The Telefunken AR70
Review by Fox Audio Research
A customer from Canada had purchased a Telefunken AR70 Stereo microphone and wanted to take it up a notch or two. They contacted Tim Campbell of Campbell Transmitters in Denmark to order a pair of Tim's delicious CT12 capsules. The customer asked Tim if anyone in Canada could install the capsules our name came up.
I was great to get this mic into the shop. This microphone retails new for something on the order of $3 000 in Canada. We don't get that kind of price point in here very often.
The AR70 gives the appearance of being a new version of the legendary AKG c24. The c24 had two capsules like the AR70 and the top one could be rotated independantly of the bottom capsule, just like the AR70.
It's close but it is not quite the whole package. Where the c24 had full multi-pattern control of both lower and upper capsules, the AR70 is a fixed Cardiod mic on the bottom while the top capsule is fully multi-pattern. You can see that clearly from the single control on the AR70 power supply below.
You might ask why would they not finish the job and provide both capsules with multi-pattern control. It's pretty simple really. The AR70 is built on the AR51 chassis. The means it has the standard contemporary seven pin XLR connector in the base of the mic. With only seven pins there is just not enough connections to finish the job. But it turns out the AR70 is a very reasonable compromise providing all but the most exotic stereo recording technique.
Stereo Recording ModesThe c24 could be used for three different stereo techniques:
- X-Y stereo: 2 cardiod mics offset at an angle
- M-S Stereo: 1 cardiod mic + one figure 8 mic at 90 degrees
MS Stereo explanation
Blumlein Stereo: 2 figure 8 mics offset 90 degrees
You can see that the AR70 can do number 1 and number 2 above, but it cannot do Blumlein. If you really need that then just buy two AR-51s available now as stereo pairs or... buy two of our c12+ mics!
What We Found
The AR70 is based on the AR51 microphone. The circuit boards actually say AR51 but there are two of them. The circuit is NOT the same as the AKG c24. There is no input cap which is the way a u47 capsule is wired. There is nothing wrong with that and it saves space!
Also there is no EQ cap like that used in c24. The EQ cap is NOT a decoupler as some writers on the internet have alluded, but rather it provides EQ that reduces the extreme high end response of the microphone to warm the sound slightly.
Other than that there were no surprises... on the surface.
The Preamp Performance
As with all my upgrades, I measure the mic when it arrives. The owner had tried to change the tube to a NOS AMPEREX 6072, to try and make it sound better. We all know here that that is not the solution.
But besides the tube change, I was VERY surprised at what I found. The internal preamps had a very weird response!
Now this did not look right at all. This is not like the AR 51.
So I had to open things up to find out what was wrong...
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