I think the tank output shield is grounded. So it does go straight to ground. The network you highlighted is just setting the gain and response of the driver. The tank input shield isn't connected to anything. Not sure why it wasn't just grounded. Some sort of bootstrapping maybe.CJ said:anybody know why the Blues Jr amp uses this grounding scheme?
in other words, why not go straight to ground ?
Thanks!
The specific location of R45 and c21 ground connection is important for ground noise pickup. Any local ground noise errors coming into that - input will be amplified by 4.7k/47 or +40 dB.CJ said:anybody know why the Blues Jr amp uses this grounding scheme?
in other words, why not go straight to ground ?
Thanks!
Because it's current-driven. The 47r resistor senses the current in the drive-coil. The capacitor makes sure there's 100% NFB at DC, so the coil does not see any significant DC current.CJ said:anybody know why the Blues Jr amp uses this grounding scheme?
in other words, why not go straight to ground ?
No, it's not! And it shouldn't be. It is essential for the coil to be floating in order to make the current-drive work.squarewave said:I think the tank output shield is grounded. So it does go straight to ground.
I said the output shield is grounded (as in connected to the shell) and that the input shield was not. So the input is isolated but the output is not. Near as I can tell this is still correct and consistent with your claims about NFB drive which make perfect sense to me as well.abbey road d enfer said:No, it's not! And it shouldn't be. It is essential for the coil to be floating in order to make the current-drive work.
And that is why grounded/insulated input is one of the many options when ordering an Accutronics tank.
I stand corrected.squarewave said:I said the output shield is grounded (as in connected to the shell) and that the input shield was not. So the input is isolated but the output is not. Near as I can tell this is still correct and consistent with your claims about NFB drive which make perfect sense to me as well.
5532 would have a little more drive capability (not much since the TL072 is not really stretched), and could be a tad lesss noisy on the recovery side, though the 10k resistor (R48) in series would need to be lowered to take real advantage of the 5532's lower input noise voltage. There may be an issue with stability, requiring an additional cap to ground at the non-inverting input.CJ said:thanks you guys!
one more question, would a 5532 be better to drive that tanks rather than the 072?
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