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Post by Vincent R. on Feb 25, 2017 17:41:14 GMT -6
topshelfmg just got an AA251 interested to hear more from him regarding the mic. I follow his Instagram and he posted about it the other day. Hand built and hand tweaked from aamicrophones maybe you can shed more light on this model π I have one as well. Very reminiscent of the Korby 251 my wife tried. It definitely has that 251 feel. I prefer it to the VMS emulation.
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ericn
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Post by ericn on Feb 25, 2017 19:04:11 GMT -6
First test with the CM49 reveal a beautifully rich sound with a natural top end. I'll do a full review once I have a little time to use it more thoroughly. So liking the M49 flavor?
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Post by topshelfmg on Feb 26, 2017 0:23:40 GMT -6
topshelfmg just got an AA251 interested to hear more from him regarding the mic. I follow his Instagram and he posted about it the other day. Hand built and hand tweaked from aamicrophones maybe you can shed more light on this model π I did! I want to start by saying, I have loved everything I have ever used from Advanced Audio. I absolutely LOVE the CM251. It is a contender to replace the CM67se as my favorite one of their microphones... which currently may be thew microphone I use the most alongside the AEA N22. I used it to record BGVs and harmonies this morning for its first true session. The singer is a soprano and she is quite sibilant, and I have been using ribbon microphones on her up until this point for this reason. I used a Cloud JRS-34 for lead vocals through my Serpent Audio SB4001 and was going to use an AEA N22 through my (slightly) modded Tube Tech LCA-2A for harmonies. I ended up using the CM251 in super cardioid, and it kicked serious ass. For male singers (when I tested just my speaking voice), I'm estimating that cardioid or wide cardioid would sound best as it would give it just a tiny bit of air. Preamp I used my RTZ 9762 Dual Combo, which is essentially an extremely well built 1073 style preamp with more clarity. Also, it is my favorite preamp of all time (bold words, I know), recommended to me by Randy Kohrs, as he said it is one of his, if not his favorite preamp as well. For lead vocals, I terminated the output transformer for a flatter and more traditional Neve sounding preamp, and for harmonies and BGVs I unterminated it for a bit of an air boost. Backing up, I originally got a CM12se from Dave at Summer NAMM for a pop singer who wanted very bright, in your face vocals. Now that I no longer work with that client, and I tend to like darker or more neutral microphones, I sent it to Dave and he was kind enough to convert it into a CM251. Plus, I have two RnB projects this month so it seemed like the logical choice. I recorded reference recordings with the CM12se before I sent it in, and when I recorded with the CM251 onto the same session file, I got very excited when I listened back. Incredibly detailed, but very smooth and neutral... almost leaning on dark, in a great way. If sibilance wasn't a problem on a female soprano, I don't think it will ever be. To me, not only is there less high end, but the bass response and low mids sound extraordinarily rich and full by comparison. Dave explained this is the psychoacoustic effect of having less high end response, but I've listened back to the comparison files a ton and it truly just sounds like a larger, more balanced recording with the CM251. I do believe the CM251 has a lower bass response, going down to 10Hz. I'm excited to try it on acoustic instruments and piano. The CM67se is an amazing counter-balance, being very balanced with just a tiny bit more air up top. My go to when recording acoustic guitar, paired with a second microphone, and many male vocals, just to name a couple. The CM67se directly beat out a well maintained U67 on a Lady Antebellum album, and they used it for vocals (both male and female), except for one song in which they used a vintage U47. It also was used to record all of the acoustic guitars on that album. I forget the other examples, but I know Fall Out Boy uses it on their guitar amps. I can see myself using the CM251 on the 12th fret with it, especially on brighter guitars like Taylors or Seagulls. I've wanted a 2nd CM67se for a while now for a true stereo recording of acoustic guitar, as well as piano, acoustic instruments, and overheads... and now I want a 2nd CM251 if I need a smoother / darker microphone. I also plan on picking up a CM47FETce or CM48FET this week to try out... since at the price, it's really hard to say no. I loved what I heard at Summer NAMM, and have heard nothing but good things about it. I will also be testing out a MT8016 mic preamp from them in a couple months here. But from what I heard when I tried out the prototype in their hotel room... I'll probably buy the unit I'm demoing. I want to say one last thing on the subject. Dave sent me comparison audio between a vintage, well maintained U87 and his CM87. They sounded so damn identical that we thought we accidentally loaded the same audio file in twice... and then again when I deleted and re-uploaded. It wasn't until I flipped the phase I could be sure. There was MAYBE 1db more in a certain section of the lower miss for the vintage U87... but it took a lot of critical listening to pick up. Nothing an extremely amount of EQ couldn't touch up, if you really wanted. And that was just the regular CM87, not the CM87se. Dave has informed me the only difference is that the CM87se has a more complex transformer, just to be able to record louder sources, like drums, without any worry of breakup. I believe the response is supposed to be identical. Hope this helped!
