Feedback with a choke ?

el156 · 17th December 2010, 06:16 PM

Hi
Does someone knows what happens if we use a choke instead of the normal resistor to the feedback loop? It would be afecting more the bass then the middle/hi freq i think ,i would like to make a test but i dont have a suitable choke to the job. Is it a nice test to do , or i should be gardening instead of messing around with tubes or maybe choose another hobby?

DF96 · 17th December 2010, 07:02 PM

If you mean a choke in series (with a resistor to ground) then the result will be gain rising with frequency. The opposite of a capacitor.

To a first approximation, the closed-loop gain pattern is the opposite of the feedback network response. So flat feedback gives flat gain. High-pass feedback (e.g. a capacitor) gives low pass gain. Low pass feedback (your choke idea) gives high pass gain.

Do some reading on negative feedback - almost any electronics textbook will cover it.

el156 · 17th December 2010, 07:16 PM

Quote:

Originally Posted by DF96

If you mean a choke in series (with a resistor to ground) then the result will be gain rising with frequency. The opposite of a capacitor.

To a first approximation, the closed-loop gain pattern is the opposite of the feedback network response. So flat feedback gives flat gain. High-pass feedback (e.g. a capacitor) gives low pass gain. Low pass feedback (your choke idea) gives high pass gain.

Do some reading on negative feedback - almost any electronics textbook will cover it.

What i was thinking is that we need feedback to lower the output impedance and distortion for the bass,without afecting the mid and hi frequency,because i prefer the mid and hi without feedback....well maybe was only a crazy idea...

DF96 · 17th December 2010, 07:36 PM

Unfortunately you can't easily separate the various different effects of feedback, except by having different amplification channels for different frequency ranges. Feedback to reduce bass output impedance also reduces bass gain, so you get a high-pass filter. You can balance off frequency effects in the forward (open-loop gain) against frequency effects in the feedback, but then it gets complicated.

17th December 2010, 06:16 PM	#1
el156 diyAudio Member Join Date: Apr 2010 Location: ALBUFEIRA ;PORTUGAL	Feedback with a choke ? Hi Does someone knows what happens if we use a choke instead of the normal resistor to the feedback loop? It would be afecting more the bass then the middle/hi freq i think ,i would like to make a test but i dont have a suitable choke to the job. Is it a nice test to do , or i should be gardening instead of messing around with tubes or maybe choose another hobby?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Help replacing a PSU choke - How to choose choke	Hubba	Tubes / Valves	2	10th September 2010 02:33 PM
Choke rating for choke input duty	cbutterworth	Tubes / Valves	14	9th November 2007 04:43 PM
Swinging choke vs std. choke in PS	Curly Woods	Tubes / Valves	2	5th March 2007 08:30 PM
Swinging Choke or Smoothing Choke	danFrank	Tubes / Valves	4	11th February 2007 11:05 AM
Feedback - Choke loaded Zen w. input buffer	Pelle	Pass Labs	9	21st August 2005 08:53 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read

17th December 2010, 07:02 PM	#2
DF96 diyAudio Member Join Date: May 2007	If you mean a choke in series (with a resistor to ground) then the result will be gain rising with frequency. The opposite of a capacitor. To a first approximation, the closed-loop gain pattern is the opposite of the feedback network response. So flat feedback gives flat gain. High-pass feedback (e.g. a capacitor) gives low pass gain. Low pass feedback (your choke idea) gives high pass gain. Do some reading on negative feedback - almost any electronics textbook will cover it.

17th December 2010, 07:36 PM	#4
DF96 diyAudio Member Join Date: May 2007	Unfortunately you can't easily separate the various different effects of feedback, except by having different amplification channels for different frequency ranges. Feedback to reduce bass output impedance also reduces bass gain, so you get a high-pass filter. You can balance off frequency effects in the forward (open-loop gain) against frequency effects in the feedback, but then it gets complicated.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)