Vintage Audio Technology for the Modern Studio
TLM49 Conversion

TLM49 Conversion to DIY M49

TLM 49: Before and After

Since the introduction of the TLM49 I have been asked to perform numerous mods on them to transform the mic to be as close to an historic M49 as can be made.  My goal was to make a modified version that sounds, feels and looks like the original NWDR developed one, without breaking the bank.  I ended up gutting the vintage looking high tech innards and replaced it with a modern inspired version of the original design.

All that is needed is a TLM49, an AC701(K) and a long weekend full of mechanical and electrical work to get to a homemade M49 that works as good as a classic one. The final cost depends on the ability and skill of the do it yourselfer. Here is a short roadmap of what I did to get a TBM49.  Please be advised that modifying your mic will void the warranty and that if not done right you can kill yourself due to the high voltages associated with tube power supplies.  I STRONGLY advise that this is not a beginner’s project and that the cost spent is about half way to a real M49.  But if you heed those warnings seriously, what is left is a fun project that gives you a quality DIY mic along with the bragging rights when the job is finished.

This road map can be changed to utilize different tubes, transformers or circuits (original 49, b, c).  The pictures shown are from a couple of different mods.  I have built several AC701 versions (the only real way to get it to sound like an M49 should), but with tubes like the 5840 it will work in the spirit of an M49. For my AC701 build I used the AMI BV11a (the very early transformer original used for the MSC2 tube) and for the 5840 I used the AMI BV11R (the one that was used for the C version).

You should read through all of the sections below before considering or starting this modification!