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RE: Possible tweak

Posted by Lew (A) on June 18, 2008 at 19:36:06

In Reply to: RE: Possible tweak posted by Jack Williams on June 18, 2008 at 17:13:51:

On ESR, you may have a point, but my filter (and probably yours) is constructed as CRCRCCCCCx, where by far most of the capacitance is downstream from the second R. Thus that downstream component is free to give up its charge to the circuit with no hindrance from the upstream Rs. I think it's advantageous to have as low an ESR as possible in that downstream C. The Rs do somewhat buffer the transformer and rectifiers from the stress of having to re-charge that huge downstream capacitance. (Granted, the effects of such small value resistors is going to be minimal.) Plus the R in a CRC filter will also help some at high frequencies, where the impedance of C is very low, much as what happens with an inductor in a CLC filter.

Are you sure Ralph said he is using 1-ohm Rs in this manner? Paul was reluctant even to go up to 0.5 ohms, and ended up recommending only 0.21 ohms in my exchange with him. Please correct me if I'm wrong, but I think Paul's published tweak recommended only 0.5 or 0.21; I don't remember which.

Tv has repeatedly stated that the 1K resistor which bridges the plus halves of the output supplies is a no-no for best sound. I'm going to try to install a switch, so I can listen to it both ways. Ralph has no problem with trying it Tv's way. During my recent saga (see below) I measured a difference of less than a volt comparing one bridged supply to the other. However, if you then place the meter across from one plus to the other plus node, the reading is more like 5V, because you are now reading V across the two (600 ohm) resistors that isolate the ground sides of the two PSs PLUS the difference between the two supplies taken separately. With the 1K R in place, this difference of 5V will cause a small current to flow across between the two plus nodes. Damned if I know the consequences of that to operation of the circlotron. Maybe Ralph can comment.

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