I need help with this amplifier... - 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 25th March 2006, 05:39 PM   #1
diyAudio Member
 
Join Date: Jun 2005
Location: Belgrade, Serbia
Unhappy I need help with this amplifier...

Hi

Original schematic use Toshiba two pair's 2SC5200&2SA1943 output transistor.I want too use TWO pair's of IRFP240&9240.

I am not sure in value of R23 and R24.Voltage on this two resistor schoud be 7.8V.This is OK,but what is with currrnet in two resistor's?

Explanation please....



Attached Images
File Type: gif amplifier1.gif (72.3 KB, 838 views)
__________________
Pa mislim sta reci!
Ce sa spun!
  Reply With Quote
Old 26th March 2006, 12:57 AM   #2
ilimzn is offline ilimzn  Croatia
diyAudio Member
 
Join Date: Feb 2005
Location: Zagreb
It would help if you posted the unmodified schematic. Basically the current you want depends on the slew rate you want. A good ballpark figure would be aboout 10mA per pair of IRFP240/9240.

BTW what happened with the amp you designed and said would build in another thread?
  Reply With Quote
Old 26th March 2006, 08:06 AM   #3
diyAudio Member
 
Join Date: Jun 2005
Location: Belgrade, Serbia
Default !

Quote:
Originally posted by ilimzn
It would help if you posted the unmodified schematic. Basically the current you want depends on the slew rate you want. A good ballpark figure would be aboout 10mA per pair of IRFP240/9240.

BTW what happened with the amp you designed and said would build in another thread?
Here is original schematic.Boraomega is the designer.
Attached Files
File Type: pdf technosema.pdf (33.2 KB, 142 views)
__________________
Pa mislim sta reci!
Ce sa spun!
  Reply With Quote
Old 26th March 2006, 08:22 AM   #4
diyAudio Member
 
Join Date: Jun 2005
Location: Belgrade, Serbia
Default !

Quote:
Originally posted by ilimzn
It would help if you posted the unmodified schematic. Basically the current you want depends on the slew rate you want. A good ballpark figure would be aboout 10mA per pair of IRFP240/9240.

BTW what happened with the amp you designed and said would build in another thread?

Here is picture of that amplifier(Legend-MK2).

Mozes i na hrvatskom na mail da mi napises nesto za doradu.
Attached Images
File Type: jpg 060310_161942.jpg (51.5 KB, 562 views)
__________________
Pa mislim sta reci!
Ce sa spun!
  Reply With Quote
Old 26th March 2006, 08:46 AM   #5
diyAudio Member
 
bogdan_borko's Avatar
 
Join Date: Nov 2005
Location: serbia, zajecar
Hi VICTOR!

Replace R23 and R24 with one resistor 390 Ohms and set 20mA trough Q11 and Q12.

MY proposition:

1. make the amplifier but don`t connect output mosfets
2. Replace R23 and R24 with one resistor 390 Ohms
3. try to adjust bias with R19 and see if you can adjust 20mA trough Q11 and Q12, and if you can`t , replace R18 with some other value to acheve this.

POZDRAV!
  Reply With Quote
Old 26th March 2006, 09:55 AM   #6
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
if you decide to go with FETs then add a gate resistor to each FET and add a zener from each gate to source.

Increase the output FET Iq to 100mA for each FET and allow your sink size to let you experiment with upto Iq=250mA per FET. This will get hot.

Move the base connection of Q8 to next to R18 and connect the wiper of VR19 back to R20.
__________________
regards Andrew T.
  Reply With Quote
Old 26th March 2006, 10:50 AM   #7
MikeB is offline MikeB  Germany
diyAudio Member
 
MikeB's Avatar
 
Join Date: Apr 2004
Location: GŁtersloh
You have to be careful with this design, "mlaen" had built it and ran into stability problems as it is a bit undercompensated...
You need to add an input filter at least. I guess when changing to mosfets you have really to readjust the feedbackcompensation.

Mike
  Reply With Quote
Old 27th March 2006, 01:22 PM   #8
diyAudio Member
 
Join Date: Jun 2005
Location: Belgrade, Serbia
Default !

Quote:
Originally posted by MikeB
You have to be careful with this design, "mlaen" had built it and ran into stability problems as it is a bit undercompensated...
You need to add an input filter at least. I guess when changing to mosfets you have really to readjust the feedbackcompensation.

Mike
MikeB,Techo is very very good and stable amplifier."Mlaen" had built Techno and he had problem's with him because he mistake too much.Mlaen has change some transistor's(they are not used in original schematic) and because that he had problem's with Techno.His Techno now work's fine because boraomega saw were is "MLAEN" mistake.

In my country,one guy has built Techno two month's ago are his amplifier work's perfect.


__________________
Pa mislim sta reci!
Ce sa spun!
  Reply With Quote
Old 27th March 2006, 01:35 PM   #9
diyAudio Member
 
Join Date: Jun 2005
Location: Belgrade, Serbia
Default !

MikeB,why are you tell me that is Techno unstable amlplifier?!People must know that TECHNO is very good and stable amplifier!Look on the schematic!You know that is good schematic!Maybe you are jealouse on boraomega amplifier's because they are better than yourse ?!
__________________
Pa mislim sta reci!
Ce sa spun!
  Reply With Quote
Old 27th March 2006, 01:45 PM   #10
MikeB is offline MikeB  Germany
diyAudio Member
 
MikeB's Avatar
 
Join Date: Apr 2004
Location: GŁtersloh
That's quite ridiculous... A single 10pf millercap in a high gain amp is not much. Mlaen did only substitute the output stage with even slower transistors...
And, i don't know which one is better... I did not intend to measure sizes now, maybe you want ? You say boraomega's amps are better, have you compared ? If not,

Mike...
  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 11:29 AM.


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