WA-251 full upgrade

We are proud to offer a full upgrade path to the WA-251, once again this is an upgrade where you send in your WA-251 tube microphone, 7 pin cable, and power supply. We fully rebuild the system to the highest standard we can, end to end, and we cover return shipping back to you via UPS GND/Signature Required.

Microphone:

This comprehensive upgrade makes the microphone all it can be. The factory voicing that this mic shipped with was, to us, very scooped, dark, and muddy. almost a rich chocolate when in this rare case vanilla was what was called for. Some folks over the years have actually liked the 'accidentally 'fat' voicing that the mic has as a specialty for certain vocal styles, and I can appreciate that. I say to those customers, just enjoy the mic for what it is and skip getting this mod. We try to preserve some of that but try to get the voicing back where it should be for a 251: a subtle top lift while remaining neutral everywhere else. Low mid and bass are well represented, but not accentuated. We make it sound far more expensive than it is, and rebuilt it to last a lifetime.

PSU:

Steel washers added to reinforce the channel frame of the mains transformer.

All electrolytic capacitors replaced with highest performance/longest life Nichicon and Panasonic parts

Full film capacitor/multilayer ceramic capacitor bypassing on all electrolytic caps

Special adhesive put down on all capacitors and on the regulator heatsink to eliminate any vibration/microphonics/parts coming loose over time

Entire board re-flowed, cleaned, all wire terminations stripped and re-soldered, wire lengths and ground paths shortened where possible. Ground plane enhancement to the PSU board's ground plane to lower impedance to ground.

Fuse and LED lubricated, re-seated, bulb housing reinforced.

Regulator for filament voltage is briefly removed so that thermal paste can be added to the heatsink bond, then re-installed and tightend in. 'Corrective' diode is removed and bypassed with a solidcore jumper to set regulator voltage to 6v opposed to 6.7v, which was overheating the tube and also probably stressing the regulator. In realworld measurements, this sets the heater voltage to about 6.1v, which is far closer to the specified 6.3v and always better to slightly underheat than overheat the tube. This will extend tube life and help with thermal control also.

Full solder re-flow on all board components, key wiring is replaced or re-done, tidied up.

Microphone:

If applicable, the capsule mount is replaced with a less resonant capsule mount (as needed).

Capsule mount and saddle are replaced as needed with higher grade/low resonance parts (as needed, because some units are OK and others need these parts to be replaced).  

Stock tube is replaced with a 12AY7 tube that we install, which is graded for low noise/low microphonics, which will be either new production EH or TAD tube, or NOS JAN tube.  If we use a new production EH or TAD valve, it is third party tested to be microphone grade.  If we use a NOS tube, we personally clean/de-scale the tube and perform a listening test to grade for low noise/low microphonics.  The original tube is returned in the return packaging, and is a suitable spare tube as long as it was in working order when it arrived to us.

Tube is fitted with an aerospace silicone pad to reduce microphonics and create a thermal barrier between the tube and output coupling capacitor. Tube pins are lubricated with DeOxit Red before insertion.

Microphone board is cleaned up and reflowed, every component. every solder point. tantalum capacitor is replaced with an over-spec'd Kemet tantalum part. Incorrect value (3.9uF) output coupling capacitor is replaced with correct value (3.3uF) axial film capacitor. We use either a JB Audio grade or Cornell polypropylene axial film part. The capacitor is wrapped in Kapton tape to act as additional thermal barrier, in addition to a Kapton film sheet that separates the tube backside of the PCB to the front side.

Ground wire added to chassis and, if needed, both ends of the yellow painted body tube will be lightly sanded from the inside with emory cloth to enhance ground conductivity.

Cable:

Cable is rebuilt on both ends to ensure quality and reliability, putting heaviest gauge wires on heater+ and heater ground where they are the most effective, and stripping back the jacketing and woven shield only to the bare minimum needed, to ensure proper RF rejection and cable durability.

System:

Microphone is burned in for 24 hours then re-calibrated, and re-tested with the same 7pin cable attached that it will ship out with.