wanted a dual differential amplifier with all fet

thanh · 1st May 2004, 03:19 AM

Hi!I like JFET and MOSFET.I want to have a dual differential power amplifier with all FET.
I need all your hepl.Thanks you!

fab · 1st May 2004, 04:23 AM

Quote:

Originally posted by thanh
Hi!I like JFET and MOSFET.I want to have a dual differential power amplifier with all FET.
I need all your hepl.Thanks you!

See http://www.borbelyaudio.com/index31.htm and enjoy!

Erno Borbely is the original designer of Hafler DH-200 amp.

Charles Hansen · 2nd May 2004, 02:03 AM

The Borbely amp has a dual (complementary) differential input stage. If you want an amp that is complementary differential from input to output, check out:

http://www.diyaudio.com/forums/showt...ht=#post334963

(At then end of the post is a zip file that you can download.)

Also, James Bongiorno had a design in Audio Amateur about 20 years ago (Ampzilla 200???) that was complementary differential from input to output, although it was 100% bipolars.

thanh · 2nd May 2004, 03:03 AM

Borbely's project has not got value of components.I is not good at designing JFET.Thank Charles Hansen and fab!
I still need that so i still need all your help!Again,thanks a lot!

fab · 2nd May 2004, 04:00 AM

Quote:

Originally posted by thanh
Borbely's project has not got value of components.I is not good at designing JFET.Thank Charles Hansen and fab!
I still need that so i still need all your help!Again,thanks a lot!

Maybe you did not check in the proper site menu. Check in more precisely in http://www.borbelyaudio.com/index15.htm. There are the "SERVO-50" and "DC-102". It includes all information including value of components.

jcx · 2nd May 2004, 12:56 PM

disctete FETs are really not good in "cookbook" projects, even professional engineers avoid them in mass production designs because of the wide individual and lot-to-lot parameter variations - simply copying a circuit based on fet part # alone could easily leave you with something that doesn't work at all due to bias errors

for diy and "hand crafted" audiophile projects they can be good but you must know enough to measure sort/match and individually trim bias as appropriate for each stage in your circuit

fab · 3rd May 2004, 12:18 AM

Quote:

Originally posted by jcx
disctete FETs are really not good in "cookbook" projects, even professional engineers avoid them in mass production designs because of the wide individual and lot-to-lot parameter variations - simply copying a circuit based on fet part # alone could easily leave you with something that doesn't work at all due to bias errors

for diy and "hand crafted" audiophile projects they can be good but you must know enough to measure sort/match and individually trim bias as appropriate for each stage in your circuit

Yes, and that is why I have indicated the "SERVO-50" and "DC-102" which only includes jfets at the input stage.

jewilson · 3rd May 2004, 04:31 AM

Borbely's project are way over priced. Heck you can buy a used Krell or a Levinson off eBay for what this guy want for his parts.
I believe that www.audioXpress.com still have some of his PCB's from passed project. You could change inputs from bipolars to FET that's is not a big deal.

Now if we only could get Charles Hansen to offer a PCB for his no feeback amp design, that would be cool.

thanh · 5th May 2004, 06:12 AM

this is JFET's formula.
Is not it a absolute formula?

jcx · 5th May 2004, 01:29 PM

a fine formula, but still an approximation that is limited to large Vds and “long channel” fets

the problem is that Idss and Vp can vary 5:1 for the same part # between batches - and smaller but still significant variations within a lot

you have no guarantee that you can select what you want yourself from any given lot of the same part # fet

you can buy fets sorted by the manufacturer to smaller ranges but fets are inherently more sensitive to normal process variations than most of the bipolar Q we use

1st May 2004, 03:19 AM	#1
thanh diyAudio Member Join Date: Jan 2004 Location: ho chi minh city	wanted a dual differential amplifier with all fet Hi!I like JFET and MOSFET.I want to have a dual differential power amplifier with all FET. I need all your hepl.Thanks you!

3rd May 2004, 04:31 AM	#8
jewilson diyAudio Member Join Date: May 2002 Location: Plano , TX	Borbely's project are way over priced. Heck you can buy a used Krell or a Levinson off eBay for what this guy want for his parts. I believe that www.audioXpress.com still have some of his PCB's from passed project. You could change inputs from bipolars to FET that's is not a big deal. Now if we only could get Charles Hansen to offer a PCB for his no feeback amp design, that would be cool. __________________ Jim W.

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
Discrete Dual Differential DAC?	dantwomey	Digital Source	18	5th March 2011 06:24 AM
Single or dual differential?	lumanauw	Solid State	346	29th November 2007 01:37 AM
Dual FETs for differential pair	jwb	Pass Labs	4	29th May 2003 07:39 PM
Dual-differential input stages	Jon T.	Pass Labs	14	2nd October 2001 08:53 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


	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

2nd May 2004, 02:03 AM	#3
Charles Hansen diyAudio Member Join Date: May 2003 Location: Colorado	The Borbely amp has a dual (complementary) differential input stage. If you want an amp that is complementary differential from input to output, check out: http://www.diyaudio.com/forums/showt...ht=#post334963 (At then end of the post is a zip file that you can download.) Also, James Bongiorno had a design in Audio Amateur about 20 years ago (Ampzilla 200???) that was complementary differential from input to output, although it was 100% bipolars.

2nd May 2004, 03:03 AM	#4
thanh diyAudio Member Join Date: Jan 2004 Location: ho chi minh city	Borbely's project has not got value of components.I is not good at designing JFET.Thank Charles Hansen and fab! I still need that so i still need all your help!Again,thanks a lot!

2nd May 2004, 12:56 PM	#6
jcx diyAudio Member Join Date: Feb 2003 Location: ..	disctete FETs are really not good in "cookbook" projects, even professional engineers avoid them in mass production designs because of the wide individual and lot-to-lot parameter variations - simply copying a circuit based on fet part # alone could easily leave you with something that doesn't work at all due to bias errors for diy and "hand crafted" audiophile projects they can be good but you must know enough to measure sort/match and individually trim bias as appropriate for each stage in your circuit

5th May 2004, 01:29 PM	#10
jcx diyAudio Member Join Date: Feb 2003 Location: ..	a fine formula, but still an approximation that is limited to large Vds and “long channel” fets the problem is that Idss and Vp can vary 5:1 for the same part # between batches - and smaller but still significant variations within a lot you have no guarantee that you can select what you want yourself from any given lot of the same part # fet you can buy fets sorted by the manufacturer to smaller ranges but fets are inherently more sensitive to normal process variations than most of the bipolar Q we use