Tweet
I played a gig on Friday night and was extremely disappointed in the performance of my 71 Deluxe Reverb. This was only the third gig in a year played with this amp. One was outdoors, in a backyard, and it was great. I had it up to about 4.5 on the volume knob, great breakup, and loud enough. I rehearse with this amp weekly and it's always been great.
So... Friday night, during soundcheck, everything was fine... empty room, 20 foot ceiling, so I figured things would change when it filled up... figured I'd have to turn it up and add some treble. But after we started, with a room full of people, I turned it up to about 5.5 (I've done this before, knowing I'd get more breakup with little, if any, volume boost) and I was getting the most distorted, washed out crap I've ever heard out of this thing! I turned it back down to about 4.5 and it was still very distorted. One thing though, I was getting great sustain! just no clean headroom. I really should have just mic'ed it, but I had no time by then.
About the amp: It was a stock early silverface when I got it with fried heater tap resistors, a fried screen grid resistor, and a few bad solder joints on brass-plate grounds. After all new caps (ALL of them) new JJ tubes, a 5v4 recto (to lower voltages a bit) and quite a few new CC resistors, just to be sure, this thing has been the greatest DR in the world for two years! (the Tone Tubby AlNiCo hempcone helped a lot!)
So... this morning I pulled the chassis out, contemplating swapping in some GT 6L6's and a solid state recto I have laying around, and thought I'd check the bias as is first. The Left tube reads 32ma @ 463V on the plate and the right tube reads 19ma @ 463V.
Did my matched JJ 6v6's go out of spec? 19 ma was where I originally biased them at (I think). The left one was noticeably hotter also...like REALLY hot!
I have read that the new JJ 6v6's are the best current tube to handle a DR's over spec voltages but I have also read that the quality control is spotty and many come defective out of the box. But mine worked great for two years. Any Ideas?
Also... I have a little 47uF 100v electrolytic cap coming off my bias pot. It's not on the AB763 ckt and I don't remember why I put it there. I did change the bias to blackface specs but left that cap. I don't remember why and I can't find any info on it... should I take it off?
So... Friday night, during soundcheck, everything was fine... empty room, 20 foot ceiling, so I figured things would change when it filled up... figured I'd have to turn it up and add some treble. But after we started, with a room full of people, I turned it up to about 5.5 (I've done this before, knowing I'd get more breakup with little, if any, volume boost) and I was getting the most distorted, washed out crap I've ever heard out of this thing! I turned it back down to about 4.5 and it was still very distorted. One thing though, I was getting great sustain! just no clean headroom. I really should have just mic'ed it, but I had no time by then.
About the amp: It was a stock early silverface when I got it with fried heater tap resistors, a fried screen grid resistor, and a few bad solder joints on brass-plate grounds. After all new caps (ALL of them) new JJ tubes, a 5v4 recto (to lower voltages a bit) and quite a few new CC resistors, just to be sure, this thing has been the greatest DR in the world for two years! (the Tone Tubby AlNiCo hempcone helped a lot!)
So... this morning I pulled the chassis out, contemplating swapping in some GT 6L6's and a solid state recto I have laying around, and thought I'd check the bias as is first. The Left tube reads 32ma @ 463V on the plate and the right tube reads 19ma @ 463V.
Did my matched JJ 6v6's go out of spec? 19 ma was where I originally biased them at (I think). The left one was noticeably hotter also...like REALLY hot!
I have read that the new JJ 6v6's are the best current tube to handle a DR's over spec voltages but I have also read that the quality control is spotty and many come defective out of the box. But mine worked great for two years. Any Ideas?
Also... I have a little 47uF 100v electrolytic cap coming off my bias pot. It's not on the AB763 ckt and I don't remember why I put it there. I did change the bias to blackface specs but left that cap. I don't remember why and I can't find any info on it... should I take it off?
Comment