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Post by topshelfmg on Feb 26, 2017 0:28:45 GMT -6
I will let you guys know once I record RnB lead vocals on Tuesday.. and I may even use it for acoustic guitar on Monday! Tuesday is female RnB vocals, and a little later in the month I will be recorded a different male RnB artist, so I will definitely report my findings. So far.. I am impressed, to say the least. I love it.
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Post by topshelfmg on Feb 26, 2017 1:20:11 GMT -6
The entire SDC line seems to have gone away, there are still some pages up if you know where to look, but they don't seem to be obvious. They ran out of stock of their tube SDC is what I was told, but they recently restocked them. The FET SDC 1084s are still under the FET column... with the tube CM28s being under the tube column. It is weird getting to it from your phone for whatever reason. On the computer it pops right up on the left hand side. Cheers
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Post by Ward on Feb 26, 2017 5:27:10 GMT -6
You mean a Capacitator? π The capacitator valve used in the rectifier that releases the excess steam that builds up from the overheated pots and pans?
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Post by Vincent R. on Feb 26, 2017 10:33:52 GMT -6
topshelfmg , if you think the CM251 is dark, wait till you hear one of the K47 offerings. I just got my CM49 and that is a rich and natural sounding mic. Much darker than the CM251. Dave also gave me a cool custom mode for my CM67 that gives it a dark, vintage sound as well as the standard sound. That's also much darker than the CM251. The CM251 & CM67 are two of my favorites. I just received the CM49 and look forward to a few friends I record with to try it. PS: the CM251 is probably my favorite mic for the legit female Broadway and jazz singers I record in my studio. The CM67 in vintage mode has been my favorite for legit male singers, including myself. I only just upgraded from it to an MK U67, and I still kept the CM67.
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Post by rob61 on Feb 26, 2017 11:14:14 GMT -6
You mean a Capacitator? π The capacitator valve used in the rectifier that releases the excess steam that builds up from the overheated pots and pans? I'm waiting for a model that uses Doc Brown's flux capacitor.
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Post by topshelfmg on Feb 26, 2017 23:19:39 GMT -6
topshelfmg , if you think the CM251 is dark, wait till you hear one of the K47 offerings. I just got my CM49 and that is a rich and natural sounding mic. Much darker than the CM251. Dave also gave me a cool custom mode for my CM67 that gives it a dark, vintage sound as well as the standard sound. That's also much darker than the CM251. The CM251 & CM67 are two of my favorites. I just received the CM49 and look forward to a few friends I record with to try it. PS: the CM251 is probably my favorite mic for the legit female Broadway and jazz singers I record in my studio. The CM67 in vintage mode has been my favorite for legit male singers, including myself. I only just upgraded from it to an MK U67, and I still kept the CM67. That is what I hear! It is just fringing on dark, at least compared to many modern condensers (many of which I don't love), but I would describe it as balanced. Have you used the CM47FETce? Considering picking one up very soon to try out, which at the price is very tempting knowing the quality. Plus it uses the same capsule as the 47VE, and CM48 Tube. Yes, I am actually talking to Dave now about the CM67se mod. He is going to give me instructions and I am going to complete the mod myself to save on shipping and time.
