03-03-2018, 12:15 AM
That’s excellent to hear, Mitch! The exact value will depend on your power tube tolerences, of course, so happy experimenting! The lows those caps pass are well beyond human hearing range, so at least your local dogs might thank you for the cap swap, lol. To make sure the lows you “do” hear aren’t cut, try to stick as close to “.1’s” as possible, try “.047’s” even. What really matters in Ampegs, especially the V-series, is that amazing preamp and the output transformer. All Ampeg output transformers, up until a certain era, were designed to output down to 40hz. All of their RMS ratings are based on measuring at 40hz. This quick and easy cap mod will also save your speakers from blowing prematurely, as those same unheard frequencies plague your speakers integrity as well.
As far as recommending tubes, I’ve never had good experiences with new 7027’s. Failure after failure a few years ago, haven’t tried or recommended them since. Of the nine V-4’s that I personally own, I think three or four of them have either groove tube or svetlana 6L6’s, the rest have USA 7027’s. Plus I was able to set aside about five USA 7027 quads for future needs ; ) Just avoid 5881’s or any 6L6 that’s actually a 5881 and chinese tubes and you should be ok. The Russian 6L6 (any brand) seems to hold up ok in there with a typical tube failure as often as a Marshall with EL34’s. Just be sure to adjust R49 appropriately. I usually just put a trim pot in series with the 75k to make biasing easier. The Tung-Sol reissue 6L6 is my next test for V-4’s, I’ll let you know how that turns out.
I’m glad I was able to help! You deserve some credit yourself, Mitch! You stuck to the thread with good observations and ultimately helped to clear a few things up. That type of communication serves this forum justice.
As far as recommending tubes, I’ve never had good experiences with new 7027’s. Failure after failure a few years ago, haven’t tried or recommended them since. Of the nine V-4’s that I personally own, I think three or four of them have either groove tube or svetlana 6L6’s, the rest have USA 7027’s. Plus I was able to set aside about five USA 7027 quads for future needs ; ) Just avoid 5881’s or any 6L6 that’s actually a 5881 and chinese tubes and you should be ok. The Russian 6L6 (any brand) seems to hold up ok in there with a typical tube failure as often as a Marshall with EL34’s. Just be sure to adjust R49 appropriately. I usually just put a trim pot in series with the 75k to make biasing easier. The Tung-Sol reissue 6L6 is my next test for V-4’s, I’ll let you know how that turns out.
I’m glad I was able to help! You deserve some credit yourself, Mitch! You stuck to the thread with good observations and ultimately helped to clear a few things up. That type of communication serves this forum justice.