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Author Topic: advanced audio microphones  (Read 7291 times)

trock

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advanced audio microphones
« on: July 14, 2008, 03:25:50 PM »

just wondering if anyone here has used them and what your experience has been like

sound quality? support? build quality etc??

http://www.aamicrophones.com/tube_mics/cm_47.htm

thanks
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maarvold

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Re: advanced audio microphones
« Reply #1 on: July 17, 2008, 11:33:15 AM »

If you're hoping this will be reminiscent of a 47, I have my doubts.  I've been auditioning 6072's lately and they definitely have a different 'thing' than the VF14/EF14 family to my ear.  That is not to say that the mic won't sound good.  
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Michael Aarvold
Audio Engineer

MI

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Re: advanced audio microphones
« Reply #2 on: July 17, 2008, 03:37:38 PM »

Tim,

My personal dealings with Dave in the past were great.
Although I have not tried his new mics.

A few years ago I bought 4 Apex fet mics from him.
He recomended a few mods that either he could do or I could
try some simple ones. I did and it helped the noise floor and
got rid of hiss. Anything more required total re-working of the
mic.

He advised he could tune the mic to a different response,
they are a little bright compared to a AKG 414.

I have some tests I did with Jean (bigbone) and those mics are
what they are (price/sound). I never bothered to do any other
mods because they're fine on some sources, and have other higher
end mics that suit me better (AKG, Neumann, Beyer, etc.)

If his own mics are designed by him, I suspect he's put in many
of the mods in already if not a totally different design.

Nothing to do with his mics, but also at the time I bought a
TEAC 80-8 from him, which turned out to be in better condition
than he said and worked without flaw.

Like I said this is personal dealings and he's a great person to
deal with. I beleive (IIRC) he used to work at Little Mountain
Sound (where Brian Adams recorded)in Vancouver so he's been
around and has experience.

Have a word with him, he's a nice guy.

Mario

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MI

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Re: advanced audio microphones
« Reply #3 on: July 17, 2008, 03:57:07 PM »

maarvold wrote on Thu, 17 July 2008 11:33

If you're hoping this will be reminiscent of a 47, I have my doubts.  I've been auditioning 6072's lately and they definitely have a different 'thing' than the VF14/EF14 family to my ear.


I must agree though, the Peluso CEK-367 capsule is a hybrid of
K-67 dual backplates & drilling pattern and K-47 size gold sputtering.

The new Peulso CEK-47 is a little more of a "copy" and a tribute to a real K-47
in terms of being a single backplate, drilling
(it looks like a copy - however machining can vary slightly)
and the gold sputtering size.

He uses a BV8 Tranny - describing it as a BV8 would suggest
use of a TAB tranny not a Cinemag, Tamura or similar.
The TAB is the closest thing to the original and probably the best choice.

I'm not sure about the tube choice however.

And as maarvold said,
Quote:

That is not to say that the mic won't sound good.


I agree.

Finally let's keep in mind the budget here...you can't compare a $850
mic to a $8000 mic is not in the same league.

Mario
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trock

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Re: advanced audio microphones
« Reply #4 on: July 18, 2008, 12:54:45 PM »

i emailed dave and he got right back to me with alot of details on the mics etc

so i was impressed with his rapid response and obvious love of what he is doing

i may be checking one out soon just to see what the deal is

the best acoustic sound i have heard from a modern mic was a wunder CM7-GT and am trying to get something like that if i can

thanks for the responses!
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aamicrophones

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Re: advanced audio microphones
« Reply #5 on: August 25, 2008, 08:55:55 PM »

Hi Guys, there are two reasons that the 6072 and the VF14 won't sound identical.  

The grid to plate capacitance is greater on the VF14 and this capacitance is multiplied by the gain of the circuit.   It is called the "miller effect" and the total effective capacitance together with the plate load impedance determine the 3db down point of the circuit in HZ.

The bottom line is the high end will roll out earlier with the VF14 vs the 6072 circuit.  They are both flat out to 20hz but the 6072 amplifier response will extend further out in frequency than the VF14 circuit.

Also, if you are lucky enough to have one of the original 200-U47 microphones the high frequencies will roll out even earlier because Neumann use a power transformer lamination which limits the high frequency transient response.

