boroman Posted November 25, 2020 Share Posted November 25, 2020 13 minutes ago, Chimike said: In the right circumstances, a well maintained 60's B15 is just such a joy to play. Was never designed to go up against Marshal stacks ! Mine hums a bit , at the 'mo, so I need to check it out, but I use it's little brother, the SB12 at open mikes with acoustic guitars. I have put a deltalite in the cab, so the efficiency helps. Just Magic ! I do have other amps, if I need more volume ! Horses for Courses. And there are modern clones available, if reliability is paramount. If you'd ever need re-cap, preservation, retube or repair of SB12, B15N, let me know. I have worked on like 30+ of them... Still have three on my workbench right now. I always dig more 68-79 era, with thiele cabs and square magnet CTS/Eminence speakers, but it's just my personal opinion... I've gone throught single baffles, double baffles, custom "factory upgrade" speakers (JBLs, Altecs etc). Of course a lot off bass players come to my place and they'd choose the early ones, etc. They all do have the same soul, and they all sound quite about the same close mic-d. Difference is usually in the open space Quote Link to comment Share on other sites More sharing options...
Reggaebass Posted November 25, 2020 Share Posted November 25, 2020 2 minutes ago, boroman said: I have worked on like 30+ of them. Do they require a lot of maintenance boroman , or once they are set up are they good for years Quote Link to comment Share on other sites More sharing options...
boroman Posted November 27, 2020 Share Posted November 27, 2020 (edited) On 25/11/2020 at 21:02, Reggaebass said: Do they require a lot of maintenance boroman , or once they are set up are they good for years I'd say good for years. They key to the sound is to find one with original speaker and original output transformer. What absolutely needs to be done for safety, great sound and reliability is - - re-cap all the power supply - clean and preserve potentiometers - remove "death cap" (can kill you someday, no joke!!!) - replace bias cap and put variable resistor for precise bias setting (on fixed bias amps) - install 3-prong grounded power cable, remove polarity switch wiring - cut the high voltage "protection" circuit from speaker cable (causes hum, can kill your speaker and output transformer, can shock you with +450V) Other things worth doing (if needed): replace the seal between cab and head, re-fit the speaker frame, clean or re-cone the speaker, change the speaker cable to 1/4" connection and good speaker wire What you should NOT do - change caps/resistors in the signal/channel circuit - they have their own sound we do love. And 99,99% times they don't need replacing. Also, don't put 6550 tubes and stuff like that, you'd kill the OT. Edited November 27, 2020 by boroman 2 2 Quote Link to comment Share on other sites More sharing options...
boroman Posted November 27, 2020 Share Posted November 27, 2020 (edited) @Reggaebass EDIT: forgot about one VERY IMPORTANT thing. It's a must to replace the damping material inside the cab. It's very dangerous for health (its "particles") not to mention it will mess with speaker too. Replace with foam that has qual damping factor to the factory "wool". It only needs a bit of damping. Not much. Too thick/too heavy and will mess with cab overall capacity. These all things should be done when you're serious about B15N performance. Edited November 27, 2020 by boroman 1 1 Quote Link to comment Share on other sites More sharing options...
Reggaebass Posted November 27, 2020 Share Posted November 27, 2020 35 minutes ago, boroman said: These all things should be done when you're serious about B15N performance. Thanks very much boroman such great knowledge 👍 1 Quote Link to comment Share on other sites More sharing options...
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