SYMEF amplifier - Page 38 - 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 16th March 2012, 10:44 PM   #371
diyAudio Member
 
Join Date: Oct 2011
Thanks for joining us pinnocchio and mrsavage.
  Reply With Quote
Old 21st March 2012, 01:34 PM   #372
diyAudio Member
 
Join Date: Oct 2011
Default comments

comments
Attached Images
File Type: jpg Aversion.jpg (190.8 KB, 545 views)
  Reply With Quote
Old 22nd March 2012, 10:27 PM   #373
PauloPT is online now PauloPT  Portugal
diyAudio Member
 
Join Date: Jan 2010
Location: Lisboa, Portugal
Send a message via MSN to PauloPT
Nice looking board!
__________________
Kind Regards,
Paulo.
  Reply With Quote
Old 24th March 2012, 05:50 AM   #374
diyAudio Member
 
Join Date: Oct 2011
Default version 2 of the PCBs

There are likely to be two version of boards on offer, heres the other technic
Attached Images
File Type: png SYMEFV2.png (66.6 KB, 481 views)
  Reply With Quote
Old 24th March 2012, 08:24 AM   #375
CBS240 is offline CBS240  United States
diyAudio Member
 
CBS240's Avatar
 
Join Date: Aug 2005
Location: K-town
Quote:
Originally Posted by AndrewT View Post
What is the peak instantaneous output voltage?

Use the formula:
Imax ~ Current Factor * Vpk / Speaker nominal impedance.

Current Factor can be around 2 for a mild reactance speaker using music that does not contain very fast starting signals nor very fast stopping signals.
Current Factor can be as high as 5 for "normal" reactance speakers when the music does contain very fast starting signals and/or very fast stopping signals.

I adopt CF=3 for my designs.

Assuming 40Vpk & 8ohm speaker.
Imax ~ 15Apk

This is a short term current peak that causes no significant heating of the output devices nor of the heatsink above the operating temperatures.
The output stage must be able to reach the estimated Imax with a sufficient amout of current gain. Even though 40V/8R is 5A, the circuit should be able to deliver 15A in short duty. And of course AC gain varies inversely proportional to frequency.
__________________
All the trouble I've ever been in started out as fun......
  Reply With Quote
Old 24th March 2012, 01:03 PM   #376
diyAudio Member
 
Join Date: Oct 2011
Hi CBS240,

I take it you will tackle the bigger version . Your contribution will be much appreciated.

kind regards,

Harrison.
  Reply With Quote
Old 31st March 2012, 12:02 AM   #377
diyAudio Member
 
Join Date: Oct 2011
Default PCB updates

harrisonaudiolabs.com

PCBs
Joel, Paulo, Raj, Brian, Evette, Mrsavage, Pinnocchio

All the best
  Reply With Quote
Old 1st April 2012, 01:28 PM   #378
PauloPT is online now PauloPT  Portugal
diyAudio Member
 
Join Date: Jan 2010
Location: Lisboa, Portugal
Send a message via MSN to PauloPT
Default Bias

Last couple of days I’ve been experimenting with different bias values. I went from 50mA up to 230mA, that is from 13mV across emitter resistors up to about 50mV. I didn’t go higher because I was afraid to fry the output transistors.

I found that the sweet spot for me is between 100mA and 200mA. Going higher that 200mA actually made the sound worst, less smooth. 50mA (13mV) is way too low and I could perceive distortion. At 100mA (23mV) the sound is much more smooth and “liquid” than at 50mA. Going higher than 100mA the sound increases in smoothness but is not a night and day difference. Somewhere about 150mA seems where going higher I couldn’t perceive any difference, except that higher than 200mA things change again but for worst sound. I have now the SYMEF biased at 150mA (33mV) and I think it will stay this way.

Drownranger, did you try different bias values? What is your perception?

Incidentally, I soldered a Muse KZ capacitor the wrong way and it became very hot and inflate the top. I wanted to see what’s inside so I opened the can. It then vented a vapor smelling like sulfer. I took some pics of what’s inside and here they are:
Attached Images
File Type: jpg IMGP7794.jpg (376.0 KB, 356 views)
File Type: jpg IMGP7803.jpg (299.5 KB, 323 views)
File Type: jpg IMGP7808.jpg (359.6 KB, 312 views)
__________________
Kind Regards,
Paulo.
  Reply With Quote
Old 1st April 2012, 01:47 PM   #379
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
For an EF output stage expect 20 to 25mVre through 0r22re.
That comes out at ~100mA of bias through each pair.
__________________
regards Andrew T.
  Reply With Quote
Old 1st April 2012, 01:54 PM   #380
diyAudio Member
 
Join Date: Aug 2009
Default nope...

hi Paulo,

I just stayed at 46mv. across two resistor emitter.theres something I read in books about gm doubling.when you try to bias a class b output as same as class a.besides my heatsink could not handle more heat.height is 3.75" which is very small.

regards,
joel

p.s.
next time be aware of the polarity and stick to safety region.
  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
Wanted: DIY amplifier builder with experience. I need a 0.7 ohm stable amplifier Audiophilenoob Swap Meet 34 16th May 2005 11:58 PM
Questions about how to decrease the PASS A-40 amplifier into a class AB amplifier. novtango Pass Labs 2 21st October 2002 01:50 AM


New To Site? Need Help?

All times are GMT. The time now is 05:03 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