The 47 Upgrade
Above is the FAR 47 Long Body that we use to prototype our circuit and capsule combinations
*** This just in! *****
We have a small quantity of these u47 look alike microphone packages. They come with the retro power supply, deluxe shockmount and aluminum flight case.
We can trick them out in the ways described below. There is lots of room inside this microphone so we can use large transformers. The AMI BV8 Classic Replica is inside our personal model. You can also ask for the Cinemag 2461 which has seriously extended bass response and slightly warmer sound on the extreme top.
The look alone takes your studio to a new level and the sound will tell the real story on your tracks.
Email and ask us for details today.
Here is a sound sample of our FAR 47 with a Thiersch M7 Capsule, 6922 triode circuit and the AMI BV8 transformer.
The 47 Upgrade is based on the sound of famous u47 Microphone, sold by the original Telefunken company and it looked very much like the microphone shown above.
The original u47 has been a part of the music industry since it first arrived on the market in 1947. Its unique sound quality has been used to good affect by Frank Sinatra, a group you may have heard of named the Beatles and countless others.
This is a more mid-range sounding microphone with a solid bottom end. The u47 also has a delicious *proximity effect.
It is the defacto standard for recording solo vocalists but it works with almost anything. You can find out more about the original u47 at this excellent web site.
*Proximity effect is a rise in bass response that ocurrs with a cardiod microphone, as the sound source gets close to microphone.
Update for 2014
We are consolidating some of our designs to simplify ordering a FAR 47 microphone.
Our primary upgrade path for the FAR 47 will begin with the NADY 1050 microphone. From that platform we know you will be getting a professional quality package with shockmount, power supply, cables and flight-case.
Of course you can always give us your microphone to modify and we will customize the job to make it all work.
The Capsule Shapes the Sound
The capsules that come with many overseas microphones are completely incorrect to create a 47 sounding microphone. They typically are a K67 design which has a response that looks like this:
Bass .................................. Mid-range ............................ Treble
The graph is calibrated so the 1K point in the middle is the reference level.
Notice the weaker Bass response at the 100 point. It should be at 0 or a little higher on graph. And in the microphone world 1dB (decibel) of difference is enough to make you say I like it or I don't like it.
You can also see the extreme lift in the Treble frequencies (10K point and above). Together these two characteristics make your microphone sound thin.
Dont' get me wrong, this high end lift is correct for a K67 design, but it requires a special equalization circuit inside the microphone to flatten the response. This is what is done in a u67 or u87 mic that uses this type of capsule. It is not done in a 47 design.
We replace the stock K67 styke capsule with a centre terminated K47 capsule similar to the one used in the later version u47s.
Currently our top quality capsule is the Peluso P K47, Gold sputtered 34x14 mm, 6 micron, dual diaphragm capsule shown below. We have some other suppliers in research phase at the time of this writing.
For budget reasons we can also use an RK47 capsule, 34mm diameter with 3 micron diagphragm, which has as very similar response but costs less. It also tends to be a touch warmer sounding than the P K47.
Notice how different the K47 response is from the K67 in the graph below.
The K47 capsule creates a slight lift in the upper mid- range that adds a unique "grit" to the sound and it rolls off gently above 11Khz for that "vintage" sound.
Upgrade the circuit...
After correcting the capsule we need to fix the circuit. There are some options we provide to help match your budget.
Option 1: The 47 BASIC Upgrade
The simplest, lowest price option is simply to fix the problems with the existing circuit. This is VERY effective since there are some fundamental things wrong with these low cost microphones. We leave the circuit configuration as is (2 triode CCDA circuit) but we do some simple circuit mods that severely reduce the harmonic distortion. The reduction is typically from about 4% before modding, down to 0.5% after the mods! This difference is critical to making a professional sounding microphone.
Add a New Tube...
One of the changes, is installing the correct tube. This is not the secret sauce some people think it is but with the right circuit changes it's part of the sauce.
We change the 12AX7 guitar amplifier tube, that came with your microphone for a 6072 vacuum tube. We hand test our tubes to make sure they have the correct gain, frequency response and most importantly meet our low noise requirements.
And the Transformer?
In the case of some microphones, and the Nady 1050 is one of them, we must change the transformer. Some overseas designs have a notch filter in the transformer that reduces high end response. This cannot be used for a 47 style microphone. For the 47 BASIC we have a Chinese made transformer that performs very well and has flat response from 20Hz to 35KHz.
