Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

Simply 3x gain preamp for OPA549
Simply 3x gain preamp for OPA549
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
Reply
 
Thread Tools Search this Thread
Old 23rd June 2005, 08:45 AM   #1
mangrovejack is offline mangrovejack  Australia
diyAudio Member
 
Join Date: Dec 2004
Location: Brisbane
Question Simply 3x gain preamp for OPA549

For the subwoofer channel on my 5.1 surround amp, I'm planning on using a single OPA549 (the other 5 channels are LM1875) as it will provide around 70-75w rms for my subwoofer.

However, upon searching the forum, people say that a gain of around 10 is the maximum you should use with the OPA549. But having said that, I'm only going to be using this chip for frequencies lower than 200Hz, so would using a gain of around 20-odd affect this region?

If it will, does anyone have a schematic for a simple circuit that will increase the gain from between 2x and 3x to use before the input to the OPA549? I've done searches of the forum, but they all seem much more complicated than I actually need (OPA627 buffers etc etc).

Thanks.
  Reply With Quote
Old 23rd June 2005, 11:14 AM   #2
jaudio is offline jaudio
diyAudio Member
 
Join Date: Oct 2004
Default Re: Simply 3x gain preamp for OPA549

Quote:
Originally posted by mangrovejack
For the subwoofer channel on my 5.1 surround amp, I'm planning on using a single OPA549 (the other 5 channels are LM1875) as it will provide around 70-75w rms for my subwoofer.

I dont think you will get that much power.


Quote:
Originally posted by mangrovejack

However, upon searching the forum, people say that a gain of around 10 is the maximum you should use with the OPA549. But having said that, I'm only going to be using this chip for frequencies lower than 200Hz, so would using a gain of around 20-odd affect this region?

It should work with no problems


Quote:
Originally posted by mangrovejack


If it will, does anyone have a schematic for a simple circuit that will increase the gain from between 2x and 3x to use before the input to the OPA549? I've done searches of the forum, but they all seem much more complicated than I actually need (OPA627 buffers etc etc).

Thanks.

Try this
Attached Images
File Type: jpg audio buffer sch2.jpg (17.5 KB, 700 views)
  Reply With Quote
Old 23rd June 2005, 04:36 PM   #3
PKS is offline PKS  Norway
diyAudio Member
 
Join Date: May 2005
Location: Dyri
Default Change.

Nice circuit, but change R1 to 2k. Non inverting so you have a 3x gain. then use 7.6x on the 549.(sorry bad english)
Use two 549 paralelled for more real power
__________________
PK; real norwegian noob.
  Reply With Quote
Old 23rd June 2005, 05:39 PM   #4
RCBandwidth is offline RCBandwidth  United States
diyAudio Member
 
RCBandwidth's Avatar
 
Join Date: May 2004
Location: New York and PA
Default Max gain of OPA549

Hi: In response to the previous concerns regarding the max gain of OPA549 chip amplifier,after reading the TI datasheet i do not see any problems with using the chip with a voltage gain of 20+.TI does not mention any possible instability problems at higher gains.If someone has info to the contrary,please post a link to that information. Thank You Robert Cottiers
  Reply With Quote
Old 23rd June 2005, 08:20 PM   #5
PKS is offline PKS  Norway
diyAudio Member
 
Join Date: May 2005
Location: Dyri
Default Re: Max gain of OPA549

Quote:
Originally posted by RCBandwidth
Hi: In response to the previous concerns regarding the max gain of OPA549 chip amplifier,after reading the TI datasheet i do not see any problems with using the chip with a voltage gain of 20+.TI does not mention any possible instability problems at higher gains.If someone has info to the contrary,please post a link to that information. Thank You Robert Cottiers

It's not a problem... But it sounds like ****... Max 10!
Make an amp, and test it out...
__________________
PK; real norwegian noob.
  Reply With Quote
Old 23rd June 2005, 10:21 PM   #6
jaudio is offline jaudio
diyAudio Member
 
Join Date: Oct 2004
Default Re: Re: Max gain of OPA549

PKS

Have you heard it used as a subwoofer amp?
  Reply With Quote
Old 23rd June 2005, 11:01 PM   #7
mangrovejack is offline mangrovejack  Australia
diyAudio Member
 
Join Date: Dec 2004
Location: Brisbane
Default Re: Re: Simply 3x gain preamp for OPA549

Quote:
Originally posted by jaudio



I dont think you will get that much power.


From the other threads discussing the OPA549, I was under the impression that was what I could get (I guess as a maximum rather than an average figure)?

I'll be using a 18-0-18 transformer and will be using a 4 ohm subwoofer, so what do you think the realistic power output would be? Either way, I think it will be enough for my fairly modest system.
  Reply With Quote
Old 24th June 2005, 12:04 AM   #8
jaudio is offline jaudio
diyAudio Member
 
Join Date: Oct 2004
Im not sure what the internal voltage drop is but my rough estimate is about 50watt rms.
  Reply With Quote
Old 25th June 2005, 08:18 AM   #9
1_C_E_M_A_N is offline 1_C_E_M_A_N  Philippines
Account Disabled
 
Join Date: Jun 2005
Location: Philippines
hi
you know RCBandwidth was right me myself tried OPA549 bridged parallel power amp for subwoofer and it sounds great
and very very loud
  Reply With Quote
Old 26th June 2005, 03:18 AM   #10
TonyTecson is offline TonyTecson  Philippines
diyAudio Moderator
 
TonyTecson's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
Simply 3x gain preamp for OPA549
opa549 can be supplied with max of +/-30 volts, whereas the opa541, +/-40 is allowed. these chips have a fixed bandwith, so that increasing the gain decreases the high frequency corner. but if you are using for subwoofer, then i see no problem with decreased bandwith, as you will not be needing it any way. i say go ahead and do it.
__________________
planet10 needs your help: Let's help Ruth and Dave...http://www.diyaudio.com/forums/plane...ml#post5010547[B
  Reply With Quote

Reply


Simply 3x gain preamp for OPA549Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
OPA549/541 at unity gain - schematic needed. nina Chip Amps 3 24th September 2007 03:46 PM
opa549 as unity gain odysseybmx414 Chip Amps 11 16th October 2005 05:34 PM
hi gain preamp ibo2 Tubes / Valves 2 27th August 2005 11:10 PM
what can be the max gain for opa549? arvin_ray Chip Amps 4 2nd May 2005 04:09 PM


New To Site? Need Help?

All times are GMT. The time now is 09:20 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki