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Post by aamicrophones on Jul 1, 2019 11:32:22 GMT -6
THIS IS DAVE FROM ADVANCED AUDIO MICROPHONES (dave@advancedaudio.ca)
I have 8 Free passes left for Summer Namm but I need the name of anyone who wants to go and their e-mail so registration can send you a scan to pick-up badge. I need this information by July 2nd before 8:00 pm.
We will be showing our CM47LE the Perfect U47 re-production. We will be taking deposits for delivery mid September. The CM47LE will sell for $1195 but it will be $1050 for pre-sales.
Cheers, Dave
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Post by aamicrophones on Nov 5, 2018 14:26:24 GMT -6
Here is a part of the article on Robert Fine where they describe using U47's until 1959 when the used 3-Schoeps M 201 mics.
"In December 1950 Fine made his first full-orchestra recording with a single microphone, documented as the first American orchestral recording, with a Neumann/Telefunken U47. The recording was William Schuman's "Judith" and "Undertow" ballet scores, performed by the Louisville Orchestra and recorded in Reeve's large scoring studio.
In April of 1951 Fine traveled to the Windy City to make Mercury's first recordings with the Chicago Symphony, under Rafael Kubelik. Having experimented with single-microphone recordings in New York studios, as well as other venues, Fine took along a Telefunken/Neumann U47 tube condenser mic, which was then relatively unknown in the States. From experiments and intuition, Fine opted to place the microphone slightly behind and above the conductor's podium. He then fine-tuned the placement based on listening to monitor speakers as the orchestra rehearsed. For this session the recording was done remotely, via a dedicated telephone line at Universal Recording Studios. Engineering legend Bill Putnam acted as tape op. Despite the fact that telephone line noise and crackle can be heard, the recording translated to mono LP excellently. Kubelik's reading of Ravel's arrangement of [Modest] Mussourksky's "Pictures At An Exhibition" quickly became a hit for Mercury's young classical division. New York Times music critic Philip Taubman described the sound "as if being in the living presence of the orchestra." The Mercury sound then became the standard-bearer for classical music in the early LP era. The U47 microphone gained its own cult status, helped along by a feature article in the Saturday Evening Post magazine.
Bob Fine and Mercury producer Wilma Cozart watched keenly as stereo playback in the home came nearer to fruition. Fine was well aware of multi-channel sound benefits and recording techniques, having worked as a film sound mixer since the 1940s. Cozart was a firm believer in the benefits of stereo for classical recording and reproduction, given the ability to add greater width and depth to the sound and more precise focus to the orchestra and its players. Mercury began doing experimental 2-channel stereo recordings in 1954, but none of the results passed muster. Fine and Cozart thought the 2-channel mic setups and techniques, be it crossed pairs or spaced omni- directional mics, either left too much of a hole in the center or constricted the sides. It also didn't allow for full-width and full-depth results. Their approach was strong-center, since the mono recordings were so successful with a single center-focused microphone.
In 1955, the Mercury team decided to record in 3- channel stereo, feeding each track on a 1/2" tape directly from left, center and right microphones. The thinking was three-fold: 1) Preserve the "gold standard" commercial viability of their mono work by keeping the center single-mic approach for the mono masters, with the assumption that mono LPs would be around for a long time, even after the stereo LP was brought to market (this happened in 1958). 2) A three channel/three mic approach is a natural outgrowth of single mic mono recording and, at the time, there was considerable talk of a 3-channel home playback format (which never materialized). 3) A 3-spaced omni mic approach makes for easy mix-down to 2-channel stereo, which was on the immediate horizon in the form of mass-duplicated 2-track reel-to-reel tapes. The first 3- channel recordings were made with the logical expansion of the single-channel technique: three spaced Telefunken/Neumann U47 mics in the omnidirectional mode of operation. The U47's coloration, an upper-midrange bump in response, was accentuated by multiplying the number of mics and increased the focus on individual instruments and sections. Cozart and Fine decided to try some other microphones. One short-lived approach was to use a U47 in the center and a pair of Telefunken/Neumann KM56 small-capsule condenser mics on the sides.
Fine had been using a Schoeps M 201 mic for single-mic mono recording since 1953. The mic was handmade by the Schoeps family in their home, and Telefunken sold the mic in the States. Its greater sensitivity, as well as a different kind of "presence bump," made it better than a U47 because it could be hung a bit further back. It could also be hung higher while still achieving excellent clarity for strings and woodwinds. From mid-1956 until early 1959, the stereo go-to setup was the aforementioned M 201 in the center and two KM56s on the sides, with a few exceptions here and there. Finally, in 1959, Fine acquired enough of the M 201s to use them exclusively on Mercury Living Presence sessions (six mics were required for the go-to travel kit, as backups were mandatory for all key pieces of gear, given the expense of gathering a symphony orchestra for a recording session). The three-channel, three-Schoeps technique was thus standardized, and all Mercury Living Presence records from 1959 through 1964 (and most thereafter) used these mics and this technique."
Cheers, Dave aamicrophones.com
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Post by aamicrophones on Nov 2, 2018 19:56:40 GMT -6
Hi Ward, I was under the impression that the WA47 was a tube microphone. The WA47jr is a fet microphone with a transformerless output circuit. They both use the same capsules.
Our CM47fet is designed like the U47fet with much more level handling capabilities than a U87. I thought the post was comparing our CM47 tube microphone to the WA47 tube microphone in front of the kick?
According to Neumann the U47fet can produce -3.3dbu before the on-set of distortion. The U47fet can produce 0dbu before the on-set of distortion according to my measurements.
I purposely reduced the output of the CM47fet circuit 3db compared to our CM87 so it wouldn't overload "pedestrian" pre-amps. Like the U47fet, the CM47fet has some negative feedback to reduce HF peaks.
I wanted the CM47fet to work everywhere the U47fet would without having to spend $4K new. I see U47fet microphones going for $3500 used on e-bay!!!
I have never heard the CM47fet overload and I love to use it live in front of the kick, on toms, bass amp, guitar amp,saxophone and trombone plus chromatic harmonic. There is a lot of transformer sound with the U47fet as the transformer has a 9:1 ratio which means it has nearly 20db of loss. In the CM47fet we drive the output transformer from the emitter, allowing us to use a 2:1 transformer with only 6db of loss.
Cheers, Dave Thomas aamicrophones.com
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Post by aamicrophones on Nov 1, 2018 0:33:41 GMT -6
Bass drum, 1 foot away I've been having a similar issue with a WA47 on FOK (centered low in front of the kick, but a few feet back). I hit on a novel solution that sounds surprisingly good: I put a spare 703 panel on a guitar stand directly between the mic and the bass drum and knocked some SPL off while keeping plenty of 60-200hz. Unconventional, but I was pretty happy with the results.The other thing you can try is to put the microphone in OMNI and put the baffle or a gobo on the other side to reduce room sound. You get 6db less output in OMNI.Cheers, Daveaamicrophones.com
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Post by aamicrophones on Oct 31, 2018 20:30:56 GMT -6
M50's are the decca tree and outrigger defacto standard on the west coast scoring stages. Angel Studios in London where Adele strings are recorded uses our CM67se microphones in the Decca Tree and our CM12se as outriggers.
This was recorded with our microphones at Angel and a KM84 over every pair of strings. Angel told me the sound got a lot thinner when they pulled out the Decca Tree.
In my experience a SDC rolls out earlier in the low end. My favourite live Orchestra recording ever is 3-U47's in OMNI across the front of the Orchestra.
Cheers, Dave aamicrophones.com
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Post by aamicrophones on Oct 31, 2018 19:36:57 GMT -6
I'm pretty pumped that I just ordered a CM28. Can't wait to try it out. Hello, thanks for ordering the CM28 from us. Here is a picture of the CM28 and our CM12se on Nashville Studio player Dave Cleveland at Sony Tree studios Nashville.
Cheers, Dave
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Post by aamicrophones on Oct 26, 2018 18:30:01 GMT -6
<snip>....Even if you picked one of on e-bay for $150 then you need to put another $200 into it to have a capsule and transformer fitted plus shipping. It just doesn't make sense to send one of these cheap microphones for upgrades when you don't know what you are going to get back Gotta disagree 100%. They don't need new capsules and they don't need new transformers. The 219's and 319's are quite nice mics when modded. They are different, and I'd take them 10 out of 10X's over a 414 or especially the normal Chinese suspects. Right now, they are my favorite tom mics. (The Joly 219's that is). These weren't 219's they were 319's and came directly from Russia. This is what the 319's that we brought in looked like inside. Michael probably made some significant changes. I have never seen inside or listened to one of the 319's that Michael had upgraded. I must admit stock the 319 did sound better than any of the low cost Chinese LDC microphones that were available in 2000. We sold some to a animation studio who used them for voice actors and they sounded better than what they were using at the time. However, I didn't think they sounded quite as good as our CM47fet in front of the kick or on toms but one is alway prejudiced when you spend time on a microphone build. Playing drums and percussion I was really cognizant when building the CM47fet that it could be used successfully up close on drums and percussion instruments. I have never used a 414eb or our CM414 in close on the toms but I like them as overheads even John Glynn style. When I worked once with Jeff "skunk" Baxter we use the two C37a tube microphones on toms. They weren't placed as close as 57's and one was positioned between the two tenor toms. The cymbal leakage was much nicer sounding that with a 57. I also like pencil condenser microphones on the snare drum. However, most of the live jazz recording I did consisted of two overheads and one microphone in front of the kick. Cheers, Dave aamicrophones.com
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Post by aamicrophones on Oct 26, 2018 12:40:30 GMT -6
I’ll give you 12000 Venezuelan VEB Or $1.20😁. I’ll cover shipping and PayPal gotta love those eBay auctions where the price is $25 but the shipping is $700! I was bringing in Oktava microphones from Russia around 2000 but the quality was very inconsistent. The ones I measured that came from Russia had a 5db rise on average at 3-5khz and the response varied plus or minus 3db from microphone to microphone. The circuit used a simple Class "A" fet driving a transformer, like the U87 circuit but without the capsule de-emphasis and the output transformer was really inferior to the Neumann. In my experience the 319 would need a capsule and transformer upgrade. Even if you picked one of on e-bay for $150 then you need to put another $200 into it to have a capsule and transformer fitted plus shipping. The MK319 is $400 new and is cardiod only. You can buy a WA47jr for $100 less. I prefer the AKG C414eb 2 stage Class "A" transformer coupled circuit which has 10-14db more headroom than a U87 depending if you have a original U87 or one made after 1988. Our CM87 with custom 2.25:1 transformer is $389 and our CM48fet is $395 which has 3-patterns and our AK47 capsule and custom transformer. We are still doing repairs and upgrades but the majority of upgrades we do is turning Apex 460's, Nady TCM1100, HST11a and other variations into our CM12se microphone. We also upgrade the Avantone CV12 which has a flaw in the circuit caused by the HP filter which reduced the headroom by a factor of 20. We have a custom made transformer that fits into the 460/CV12 body. At the moment we are restoring an AKG C24 and a Rode Classic. The cable for the Rode Classic was re-wired with the pin-outs reversed so it blew up the filament and plate supply which we had to re-build. We still replace a lot of capsules in old U87's. Both fronts of the CK12 capsules are failing when addressed with close vocals. I still get a few DIY microphone builds to restore. These are always fun as not only can there be wiring inconsistencies like the M49 DIY I re-built for my good friend Tom Graefe (MXP3036 designer) which I had to re-design the circuit and replace the power supply that was "dangerous". He bought it used and was told it was working. It worked but sounded no where close to a M49 and a stock APEX 460 sounded better. Once we corrected the circuit issues and re-designed the power supply the hum went away and it sounds like a world class microphone again. We are not getting a lot of requests anymore to put better capsules in low cost fet transformerless microphones like the APEX 425, MXL V69 or 990. You can buy the Warm audio transformerless WA47jr which has 3 patterns for $295. It comes with a capsule like the one that would be used to upgrade these low cost fet microphones. So, by the time you buy a "$169" microphone plus shipping, have a capsule fitted and shipped back then you usually end up spending at least $15 more than buying a new WA47jr. We sell our CM47fet which has two patterns, a 2 stage, class "A" transformer coupled circuit with 15db more headroom than a U87 and a HD shock-mount with flight case for $295 less a 10% discount for RGO members. Its my goto in front of the kick, guitar/bass amp and saxophone microphone. It just doesn't make sense to send one of these cheap microphones for upgrades when you don't know what you are going to get back and you can pick up a really good new microphones that gets great reviews from real users for the same price or less. Also, I think most folks who bought those cheap under $200 LDC microphones have got rid of them by now or have had them upgraded in the past. I liked Michael and met him at a couple of Pro Audio events. I wish him the best for his new venture. Cheers, Dave Thomas aamicrophones.com
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Post by aamicrophones on Oct 22, 2018 13:18:53 GMT -6
Hi John, you are correct that the sound of speed changes with humidity. The speed of sound at sea level can change from 343 m/sec at very low humidity to 345 m/sec for 100% humidity.
Howard Tremaine mentions in his Audio Enclyclopedia book that they would mist the air to increase the humidy on sound stages in the early days of recording dialogue for film.
The speed of sound also varies with temperature. At 35c it travels at 351m/sec in a standard atmosphere and at 15C it travels 340m/sec.
Cheers, Dave aamicrophones.com
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Post by aamicrophones on Oct 22, 2018 10:50:02 GMT -6
Hello, yes you are right!!! Its the WA47jr that has the Schoep transformerless output circuit. I thought someone was comparing it to a U47fet? The WA47 uses an AMI T47 transformer with a 12AT7.
The 12AT7 has too high an output impedance to drive a T47 properly unless its configured as a CCDA circuit like our CM47.
Cheers, Dave
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Post by aamicrophones on Oct 21, 2018 20:45:00 GMT -6
johneppstein , aamicrophones probably meant 50 hz. I’m curious if anyone has put a WA-47 next to a FleA 47 on some sources. I did listen to the Zen Pro Clipalator stuff, but was curious if there were any others. I’m also curious if anyone has attempted to mod the WA-47 yet, and what the outcome was. Hi Guys, sorry!!! That was a typo the U47 circuit has a natural roll-starting at about 50hz depending on the capsule's capacitance and the input impedance of the tube circuit. Neumann specified a capsule with a 78pf to 83pf capacitance and the majority of U47's have a 60 meg input resistance. Here is our AK47 on the left and the K47 on the right from a 1959 U47. Cheers, Dave
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Post by aamicrophones on Oct 5, 2018 19:04:19 GMT -6
This mic isn't about having a 47. Its about looking like you have a 47. I already figured this out a while ago. Hi Adam, you are exactly right. We have a client that loves our current microphones and carries several with him but asked if we could build ones that looked like the original U47 and M49. He scores films and time is worth about $50 a minute in the studio. He works in some very prestigious studios that have a handful of U47, M49 and C12/ELA M251 microphones. However, these vintage microphones are getting long in the tooth and when you have a dozen of them up on a orchestral session it is not unlikely that one will start to crackle, hiss or fail. Re-recording a 12 minute score costs about $600 plus you now have the players for 12 minutes less. Our film client asked if we could build microphones that would look exactly like the original "vintage" ones but would sound as good as the originals or better, are more reliable, impress the client and are affordable enough that they can budget $15K to $20K for 12 full body tube microphones. The dilemma is which one do you build and try to emulate. With the U47 there were 5 different transformer versions and those made before 1959 had M7 capsule in late 1958 they starting using K47 capsules and by1961 they were using a 6CW4 nuvistor tube instead of the VF14m. As, you guys have observed you can argue for decades over which is the best transformer. For, example the first 200-BV08 transformer were wound on a power supply transformer core. These are claimed to sound warmer but in my experience their simpler core/lamintation would roll the highs out earlier. However, Once U47 sales caught on, Neumann designed the first BV08 with a core and laminations designed for audio. There is a version of the BV08 that would roll out the low end more agressively from 200hz down used by broadcasters. Oliver mentioned that these could be re-assemble to have the "standard" U47 roll-off which means moving the laminations around which will change the inductance of the transformer. The .5ufd coupling capacitor and the inductance of the BV08 create a 12db/octave roll-off with a 3db down point somewhere around 50hz depending on the BV08 or T47's inductance. The T47 seems to act like the BV08 in my measurements with a .68ufd capacitor. This roll off will also change with the output impedance of the tube. For, example the 5751 is probably being operated as a CCDA circuit to have a low enough plate impedance to drive a T47. The 5751 has a plate impedance of 56K or 28K ohms if you parallel both halves. If you configue it as a CCDA circuit then you can get an output impedance down at 1K ohms. We use the CCDA circuit in our current tube microphones with a 6072a tube and get and output impedance down at 600 ohms. Our microphone are flat down to < 20hz. The U47 has a plate impedance from my calculations of about 14K and therefore you really need a tube with a voltage gain of 18 and a plate impedance of 14K ohms to get the output transformer to react the same as it does with a VF14. Also, it is important that the input impedance of the tube circuit whether a VF14m or replacement is 60 Meg as this with the 78pf to 83pf capacitance of the capsule will roll the low end out 6db/octave again around the 50khz area. This is one of the design "features" that makes the U47 work well for vocals and be very quiet, considering it had an metal clad VF14m tube. If you reduce everything below 60hz at 18db per octave then this give you an advantage when measuring signal to noise. The relationship between the plate impedance, coupling capacitor and inductance of the output transformer will also cause a slight rise in the low frequency response of about 2db around 200hz. I have had the rare privilege of being lent a perfectly working NOS VF14 tube for a few weeks this summer. This tube operates perfectly and is quiet, so its worth more than a pair of my current tube mics. This was a spare VF14 found during cleanup in the back of the repair shop of a large recording complex in Europe. I was sent the tube to determine if it works. I built a regulated dc filament supply and plate supply. When I measured 34v dc on the plate as displayed on the schematic I measure .5ma of current which is also specified on the schematic. I measured an output level of +12dm <1% distortion with a 10K load on the output of the T47 and +8dbu <1% distortion int a 1k ohm load on the output of the T47 I duplicated the simple class "A" U47 circuit but used a GE/JAN 5654w tube with the same transformer and input impedance resistor and output coupling capacitor. By tweaking the plate/cathode resistor in the 5654W circuit, I was able to get the gain of the two circuits within < 2db of each other. The distortion figures with the 5654w being about 1db better when operated at 125v as opposed to the 105v on the VF14m. The 5654w is a socketed 7 pin and like the VF14 it has to be selected to be quiet enough for an LDC impedance converter. However, we reject much less than Neumann did with the VF14. The GE/JAN5654w was designed for use in military aircraft so it much less prone microphonics and vibration than the VF14. The other important design point when trying to duplicate a U47 is that the M7 or K47 type capsule is polarized passively in Cardiod. When you passively polarize the capsule you get 3db more output than when you match the rear diaphragms polarizaton voltage to the back-plate. That's why the prototype of our CM47Le has a switch on the microphones as well as a 9 pattern power supply. When switched to the left its passive cardiod and when switched to the right its variable pattern. The proximity effect also changes and it seems wider in passive cardiod during our recent testing. Our CM48T microphone also has passive cardiod polarization and a 5654w but with the smaller footprint BV8 pictured below and our AK47 capsule. You can see the custom BV08 that we plan to use pictured on the left of the T47. BTW, the WA-47 has a Class A/B Shoep transformerless circuit. Our CM48 and CM87 have a class "A" 414eb circuit having nearly 14db more headroom than a U87 circuit. The CM48 has a very "hifi" output transformer with dual bobbins and bi-metal laminations its the exact same size as the BV18 pictured above but with a 2.25:1 ratio to work in the emitter follower circuit. That's what I have learned from measuring the VF14m tube wired into a U47 circuit. Cheers, Dave aamicrophones.com Attachments:
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Post by aamicrophones on Oct 1, 2018 16:05:19 GMT -6
I realize this may seem like a bit of an apples to oranges type of comparison, but the price of some of these La2a clones puts it in the same ballpark as the JLM La500a, though the kit would be cheaper. I've not heard any of these La2a clones or the La500a but I've heard a lot of good things about the JLM and the La2a (or its clones) is, well, the La2a. I realize that the La500a is not directly trying to be a La2a (or clone), but a lot of people seem to rave about it on vocals. If you were looking for something to primarily use on vocals, would you prefer the La500a or a La2a clone? Hi Quint, I have 4-LA610 preamps which have an LA2 attached. I love these on vocals but I have modified mine by changing the output tube in the preamp section and compressor section to those in the original LA2 and changed the plate resistor value on the circuit board to optimize these tubes.
The LA500 runs on + and - 16 volts as does all 500 gear which means you have maximum headroom of +18dbu from the LA500.
Now, the LA610 after the upgrade has the same headroom +18dbu before the onset of distortion but as we all should know a tube circuit appears sonically to have 20db more headroom than an equivalent solid state circuit. The other advantage of the LA610 other than tubes is that is also has some tube EQ which is subtle but lovely on vocals.
The EQ is selected at 10Khz/7Khz and 4.5Khz for the HF section and 200hz/100hz and 70hz for the low frequency section. 2-3db at 200hz yields a more U47 sound.
I have two more used fully upgraded LA610MKII that I would sell for $1095 USD each plus shipping. I will be posting these unit on Reverb.com later in the week.
Cheers, Dave aamicrophones.com
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Post by aamicrophones on Oct 1, 2018 15:40:55 GMT -6
Hi Guys, just got confirmation that two sample CM49LE bodies and head-grills are on the way. We are also having 100-large frame T49 and BV08 type transformers wound to our specs. I also just finished building up 2-CM47LE samples. I was lent a very rare and very expensive NOS VF14 tube and was able to build an exact U47 circuit with parts exactly like the original. I was able to determine that this VF14 could deliver .5ma at 34 volts just like the original circuit and this VF14 tube was extremely quiet.
The production models will not have any chrome and will look like the original U47 body but with a more friendly shock-mount and connector.
I am just about finished writing a blog regarding this process will be posting in the next couple of weeks.
We expect the samples withing 10 days. I am busy doing a MCI 636 Studio Console installation later this week that I hope to have finished before the M49LE bodies arrive.
Quickly, what I have learned from the VF14/U47 circuit is the following:-
1) The VF14/U47 circuit has a voltage gain of 18 which translates into 25db of gain while the BV08 transformer has a loss of 16.2db.
2) The 60meg or 100meg (after 1959) input resistor causes the low end to roll out about 6db/octave starting at around 60hz if the capsule measures 78 to 83pf.
3) A .5 capacitor in series with the BV08 output transformer yields about a 2db bump at around 200hz and starts to roll out the low end just below 200hz and is down 6db by 50hz and 25hz will be down will be down nearly 18db. This is why the U47 is well suited for vocals and it really rejects rumble and low frequency thumps while sounding really warm on vocals.
This is also the reason a properly working U47 is quiet because the bottom octave rolls off so drastically.
Changing the value of this output capacitor will change the sound in the low end.
4) The U47 will produce and output of nearly +14dbu with less than 1% distortion into a 10K load. It produces and output of +8dbu with <1% distortion into 1K load (Neve 1073).
In contrast a U87 will only yield a maximum output of -5.9dbu before the onset of distortion.
5) The U47 capsule polarization must be passive to produce a true U47 sound in Cardiod. With Passive polarization (no voltage to the back-plate) the microphone has 3db more output than with the 9-pattern selection mode where the rear diaphragm is polarized at the same potential as the back-plate. Our CM47Le has a switch on the front to provide Passive Cardiod or multi-pattern selection from the power supply. We also noted that the proximity effect was much wider in passive cardiod and of course this extra 3db of level increase the signal to noise ratio in the microphone compared to active polarization.
6) When we placed the GE/JAN 5654w tube in the same circuit but optimized the tube bias for a GE/JAN 5654w, we then get the same output level and gain before distortion. Being able to measure the parameter of the VF14 tube in operation allowed us to match the 5654w and produce the same sonic result. In other words the VF14 is not particulary special and acts like a typical pentode. However, Neumann is running the plate voltage down a 34v which is off the chart when you look at the VF14 tube curves so it is nearly impossible to calculate what is going on until you make measurements. The 5654w in an optimized circuit appears to perform exactly like a properly working VF14 tube in our investigation.
In conclusion.
****The VF14 tube does not have a magical sound of its own. The sound is completely dependent on the selection of circuit component values and the inductance of the output transformer and the load impedance (preamps input impedance) the microphone is driving******
Now, the other component is the capsule. However, we believe that that's just a personal choice between a M7 or K47 type capsule. We have heard some great sounding microphones with both M7 or K47 type capsules skinned with 6 micron mylar that measure between 78pf and 83pf.
Now, I recorded a female vocalist singing Brazillian Jazz and I put up the CM47LE which will sell for around $1295 and our CM47 which sells for $735.
On this recording I preferred the CM47 although the CM47LE did not sound bad just the CM47 seemed to work better for the sultry jazz Portuguese vocals.
I will pull the CM47 and CM47LE files from my Radar later today and post them.
In haste, I now have to pull two failing capsulesfrom a AKG C24 that we just got a purchase order to re-build for a recording school.
I have to get these out to Tim Campbell for re-skinning.
Cheers, Dave aamicrophones.com
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Post by aamicrophones on Jun 22, 2018 18:10:44 GMT -6
Yikes, lost the internet halfway through the last sentence. I have been occupied with a NOS VF14 that came into my possession for a short time. I have breadboarded up and exact U47 circuit with this tube and have been measuring all the parameters. I had to build up a custom regulated 35v dc supply as not damage the filamen and run it like Neumann did. Going to try and runs some audio through it tonight. Cheers, Dave Attachments:
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Post by aamicrophones on Jun 22, 2018 17:52:22 GMT -6
Yikes, lost the internet halfway through the last sentence.
I have been occupied with a NOS VF14 that came into my possession for a short time. I have breadboarded up and exact U47 circuit with this tube and have been measuring all the parameters. I had to build up a custom regulated 35v dc supply as not damage the filamen and run it like Neumann did.
Going to try and runs some audio through it tonight.
Cheers, Dave
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Post by aamicrophones on Jun 22, 2018 17:48:46 GMT -6
<abbr data-timestamp="1529516655000" class="o-timestamp time" title="Jun 20, 2018 10:44:15 GMT -7"> Jun 20, 2018 10:44:15 GMT -7</abbr> Vincent R. said: jeremygillespie 's M49C had some real magic when I tried it. Had a K47 and was a type C. It's funny because so many people reach for the M7 versions and the type B. My FleA 49 is a type B circuit, but I had them put in the K47 instead and it really does sound wonderful. I've only really tried the FleA 49 (3 incarnations; M7 + stock tube, K47 + stock tube, and M7 + NOS AC701K). I really went back and forth on AC701k for a while. All of the people who are my go to for advice had differing opinions. Ultimately I didn't want to fall into the trap of having to find an AC701K down the line and just went with the stock tube. I really love the sound I'm getting from it, especially the American song book stuff or the Mario Lanza stuff I do.
The only other M49 style mic I've used is the CM49 which is a good microphone, but a bit brighter and less beefy than my FleA. It also uses a K47. Shannon has offered to tweak it for me at a fair price, but I've just kind of let it be for now. Hoping to demo aamicrophones ' new CM49LE which should be out in the fall. I enjoy that the CM49 is gain staged almost identically to the FleA 49 making it easy to use them as a pair. I've used them in a blumlien in the room. Yes the CM49 is a bit brighter, but I can even them out with EQ, or use them creatively by aiming the bright mic at the darker source, etc. I'd love to have one that was closer in sonic quality to the FleA, but after that purchase I am strapped for a while and the CM49 is no slouch as an extra mic to have around. It's still my favorite of the AA Mics. Actually I had it next to Jeremy's M49C and sonically it sounded in between the M49C and the M269. It really held it's own in that shoot out. I have to finish that video...
The Beesneez looks cool. It looks like they have two versions, their Clone which is on sale for $1500 at the moment. Looks like that is an edition which allows them to save on construction by keeping the sonic sound, but allowing for different circuitry. They also have the Tribute 4 which is over 4k like other replicas I've seen.
rms also has a full replica and a tribute version. The RMS49 is a full blown replica for $4399 which includes a k47 or an M7 for an additional $100. Then they have the RMS49LE for $2999. It also comes with the K47 stock or the M7 as an upgrade. Both use a NOS 5703 tube, which he feels is sonically close the the AC701k. It works really well in my RMS269. Rob will also make it with however you want. If you grab a Thiersch M7 and want him to install it he will. If you grab a Neumann K47 he would install that for you as well. I've mentioned in passing that I'd like to try his RMS49LE at some point. I'm so busy with performances and my Christmas album there is just no time to film and edit a new video for my channel, so I haven't really pressed the issue. Maybe when AA is ready with their new CM47LE I'll try and get demos of each and make a video comparing all of them and my FleA 49. People can then hear M49 clones at 3 different price points. Hi Vincent, I have the prototype of the CM49LE working and I used it last night on a vocal. Still waiting inline for the larger CM49LE head grills to be manufactured. The other thing that has been keeping me occupied is that I
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Post by aamicrophones on Nov 21, 2017 23:47:50 GMT -6
Yeah, you have got to value that spooky obsession. There are too many 'me too's out there. Hi Guys, that was what I was pointing to. A 1976 U87 is a different animal than a 1988 or later U87AI. We had two U87's at Ocean and 3 later version U87ai's. In critical listening tests the majority of folks preferred the original U87. When folks state, U87 which one are they referring to? In 90% of the time the U47's, C414eb, C37a microphones were preferred over the U87 on vocals. However, we often used the U87's on horns, strings and for room miking. Neumann used tantalum capacitors across the power supply and in the audio chain of the U87. Tantalums are twice as fast as electrolytic's but they are more partial to early failure. I have repaired several U87's with a failed (shorted) C12 and the odd C10. I have also found older U87's with a failing C7 or C8. I recently repaired one where C8 measured 800 ohms and there was absolutely no gain. Usually, tantalums get noisy before they fail but not always. If you use an electrolytic to couple the audio then you need to bypass it with a .1-.01ufd metal film. The circuit requires the use of a 20ufd at C8 but C7 in the U87 is a 1ufd. Metal film capacitors which are over twice as fast as tantalums can be found in a small enough size to fit the circuit board. However, the 20ufd C8 either has to be an electrolytic bypassed or a tantalum. Also, the power supply capacitors can be replaced with electrolytics to improve reliability. In our CM87 we did not copy the U87 circuit. We used a more reliable, more efficient capsule, that has a response we really like, without de-emphasis. Its has the same rise in the upper midrange as the original U87 but is on average 2db brighter at 12khz without the de-emphasis. It has the same polarization circuit as the U87Ai. However, it has a 2-stage emitter follower Class "A" transformer coupled circuit with 14db more headroom than the U87. There is 20db of loss in the U87 with a 10:1 ratio transformer, 17db of loss with a 7:1 ratio transformer, 14db of loss with a 5:1 transformer ratio. Simply by adding another transistor configured as a emitter follower, the output transformer can have a 2:1 ratio (6db loss). So, we drop the gain of the first stage by 14db compared to the U87 at 10:1. This increases the headroom of the circuit and reduces the circuit noise by approximately 14db. So, I never found any reason to copy or clone the U87 build. However, to get the "mystical" sound of the U47 one has to "dumb" down the circuit compared to our CCD circuit which can drive the transformer from 600 ohms. 1) The reactance of the drive circuit must be the same as a VF14m would be, driving an original BV8. The output capacitor should be .5ufd in order to "react" correctly with the Bv-08's inductance. 2) The VF14m had an input capacitance of <9pf. Newer tubes have an input capacitance <4pf and to match the VF14m a small capacitor must be fitted to "dumb" down the amplifier so it has the same HF turn-over point as the VF14m circuit. 3) Also, the U47 had much smaller value, input resistors compared to newer circuits. The original few U47's had 60 megohm but later they were 100meg today we use 1G but to get the same LF roll-off curve as the original they should be lowered to 100m. Between, the lower value input impedance, the correct reactance in the output stage, matching the gain and current draw of a VF1m, the circuit should react like the average U47 did. I have a working VF14m arriving in the New Year and I will be able to calculate the plate resistance and gain when it is wired as a triode configured like the U47 circuit. IPA is a bit like the U47 circuit which was a magical "work around" to buid a "HiFi" circuit in 1947. Indian Pale Ale was shipped by sailing ship from Britain to the colonies and by the time it reached India it was going bad. So, they increased the HOPS content in later shipments which is a natural preservative and it made the trip but increased the alcohol content and that made it popular. Cheers, Dave
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Post by aamicrophones on Nov 21, 2017 14:51:37 GMT -6
Well, I got in front of the FLEA 249 with the stock M7 and stock tube. The 249 is exactly the same as the 49 except the cable connector. I also got in front of a FLEA 49 with the stock M7 and an AC701k tube. I'll post my thoughts when I have a brain. It's a trek to get out to Orange, CT from my place on Long Island. There were differences in the set up he had and that I have, but I think the biggest difference was the room, which was much more live than my room. What I will say is I thought the difference between the K49 capsule and the M7 was really minor. What struck me is how much of a difference the AC701k made. It was about as different from the stock tube version as the CM49 was from the FLEA. Gotta sit on everything a few days and make a decision. Hi Vincent, I don't think you are hearing the tube make a difference. It is more likely C6 which was placed on the output of the AC701 to roll-off the HF rise at 10khz. Notice both these schematics use a AC701 but one has a 150pf roll-off and one has a 600pf roll-off capacitor. There are also another schematic of an M49 version I have seen without C6 installed. C6 would affect the shimmer more than any tube difference. Also, one schematic has negative feedback and one doesn't. Negative feedback increase the gain so the input capacitance in a tube circuit is multiplied by that gain. The higher the resultant input capacitance the lower the HF cutoff point of the amplifier circuit. Tubes do not have a "sound signature" of their own. However, they react differenctly with different component choices, different bias methods, different plate supplies and different circuit configurations. The difference between these two circuits both with AC701a tubes is not only C6 but one has fixed bias and one has cathode bias. According to Klaus there were of 1/2 a dozen different M49 circuit variations. Again, which one is the "holy grail" of M49 circuits? I just got my T49 transformer sample. So, I will be starting to do measurements and testing with our M49 AC701 replacement circuit and the larger T49. Cheers, Dave Attachments:
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Post by aamicrophones on Nov 21, 2017 14:20:43 GMT -6
Bob Rock rocks. Missed a chance to work with him when we worked with Bruce Fairbairn 'cause we recorded on the East Coast instead of Vancouver. Hi Guys, I got to work with Bob a few times. He use to "sneak" over to Ocean Sound to record vocals on our U47 as they only had U87's at Little Mountain. Part of Bob's famous drum sound was the loading bay at Little Mountain Sound. Bob would send the drums out to a speaker in the loading bay and mike the bay. We didn't have a big loading bay at Ocean so we use to take a DAT recorder across the street and sample a snare drum in the underground parking lot and then drop it into the track with a sampler. Cheers, Dave aamicrophones.com
