diyAB Amp - The "Honey Badger" - Page 89 - 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 2nd January 2013, 01:15 PM   #881
diyAudio Member
 
keantoken's Avatar
 
Join Date: Aug 2006
Location: Texas
Blog Entries: 2
Oh no!

KSA992 in the current mirror! This needs corrected. These have abysmal Vcesat. It is so frustrating how long it took for me to learn about quasi-saturation in BJTs. This one thing may be holding the real DiyAB back.

Look at the datasheet. I'll make it terrifyingly obvious:

http://www.fairchildsemi.com/ds/KS/KSA992.pdf

Look at the Vce vs. Ic chart. You'll see that at .6V Vce, the collector has a V/I slope of 143. This is the definition of a collector impedance of 143R! To see the effect of this in simulation, put a 280R resistor across the CM collectors.

This is a mistake I made when designing my Kmultipliers. NEVER use high-voltage BJTs for Vce below 2V!

The simulator doesn't show this because quasi-saturation is not modeled.

I tested a number of transistors in the Kmultipliers and 2N5551/5401, 2N5089, KSC1845/A992, and so on always fell short. Ultimately the BC5x0 and BC3x7 series were the best. These have high collector impedance at very low voltages. The BC3x7 are the best, but are slower - but with low Re/Rb and great surge capability, perfect for a frontend C-multiplier filter.

I suggest BC560C for the current mirror. I've also measured these, and found they were generally within 300uV Vbe (OnSemi IIRC), so you'll have almost perfect current balance from the start.

If you want to try it, just replace Q5 and Q6 with BC560C. Schematic:

http://www.diyaudio.com/forums/image...-schematic.pdf

Last edited by keantoken; 2nd January 2013 at 01:26 PM.
  Reply With Quote
Old 2nd January 2013, 01:39 PM   #882
clm811 is offline clm811  United States
diyAudio Member
 
clm811's Avatar
 
Join Date: May 2002
Location: Northern California
Quote:
I built the mongrel amp (which this design came from) with the 2 output transisters NJW03, NJW0281 mounted on a conrad 300 heasink for each channel and a single 300va 45v transformer 60v rails. This ran fine while driving 6 ohm speakers, however blew the outputs when I cranked up the volume
Please note that I'm using two 4281 and two 4302 on one heat sink per channel.

Still at risk here?

-Chas
  Reply With Quote
Old 3rd January 2013, 05:05 AM   #883
diyAudio Member
 
Join Date: Sep 2008
Location: Brisbane
Quote:
Originally Posted by repeet View Post
I'm no expert but can say from experience that it is risky. I built the mongrel amp (which this design came from) with the 2 output transisters NJW03, NJW0281 mounted on a conrad 300 heasink for each channel and a single 300va 45v transformer 60v rails. This ran fine while driving 6 ohm speakers, however blew the outputs when I cranked up the volume on a set of diy mini statements which go down to 4 ohm.
I agree. This amp seems a bit fiddly to get right.
  Reply With Quote
Old 3rd January 2013, 05:13 AM   #884
diyAudio Moderator
 
JojoD818's Avatar
 
Join Date: Mar 2003
Location: searching...
Happy New Year everyone!

The Honey Badger prototype I used in the build guide has already survived two New Year's eve celebrations. ;D
  Reply With Quote
Old 3rd January 2013, 05:14 AM   #885
diyAudio Moderator
 
JojoD818's Avatar
 
Join Date: Mar 2003
Location: searching...
Quote:
Originally Posted by ostripper View Post


First of all , Jojo's construction PDF is VERY well done ... and the boards are so nice I am considering a purchase.

I test all types of used speakers and sources at the thrift shop I work at. And guess what I use ? .... the original AX/(badger)! I blew the rail fuses twice with
PA speakers(cheap/4R) , one time just the negative rail fuse blew and the amp sounded distorted but had no offset.

I started using this amp because the OEM test amps would not survive too long.
The badger is also much better at auditioning all these used speakers (they sell quick after the customer hears all that headroom ) I repair many Sherwood/KLH/Sony discrete receivers/amps and they are inferior (sound/durability).

As far as instability , !! With 10pf miller compensation .. maybe ? (I detected minor ringing with a single 22pf silver mica) ,but the amp still was rock solid.

The DIYaudio badger PCB has a better layout than my "hacked" (recycled)
prototypes , so it should be even more bulletproof.

Really good work.. guys !!
BTW , my account was not hacked .. my brain was .


OS

Thanks man, and welcome back.
  Reply With Quote
Old 3rd January 2013, 05:52 AM   #886
diyAudio Member
 
Join Date: Sep 2008
Location: Brisbane
Quote:
Originally Posted by JojoD818 View Post
The one you remember having busted outputs immediately after building the amp has been figured out already. It was the builder's fault not the circuit, he forgot to mirror the pcb when he cloned it, hence, most of the transistor leads were installed the other way around...
I do believe this may be my amp you are talking about. It is true I built the boards as a mirror image but "untrue" that this was to blame for the amp blowing power transistors as the transisters were installed mirror image to suit the mirror imaged board.

Quote:
Originally Posted by kclusa@yahoo.co View Post
Hello,

I am having issues of burned out power transistor.

If anyone do not have burned out issue yet, it may simply indicating that those three transistors are not fighting hard enough yet.

I also remember someone else has the similar issue immediately after building the amp.

Any thought ? Any input is appreciated.
With this board ostripper had many options for builders during the build. 2 different cascodes/current mirrors to choose,2 different vas compensation modes, a choice of the builder for their vas standby current, choice of R27 size and the choice of using an lead compensation capacitor as well(I do not recommend using an LC cap), as well as many transistor choices as well. All these will have an effect on how stable this amplifier will perform in the real world.
I can only recommend the choices I made to cure my amp issues (which weren't a result of a mirrored pcb). It gets quite warm here in summer as repeet would be able to attest to. 38deg c yesterday. I found that q10,q11,q12 heatsink got quite warm and needed a larger heatsink, or better yet tie those transistors to the main heatsink instead of using a separate smaller one.

The choices that were made for my amp were
1. Use the zener referenced cascode/current mirror.
2. For vas compensation I used option 1 the CMC compensation method.
3. Did "not" use a Lead compensation cap. This was tested and the resultant sound was horrible.
4. Changed R27 to 100r. And adjusted to 0.6v across it (6ma).
5. The larger heat sink for q10-12 as stated before.

Has been running like a dream with no blown transistors since.

Regards

Simon

PS. The amps is different to the pic now and a bit neater. The remote volume control boards at the front are removed (chinese ebay type I dont recommend). Solid state relay at top left is removed as well. Now it just houses the soft start and power amplifiers.
Attached Images
File Type: jpg IMGP1209.JPG (195.9 KB, 622 views)
  Reply With Quote
Old 3rd January 2013, 06:00 AM   #887
diyAudio Moderator
 
JojoD818's Avatar
 
Join Date: Mar 2003
Location: searching...
Quote:
Originally Posted by niss_man View Post
I do believe this may be my amp you are talking about. It is true I built the boards as a mirror image but "untrue" that this was to blame for the amp blowing power transistors as the transisters were installed mirror image to suit the mirror imaged board.
Hi niss_man,

I can hardly remember if it was yours but thanks for clarifying. I think I remember that the amp was powered up before it was discovered that it ain't a mirror image of the board, or was it?

Anyway, what caused them output transistors to blow up again?

It is no secret that I've been trying to blow up this amp ever since I built it.
  Reply With Quote
Old 3rd January 2013, 05:31 PM   #888
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Albany , NY (smallbany)
Quote:
I found that q10,q11,q12 heatsink got quite warm and needed a larger heatsink, or better yet tie those transistors to the main heatsink instead of using a separate smaller one
2 ways to fix this...

A. - Lower the [CCS adjust] , this will bias the VAS differently. 2.5ma in the CCS will equate to approximately 6.5ma in the VAS.

B. - Change R27 as nissman pointed out. Member MJL21193 often stated that 5-6 mA was the "sweet spot" for the 1381/3503 pair. This would allow for running the CCS at 3-4ma as recommended.

Member Keentoken also has a point
Quote:
KSA992 in the current mirror! This needs corrected. These have abysmal Vcesat. It is so frustrating how long it took for me to learn about quasi-saturation in BJTs. This one thing may be holding the real DiyAB back.
about the current mirrors.

Replacing Q 5/6 would be simple , only the pair would be back-back instead of face-face. This improved current balance would indeed reflect on the sonics .. even if only by a small amount. This is explained in Hugh Dean's AKSA threads.

Quote:
It is no secret that I've been trying to blow up this amp ever since I built it.
Same here.. but I have almost 2 years on mine.

OS
__________________
Mongrel website , always current and updated :
http://www.fidelityforce.com/ostripper
  Reply With Quote
Old 5th January 2013, 07:50 PM   #889
Variac is offline Variac  United States
diyAudio Editor
 
Variac's Avatar
 
Join Date: Dec 2001
Location: San Francisco, USA
Quote:
Originally Posted by ostripper View Post

First of all , Jojo's construction PDF is VERY well done ... and the boards are so nice I am considering a purchase.
Really good work.. guys !!
OS
Just PM me your address and we'll send you a couple of pairs!

Welcome back, we all need a break now and then..

Mark
  Reply With Quote
Old 6th January 2013, 12:13 AM   #890
tsip is offline tsip  Greece
diyAudio Member
 
Join Date: Mar 2008
if Q5-Q6 can be replaced by BC560 i guess that BC550C would be ok as well
what about Q9? Can we replace with BC560 or BC550?
thanks
  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
diyAB Amp The "Honey Badger" build thread Variac Solid State 1150 2nd July 2014 11:45 AM
Honey, I smoked the Weller 8200 jackinnj Equipment & Tools 5 25th April 2011 06:07 AM
Badger Badger Badger..... Mushroom !! 5th element Everything Else 15 20th September 2003 03:16 PM


New To Site? Need Help?

All times are GMT. The time now is 01:39 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