Randy Slone's multislope VI limiter - 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 10th May 2013, 04:09 PM   #1
danny92 is offline danny92  Portugal
diyAudio Member
 
Join Date: Nov 2012
Location: Lisbon
Default Randy Slone's multislope VI limiter

Hi everyone,

I'm thinking about using this circuit to protect the output of the amplifier that I'm projecting, but I don't know if this is a good circuit, it was told me that this circuit could bootstrapp the output at high frequencies is this true?
What's the purpose of the two capacitors?
Does anyone tested this protection system?

Thank you very much for your attention,
Best regards,
Daniel Almeida
Attached Images
File Type: png Randy_Slone's based protection system.png (27.4 KB, 245 views)
  Reply With Quote
Old 10th May 2013, 09:57 PM   #2
diyAudio Member
 
Join Date: Apr 2010
Location: Coffs Harbour
Which 2 capacitors are you referring to? If it is to pairs C8/9 or C10/11, there is a film capacitor intended to improve the HF performance of the electrolytic which acts as local supply bypassing (aka decoupling). At these values with good quality electrolytics, it seems misguided in the light of a little analysis but when the book was written, it was probably still common practice. 'Trust that's what you meant.
__________________
Ian
  Reply With Quote
Old 10th May 2013, 11:26 PM   #3
Banned
 
Join Date: Oct 2010
Location: Chigwell, Essex
First I don't think it's a "multislope limiter"; I suspect it's merely a single slope single breakpoint limiter. Secondly, because it is refered to ground, the position of the protection locus would vary with changes in the supply rails.

If you mean the capacitors across the base collector junctions of the protection transistors, these are meant to prevent limiter activation at HF, but are misconceived because in this position they actually increase distortion. This is because they shunt the output stage out of the feedback loop at HF; far better to place them across the base emitter junctions of the limiter transistors.

Read that paper I sent you on VI limiters.
  Reply With Quote
Old 11th May 2013, 12:22 AM   #4
danny92 is offline danny92  Portugal
diyAudio Member
 
Join Date: Nov 2012
Location: Lisbon
Thank you for your help,
I will read your paper,

Best regards,
Daniel Almeida
  Reply With Quote
Old 11th May 2013, 01:19 AM   #5
Bonsai is offline Bonsai  Taiwan
diyAudio Member
 
Bonsai's Avatar
 
Join Date: Jul 2003
Location: Taipei, Taiwan
My website is down at the minute. When it's back up, I will post your paper up Michael.
__________________
bonsai
Amplifier Design and Construction for MUSIC! http://hifisonix.com/
  Reply With Quote
Old 11th May 2013, 11:07 AM   #6
JMFahey is offline JMFahey  Argentina
diyAudio Member
 
JMFahey's Avatar
 
Join Date: Mar 2009
Location: Buenos Aires - Argentina
That protection circuit is good but there's a problem with your implementation.

The way it's drawn it tries to clamp the gate drive voltage when load is shorted , so far so good, but you show it connected to the driver transistors emitters, which are able to supply *a lot* of current.
Those TO220 TIP will *murder* those little 2N5xxx .

1) the clamping action will be quite undefined.

2) either the drivers or the clamping transistors or both will die.

You must clamp the driver transistors *base* and you must add a series resistor to each (typically around 470 ohms) to provide a defined impedance to work with.

As of C2 and C3 the value and position (clamping transistors base to collector) is fine, they are used because is common for the amplifier to oscillate wildly while clamped so the added caps kill HF response *while protecting* .

There is no effect on the amplifier under normal conditions of use, since they are not activated and besides, they are separated from the circuit by those 1N4148 diodes until called on duty.

I think you cut and pasted elements (or pulled ideas) from different schematics, which are not compatible with each other.
  Reply With Quote
Old 11th May 2013, 11:32 AM   #7
Banned
 
Join Date: Oct 2010
Location: Chigwell, Essex
Quote:
Originally Posted by Bonsai View Post
My website is down at the minute. When it's back up, I will post your paper up Michael.
Ok.
  Reply With Quote
Old 11th May 2013, 11:39 AM   #8
Banned
 
Join Date: Oct 2010
Location: Chigwell, Essex
Quote:
Originally Posted by JMFahey View Post
As of C2 and C3 the value and position (clamping transistors base to collector) is fine.....
No.
  Reply With Quote
Old 11th May 2013, 05:31 PM   #9
JMFahey is offline JMFahey  Argentina
diyAudio Member
 
JMFahey's Avatar
 
Join Date: Mar 2009
Location: Buenos Aires - Argentina
Quote:
Originally Posted by michaelkiwanuka View Post
No.
Well, you are entitled to your own opinion.
Pity Pro designers don't share it

Just a few examples (out of tens of thousands) of real world amps (not "simulations") who *do* use BC caps in the protection transistors.

Would you trust Dynaco 400?

AmpegB3/VH140/SVT200?

Dynaco ST?

Crate 1200?

Gibson Lab Series?

Peavey Commercial PA amplifiers?

What do they all have in common?

*All* are high power amps, meant for grueling PA/stage/live sound, driving long cables, funky impedance speakers, high probability of shorts, continuous abuse; no cork sniffing designs survive or perform there.
Attached Images
File Type: gif Dynaco400.gif (115.1 KB, 154 views)
File Type: gif AmpegB3.gif (26.4 KB, 132 views)
File Type: gif Ampeg-VH140C-schematics_Page_8.gif (138.4 KB, 131 views)
File Type: gif SVT200Tschem_notes.gif (116.0 KB, 123 views)
File Type: jpg Dynaco-ST410sch_det.jpg (113.8 KB, 72 views)
File Type: gif Crate1200H.gif (39.2 KB, 68 views)
File Type: gif Lab_Series_L5_L7_L9_L11_scheme.gif (87.6 KB, 62 views)
File Type: gif Peavey CS400.gif (22.5 KB, 69 views)
  Reply With Quote
Old 11th May 2013, 06:43 PM   #10
Banned
 
Join Date: Oct 2010
Location: Chigwell, Essex
I KNOW for a fact that placing capacitors across base-collector junctions of VI limiter transistors is a bad idea. Send me your email address and I'll send you paper on the issue.

And every single example you've shown is a poor design in almost all respects.

Last edited by michaelkiwanuka; 11th May 2013 at 06:45 PM.
  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
Randy Slone's "Fig 11.4" (Self's "Blameless"?): PCB layout tcpip Solid State 128 23rd September 2013 04:45 PM
Randy Slone's Optimos power amp demo Sydney Sunday Nov 9 2008 HiFiNutNut Solid State 17 2nd September 2009 08:15 AM
My 50 Watt RMS design using Randy Slone's formulas corrieb Solid State 18 14th January 2007 12:22 AM
Trouble with speaker protection circuit (Randy Slone's circuit) whalefat Solid State 3 13th April 2005 10:13 AM


New To Site? Need Help?

All times are GMT. The time now is 05:22 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright ©1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2