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Updating & Refining the " DCR " Topic


Hi you all,

My friend Dennis sent me a couple emails today that I 'd like to share up here - with any of those DIYers who have an interest :

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Hi Jeff!

You're right on your latest Forum stuff-- but you needed to point out that low-DCR is MOST CRITICAL in DRIVEN stuff.

ACTIVE stuff-- (That is-- the SOURCE for the power in the Power Supply (transformer & rectifier) NEED NOT be low-DCR-- as it is electrically DRIVING the circuit-- and can instantly change to accommodate current demand-- its own internal resistance is MUCH LESS a factor-- it is still there-- but it doesn't count for much.

Low-DCR is necessary in anything downstream from this-- all the devices which work on the power supplied must be low-DCR-- or the current/voltage losses will result in timing errors-- when current is tried to be re-supplied..... it will get there TOO LATE.


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Hi Jeff!

That last email is a bit muddy.

Here's the goodies:

(1) The Power Transformer can benefit a little bit by being low-DCR-- but the largest
benefit will come from extra current capability, regardless of DCR.

(2) The rectifier doesn't matter at all-- as to DCR. It is super-active, and can address current/voltage changes rather instantaneously. BUT-- just as in the transformer-- extra current capability here is a winner, regardless of DCR.

(3) The input choke should be low-DCR. This is because we want a TIGHT COUPLE to the rectifier output. Once the power leaves the rectifier, it is no longer adjustable-- actively. Now, we have passive components, unless we install voltage/current regulation-- but we don't want to listen to those things struggling to "keep-up" with music.... so they're best left out.

(4) Capacitors should be low-capacitance. This is because we want any "tuned" circuits to stay above human hearing--- by several orders. You can say here that we want SPEED. That simplifies it.

(5) Rules-of-thumb in designing the total amplifier:

(A) High-Current power transformer.

(B) High-Transparency rectifier.

(C) CHOKE-INPUT.

(D) low-DCR chokes.

(E) SMALL capacitors.

(F) Low-DCR wiring-- everywhere.

(G) Anything that is in-series with power or signal-- low-DCR, and physically short.

(H) Anything that LOADS power-- or signal---- (plate & cathode resistors, input impedance, etc.) , ---- VERY high DCR.

OK-- Now they can get to arguing again. ----D----

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Jeff Medwin


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Topic - Updating & Refining the " DCR " Topic - drlowmu 12:10:47 03/07/07 (85)


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