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-   -   Emitter Resistors (http://www.diyaudio.com/forums/solid-state/72729-emitter-resistors.html)

hawkfeather 27th January 2006 01:33 PM

Emitter Resistors
 
What would be a good choice for emitter resistors in a 50W-100W design?

richie00boy 27th January 2006 01:54 PM

Anything in the range 0.1 ohm to 0.47 ohm, it's a trade off of temperature stability and distortion. Higher the resistance better the temp stab.

CBS240 27th January 2006 03:59 PM

One must consider Zout when choosing this value.:)

richie00boy 27th January 2006 04:15 PM

Not really, since they are inside the negative feedback loop.

AndrewT 27th January 2006 06:41 PM

Hi,
for your range of power it looks like a 1pair or 2pair output stage is suitable.
I suggest about 3W wire wound.

I have seen on this forum a suggestion that the emitter resistors should be non inductive but I cannot confirm this.
If non inductive is important then wirewound is not suitable unless they are specially wound to eliminate inductance. I believe a few manufacturers can supply this specification.

boraomega 27th January 2006 09:02 PM

2 Attachment(s)
It is neither expensive nor particularly complicated to make them non-inductive if one does that this way as I am doing last 20+ years. If you use metal-film 1% 1/2W resistors, this way you have practically non-inductive 5W resistor that occupy les space and is much cheaper than some exotic "audiophile-grade" types. Please note that there are TWO emitter resistors of 0,1 ohm on the picture! This might be useful idea for someone.

hawkfeather 27th January 2006 10:17 PM

RCD
 
I just bought a lot of 100 RTD135, 0.4 Ohm, 3W for $12.00. Think they will work OK?

anatech 27th January 2006 10:26 PM

Hi hawkfeather,
Yes. As long as the value is okay. Are they the flat "plate" low inductance resistors?

-Chris

hawkfeather 27th January 2006 11:02 PM

RCD info...
 
2 Attachment(s)
Hey Chris...

I'm attaching the data sheet... seems like they are pretty decent ones. Guess I got a good deal after all!

anatech 27th January 2006 11:32 PM

Hi hawkfeather,
Quote:

INDUCTANCE: small sizes have inductance of 1- 50uH typ.
May or may not present a problem.

-Chris


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