Before i mount my lvl 1 hot rodded dcb1 into the chassis, i was wondering if it would be better to use the bottom of my chassis (bottom alu sheet measures ~ 350mm x 430mm x 4mm thickness) as the heatsink instead of the heatsinks that i'm using right now. I realize with these heatsinks i can only rest my finger there for at most 5 seconds - it is really quite hot.
No, I'm thinking the same thing. My heatsinks is a bit bigger than yours. I don't plan to mount to the chassis and want to make sure it is OK. Now you reported "HOT". Would the DCB1 be stable?
Before i mount my lvl 1 hot rodded dcb1 into the chassis, i was wondering if it would be better to use the bottom of my chassis (bottom alu sheet measures ~ 350mm x 430mm x 4mm thickness) as the heatsink instead of the heatsinks that i'm using right now. I realize with these heatsinks i can only rest my finger there for at most 5 seconds - it is really quite hot.
Would it be a good idea to heatsink the 10 ohm caddocks?
OK, i finished my DCB1, and
Output offset is: Right -1.2 mV and Left -12.5 mV
On Test points i have: -10.21V 197.6mA and +10.28V 224.1mA
On 10R i have: 2.080V 276.2mA and 2.323V 315.7mA
What can be problem ?
Those tell me 208mA & 232mA.
Measure again the -12.5mV offset. If its there still, its the only issue and that side will need better JFETS matching.
Thanx !
Measured again, same thing, i put ANOTHER set of "matched" JFETs - and results are diferent but still way diferent what should be - thanx to guys who are selling "matched" quads .. !
Will try again, maybe will solder sockets and test diferent JFETs until i got what i need ...
Thanx for advice, i measure IDSS in about 14 JFETs i got - and closest values i got vas 2x 0.71mA and 2x 0.72mA !
I solderd them, and now i have 0.00mA and 0.14mA on output ...
Right, i am too tired this evening, desoldering, soldering, measuring, matching etc ...
JFETs are 2x 7.71mA and 2x7.72mA ...
B U T ...
You are right, i was measuring mA on output - not voltage ...
on Outpur voltage is: -1.3mV and 6.9mV :-(
Is the amp you gonna drive DC input? Or it has a capacitor? The goal is under 5mV offset in order not to be highly multiplied by a DC input amp. Last chance with the JFETS you got, mutually exchange positions in those two associated with the 6.9mV offset. Maybe you luck out and they will fall a bit more, or they simply go higher offset and you put them back as they were.