Note about modding your mic:
If you send us your mic for a 47 BASIC upgrade and we find that it does not need a transformer we will not change it. This saves you money.
Option 2: The 47 Special Edition
The next level upgrade is to re-wire the circuit to come closer to the u47 circuit. This means using a single stage "plate follower" circuit. This is a lower noise circuit and adds a special transparency to the sound. We use the same tube, the 6072A but it is wired completely differently. We have researched a way to wire the 6072 so that it's output characteristics are closer to the old tube used in the u47. It's called "parallel triodes" and it increases the output power that the circuit can generate. We do it by simply connecting both triodes inside the 6072 bottle together so they function like one tube with twice the power handling. This configuration lowers the output impedance by 50% getting it closer to the old VF14 output impedance.
We also implement a fixed bias voltage circuit which extends the low end response.
By switching to this parallel triode mode we get to keep the lower noise and transparency of a single triode circuit.
We also swap out the transformer for a special little unit we had made by a USA Transformer maker. This little transformer was chosen to give you a solid low distortion bottom end and a vintage sounding high end.
Our custom wound transformers were selected to create a big sound in a little package.
Option 3: The 47 Custom Edition
Big IRON at it's best. The NADY TCM1050 fitted with the CM-2461
Hands down our most successful 47 style mic is shown in the photo above. This mic combines the large Cinemag 2461 transformer with what we feel is the best modern triode for the job of replacing the veneral,old and extremely expensive VF14. That tube is the ECC88/6922.
In the 47 CE we wire up a single triode in a replica u47 circuit.
Here is a voice recording done at Four Legs Records, proud owners of a FAR 47 Custom Edition with a Peluso capsule and the CM-2461 transformer as shown in the photo
Big thanks for Steven Goldman at Four Legs Records for making and publishing this demo
Why the ECC88/6922
One of the characteristics of the u47 was a low ratio 6:1 transformer. What this means is that the tube must do much more work to drive that transformer and to do that it needs low output impedance. The 6072 in a common circuit has an output impedance of 20,000 ohms. The ECC88 has an output impedance in a similar circuit of only 2,500 ohms. To be fair in the very low current circuits used in tube mics it is probably closer to 3500 ohms, but that happens to be very close to our estimation of the impedance of the VF14 in the u47 circuit.
The ECC88/6922 at low currents also creates some of the compression we expect from 47 style microphone.
And last but not least is very low noise and distortion.
So although many people have tried using other Pentode tubes wired as triodes, we feel the ECC88 gives us a great tube for the job at a reasonable price.
Maximum Respect
To be the most accurate to original u47, we can remove the multi-pattern feature of the circuit and make a cardiod only version of this microphone. This is how the u47 was connected. The diagphram of the capsule connects directly to the tube input. Nothing is connected to the back of the capsule. Pure and simple design.
We Measure the Improvements
All Fox Audio Research microphones are tested for electrical and acoustic characteristics and you get the published results of the testing. The same rules apply whether we provided the microphone or you sent us one to upgrade.
And your ears will tell you the real difference the moment you lay down your first track.
FAR 47 Sound Examples
These examples were recorded simultaneously using four microphones.
You can hear all the files on one page here.
The tracks below were recorded direct into our Presonus Firestudio project. The DAW was Logic Pro 8 and the sample rate was 44.1Khz. No compression or EQ was used.
A common complaint with some low price condenser mics is call the "eshy" sound.
This recording demonstrates the "S" sound in the FAR 47.
FAR 47 Custom Edition
Female vocal by Lisa Braid (New Zealand) Recorded with compression, no EQ on a FAR 47 Custom Edition built in the SE Electronics "ICIS" microphone body.
Lisa Braid on the FAR 47 with 6922 tube and AMI T8 transformer
Tommy Read sings White Christmas on his FAR 47 CE
Voice Artist examples:
Male announcer at 24 inch distance
Male announcer at 5 inch distance
Graeme Spicer using a FAR Modified AA CM-47, Q47 capsule
Acoustic Guitar Example
This guitar was recorded about 20 inches in front of the guitar with the mic above the height of the guitar.
To get a quote for your 47 Upgrade
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