Jfet input, Lateral output 2nd version

Tekko · 18th October 2011, 07:02 PM

Heres something i plan to try, using the laterals i got in the big transistor score a few months ago:

http://i.imgur.com/xhqtH.png

In simulation it sez flat from DC to 400kHz and a dc offset of 60-100 microvolts with the input floating and 1millivolt with the input shorted to ground. Around 50-100 watts per channel with a 2x35-45VDC 300VA psu.

I yet don't know if this will actually work in reality but i think it should, may try it this coming weekend if i feel up to it.

I also plan to use a very similar jfet input stage in a big subwoofer amplifier using five pairs of MJW21195's and MJW21196's with MJL4281 and MJL4302 as drivers, i expect up to 500 watts short term(pulse) and around 300 watts continous into 4 ohms from this one as my biggest psu is 500VA and offers around 2x70V at the caps.

Tekko · 23rd October 2011, 02:14 PM

Heres a CFP version if you can call it that with lateral outputs, in simulation offering 0.0005% THD at 1kHz at some 30 watts output which is about all i can do without exceeding the SOA of the output pairs:

http://i.imgur.com/aOhaz.png

Tekko · 23rd October 2011, 08:27 PM

And a video: Jfet input Lateral mosfet output Power Amplifier - YouTube

Tekko · 24th October 2011, 08:56 PM

Oscillation issues solved: http://i.imgur.com/Lo3a7h.png

New video: Jfet input Lateral Mosfet output Power Amplifier - YouTube

Tekko · 25th October 2011, 09:52 AM

A board have been cadded for this thing: http://i.imgur.com/rq2Gq.png

Tekko · 28th October 2011, 03:17 PM

On this amp design, all on scope visible crossover distortion pretty much goes away with just 10-15mA of bias current per pair of output fets.

And i cant really hear any difference between 15mA and 75mA.

I find that rather unusual since most bjt designs wants atleast 20-30mA for the crossover distortion to even begin to disappear, and most mosfet designs needing 100+mA according to some.

Tekko · 29th October 2011, 06:51 PM

Some pics of the prototype, the second channel is under construction now.

Power stage:
http://i.imgur.com/u4der.jpg

Frontend and drive board:
http://i.imgur.com/ECvco.jpg

Tekko · 30th October 2011, 01:09 PM

Both channels built and ready for testing:

http://i.imgur.com/9S3bh.jpg
http://i.imgur.com/1aqvf.jpg
http://i.imgur.com/oNLM4.jpg

Tekko · 30th October 2011, 02:35 PM

And the prototype now in stereo is done: Jfet input Lateral mosfet output amp - YouTube

Nico Ras · 30th October 2011, 07:49 PM

Personally I would not try and demonstrate an amp's sound by recording it with a cellular phone microphone and putting it on youtube. It sounds absolutely rubbish. Nobody would want something sounding like that.

18th October 2011, 07:02 PM	#1
Tekko diyAudio Member Join Date: Jan 2005	Jfet input, Lateral output 2nd version Heres something i plan to try, using the laterals i got in the big transistor score a few months ago: http://i.imgur.com/xhqtH.png In simulation it sez flat from DC to 400kHz and a dc offset of 60-100 microvolts with the input floating and 1millivolt with the input shorted to ground. Around 50-100 watts per channel with a 2x35-45VDC 300VA psu. I yet don't know if this will actually work in reality but i think it should, may try it this coming weekend if i feel up to it. I also plan to use a very similar jfet input stage in a big subwoofer amplifier using five pairs of MJW21195's and MJW21196's with MJL4281 and MJL4302 as drivers, i expect up to 500 watts short term(pulse) and around 300 watts continous into 4 ohms from this one as my biggest psu is 500VA and offers around 2x70V at the caps. __________________ The point of life is to build atleast one audio amplifier before you die.

23rd October 2011, 02:14 PM	#2
Tekko diyAudio Member Join Date: Jan 2005	Heres a CFP version if you can call it that with lateral outputs, in simulation offering 0.0005% THD at 1kHz at some 30 watts output which is about all i can do without exceeding the SOA of the output pairs: http://i.imgur.com/aOhaz.png __________________ The point of life is to build atleast one audio amplifier before you die.

23rd October 2011, 08:27 PM	#3
Tekko diyAudio Member Join Date: Jan 2005	And a video: Jfet input Lateral mosfet output Power Amplifier - YouTube __________________ The point of life is to build atleast one audio amplifier before you die.

24th October 2011, 08:56 PM	#4
Tekko diyAudio Member Join Date: Jan 2005	Oscillation issues solved: http://i.imgur.com/Lo3a7h.png New video: Jfet input Lateral Mosfet output Power Amplifier - YouTube __________________ The point of life is to build atleast one audio amplifier before you die.

25th October 2011, 09:52 AM	#5
Tekko diyAudio Member Join Date: Jan 2005	A board have been cadded for this thing: http://i.imgur.com/rq2Gq.png __________________ The point of life is to build atleast one audio amplifier before you die.


	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

28th October 2011, 03:17 PM	#6
Tekko diyAudio Member Join Date: Jan 2005	On this amp design, all on scope visible crossover distortion pretty much goes away with just 10-15mA of bias current per pair of output fets. And i cant really hear any difference between 15mA and 75mA. I find that rather unusual since most bjt designs wants atleast 20-30mA for the crossover distortion to even begin to disappear, and most mosfet designs needing 100+mA according to some. __________________ The point of life is to build atleast one audio amplifier before you die.

29th October 2011, 06:51 PM	#7
Tekko diyAudio Member Join Date: Jan 2005	Some pics of the prototype, the second channel is under construction now. Power stage: http://i.imgur.com/u4der.jpg Frontend and drive board: http://i.imgur.com/ECvco.jpg __________________ The point of life is to build atleast one audio amplifier before you die.

30th October 2011, 01:09 PM	#8
Tekko diyAudio Member Join Date: Jan 2005	Both channels built and ready for testing: http://i.imgur.com/9S3bh.jpg http://i.imgur.com/1aqvf.jpg http://i.imgur.com/oNLM4.jpg __________________ The point of life is to build atleast one audio amplifier before you die.

30th October 2011, 02:35 PM	#9
Tekko diyAudio Member Join Date: Jan 2005	And the prototype now in stereo is done: Jfet input Lateral mosfet output amp - YouTube __________________ The point of life is to build atleast one audio amplifier before you die.

30th October 2011, 07:49 PM	#10
Nico Ras diyAudio Member Join Date: Nov 2005 Location: Amanzimtoti - East Coast of South Africa	Personally I would not try and demonstrate an amp's sound by recording it with a cellular phone microphone and putting it on youtube. It sounds absolutely rubbish. Nobody would want something sounding like that. __________________ Kind regards Nico

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

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
JFET input, MOSFET VAS, LATERAL output = Perfect!!	lineup	Solid State	2281	28th April 2012 07:03 PM
Complementary JFET-JFET cascode input, BJT VAS-Drivers, Lateral Output	Neutrality	Solid State	53	23rd October 2011 06:53 PM
Lateral output amp with jfet input	Tekko	Solid State	2	4th August 2011 06:43 PM
10 Watt Single End, JFET input - Lateral N-MOSFET output	lineup	Solid State	82	30th July 2009 06:23 PM

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