R/E/P > Klaus Heyne's Mic Lab

Is there a Replacement for the Telefunken AC701k?

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klaus:
Not sure what you mean by "replacement" tube, because I am unaware that there is such thing.

The AC701 is unique- it was made by Telefunken specifically for condenser mics offered by three companies only. Any mic originally designed to be powered by that tube will either not work with a substitute tube, will need to have circuitry, cable or power supply modified to even function, and if these hurdles are overcome too, none of these mics will ever sound the same as those with the original AC701.

But I understand the temptation; when a tube costs a lot of money, people will search for, and suppliers will offer supposed substitutes.
That path and its poor results are amply demonstrated in the field of capsules: sourcing Neumann and AKG capsules has become expensive, so it is tempting to be lured by aftermarket "reskinning" offers. Never mind the inevitable loss of value or sound quality.





blackacre:
There are a few options marketed as drop in replacement tubes that don’t require circuit or power supply changes.

Drefahl Audio and Phaedrus Audio both make drop in replacements that I considered as a back up if only because even after finding an AC701, and spending a lot of money, the tube may not work, let alone be up to spec.

At this point we may be approaching the end of the era of these microphones as they were originally built. Unfortunately my M49 had an M7 capsule that is also shot like every other m7 at this point. Tom is going to switch to a K47 and I am going to frame the M7 in a display case.

Thanks for all your perspective and experience.

klaus:

--- Quote from: blackacre on November 14, 2021, 02:51:09 PM ---There are a few options marketed as drop in replacement tubes that don’t require circuit or power supply changes.
Drefahl Audio and Phaedrus Audio both make drop in replacements ...

--- End quote ---

Let's be clear: these are transistorized solid state devices that try to emulate the sound of tubes.

blackacre:
So, not a tube, despite marketed as a tube. Frustrating.

Spindrift:

--- Quote from: blackacre on November 14, 2021, 07:21:05 PM ---So, not a tube, despite marketed as a tube. Frustrating.

--- End quote ---

You have a mic which is probably pushing northward of $15,000 in value. I wouldn’t bat an eye spending upwards of $1000 or a bit more for a NOS AC701 tube from a reputable source. Devaluing your vintage Neumann with an aftermarket “tube” is illogical.

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