolytic is unavoidable (or all-but-unavoidable?)
I'm putting together some EMI/REDD 47 preamps right now that specify a 100µF cap for cathode bypass of both tubes. Since 100µF film/foil caps are scarcely available (if at all), I chose to increase the values to 220µF and 470µF with a nice Nichicon KZ cap, bypassed with 2.2µF and 4.7µF polyprop film/foil, respectively. I have high hopes that this will perform better than the stock 100µF electrolytic alone, but experimental listening will tell the tale, when I get that far (a few weeks away perhaps).
This is sort of drifting off-topic now, so my apologies... but in the general context it is relevant.
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I now remove the bypass caps from mics previously modified by me when I did not know any better, and I upgrade the f+f caps while I am at it.
The before-and-after effect is clear to my ears, every time I undertake this change.
A bypass cap cannot improve (bass- and midrange-) distortions caused by a (much bigger) bad electrolytic cap.
These distortions are measurable under certain conditions, not just imagination!
Look here for an overview:
http://www.co-bw.com/Audio_Capacitor_Distrotion_Mechanisms.htm
See here for details:
http://waltjung.org/PDFs/Picking_Capacitors_1.pdf
http://waltjung.org/PDFs/Picking_Capacitors_2.pdf
So going the route of replacing bad caps by better ones sounds 100% senseful to me.
A small bypass cap only improves the HF impedance of a bigger one, that's all.
It doesn't cure any other problems.
E.g. without those (ceramic caps for HF blocking), no modern computer ever since would have worked. But that's in a frequency range of 10 MHz to 4 GHz, far beyond audio.
Ceramics, BTW, have very bad distortion figures, don't use them for audio.
For audio, bypassing even bigger foil caps with smaller ones of the same make, can improve low impedance circuits. JBL demonstrates this for ages with their passive speaker x-overs.
In a tube mic no cap is used in a real low impedace audio configuration, where the situation is most critical. The (usually 0.5 - 2 uF) coupling cap to the output transformer is what comes closest to this.
Here the 12 dB/Okt high pass function in conjunction with the transformer can bring a bad cap into a situation where it causes distortion, although it's DC bias helps a lot.
The standard U47 0.5uF paper-metal foil cap e.g. is not suspicious at all.
But it's big, this size cap does not fit into every kind of mic.
Regards
Kai
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All I can tell you is that my story is not about bypassing bad caps, but very good caps, and the result, in hindsight of a decade or more, was a decrease in resolution and an increase in mid range smear. I let other people's talk get in the way of making a decision based on my own experience and what I hear. Removing the bypasses relaxed the sound of virtually every mic that had one installed considerably, without any discernible loss in audio quality.
This may be a different story in "bad cap" situations. However, I cannot foresee a microphone application where I would keep a low quality cap in the circuit in the first place, to mitigate its lossy performance. I would simply replace it with the best quality cap my ears can discern and my pocket book can afford.
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...and that would physically fit, of course!
Thanks, Klaus.
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All I can tell you is that my story is not about bypassing bad caps, but very good caps
It's good you made this clear.
My imagination was you could have left the original cap (in a vintage, historic mic) in place to guarantee reversibility of the mod, and add a bypass.
Seems you not.
Today we have more, better (and sometimes only cheaper) choices then in those days.
So it should be possible to find a single cap that sounds good in a certain application.
Still I find the mentioned articles interesting, specially the part where you can see that higher voltage caps in general (not only electrolytics) perform better.
Regards
Kai
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I would consider any electrolytic cap formulation to be a poor choice for quality audio. None of them can approach the sonics of a quality film cap. A quality film cap cannot approach the sonics of using no cap at all.
Unfortunately, single ended power supply designed audio circuits must use a cap to block DC. If one designs with bipolar power supplies, you can design out those caps. Nearly all tube mic and 48 volt powered mics forbid those choices. You would need to scrap the 48 volt single ended powering designs for a bipolar power design, that would take more then the 3 wires in an XLR cable.
There are plenty of undiscovered audio designs that could be tried out in microphones. Unfortunately, most are content with the current offerings and 2014 marketing forces will not reward such advanced designs. They remain oddities and reside in private collections. Larger manufacturers will not upset their apple carts as most are satisfied with the current state of microphone design, as long as they keep selling.
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Fascinating discussion, thanks guys!
Question:
"You would need to scrap the 48 volt single ended powering designs for a bipolar power design, that would take more then the 3 wires in an XLR cable."
The Neumann KM1xx series uses the 48Vdc to power a 60Vdc bi-polar supply. Would it be possible to run a sub-mini tube with that?
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Not likely with 10 ma of available current and no heater voltage available. That is the reason tube mics have several wires in their cables, high voltage, heaters, ground and differential audio.
A bipolar powered transistor mic would require a + voltage, - voltage, ground and polarization voltages. The advantages are no current limiting, no single ended audio paths and capacitors, higher headroom and lower noise. Remote control of patterns would also be possible.
20 years ago there might have been some excitement and buyers for such designs, but with a busted recording biz there are no takers.
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AT makes a tube mic that can run on 48Vdc at 3mA, the AT3060:
"This is the first tube mic I've encountered that doesn't need a separate power supply — it runs from regular 48V phantom power and draws only 3mA of current. This seems impossible when you consider that conventional tubes require high plate voltages and high heater currents, but the AT3060 uses no conventional tube. It doesn't even use a miniature military-grade Nuvistor tube. Instead it uses a miniature low-current tube developed for use in hearing aids, the aim being to achieve tube warmth at a lower UK price point and without the need for bulky power supplies."
http://www.soundonsound.com/sos/jul03/articles/audiotechnica3060.asp
Heater should be no problem, there are tab-type switching dc-dc chips that can output 6-12 Vdc from 48Vdc.
I've actually seen the tube-type hearing aids, shirt pocket size with an earphone, they ran on 15 Vdc batteries.
Hmmm, maybe we should start buying up the NOS Raytheon CK series peanut tubes...
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With heaters, it's not usually the voltage required that's difficult, but rather the current drawn.
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Right, but a 6148 heater only needs 10mA at 1.25V and plate at 15Vdc, no problem from standard 48Vdc/10mA phantom.