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Post by ludwigvanbeartrap on Feb 27, 2017 2:02:28 GMT -6
The capacitator valve used in the rectifier that releases the excess steam that builds up from the overheated pots and pans? I'm waiting for a model that uses Doc Brown's flux capacitor. I prefer an incapacitator.
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Post by Vincent R. on Feb 27, 2017 9:53:47 GMT -6
First test with the CM49 reveal a beautifully rich sound with a natural top end. I'll do a full review once I have a little time to use it more thoroughly. So liking the M49 flavor? I'm still getting a feel for it and I find I'm of the same opinion I was when I tried both the Korby 67 and the custom Korby 49. Singing into my MK U67 and my AA CM49 there is something about how the U67 sound on my voice that just sounds like my voice. The M49 flavor has the unbelievably natural and smooth sound. It is the opera sound from the 60s and 70s that I know, from Franco Corelli and Maria Callas, but I find it creates a darker color than my voice actually is. I expect that's because to get the proper sound it should be 3 to 6 feet away in a hall, instead of 2 feet away in a treated basement. I'm really glad to have it though. I have a basso profundo friend who's EP I can't wait to work on. He will probably use the CM49 to great effect. My sister is a heck of a jazz singer too. I imagine she will sound great on this. We've been using the CM251 which sounds dynamite on her. Knowing how many great female jazz vocalists use an M49, I'm excited to try it on her.
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Post by Vincent R. on Feb 27, 2017 10:18:24 GMT -6
topshelfmg , if you think the CM251 is dark, wait till you hear one of the K47 offerings. I just got my CM49 and that is a rich and natural sounding mic. Much darker than the CM251. Dave also gave me a cool custom mode for my CM67 that gives it a dark, vintage sound as well as the standard sound. That's also much darker than the CM251. The CM251 & CM67 are two of my favorites. I just received the CM49 and look forward to a few friends I record with to try it. PS: the CM251 is probably my favorite mic for the legit female Broadway and jazz singers I record in my studio. The CM67 in vintage mode has been my favorite for legit male singers, including myself. I only just upgraded from it to an MK U67, and I still kept the CM67. That is what I hear! It is just fringing on dark, at least compared to many modern condensers (many of which I don't love), but I would describe it as balanced. Have you used the CM47FETce? Considering picking one up very soon to try out, which at the price is very tempting knowing the quality. Plus it uses the same capsule as the 47VE, and CM48 Tube. Yes, I am actually talking to Dave now about the CM67se mod. He is going to give me instructions and I am going to complete the mod myself to save on shipping and time. I haven't used the CM47FETce. I debated picking it up a few times, but never had a real reason to. When you do the Mod for the CM67, just note that in cardioid it seems to be missing a little top end. I generally use it one notch toward Omni. That's the nice thing about having 9 polar patterns. I find it matches my I/O Audio MK U67 really well on that setting. The MK U67 is about as close as you can get to a brand new U67. It's a kit that plugs into the TLM67 and U87AI that uses the Neumann capsule of the host mic and uses a near exact replica of the U67 circuitry. There's at least two threads discussing that kit on here. So that's my experience with the CM67 anyway. I started recording a friends album with the CM67 in that mode and am finishing it with the MK U67. My U67 thread: realgearonline.com/thread/6267/u67-style-microphone
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Post by topshelfmg on Feb 27, 2017 20:53:14 GMT -6
That is what I hear! It is just fringing on dark, at least compared to many modern condensers (many of which I don't love), but I would describe it as balanced. Have you used the CM47FETce? Considering picking one up very soon to try out, which at the price is very tempting knowing the quality. Plus it uses the same capsule as the 47VE, and CM48 Tube. Yes, I am actually talking to Dave now about the CM67se mod. He is going to give me instructions and I am going to complete the mod myself to save on shipping and time. I haven't used the CM47FETce. I debated picking it up a few times, but never had a real reason to. When you do the Mod for the CM67, just note that in cardioid it seems to be missing a little top end. I generally use it one notch toward Omni. That's the nice thing about having 9 polar patterns. I find it matches my I/O Audio MK U67 really well on that setting. The MK U67 is about as close as you can get to a brand new U67. It's a kit that plugs into the TLM67 and U87AI that uses the Neumann capsule of the host mic and uses a near exact replica of the U67 circuitry. There's at least two threads discussing that kit on here. So that's my experience with the CM67 anyway. I started recording a friends album with the CM67 in that mode and am finishing it with the MK U67. My U67 thread: realgearonline.com/thread/6267/u67-style-microphoneThanks for the heads up! Yes I love being able to adjust the polar pattern, almost as a form of subtle EQ while recording. I figure the CM47FETce or CM48FET will hold me over till I get a CM47ve. The CM49 looks great also, so it is good to know you have been enjoying it so far. I have to unfortunately prioritize utility purchases at the moment such as a new patch bay and DB25 snakes, as well as building some more GOBOs and continue saving for a larger facility. Plus, it'll be nice having a U47FET style microphone where FET is called to opposed to a tube microphone I figure, for certain vocals, upright bass, electric guitar, and drums. I actually recently read the one thread, and they look badass! Still very much a beginner as far as DIY, but I will get there, sooner rather than later hopefully. About to start work on some CAPI kits now that Jeff just got a new batch of transformers, and I may even build a JLM LA500A or a pair of them, if I decide to go that route over a Serpent Audio Chimera. Also will end up with a Brute at some point, but that has a sound of its own, and isn't necessarily LA3A-ish.
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Post by mitchkricun on Feb 28, 2017 6:30:39 GMT -6
I haven't used the CM47FETce. I debated picking it up a few times, but never had a real reason to. When you do the Mod for the CM67, just note that in cardioid it seems to be missing a little top end. I generally use it one notch toward Omni. That's the nice thing about having 9 polar patterns. I find it matches my I/O Audio MK U67 really well on that setting. The MK U67 is about as close as you can get to a brand new U67. It's a kit that plugs into the TLM67 and U87AI that uses the Neumann capsule of the host mic and uses a near exact replica of the U67 circuitry. There's at least two threads discussing that kit on here. So that's my experience with the CM67 anyway. I started recording a friends album with the CM67 in that mode and am finishing it with the MK U67. My U67 thread: realgearonline.com/thread/6267/u67-style-microphoneThanks for the heads up! Yes I love being able to adjust the polar pattern, almost as a form of subtle EQ while recording. I figure the CM47FETce or CM48FET will hold me over till I get a CM47ve. The CM49 looks great also, so it is good to know you have been enjoying it so far. I have to unfortunately prioritize utility purchases at the moment such as a new patch bay and DB25 snakes, as well as building some more GOBOs and continue saving for a larger facility. Plus, it'll be nice having a U47FET style microphone where FET is called to opposed to a tube microphone I figure, for certain vocals, upright bass, electric guitar, and drums. I actually recently read the one thread, and they look badass! Still very much a beginner as far as DIY, but I will get there, sooner rather than later hopefully. About to start work on some CAPI kits now that Jeff just got a new batch of transformers, and I may even build a JLM LA500A or a pair of them, if I decide to go that route over a Serpent Audio Chimera. Also will end up with a Brute at some point, but that has a sound of its own, and isn't necessarily LA3A-ish. While the CM47FETCE is definitely a versatile mic, vocals is not it's best trick imho. In that price range, you may want to take a peak at the Roswell Mini k47. Good luck!
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Post by Vincent R. on Mar 3, 2017 16:01:27 GMT -6
mitchkricun have you used the mini K47? How is it? I've spoken with Matt a few times through Microphone-parts.com. I have one of the first modded Studio Projects C3s when they started offering to mod it for you. It's not quite a real U87, but it's a good mic to have around. I know a few people who speak highly of the K47.
