300w mos-fet amp

raszvan · 24th April 2005, 03:53 PM

i need a mos-fet amp schematic...with pcb...
rms-aprox 300w
i can't find one...

bigpanda · 24th April 2005, 04:46 PM

Did you look at AV400 by Holton

edl · 24th April 2005, 06:45 PM

lets bulid Quasi's great quasi-complementary design.
that gives 350W(rms) to 4ohm. of course with lower rails (and maybe a few modifications) the power will be less, so if 250-300W is enough, you can use 60-70V idle rails.

Power amp under development

on the last page of the thread you will find the attached schematic in "pdf".
there is pcb-drawing there, too.

it's recommended to read the whole thread!

Regards

(instead irfp450 you can use the cheaper irfp240 in the output)

ezis666 · 25th April 2005, 11:51 AM

Yes, i have tested and this is good

quasi · 26th April 2005, 01:48 AM

The amp suggested by edl and ezis666 has been running now for more than a month without any issues. It is very quite when idle and very clean under power.

Last week I took it to a friends house for it's first public audition.

We ran a NAD CD player and NAD receiver as the pre-amp into the power amp driving a set of IMF transmission line speakers (very nice speakers).

Everyone was impressed with the amp and another amp will be built by the host and his son as a project.

If you decide to build it, contact me if you want any advice.

Cheers

amplifierguru · 26th April 2005, 02:01 AM

Hi quasi.

Does your amp have a turn on thump? Have you tried to DC couple it to eliminate the electro's from the signal path?

Greg

quasi · 26th April 2005, 02:51 AM

Quote:

Originally posted by amplifierguru
Hi quasi.

Does your amp have a turn on thump? Have you tried to DC couple it to eliminate the electro's from the signal path?

Greg

Well yes and no.

The amp boards themselves do when they are first turned on and the woofers do pop a bit.

The completed amp has speaker delay via the protection circuit and this comes in about 4 seconds after the amp is turned on so no thump is sent to the speaker.

You will note that I also a have a soft turn on cct for the powersupply and this lasts about 1.5 seconds. This means that the voltages for the amp modules rise slowly and a speaker delay is required to prevent any problems here.

Cheers

amplifierguru · 26th April 2005, 03:21 AM

Just wondering. I used to make PA amps similar to this topology in the 70's but with complementary feedback triples using MJ15003/4. There's probably a few still floating around there they were installed in a lot of clubs and discos.

They didn't us a relay output so I dethumped the turnon by using a long RC timeconstant feed to your T7 which simulated the slow charge-up of the primitive bootstrap which never thumped.

You don't mind having electro's in the signal path?

Have you tried cascoding the input stage/ FETs instead of the bipolars? dead easy with no circuit changes just drop in.

quasi · 26th April 2005, 03:35 AM

The final version of the amp does not use a cascode input stage but rather a current mirror. A FET input stage would work well as you sugested and would be a "drop in" provided the FETs were rated to at least 75v. In my amp I use a 1uf MKT style capacitor for the input.

Cheers

Coulomb · 26th April 2005, 03:49 AM

Check this thread.

Hitachi 2SK/2SJ 300 Watt Class A/B Amp Completed

24th April 2005, 03:53 PM	#1
raszvan diyAudio Member Join Date: Apr 2005 Location: bucharest	300w mos-fet amp i need a mos-fet amp schematic...with pcb... rms-aprox 300w i can't find one...

26th April 2005, 01:48 AM	#5
quasi diyAudio Member Join Date: Sep 2004 Location: Adelaide, Australia	Hi Rasvan The amp suggested by edl and ezis666 has been running now for more than a month without any issues. It is very quite when idle and very clean under power. Last week I took it to a friends house for it's first public audition. We ran a NAD CD player and NAD receiver as the pre-amp into the power amp driving a set of IMF transmission line speakers (very nice speakers). Everyone was impressed with the amp and another amp will be built by the host and his son as a project. If you decide to build it, contact me if you want any advice. Cheers __________________ http://sites.google.com/site/quasisdiyaudiosite/

26th April 2005, 03:35 AM	#9
quasi diyAudio Member Join Date: Sep 2004 Location: Adelaide, Australia	The final version of the amp does not use a cascode input stage but rather a current mirror. A FET input stage would work well as you sugested and would be a "drop in" provided the FETs were rated to at least 75v. In my amp I use a 1uf MKT style capacitor for the input. Cheers __________________ http://sites.google.com/site/quasisdiyaudiosite/

26th April 2005, 03:49 AM	#10
Coulomb diyAudio Member Join Date: Jul 2002 Location: Ancaster, Ontario	Check this thread. Hitachi 2SK/2SJ 300 Watt Class A/B Amp Completed __________________ I like to stay current!

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


	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

24th April 2005, 04:46 PM	#2
bigpanda diyAudio Member Join Date: Jun 2004 Location: HKSAR	Did you look at AV400 by Holton

24th April 2005, 06:45 PM	#3
edl diyAudio Member Join Date: Oct 2004	lets bulid Quasi's great quasi-complementary design. that gives 350W(rms) to 4ohm. of course with lower rails (and maybe a few modifications) the power will be less, so if 250-300W is enough, you can use 60-70V idle rails. Power amp under development on the last page of the thread you will find the attached schematic in "pdf". there is pcb-drawing there, too. it's recommended to read the whole thread! Regards (instead irfp450 you can use the cheaper irfp240 in the output)

25th April 2005, 11:51 AM	#4
ezis666 diyAudio Member Join Date: Mar 2004 Location: Riga	Yes, i have tested and this is good

26th April 2005, 02:01 AM	#6
amplifierguru Account Disabled Join Date: Aug 2004 Location: Earth	Hi quasi. Does your amp have a turn on thump? Have you tried to DC couple it to eliminate the electro's from the signal path? Greg

26th April 2005, 03:21 AM	#8
amplifierguru Account Disabled Join Date: Aug 2004 Location: Earth	Just wondering. I used to make PA amps similar to this topology in the 70's but with complementary feedback triples using MJ15003/4. There's probably a few still floating around there they were installed in a lot of clubs and discos. They didn't us a relay output so I dethumped the turnon by using a long RC timeconstant feed to your T7 which simulated the slow charge-up of the primitive bootstrap which never thumped. You don't mind having electro's in the signal path? Have you tried cascoding the input stage/ FETs instead of the bipolars? dead easy with no circuit changes just drop in.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
300W P.A. amp	drummer_Dave	Solid State	4	19th February 2009 10:45 PM
300w rms amp	leander	Solid State	10	10th June 2007 08:33 PM
300w rms amp	leander	Parts	1	8th September 2005 09:43 AM
300w sub amp help	zoki_g	Solid State	3	1st May 2003 10:49 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