Output stage on amp

kpero · 1st June 2005, 08:31 AM

Ok. First and only question is about output transistor. This shematic is orginal and has only one pair of output transistor. It's drive about 120 W in 4 ohms but it also can drive 160 W in 2 o.hms.
Now, is it posible to add one pair of output transistor. Power disipation wil bee far lower on every transistor and there will be little more gain on output. Which modification must be made ,if this can be done?

Thanks

Sory on bad English

darkfenriz · 1st June 2005, 09:28 AM

Quote:

Originally posted by kpero
is it posible to add one pair of output transistor.

sure, but it would be safer if emitter resistors were increased from 0.1 to 0.22

kpero · 2nd June 2005, 08:37 PM

Ok. I put two transistor in shematic. Blue line.
Is this good or I must conect diode on colector like D213 and D214 on firs pair.

Thanks

AndrewT · 3rd June 2005, 06:31 AM

Hi,
I don't know what the diodes are doing.
But they are connected to the power rails.
So so do not need to duplicate them.
I just ran an SOAR for one pair MJ15003/4 and your amp is struggling with this loading. For 2 ohm resistive you need about 15mF+15mF smoothing to keep the ripple low enough and must keep the output case temp below 28degC to be right on SOAR limit.

kpero · 3rd June 2005, 07:06 AM

This is car amp so power capacitor won't be so big. Output transistor are 2sa1673 and 2sc 4300. I don't know is this change thing?
You say it is struggling with one pair. If i put two pair will thing be better?

amplifierguru · 3rd June 2005, 07:12 AM

We have laws against LOUD car amps here and my past experience of driving in Bangkok ( dodge-em-cars/drag racing no rules) daily are much more relaxed and 'in control' with milliwatts of distraction from the horrible drivers.

Sorry , can't help.

AndrewT · 3rd June 2005, 07:26 AM

Hi,
I don't have SOAR data on 1673.
2 pairs will share the load and get you much safer on current draw through each transistor.
Since it is current that produces heat then you are reducing heat stress.
BUT car amp!! What temp are the transistor cases running at? (Tc).

kpero · 3rd June 2005, 07:53 AM

From data-shet Tc is 25 °C with 80 W power. Is that what you looking for?

Temperature range is -20 ,+150. I don't know on which temperature will operate in because i don't have technical info

Duo · 3rd June 2005, 08:12 AM

It appears that the diodes are there to prevent forward biasing of the CB junctions in the driver transistors.

3rd June 2005, 08:12 AM	#9
Duo diyAudio Member Join Date: Jun 2002 Location: Victoria, BC, Canada	It appears that the diodes are there to prevent forward biasing of the CB junctions in the driver transistors. __________________ -- Duo, W1ngs, VA7MON, and lesser known handles. -- -- http://www.w1ngselectronics.com -- My Work and Projects --

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
3C24 in a SE output stage - output transformer impedance recommendation !!!	aldovan	Tubes / Valves	15	6th September 2008 10:18 AM
preamp output stage resistor from output to V- ? ?	Bernhard	Solid State	4	19th October 2007 02:55 PM
Output stage biasing, with the driver stage	andrew_whitham	Tubes / Valves	0	19th May 2007 11:14 AM
Adding secondary of output transformer into cathodes of output stage ? Eico ST-70	freddymac406	Tubes / Valves	3	21st April 2007 06:15 PM
TV Horzontal Output Transistor for output stage..?	ronybc	Solid State	46	10th October 2005 02:26 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

3rd June 2005, 06:31 AM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, I don't know what the diodes are doing. But they are connected to the power rails. So so do not need to duplicate them. I just ran an SOAR for one pair MJ15003/4 and your amp is struggling with this loading. For 2 ohm resistive you need about 15mF+15mF smoothing to keep the ripple low enough and must keep the output case temp below 28degC to be right on SOAR limit.

3rd June 2005, 07:06 AM	#5
kpero diyAudio Member Join Date: Apr 2005 Location: Croatia	This is car amp so power capacitor won't be so big. Output transistor are 2sa1673 and 2sc 4300. I don't know is this change thing? You say it is struggling with one pair. If i put two pair will thing be better?

3rd June 2005, 07:12 AM	#6
amplifierguru Account Disabled Join Date: Aug 2004 Location: Earth	We have laws against LOUD car amps here and my past experience of driving in Bangkok ( dodge-em-cars/drag racing no rules) daily are much more relaxed and 'in control' with milliwatts of distraction from the horrible drivers. Sorry , can't help.

3rd June 2005, 07:26 AM	#7
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, I don't have SOAR data on 1673. 2 pairs will share the load and get you much safer on current draw through each transistor. Since it is current that produces heat then you are reducing heat stress. BUT car amp!! What temp are the transistor cases running at? (Tc).

3rd June 2005, 07:53 AM	#8
kpero diyAudio Member Join Date: Apr 2005 Location: Croatia	From data-shet Tc is 25 °C with 80 W power. Is that what you looking for? Temperature range is -20 ,+150. I don't know on which temperature will operate in because i don't have technical info