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Post by mitchkricun on Mar 4, 2017 5:38:28 GMT -6
mitchkricun have you used the mini K47? How is it? I've spoken with Matt a few times through Microphone-parts.com. I have one of the first modded Studio Projects C3s when they started offering to mod it for you. It's not quite a real U87, but it's a good mic to have around. I know a few people who speak highly of the K47. Hi Vincent, honestly, I only heard it once but it sounded instantly familiar to a very expensive U47 clone that I'm very familiar with. I was very impressed. Hope this helps. Peace.
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Post by Vincent R. on Mar 4, 2017 10:11:32 GMT -6
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Post by aamicrophones on Mar 7, 2017 3:41:44 GMT -6
Hey Dave - thanks for being here! Question. Why are there not darker options available in both sdc and ldc? The number one complaint I hear is that more affordable mics are too brite, yet I can't think of a single one that some might consider darker. For my personal taste, I would much rather put that top in with my own eq than try to dig it out. Hi John, there's are a few dynamics involved. A good deal of "affordable" LDC and SDC microphones have capsules skinned with 3 micron mylar. You get a curve with 3 micron skinned LDC capsules that looks like this. The black line is a K47 type and the red curve is the C12 type. courtesy When you skin the capsule with 6 micron mylar you get curve like these below. This is our AK47 response This is our AK12 response You can see that the peaks and valleys with the 6 micron skinned capsules are not as steep as with the 3 micron skinned capsules. Once you get capsule that look like our curve then you select through them for ones that have the smoothes sounding response. A C12 would have a response very close to the AK12. Our capsule tend to be a db or two brighter at 12khz at the most as the design is more efficient. However, when you bring down the rise at 12khz with a capacitor by 3db it will bring 6khz down 1.5db and the microphone will sound darker than a C12 like the ELA M251. So, in our CM251 we roll out the high end just like in the original design while the CM12 with the same capsule and no HF bypass capacitor is true to the original C12 circuit. As a designer/engineer I also want to give the producer & musician everthing that the capsule can capture and let the producer/engineer limit the response. The CM251 is our only deviation from that mission at this time because its such a iconic microphone. However, just rolling 3db out at 10khz with a shelving EQ will give the CM12se microphone a darker sound more vintage sound as it will to a CM67se. I prefer to cut than boost but that's because I come from the days of tape where you never wanted to brighten a track from tape because it would bring up the tape noise. Although, cutting increases the headroom at the cut frequencies and boosting reduces the circuits headroom at the boost frequencies. I also come from the Legendary Roger Nichol's School of "Individual Microphone EQ is frowned upon". EQ does changes the phase so it should be refrained upon when possible. Although, having said that I am phasing the hell out of some drum tracks for an effect... but while doing that I have my engineer/producer hat on LOL. We have built custom Limited Editions were we change the HP filter switch for a LP filter switch that will give a Bright/modern curve or a Dark/Vintage curve. But again my preference is I would much rather duck 3db at 10-12khz than add it if I had a choice. In my experience of multi-track recording what often sounded right in solo, wasn't bright enough by the time we got to the mix. Now, if you couple a 3 micron skinned capsule into a transformless discrete or IC circuit; the rise in the HF response from the capsule will be more exposed and quite likely could fall beyond the realm of being able to be fixed with EQ. All our LDC FET microphones have transformer coupled Class "A" FET/discrete circuits because I think they sound warmer and more forgiving. Our most popular "POP" vocal microphone is the CM67se. The AK67 capsule has very little rise if any in the 3-5khz area compared to the AK47 but it has a 5db rise at 12khz. This capsule has the same hole pattern design as the Peluso CEK367 / K67 re-design by John Peluso and Verner Ruvalds which reduces the rise in the 3-5khz area. Then its up 2db at 6khz and continues to rise up to 5db at 12khz on average with the 67 head grill. Now, again we could reduce this rise with a capacitor or shelving EQ but I really like to have that sizzle