Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

Use this form to submit comments directly to the Asylum moderators for this forum. We're particularly interested in truly outstanding posts that might be added to our FAQs.
You may also use this form to provide feedback or to call attention to messages that may be in violation of our content rules.

You must login to use this feature.

Inmate Login

By default, logging in will set a session cookie that disappears when you close your browser. Clicking on the 'Remember my Moniker & Password' below will cause a permanent 'Login Cookie' to be set.

Moniker/Username: The Name that you picked or by default, your email. Forgot Moniker?	Examples "Rapper", "Bob W", "joe@aol.com".
Password:	Forgot Password?
	Remember my Moniker & Password ( What's this?)

If you don't have an Asylum Account, you can create one by clicking Here.

Our privacy policy can be reviewed by clicking Here.

Inmate Comments

From:
Your Email:
Subject:

Message Comments

Original Message

Updating & Refining the " DCR " Topic

Posted by drlowmu on March 7, 2007 at 12:10:47:

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 :
- - - - - - - - - - - - - - - - -
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.

- - - - - - - - - - - - - - -
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----
- - - - - - - - - - - - - - - - - - -
Jeff Medwin