29-10-2012, 04:49 PM
(This post was last modified: 29-10-2012, 05:21 PM by Radio Fixer.)
Hi Lawrence
You didnt comment on that if the 450r speaker produces enough volume with a 2.2K padder, in shunt, it may as well be moved to be series fed saving 40mA off the rectifier and reducing heat in the cabinet. Seems sound to me, but I described the modification incorrectly (its OK on my diagram but I got in wrong in translation). Sorry to confuse.
"The alteration would be to put the 450r field, with no padding 2K2, before the 250r that produces the -ve bias (no change to this). The reservoir cap (100mF) -ve end would go to the 450r free end. If the HT current stayed the same and scaling the voltage across the 250 R (7.8V) the 450r field would drop 14V but this is likely to be compensated for by a rise in HT voltage. Just need to try it..."
Gary
You didnt comment on that if the 450r speaker produces enough volume with a 2.2K padder, in shunt, it may as well be moved to be series fed saving 40mA off the rectifier and reducing heat in the cabinet. Seems sound to me, but I described the modification incorrectly (its OK on my diagram but I got in wrong in translation). Sorry to confuse.
"The alteration would be to put the 450r field, with no padding 2K2, before the 250r that produces the -ve bias (no change to this). The reservoir cap (100mF) -ve end would go to the 450r free end. If the HT current stayed the same and scaling the voltage across the 250 R (7.8V) the 450r field would drop 14V but this is likely to be compensated for by a rise in HT voltage. Just need to try it..."
Gary
