a wonderfull sziklai - Page 6 - 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 22nd December 2008, 11:34 PM   #51
catalin is offline catalin  Romania
diyAudio Member
 
Join Date: Jun 2007
Yes but don't forget that is the real measurement and that is the sum of the (thd_alc889+gain*thd_alc889+thd_amp) !I will measure more acurate on the future.I still think that this stage is superior mos fet and ef..(for the sound and thd).
Below are the results of the alc (only).
Attached Files
File Type: zip realtek hd audio output.zip (98.1 KB, 128 views)
  Reply With Quote
Old 23rd December 2008, 03:25 PM   #52
diyAudio Member
 
megajocke's Avatar
 
Join Date: Jan 2003
Quote:
Originally posted by catalin
Ok ! Thank's for your feedback ! .
The others comercial amp's (up) was designed a little underrated ,no ?The engineers who design those make them underrated ?
If someone wants to listen this amp with no worries than it must 3 pairs of output devices . I must accept that the documentation about reactive load and the designing an final stage with reactive load (design about SOA vs power ) i haved miss a little.Please if you have some, maybe you can indicate to me.
I want to study all that problem in designing an proper final stage for various impedance..If you can ,give me some documentation .
Thank you again for your feedback !
A good day !
I believe you will be fine with 2 pairs like you have from a SOA perspective for 4 ohm speakers and music, that's what almost everyone selling amplifiers at this power level uses.

But without emitter resistors it will probably be unreliable! Did you check sharing during high power?
  Reply With Quote
Old 23rd December 2008, 05:52 PM   #53
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Default 2pair 2sa1943/c5200

Quote:
Originally posted by AndrewT
Finally,.......... Fitting a 33Vac 400VA 4%regulation transformer with +-45mF on each channel turns your crippled output stage into a real 4ohm capable amplifier for domestic duty (the heatsink must remain cold).
My model still predicts 200W into 4r0 and on the 100mS 25degC soar when 55degree phase angle.
That's what I said.

It's all down to adopting appropriate Vcc & Vee.

1943/5200 do not tolerate high voltages as well as other transistor types.
__________________
regards Andrew T.
  Reply With Quote
Old 23rd December 2008, 07:14 PM   #54
diyAudio Member
 
megajocke's Avatar
 
Join Date: Jan 2003
But as long as there are no emitter resistors current sharing might be so bad that it won't matter if 1 or 3 or 8 pairs is used, probably one transistor of each polarity will be taking much more load than the others. This is a much bigger problem.

Observe that at idle the current might still share well even without emitter resistors because transconductance is proportional to collector current and low at idle.
  Reply With Quote
Old 23rd December 2008, 07:43 PM   #55
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
Default when i was 6 years old .....

Quote:
Originally posted by megajocke
But as long as there are no emitter resistors current sharing might be so bad that it won't matter if 1 or 3 or 8 pairs is used, probably one transistor of each polarity will be taking much more load than the others. This is a much bigger problem.

Observe that at idle the current might still share well even without emitter resistors because transconductance is proportional to collector current and low at idle.
i was surprized by a loud tock tock noise created in the subway so asked my father about it and he told me that this was created by the gap between the rails that was there to prevent the rails from expanding due to summer heat ......

almost 15 years after that on my first trip abroad i was in stocholm exploring swedish ...... amplifiers he he he i realized that in swedish subway there was no gap between the lines and actually the lines were welded......

this totaly meesed me up i god all puzled and ask the first swedish engineer in front of me ( since i thought big time of my dad and he was also a mechanic , and since that was one of the first things i ve learned from him )

the mechanic said to me :

in the first years there was a gap ...now days they realized that rails may distribute the heat and expand side wise instead of lengthwise ...especially if they are welded ...... prooved my dad wrong and by the time i visit the greek subway again all lines were welded .....

what i am trying to say is that may transistors on this application do not need resistors , may the diference is converted to heat and then equally distributed to heat sink .... or may be some diference is not enough to make amplifier not working properly

but this is just an example of prospect farther testings by more experts is to be done to proove this right or wrong .....

just after next year i will produce a pcb and proceed on my own testings and let you know

happy regards !!!!!!!!!!!!!!!
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  Reply With Quote
Old 23rd December 2008, 07:57 PM   #56
catalin is offline catalin  Romania
diyAudio Member
 
Join Date: Jun 2007
Practically I didn't test current sharing yet,I just simulate same transistor with different beta .It didn't seems that the current is different .It helps the negative reaction by the 2sc5171,1930..But as I said ,if you don't want to implement an stage protection it's better to put R in emitter ..(I'm not totaly 100% sure yet).I will calculate and simulate better when I will have time .
Excuse my english !
Before the sziklai stage I try EF a lot .That sziklay it seems to me that the heat is better than the EF.
Merry Christmas !
  Reply With Quote
Old 23rd December 2008, 08:11 PM   #57
diyAudio Member
 
megajocke's Avatar
 
Join Date: Jan 2003
Hi!

A standard simulation will not show this effect because it depends on positive thermal feedback (reducing Vbe for same Ic with increasing temperature). In a standard simulation transistor junctions are all at the same temperature.

The driver stage won't help the current sharing (it can't detect differences between left and right transistors neither control them separately). If using separate drivers for each output device connected to their respective collector resistor they will force current sharing though.

Bias current will be stable in your circuit as it is set by the CFP driver. Also, bias current will probably share pretty good at idle as transconductance of output devices (and thus the positive thermal feedback) is pretty low then.

If the problem exists it might not be immediately obvious because even if sharing is way off the 1 pair doing all the work will still be able to do it for a while, but not reliably at all.
  Reply With Quote
Old 23rd December 2008, 08:49 PM   #58
catalin is offline catalin  Romania
diyAudio Member
 
Join Date: Jun 2007
Beta on the final stage depends by the temperature of the bipolar case ....The effect is the same. Vbe get low ~ higher beta . I don't know why we discuss that problem who have a simple answer... I said that you will put R in emittor ..
Happy.. day !
  Reply With Quote
Old 23rd December 2008, 10:26 PM   #59
diyAudio Member
 
megajocke's Avatar
 
Join Date: Jan 2003
Just check it in the amp under heavy load and see if it's good enough.
  Reply With Quote
Old 24th December 2008, 12:44 AM   #60
Banned
 
Join Date: Apr 2005
Location: Stockholm
Hi,
emitter resistors are needed for current sharing but try to keep them small as they will worsen the already troublesome crossover distortion.
  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
Sziklai output Moby Solid State 68 27th January 2011 11:39 AM
Hybrid Sziklai CFP Stee Solid State 0 27th December 2008 11:53 AM
ccs-loaded sziklai ionomolo Solid State 132 30th June 2008 07:39 AM
My DIY project - Wonderfull Loudspeakers ! Emeric Multi-Way 6 9th May 2008 03:38 AM


New To Site? Need Help?

All times are GMT. The time now is 10:54 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