However, with our circuit the plate load impedance is much higher, the grid to plate capacitance is less and we use about 4db less gain by using the second half of the 6072 configured as a classic Blumlein cathode follower line driver circuit.    The cathode follower then drives the output transformer at a much lower output impedance.  There is only one additional resistor need to add the the cathode follower line driver.  Which, creates a bit more punch than a 6072 with a plate output circuit. This is a very "Hi Fi" circuit and one used by Universal audio in the LA2 and other "state of the art" tube circuits from the late 50's and early 60's.

The second reason is that the VF14 tube are notoriously microphonic, and on close vocals part of the tube is adding some extra harmonics back into the midrange.  
This is what gives them part of their distinctive sound on close vocals.  The 6072 is a later glass tube design and less prone to microphonics than the metal clad VF14.  The 6072 can be optimized to out-perform the old VF14.

I had two original U47 microphones during my tenure at Ocean and one did not sound like the other!!!  However, they both sounded good.  One was slightly more microphonic and probably the older of the two.

I recently had the chance to hear our circuit against a VF14 circuit with both a M7 capsule fitted and a CEK367 Peluso capsule.  I really couldn't justify spending the extra $450 on the tube and the difference between the Peluso capsule and a new M7 that came from a Gefell UM70 was very subtle.  The midrange of the PVC M7 was a bit more woody sounding and the CEK367 had one or two db more 12khz o 14khz than the PVC capsule.

The transformer we use are dual bobbin wound to the original blueprints.  They are within 1db of the original Telefunken transformers.  For example, our BV8 is flat down to 7hz and can handle +24dbu with less than 1% distortion.

It would only be possible to hear a subtle difference between the more expensive TAB output transformers and our dual bobbin transformers on something like a full grand piano or symphony Orchestra and it would be very, very, sublte.  One transformer is going to saturate at a little differerent frequency than the other.
 

We prefer the 5:1 BV11 to the Cinemag CM2480 that we were originally using.  The BV11 type transformer that fits our CM12 body has 3db more output than the stock transformer and will handle twice as much level.  The BV11 will handle +18dbu with less than 1% distortion.  The BV8 is larger and has the same ratio as the one in the U47 and will fit our CM47 body.

We will have more stock of our CM12 and CM47 tube microphone by late September once the testing is completed.

By late September we will have caught up to all our back orders  and have more tube microphones ready for sale.  We really appreciate our clients patience and understanding as struggled to get the new shop set-up.

We still can upgrade Chinese tube and some of the Chinese fet microphones for folks.  We have replacement capsules for the U87, U67, M147 and M149 or can have defective capsules re-skinned for you.

I just sold one of our CM47 microphones to Edan Everly and he was thrilled with it and used it to record his dad Phil a couple of weeks ago.

I am convinced our microphones have increased the quality of recordings and have done this for very good value.  Will they sound exactly like an original U47 or C12.  Probably, not but they do seem to sound very good doing the same chores.

Dave Thomas

www.aamicrophones.com









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trock

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Re: advanced audio microphones
« Reply #6 on: August 26, 2008, 06:41:53 PM »

see what i mean?

thanks Dave

I will be checking out a 47 soon!

thanks
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aamicrophones

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Re: advanced audio microphones
« Reply #7 on: August 29, 2008, 02:22:34 PM »

Hi Tim, I had two original U47 microphones during my tenure at Ocean but generally preferred the AKG 414eb on acoustic guitar.  

I like the AKG capsule or a good pencil in OMNI as they seem to yield a bit more of the pick sound on the strings which really helps the guitar cut through in a busy mix.  

I have a couple of local guitar virtuosos who really like our CM54 in OMNI on acoustic.  Using OMNI with any really good microphone eliminates the proximity effect.

I am not sure if I would pay $3500 for an acoustic guitar microphone.  I would think that a bigger improvement to the sound would be to put the $3500 into finding a marvelous sounding guitar.  We had a wonderful Martin D35 that my partner owned at Ocean and I think it was the main contributor to a great guitar acoustic guitar sound.  The U47 and the Martin were bought in the late 70's for less than $2000 but gas was less than $1 per gallon.


Cheers, Dave Thomas

www.aamicrophones.com
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