available which is not "edgy or shrill". We made sure there was enough headroom in our circuit to handle this nearly 6db rise at 12khz. David Royer and believe that the TLM type transformerless IC circuit does not handle complex waves and transients as well as a tube circuits or Class "A" FET circuits. David showed me that the circuit didn't respond well when he applied a square wave to the input to the FET in a TLM103. I just got a TLM103 for reference and I am going to test that theory on my friends Yamaha C3 in the following weeks. I think the Shoep circuit performs better than the TLM transformerless IC circuit to my old ears. I prefer our AK47 capsule with the Shoep discrete transformerless circuit. The rise in a K67 or C12 type capsule is more exposed even with the Shoep circuit but this circuit can produce a more detailed response in some situations. However, some of the "affordable" versions use an exact copy of the original K67 used in the U67 and U87 microphones and the curve looks like this without de-emphasis. Neumann used de-emphasis (HF cut) in both the U67 and U87 microphones to tame the rise in the much easier to produce K67 capsule. If you build an original K67 version with 3 micron skinned mylar and use a transformerless circuit without de-emphasis YIKES!!!! It would be rather shrill in my experience. Now, changing the head grill will also effect the high end a db or two in LDC microphones. The difference between our CM47 with its AK67 capsule and 47 cylindral head grill and the same capsule with the 67 trapezoidal head grill is 2db at 10khz. So, the microphone will sound slightly darker if its a 47 type 6-micron skinned capsule with a tube/transformer circuit and the 47 style head grill. SDC's Microphones are a bit more difficult to get perfect. 1) We have experienced much more variations in the rise at 8khz between capsule with the 22mm pencil capsules. We rejected capsule with as much as a 9db rise at 8khz. Our Cardiod capsule that fits our CM1084 tends to be 2db brighter at 8khz than a KM84 and we have to discard about 15% to 20% of capsules to achieve this. However, the Super Card capsule has an almost identical response to the KM84 capsule but with a slight narrower focus. 2) The majority of affordable SDC microphones on the market use the Shoep transformerless discrete circuit. The Neumann KM184 uses a TLM type transformerless circuit. The original KM84 used a class "A" transformer coupled circuit identical to the U87 circuit without the pattern selector circuitry. In our CM1084 we use a Class "A" transformer coupled circuit identical to our CM414 without the pattern selector circuitry. I wanted to have the extra 14db of headroom so I can use the CM1084 on snare and toms. 3) The majority of the affordable pencils will have 3 micron skinned capsules and a transformerless circuit. Our capsules have 6 micron skinned diaphragm but we still get a slight rise at 8khz. We had a "rocket science" friend of our that actually works for Nasar designed us a resonator disk made on a 3d printer that smooths out the 8khz rise. We have sent two of these prototype cardiod capsule with the resonator disks to our friend in the UK who is an independent classical engineer and works out of Angel Studios. Angel Studios in London have 30-KM84's and on large Orchestral sessions will put one KM84 over each pair of string players. So, he will report back in a few week after he tries them on different sessions against the KM84's. Cheers, Dave Thomas aamicrophones.com
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Post by wiz on Mar 7, 2017 4:49:46 GMT -6
Great post!
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Post by stratboy on Mar 7, 2017 5:09:49 GMT -6
I agree. Thank-you, Dave!
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Post by Vincent R. on Mar 7, 2017 6:49:44 GMT -6
Thanks aamicrophones. You and Scotty have always been so cool about providing info on how you make your mics and answering questions. I own four of your microphones. Two are custom limited editions featuring more vintage sounding modes, my CM12 & CM67. Yup guys, I'm one of those customers. Lol.
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Post by iamasound on Mar 7, 2017 6:52:21 GMT -6
Absolutely a great post and one that explains the mechanics of tuning a microphone in a very straightforward and accessable way that even my half witted and addled brain could make perfect sense concerning this complex artform of manufacturing a capsule under discussion. My gracious thanks.
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Post by Guitar on Mar 7, 2017 8:05:30 GMT -6
Wow, great info.
