Bias resistor

nhuwar · 18th January 2007, 09:48 PM

Ok i know it's a good idea to put a bypass cap in parallel with resistor to adjust the individual grid bias on each tube

But what is a good cap value???

dsavitsk · 18th January 2007, 10:37 PM

You really should buy the Morgan Jones book. It explains how to figure this out in gory detail. The short answer is, large enough such that the frequencies above about 2Hz are not rolled off.

nhuwar · 18th January 2007, 10:40 PM

Ok so just simple cap reactance formula

Just wanted to make sure audio seams to be such a diffrent animal then rf some times I figuared id ask.

Thanks

nhuwar · 18th January 2007, 10:41 PM

Oh whats the title of the book?

Nick

nhuwar · 18th January 2007, 10:50 PM

Wow it's a pricey book for a paperback $46.76

Sherman · 18th January 2007, 11:03 PM

Quote:

Originally posted by nhuwar
Wow it's a pricey book for a paperback $46.76

And worth every penny!

This formula will give you the value of the bypass cap in microfarads.

1/(2pi*f*i)*1000000

Where 'f' is the desired -3dB frequency and 'i' is total impedance computed as

i = (rp of tube * plate resistor)/(mu of tube +1)

SY · 18th January 2007, 11:06 PM

Quote:

Originally posted by nhuwar
Wow it's a pricey book for a paperback $46.76

A 600+ page paperback.

It quickly became the most-used book on my tube electronics shelf. Truly worth it, trust me- it will save you from enough dumb mistakes to pay for itself in no time.

Victoria · 18th January 2007, 11:28 PM

Sy,
Which of his books are you referring to? Thanks, Victoria

refference · 18th January 2007, 11:47 PM

Hi all ,

“ Valve Amplifiers by Morgan Jones “
Great , fantastic , well written , easy to understand and
very didactic , too .

I bought mine , due to many advises from SY , on this
forum , and the book really worth every cent of dollar .

Hi nhuwar ,

I don’t know why you are speaking about USD$ 46.76 ,
because I paid USD$ 49.94 ( book + shipping ) delivered
at my door ( Sao Paulo , BRAZIL ) from Amazon.com ,
5 months ago . Inside USA , the price must lower !!!??

Carlos

SY · 18th January 2007, 11:55 PM

No, it's not really any cheaper here.

Victoria, yes, "Valve Amplifiers," Morgan Jones, 3rd Edition. Jones has a rare knack for explaining- I wish he'd do a few more books.

18th January 2007, 09:48 PM	#1
nhuwar diyAudio Member Join Date: Jan 2007 Location: Tomball Texas	Bias resistor Ok i know it's a good idea to put a bypass cap in parallel with resistor to adjust the individual grid bias on each tube But what is a good cap value???

18th January 2007, 11:55 PM	#10
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	No, it's not really any cheaper here. Victoria, yes, "Valve Amplifiers," Morgan Jones, 3rd Edition. Jones has a rare knack for explaining- I wish he'd do a few more books. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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18th January 2007, 10:37 PM	#2
dsavitsk diyAudio Member Join Date: Jan 2005 Location: Chicago	You really should buy the Morgan Jones book. It explains how to figure this out in gory detail. The short answer is, large enough such that the frequencies above about 2Hz are not rolled off.

18th January 2007, 10:40 PM	#3
nhuwar diyAudio Member Join Date: Jan 2007 Location: Tomball Texas	Ok so just simple cap reactance formula Just wanted to make sure audio seams to be such a diffrent animal then rf some times I figuared id ask. Thanks

18th January 2007, 10:41 PM	#4
nhuwar diyAudio Member Join Date: Jan 2007 Location: Tomball Texas	Oh whats the title of the book? Nick

18th January 2007, 10:50 PM	#5
nhuwar diyAudio Member Join Date: Jan 2007 Location: Tomball Texas	Wow it's a pricey book for a paperback $46.76

18th January 2007, 11:28 PM	#8
Victoria diyAudio Member Join Date: Jan 2006 Location: SF Bay area	Sy, Which of his books are you referring to? Thanks, Victoria

18th January 2007, 11:47 PM	#9
refference diyAudio Member Join Date: Jan 2006 Location: SAO PAULO - SP	Hi all , “ Valve Amplifiers by Morgan Jones “ Great , fantastic , well written , easy to understand and very didactic , too . I bought mine , due to many advises from SY , on this forum , and the book really worth every cent of dollar . Hi nhuwar , I don’t know why you are speaking about USD$ 46.76 , because I paid USD$ 49.94 ( book + shipping ) delivered at my door ( Sao Paulo , BRAZIL ) from Amazon.com , 5 months ago . Inside USA , the price must lower !!!?? Carlos

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