opa549 class a

odysseybmx414 · 13th October 2005, 07:06 PM

anybody try opa549 biased into class A??

sss · 14th October 2005, 03:54 AM

how can u bias the chip intu class A?

the bias is internally set for class ab operation

carlosfm · 14th October 2005, 06:27 PM

Quote:

Originally posted by sss
how can u bias the chip intu class A?
the bias is internally set for class ab operation

The same way as you can bias any op-amp.

odysseybmx414 · 14th October 2005, 10:02 PM

how exactly would that be done if im using a +-21v supply? i dont have any transistors so thats out of the picture unless thats the only way to do it. is there any other way? i heard of using a resistor from the neg sup rail to output but i dont know what size etc. any tips?

carlosfm · 14th October 2005, 10:52 PM

Search around, I tried it with the LM1875.
Didn't like the results, though...
Yes, you can use high wattage resistors.

sss · 15th October 2005, 01:40 AM

Quote:

Originally posted by carlosfm

The same way as you can bias any op-amp.

oh , u mean that way , thats not really a class a operation .
anyway all thats gonna do is heat up the poor chip .

carlosfm · 15th October 2005, 01:49 AM

Quote:

Originally posted by sss
oh , u mean that way , thats not really a class a operation .
anyway all thats gonna do is heat up the poor chip .

Yes, it heats a lot. It's not pure class-A, of course.
If I remember, I biased up to around 500ma.
Hot heatsinks...

The sound was too smoooooth for my taste, the more the bias the more the smooothness. Then the detail vanished.
It will surely work better (but probably not well) with VERY easy to drive and sensitive speakers, but why bother?

tschrama · 15th October 2005, 11:16 AM

no no no no that's a .. well let's say.. less elegant way to do it.. but ...NP has published a few pdf ideas to play around with chipsamps .. one of those ideas was to use 2 power opamp in a balanced config, eg 2x lm3886 , biasing them at some arbitrairy Iq.. so that the work in class A PushPull ...

anybody remember that theads' name?

odysseybmx414 · 15th October 2005, 07:28 PM

NP?? whats this pdf?

13th October 2005, 07:06 PM	#1
odysseybmx414 diyAudio Member Join Date: Feb 2005 Location: Watertown, NY	opa549 class a anybody try opa549 biased into class A??

14th October 2005, 03:54 AM	#2
sss diyAudio Member Join Date: Jul 2003 Location: Israel , haifa	how can u bias the chip intu class A? the bias is internally set for class ab operation __________________ if you are not living on the edge you are taking too much space

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
Opa549	Treefingers	Chip Amps	1	23rd September 2005 08:37 PM
Fs: Opa549	bigmike216	Swap Meet	3	26th August 2005 12:08 AM
OPA549 GC for Car	abid_rehan	Chip Amps	11	13th June 2005 04:09 PM
OPA549 amp	Freddie	Chip Amps	8	29th February 2004 08:51 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

14th October 2005, 10:02 PM	#4
odysseybmx414 diyAudio Member Join Date: Feb 2005 Location: Watertown, NY	how exactly would that be done if im using a +-21v supply? i dont have any transistors so thats out of the picture unless thats the only way to do it. is there any other way? i heard of using a resistor from the neg sup rail to output but i dont know what size etc. any tips?

14th October 2005, 10:52 PM	#5
carlosfm Banned Join Date: Mar 2003 Location: Lisbon, Portugal	Search around, I tried it with the LM1875. Didn't like the results, though... Yes, you can use high wattage resistors.

15th October 2005, 11:16 AM	#8
tschrama diyAudio Member Join Date: Jul 2001 Location: The Netherlands	no no no no that's a .. well let's say.. less elegant way to do it.. but ...NP has published a few pdf ideas to play around with chipsamps .. one of those ideas was to use 2 power opamp in a balanced config, eg 2x lm3886 , biasing them at some arbitrairy Iq.. so that the work in class A PushPull ... anybody remember that theads' name?

15th October 2005, 07:28 PM	#9
odysseybmx414 diyAudio Member Join Date: Feb 2005 Location: Watertown, NY	NP?? whats this pdf?

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