MatthewF
Well-known member
Hi all,
It's been a few years since I've been around this way, been spending more of my spare time writing and playing recently! That has, however, finally brought me around to finishing this mic so I could enjoy recording my work with some proper home grown equipment!
So, here is my attempt at a U47 inspired DIY mic. The body is from Skylar's 1st run of EQU47s and the capsule is from Dale's 2nd run of M7s. Having purchased one of Max's BV08C output transformers, I laid out a small PCB to carry the trafo and a few of the passives. The final element which took a while to source was the valve; Rodabod and I bought a number of NOS EF14s and burnt them in with a purpose built PSU. After assembling the mic, each valve was tested for noise and microphonics and the best example selected for use here. The photos and comments below offer a little more detail (click on the thumbnails for hi-res images). This is probably the longest running project I've embarked upon - I bought the capsule from Dale in Jan '09!
First of all here's a quick sample of how it sounds (recorded through a JLM Baby Animal preamp, no further processing applied):
https://www.dropbox.com/s/5c9gxjkw0qe00bg/Mic%20Check.wav
Here's the initial assembly with Max's transformer mounted on the PCB, along with some passive components, and the output coupling cap (a Russian PIO part) mounted behind the board:
I built the high impedance part of the circuit on phenolic board using PTFE insulators. The pattern switching arrangement is as per the original U47 schematic, but executed with a relay.
Next up is the valve base and a few nearby resistors. The rubber band mounting ring is a piece of inner tube from a downhill mountain bike. If you go down this route be sure to get a proper downhill race type tube - they're larger diameter and much thicker walled than a normal bicycle inner tube!
Now it's time to install a valve! The smaller steel bodied Telefunken unit is a more comfortable fit than the RFT part...
The PSU comprises a heavily filtered and regulated filament supply, which is also used to derive the bias voltage. The B+ is a straight forward CRCRCRC affair. Getting the grounding scheme right proved crucial in getting this mic operational. The lovely PSU case was made by GrandMasterAudio.
The finished piece, sans outer shell and headbasket, from both sides:
And finally, this unit gets a feel for how loud I like to play guitar
Massive thanks goes to Dale, Skylar and Max for the incredible amount of effort they invested in recreating the key components of the U47 to make a build like this possible. Thanks so much guys!
Matthew
It's been a few years since I've been around this way, been spending more of my spare time writing and playing recently! That has, however, finally brought me around to finishing this mic so I could enjoy recording my work with some proper home grown equipment!
So, here is my attempt at a U47 inspired DIY mic. The body is from Skylar's 1st run of EQU47s and the capsule is from Dale's 2nd run of M7s. Having purchased one of Max's BV08C output transformers, I laid out a small PCB to carry the trafo and a few of the passives. The final element which took a while to source was the valve; Rodabod and I bought a number of NOS EF14s and burnt them in with a purpose built PSU. After assembling the mic, each valve was tested for noise and microphonics and the best example selected for use here. The photos and comments below offer a little more detail (click on the thumbnails for hi-res images). This is probably the longest running project I've embarked upon - I bought the capsule from Dale in Jan '09!
First of all here's a quick sample of how it sounds (recorded through a JLM Baby Animal preamp, no further processing applied):
https://www.dropbox.com/s/5c9gxjkw0qe00bg/Mic%20Check.wav
Here's the initial assembly with Max's transformer mounted on the PCB, along with some passive components, and the output coupling cap (a Russian PIO part) mounted behind the board:
I built the high impedance part of the circuit on phenolic board using PTFE insulators. The pattern switching arrangement is as per the original U47 schematic, but executed with a relay.
Next up is the valve base and a few nearby resistors. The rubber band mounting ring is a piece of inner tube from a downhill mountain bike. If you go down this route be sure to get a proper downhill race type tube - they're larger diameter and much thicker walled than a normal bicycle inner tube!
Now it's time to install a valve! The smaller steel bodied Telefunken unit is a more comfortable fit than the RFT part...
The PSU comprises a heavily filtered and regulated filament supply, which is also used to derive the bias voltage. The B+ is a straight forward CRCRCRC affair. Getting the grounding scheme right proved crucial in getting this mic operational. The lovely PSU case was made by GrandMasterAudio.
The finished piece, sans outer shell and headbasket, from both sides:
And finally, this unit gets a feel for how loud I like to play guitar
Massive thanks goes to Dale, Skylar and Max for the incredible amount of effort they invested in recreating the key components of the U47 to make a build like this possible. Thanks so much guys!
Matthew
