mikebse2a3 Posted July 11, 2014 Share Posted July 11, 2014 Optimum bias will depend on voltage drop across the output tube as well as many other design factors. If Jolida suggest running the bias at 20ma instead of 30ma and you like the sound and output power is sufficient for your needs then your good. miketn Quote Link to comment Share on other sites More sharing options...
NOSValves Posted July 12, 2014 Share Posted July 12, 2014 I honestly think it would be hard to figure out which Jolida you should contact or believe with a 10 year old amp with the current state of the two Jolidas... I say 20 mA is on the cool side for any and all EL84 amps that I have worked on which is countless.... many are at least 25 mA and most are 30mA... Quote Link to comment Share on other sites More sharing options...
NOSValves Posted July 12, 2014 Share Posted July 12, 2014 Why would you put any of that over prided/hyped craps in your garage when the real deal is right in front of your face by the way my very best system in in my garage/shop...most folks that hear it become life long customers/believers... I put the "over prided/hyped craps" in the various systems inside the house and I use the "cheap Chinese POS" in the garage. Works for me, YMMV. Man, a fellow needs some thick skin around here, lucky for me I have it. I just run the stuff, I didn't design it.... Wow how refreshing someone that can take a joke!!! My hat is off to you.... Quote Link to comment Share on other sites More sharing options...
NOSValves Posted July 12, 2014 Share Posted July 12, 2014 Why would you put any of that over prided/hyped craps in your garage when the real deal is right in front of your face by the way my very best system in in my garage/shop...most folks that hear it become life long customers/believers... I put the "over prided/hyped craps" in the various systems inside the house and I use the "cheap Chinese POS" in the garage. Works for me, YMMV. Man, a fellow needs some think skin around here, lucky for me I have it. I just run the stuff, I didn't design it.... yep I've got some of those "over prided/hyped craps" too. Some Quicksilver Horn Monos. I also have a BBX Extreme with Cream and the delectable new Maxim Mods that I have dubbed the NBS Killer good luck when it goes up in a fire show please report back.... Quote Link to comment Share on other sites More sharing options...
russ69 Posted July 12, 2014 Author Share Posted July 12, 2014 I honestly think it would be hard to figure out which Jolida you should contact or believe with a 10 year old amp with the current state of the two Jolidas... I say 20 mA is on the cool side for any and all EL84 amps that I have worked on which is countless.... many are at least 25 mA and most are 30mA... I have an early one before all the probems with the "two Jolidas". I talked to the same people that the amp came from back in the day. I'm thinking 25mv might be a good number for my usage. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted July 12, 2014 Share Posted July 12, 2014 Russ if you are adventurous you are welcome to contact me some time with some photos of the actual amp under chassis and we can take some critical measurements and figure it out for sure. Just wait until the dead of winter when I have more free time and we can get to the bottom this without hearsay... It will be rather simple. Quote Link to comment Share on other sites More sharing options...
russ69 Posted July 13, 2014 Author Share Posted July 13, 2014 Russ if you are adventurous you are welcome to contact me some time with some photos of the actual amp under chassis and we can take some critical measurements and figure it out for sure. Just wait until the dead of winter when I have more free time and we can get to the bottom this without hearsay... It will be rather simple. Thanx. Quote Link to comment Share on other sites More sharing options...
russ69 Posted July 16, 2014 Author Share Posted July 16, 2014 I didn't like the JJ tubes (too soft/loose bass) so I installed some Mullard re-issues. I like the construction and the sound of the Mullards, seem like quality tubes for the price. I pulled a number out of my butt and biased the new tubes at 22 mv, thinking 10% over factory recommendation sounded reasonable. I'll save the re-engineering for another day. Being a retired engineer, the operative word is RETIRED! Plus I have a dozen other projects going right now. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted July 17, 2014 Share Posted July 17, 2014 Retired...one can only dream! Quote Link to comment Share on other sites More sharing options...
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