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Post by Vincent R. on Mar 20, 2017 8:14:21 GMT -6
aamicrophones, I have to compliment you on your fantastic CM49. I've had mine for a couple of weeks now, and I've thrown my voice at it in numerous styles and had my sister, who is predominantly a jazz/ American songbook vocalist, record with it as well. Not only has it sounded excellent in all of these styles and sources so to speak, but I barely need to EQ it at all. It's pretty scary how good this microphone sounds. I'm really looking forward to hearing my wife sing through it. I think it may best your CM251 on her voice, and that shocks me. Frankly, on my voice it's pretty fantastic. While I love and prefer the 67 sound on my operatic vocals, for crooning or crossover work I think I'm leaning toward the CM49. Thanks ericn. You may have given me my new microphone obsession.....M49.
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Post by aamicrophones on Mar 20, 2017 13:14:38 GMT -6
Hi Vincent, thanks again for your wonderful comments. You are in great company!!! I got a call late last year from Erin Dickens one of the founding members of the Manhatten Transfer. Our good friend Wes Maube at RAK Studio in London is mixing her new album and he suggested she talk to us about buying a tube microphone to record the vocals in New York. After talking with Erin about the material she was recording and what she used on original Manhatten transfer tracks, we picked the CM251 and CM49. I sent both out to her and she and her engineer choose the CM49 for her voice on the new material. She returned the CM251 along with a sample pack of her incredible JAZZ SEASONINGS which we have been using non-stop in our kitchen. static.wixstatic.com/media/444e84_f7e14e242a4a47629f65a52e072aad49~mv2_d_1648_1482_s_2.jpg/v1/fill/w_528,h_487,al_c,q_80,usm_0.66_1.00_0.01/444e84_f7e14e242a4a47629f65a52e072aad49~mv2_d_1648_1482_s_2.jpg I think someone on one of these posts mentioned the microphone cables. We measured the capacitance between conductors on the cables we use and we could not find or measure any significant difference between the cable we use and Gotham cable or Mogami. Our 30' cable will just start to show some loss of the HF response up at 70 Khz with a 1500 ohm load (Neve 1073, John Hardy 990, AA MT8016, API 512). However, the Gotham cable has two conductors which are 20 gauge and the rest are 26 gauge. The 20 gauge are high currect conductors for the filament supply. The filaments of a 6072a draws 350ma at 6.3 volt. in our cable we use 24 gauge cable. However, the filament supply is held at 6.5v dc with a regulator in the power supply and the 26 gauge wire drops the filament .54 volts over a 30' cable. The filament voltage is specified at 6.3 volts A/C which means the voltage varies from 0V to 6.3v with 60hz AC 60 times a second. This means that 6.3v a/c would be equivalent to 5.8v dc. Which is closer to what we get with the .54 voltage drop across the 30' cable. In our new CM48T and the proto-type CM800T that we are just developing and have operating on the workbench today. The GE/JAN 5654w in these microphones draws 175ma or .175a so it will drop about .25v over the 30' run. The job of the filament is to heat the cathode up to about 2000 Celcius which allows the electrons to "run free" and create an electron cloud. These electrons will rush to the plate when the anode or plate has a positive voltage (plate voltage) applied. A small audio voltage sent to the control grid will control the larger stream of electrons flowing between the cathode and the plate when the cathode is referenced to ground and the plate is held at a high positive voltage. It takes real U47 about 50 minutes before the cathode gets up to 2000 Celcius because of the large wire wound resistor in the base of the U47 allowing the filament to slowly rise up. This is why the VF14 lived so long in this 1947 design. The filament of the VF14 in the original U47 is slightly under powered so that it takes the U47 about 50 minutes before the cathode temperature is optimized. With today's solid state regulation we can heat the cathode up to 2000 C within 2 minutes while still allowing the 6072a to maintain its full life expectancy. One of our design technologies is to use modern technology where possible without negatively effecting the "vintage" sound of our tube microphones. For, example we use capacitors and resistors with much higher tolerances than those components available in the 50's and 60's. We are also able to used solid stage rectification and regulation which was not available in the early days of tube microphones. These just allows the electronic specification of the circuit to remain much more consistent between individual microphones than the original circuits. So, all we hear today are variations in capsule types, capsule response, transformer differences and circuit types. Cheers, Dave
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