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Post by aamicrophones on Nov 21, 2017 14:11:24 GMT -6
It's embellished hype, and Warm knows exactly what they're doing. It's the same as Slate saying his VMS sounds indistinguishable... It doesn't. The only affordable mic I've heard that is indistinguishable to the original it copies, is the Stam 87. Hi Ragan, The problem is indistinguishable to which original? Which microphone did Stam or Slate "clone". The original U87 had a double sided separated K67/87 capsule and the polarization voltage was lower at 47 volts plus the original transformer had a 5:1 or 10:1 turns ratio(50 ohms/200 ohms). The polarization was passive and they swapped the polarity on each half of th capsule to get the FIG 8. All U87ai microphones made after 1988 had a voltage tripler circuit that placed 60v on the double sided K67/87 capsule's back-plates which are tied together. Instead of swapping the polarity of the two halves, the U87ai had 120 volts on the rear diaphragm for FIG 8 and 60v on the back plate. This higher polarization voltage increases the output a few db decreasing the headroom and it increases the upper mid rise a couple of db. The U87ai is brighter than the original U87 plus the U87ai has a single 7:1 ratio wound transformer. We have service many original U87 microphones and they always sound mellower/smoother to our old ears than the U87AI. Cheers, Dave
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Post by aamicrophones on Nov 16, 2017 17:31:19 GMT -6
Omni is the "bomb" for acoustic guitar recording. Now, its OMNI so the room has to sound good and the isolation should be approaching the NC5 noise criterion.
You can also gobo off around the microphones to reduce the room reflections and room tone but you still have no proxity affect and as stated by John no off-axis coloration.
My favourite Classical recording was part of the Merury Living Presence recordings from the 50's with 3-U47 microphones in OMNI across the front of the Orchestra recorded to the magnetic strips on a 3 track film recorder.
Except for the tape hiss in the very, very quiet sections it sounds like you are sitting in front of an orchestra. We don't build any cardiod only microphones even our CM47fet has an omni option. Our pencil microphones all come with OMNI, CARD and super-cardiod capsules.
Cheers, Dave
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Post by aamicrophones on Nov 16, 2017 15:18:56 GMT -6
It's embellished hype, and Warm knows exactly what they're doing. It's the same as Slate saying his VMS sounds indistinguishable... It doesn't. The only affordable mic I've heard that is indistinguishable to the original it copies, is the Stam 87. Hi Jake, its really all personal taste. We had two U47's, two original 414eb's, two C37a tube microphones and 5-U87's during my 20 tenure at Ocean Sound Studios and the U87 was the least favourite for vocals. However, it was the goto microphone for voice-over work and strings. When KD Lang and Roy Orbison came in to sing "Crying" Dusty Wakefield put up one of the U47's and never even asked if we had a U87. We had two U87's pre-1988 and 3-U87AI microphones. Even then I was convinced the U87 was the most over priced microphone on the market. When I built my CM87 a purposely designed 14db more headroom into the circuit and tried in my humble opinion to improve it not copy or clone it. Cheers, Dave
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Post by aamicrophones on Nov 16, 2017 15:02:20 GMT -6
However, I also love the extra feature that our 9 pattern supplies provide just like the WA47 does but its imperative that the rear diaphragm and back-plate are at the same potential for true cardiod. Even when the rear and backplate voltages are perfectly matched, it sounds different to front only true-cardioid. I've tried this by connecting a rear diaphragm directly to the backplate, for exactly the same voltage on both. Still didn't fully cancel out the rear. Only way to get true-cardioid is by leaving the rear out of circuit. M49's have an internal switch just for this purpose. Hi Jake, thanks for your reply. Yes, that is why we use the passive polarization method in our CM48T which leaves the back diaphragm disconnected but gives you the U47 and U48 options with OMNI & FIG8. You are right even a regulated power supply takes nearly 10 seconds for the power supply voltage to stabilize but this is a lot better than the 50 plus minutes it takes a U47 power suppy to normalize. As, I previously stated, the filament has to warm up first so no plate current will flow until the filament gets the cathode up to temperature. The filament starts as a low resistance and then ramps up as it starts to light up. You certainly can get zapped if you hold onto the body of the microphone and the metal of the XLR when you hot swap it. However, it won't kill you as it can't deliver enough current through you high resistance skin but it can catch your attention. Proper protocol is to plug the microphone in first and then turn on the supply. However, when I am working on microphones in the shop its too time consuming to power off the supply 50 times a day. I have learned to plug the XLR in while holding the rubber strain relief. I am working on a design like the M49 for my new CM49LE which will feature a switched passive Cardiod option as well as the standard 9 pattern option. Cheers, Dave
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Post by aamicrophones on Nov 16, 2017 3:08:54 GMT -6
Hello, our CM67se microphone has a -10db pad and we can easily customize it with our CM47 head grill but its about $200 for the larger body, -10db pad and HP filter options.
I often use the CM67se microphones as drum overheads usually with the 10db pad engaged.
Cheers, Dave
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