mu followers --- current --- please help

soundbadger · 20th October 2007, 10:06 PM

i have designed a mu follower circuit based on the one in morgan jones valve amps book,,, just wondering what the current drawn by a mu follower is.. also how do i work out what power rating resistors to use ,,

cheers
soundbadger

Miles Prower · 20th October 2007, 11:21 PM

Ina word, Loadlines (See under "Technocal Reports"; he has a five-parter that tells all about it.)

ray_moth · 21st October 2007, 01:09 AM

Miles's link didn't work for me but I think he meant that the operating point needs to be chosen according the the plate curves. The load line itself will be almost horizontal b ecause of the high impedance that the mu-follower provides as a plate load to the lower tube. However, you still need to select an operating current based on the tube's characteristics. A rule-of-thumb approach is probably good enough here, i.e. use a high enough current for linear performance but don't go for too much plate dissipation.

pftrvlr · 21st October 2007, 03:54 PM

I am building one mu-follower as headphone amp - with extra 6bx7 output cf stage. I use SPICE to set the operating point and check component power rating. Works fine for me.

Jeb-D. · 21st October 2007, 04:39 PM

Speaking of Spice. Soundbadger, your icon looks like it's from circuitmaker. I use the student edition which I got while in school. If that is what you have, I figured out to alter the model folder so that you can add more tubes to the library. I'll let you in on the trick if that's what you use.

soundbadger · 24th October 2007, 07:46 AM

ive not used spice before, at college we use ewb multisim which is a bit limited. i just got a copy of pspice so ill see how i get on. i

20th October 2007, 10:06 PM	#1
soundbadger diyAudio Member Join Date: Sep 2007	mu followers --- current --- please help i have designed a mu follower circuit based on the one in morgan jones valve amps book,,, just wondering what the current drawn by a mu follower is.. also how do i work out what power rating resistors to use ,, cheers soundbadger

20th October 2007, 11:21 PM	#2
Miles Prower diyAudio Member Join Date: May 2005 Location: USA Blog Entries: 2	Ina word, Loadlines (See under "Technocal Reports"; he has a five-parter that tells all about it.) __________________ There are no foxes in atheistholes www.dolphin-hsl.com

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21st October 2007, 01:09 AM	#3
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	Miles's link didn't work for me but I think he meant that the operating point needs to be chosen according the the plate curves. The load line itself will be almost horizontal b ecause of the high impedance that the mu-follower provides as a plate load to the lower tube. However, you still need to select an operating current based on the tube's characteristics. A rule-of-thumb approach is probably good enough here, i.e. use a high enough current for linear performance but don't go for too much plate dissipation.

21st October 2007, 03:54 PM	#4
pftrvlr diyAudio Member Join Date: Feb 2007 Location: SoCal	I am building one mu-follower as headphone amp - with extra 6bx7 output cf stage. I use SPICE to set the operating point and check component power rating. Works fine for me.

21st October 2007, 04:39 PM	#5
Jeb-D. diyAudio Member Join Date: Nov 2005 Location: SoCal	Speaking of Spice. Soundbadger, your icon looks like it's from circuitmaker. I use the student edition which I got while in school. If that is what you have, I figured out to alter the model folder so that you can add more tubes to the library. I'll let you in on the trick if that's what you use.

24th October 2007, 07:46 AM	#6
soundbadger diyAudio Member Join Date: Sep 2007	ive not used spice before, at college we use ewb multisim which is a bit limited. i just got a copy of pspice so ill see how i get on. i

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