Opa549 - Page 4 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 16th February 2003, 03:07 PM   #31
protos is offline protos  Greece
diyAudio Member
 
protos's Avatar
 
Join Date: Mar 2002
Location: Athens+Addis Ababa
Hi Jazz,
I got one channel working perfectly.I originally had the same problem till I realized that I hadn't connected the Ref pin to ground(I used no current limit).So Ilim pin is connected directly to Ref and they are connected to Ground.Enable pin is open.I had problems though with the other channel because it was giving me about 4-5V of offset and I didn't manage to get it right.I have ordered some more samples in case I managed to damage that one although I don't see how with all those safety features they have they should be practically indestructible.However this gave me the chance to substitute a LM3875 on hand and make some interesting A/B comparisons.
Overall I would say my preference went to the 549.More neutral,less peaky in the upper mids and more power and control.
More testing is in order since they haven't broken in completely yet.
  Reply With Quote
Old 16th February 2003, 05:02 PM   #32
diyAudio Member
 
JAZZ2250's Avatar
 
Join Date: Mar 2002
Location: Seoul. Korea
Quote:
Originally posted by protos
I originally had the same problem till I realized that I hadn't connected the Ref pin to ground(I used no current limit).
Indeed, I didn't connect the Ref pin to ground. Now, OPA549 with unity gain works. Next, I'm gonna give some gain to it. Thanks, protos.
  Reply With Quote
Old 17th February 2003, 11:36 AM   #33
diyAudio Member
 
Join Date: Mar 2001
Location: Brazil
Default Parallel

Has anyone paid attention to this parallel arrangement suggested on the OPA549 data page?

Would it work for a power amp?

It's interesting to note that there's no power amp circuit suggested on the data. I wonder why.


Carlos
Attached Images
File Type: gif opa549_parallel.gif (9.6 KB, 1896 views)
  Reply With Quote
Old 17th February 2003, 05:26 PM   #34
diyAudio Member
 
Join Date: May 2001
Location: Denmark
Question parralel/bride of opa549

http://focus.ti.com/download/trng/do.../sigcond_5.pdf

page 20 the super power amp.

Have any body build this circuit used for audio.
does the resistors have to mached ?

It look very simple I wonder if the parralel side will "fight" and get very hot.

jc dk.
  Reply With Quote
Old 17th February 2003, 06:47 PM   #35
diyAudio Member
 
Join Date: Mar 2001
Location: Brazil
Default TI parallel circuit

The reason I was asking for comments over that OP549 parallel arrangement, is because they do not a very good thing, as pointed up to me by Kuei Yang Wang over a bridging circuit I had seen.

The output of amp A1 feeds the input of amp A2, which means it's feeding distortion and all that.

Once again, it was no suggested specifically for audio. So I wonder.


Carlos
  Reply With Quote
Old 17th February 2003, 06:53 PM   #36
Banned
 
Join Date: Apr 2002
Location: Germany, Clausthal
why should one parallel them? isnīt 8 or 10 A enough? If you really need more, use some paralleld really big sourcefollowers behind them?
  Reply With Quote
Old 17th February 2003, 07:00 PM   #37
diyAudio Member
 
Join Date: Mar 2001
Location: Brazil
Default Parallel

Quote:
Originally posted by till
why should one parallel them? isnīt 8 or 10 A enough? If you really need more, use some paralleld really big sourcefollowers behind them?
No, I have nothing against paralleling amps. I even opened a specific thread on this Forum willing to discuss bridging and paralleling gainclones.

What I don't know is if this way suggested by TI, different from the one I knew and also suggested by National, was a valid one audio wise.


Carlos
  Reply With Quote
Old 18th February 2003, 12:15 PM   #38
Rookie is offline Rookie  Serbia
diyAudio Member
 
Rookie's Avatar
 
Join Date: Nov 2002
Location: Serbia
Protos,

How much is the capacitance in the power supply you used? I know that OPA549 has less PSRR than LM3875.
  Reply With Quote
Old 28th February 2003, 05:34 AM   #39
diyAudio Member
 
JAZZ2250's Avatar
 
Join Date: Mar 2002
Location: Seoul. Korea
Default Heatsink

Quote:
Originally posted by till
have to drill a lot of holes?
10 holes per OPA549...

I tried making a prototype heatsink with an aluminum plate measuring 9x4x0.25". I copied the mechanical drawing to PPT and adjusted its size to exactly the same as shown in the drawing. Then I printed it out on a paper, cut it, pasted it on the aluminum plate, punched, then drilled 10 holes using drill press. The whole process could be done in 10 to 15 minutes except for the making taps for mounting the amp. Before installing the amp to the aluminum plate, all the pins were masked (insulated) with heat-shrinkage cable cut to the 2/3 of the length of the pin.

In short, drilling holes is not so much time-consuming and you have enough area, which will contact the amp, for heat transfer. If you can find a heatsink for TO3 devices without any pre-drilled holes, you have no problem.

I'll post some photos if you're interested.
  Reply With Quote
Old 28th February 2003, 07:38 AM   #40
diyAudio Member
 
Join Date: Feb 2002
Location: Vancouver, BC, Canada
Send a message via ICQ to ThingyNess
The reason for paralleling them is not so much for current, but for power dissipation reasons. If you run those opamps with 8A with their maximum supply voltage for any length of time with any voltage across them (like in a linear amp), they will go into thermal shutdown and not work well. Paralleling them makes the effective allowable power dissipation be equal to the sum of the power dissipation ratings of the opamps, and will allow for greater output power.
  Reply With Quote

Reply


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


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 ctardi Chip Amps 6 8th May 2005 07:43 PM


New To Site? Need Help?

All times are GMT. The time now is 08:17 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright Đ1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2