Zobel Or No Zobel ? - Page 4 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 4th April 2008, 04:28 PM   #31
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Default Re: no ..... but

Quote:
Originally posted by sakis
then the next thing we iwill do is to send a satelite to the moon with few amplifiers on it also ha ha ha
but it will overheat and fail.
__________________
regards Andrew T.
  Reply With Quote
Old 4th April 2008, 04:52 PM   #32
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
Default thanks andrew t

your presence here is an honour ......

thanks also for your comments and help about the ltp stage of the legend 4 that i try to play with ....

to make this not off topic .....

all the progress ive made all test and all mods ive made was with out an inductor at the output of the amp ....

me !!!!! who constructed more than 300 amps so far and then troubled with this legend 4 for so long missed such a critical thing ......

i instaled the inductor to a working legend 4 i have and it has incredible diference

i am banging my head on this for the latest 8 hours ....


you see ....both schematics and pcb was given to me by dr Bora and since inductor wasnt included on the pcb i didnt put one ......

any way now i am running legends in no more than 40.000 volts per rail since after your recomendation that 40.013 is too much !!!!!.....

thanks andrew
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  Reply With Quote
Old 4th April 2008, 08:20 PM   #33
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
Quote:
Originally posted by teemuk
I wonder… since the Zobel network is mainly used to compensate the capacitive and inductive properties of a real loudspeaker load (including the cable) how would a following configuration work: The speaker load is relay switched and Zobel network is attached to speaker output jack, thus a bit away from the power amplifier board. While the load is unconnected (mainly during start up) the Zobel network is unconnected as well and the amplifier is only loaded by a moderately high value resistor (e.g. 10 kilo-ohms). What is the general consensus, will something like this be unstable?
Yes it may burst into oscillation at power up. Why would you not want to locate the Zobel on the switch side of the relay or even better on the amp board. The closer it is to the output node the better really.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  Reply With Quote
Old 5th April 2008, 04:55 AM   #34
GK is offline GK  Australia
Account disabled at member's request
 
Join Date: Jan 2006
Don't know if this design (just for example) is incompetent, but I seen no mention anywhere of an RC Zobel hanging on the output (just a 500nH in parallel with 0.5ohm):

Wow.

http://www.cordellaudio.com/papers/MOSFET_Power_Amp.pdf
  Reply With Quote
Old 5th April 2008, 10:25 AM   #35
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
Default seen some amps

that had inductor installed to the pcb but zobel was located on the binding post of the amplifier .....

also the location of the inductor very next to mosfet outs seem to make some sense to me .....if we talk about mosfet amps

after 2 days of very carefully listening to legend 4 by dr BORA that previously operated without any inductor at all ( a simply made bootstrap with 4 irfp240 quasi ) 40+40rails

and after palying with a few inductors it prooves that makes grate diference which i havent notice before ....

amp was smooth and clean any way but up to a certain level and when you you drive it more than 50% of the power started to get dirty and hassy especially on the upper end .....

after the inductor it works a hell of a lot better and keep the same smoothnes of high at all levels ....

happier now .....
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  Reply With Quote
Old 5th April 2008, 08:50 PM   #36
diyAudio Member
 
Join Date: Nov 2004
Location: Florida
Any of you use a larger cap than the standard 0.1uf? (100nf)

I've seen amps use 0.15uf before.

Last large amp I built uses a 4.7ohm + 0.22uf 250V cap I got from computer PSU, and I get good results.
  Reply With Quote
Old 6th April 2008, 09:07 AM   #37
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
stick some numbers into Cherry's formulae and you'll soon see there is a range of acceptable cap values.
The cap can be upto around 220nF particularly if you use low impedance speakers.
__________________
regards Andrew T.
  Reply With Quote
Old 6th April 2008, 07:59 PM   #38
diyAudio Member
 
Join Date: Sep 2006
Quote:
Originally posted by G.Kleinschmidt
Don't know if this design (just for example) is incompetent, but I seen no mention anywhere of an RC Zobel hanging on the output (just a 500nH in parallel with 0.5ohm):

Wow.

http://www.cordellaudio.com/papers/MOSFET_Power_Amp.pdf

Hi Glen,

That amplifier actually had a Zobel network right at the MOSFET source outputs of 0.047 uF and 22 ohms. The schematic in the JAES article did not show either the Zobel network or the L-R network for simplicity. Sorry for the confusion.

BTW, I believe that Bryston often uses a capacitor directly to ground right at the speaker terminal side of the coil.

Cheers,
Bob
  Reply With Quote
Old 6th April 2008, 08:26 PM   #39
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally posted by Bob Cordell
I believe that Bryston often uses a capacitor directly to ground right at the speaker terminal side of the coil.
that's the other limiting version given by Thiele.
__________________
regards Andrew T.
  Reply With Quote
Old 6th April 2008, 09:34 PM   #40
suzyj is offline suzyj  Australia-Aboriginal
diyAudio Member
 
suzyj's Avatar
 
Join Date: Jan 2006
Location: Sydney
Quote:
Originally posted by Bonsai
[B]Even Self seems not to be able to explain precisely why the universally optimum values are 10 Ohms and 0.1uF for the Zobel network .
It's not something that has any effect at audio frequencies, so there's no point optimising it. The actual values used can legitimately be whatever you've got to hand, within a decade or so. As long as the amp sees some reasonably low impedance at high frequencies.

As for the output L//R, I didn't bother on my amp, after testing it with a 10KHz sinewave clipping hard into an 8R//2u2, and finding that it behaved quite happily.

I should mention that the other use for the Zobel R-C network is as a test to see if the amp is oscillating, without using an oscilliscope. If the resistor catches fire, you can be reasonably sure of a healthy RF oscillation.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Do I need a Zobel ? chasingame Multi-Way 22 7th August 2009 11:45 AM
which cap do you like in zobel ? sandro600 Solid State 2 28th January 2007 10:36 AM
zobel Streets97f Subwoofers 4 19th November 2006 04:44 AM
the zobel bigpanda Solid State 9 13th May 2006 03:56 PM


New To Site? Need Help?

All times are GMT. The time now is 06:22 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2