The Sterling ST69 is becoming our #2 seller, behind the Warm Audio WA-47 mod/upgrade, and we have a lot of fun doing them. The ST69 is really a diamond in the rough, and when a good specimen is fully modded, I truly feel it has the charm and beauty of mics costing many thousands of dollars. But the quality these arrive to me in is sometimes hit or miss.
The reason I have not gone 'all out' in replacing all capacitors on this mic in the past, as I do with the WA-47; is that more often than not, what's been in the Sterlings has been pretty good. Sometimes they have good 6205 subminiature valves in them and sometimes they have the Groove Tubes re-branded 6205's that I find a bit muddier, or sometimes even unusable due to noise. Sometimes they have Rubycon capacitors (or a well made counterfeit), and sometimes they have pretty generic stuff. They always have a poor 33pF Mica cap in the feedback section that I replace with a superior and higher rated silver Mica part when it is already out (which is often), but otherwise leave it alone. What I've always focused on with these, thus far, is the re-voicing: fixing the capsule design and removing the disc resonators, replacing the transformer, and replacing the WIMA cap in the high-Z section with a really good Polystyrene. Of course, I also added a chassis ground connection to both the mic and the PSU for improved ground contact, among other tweaks.
But, in the interest of consistency and because I really do feel this mic deserves to be brought out to the absolute fullest potential that it has; I want to announce that, going forward, it's going to be given an even more intensely thorough upgrade. I have finally spent the time to source out everything and so from now on, any ST69 upgrades sent in will have EVERY electrolytic capacitor replaced (PSU and mic) with the most long life/high temp/high performance Panasonic or Nichicon parts, will ALWAYS have both the MICA capacitor upgraded and the high Z capacitor upgraded, will have the capsule replaced if the capsule is bad (we stock the original Frank He 3 micron K67 now that it was designed with), and will have the tube replaced with a military spec NOS JAN RAYTHEON 5840W that has been pre-tested for me if the stock tube 'so much as looks at me wrong' LOL. If the stock tube is perfectly fine, I won't change it; but if I think that it is in any way deficient in regards to tone or noise, it will get changed. Because the 5840W tubes I have in stock sound exceptionally good in that microphone, smooth and well balanced and very low noise... so from now on, I will consider those tubes the benchmark in which the stock tube has to live up to.
This way, there will no longer be any inconsistency in the performance of this mod based on inconsistencies in the mic's initial production. Every one I do from here on out should come out the same, and be the best that it can be.