| Leolabs |
| What is the usable gain setting and do signal/feedback caps are required???Can it be build using the usual approach of a normal 3875 GC(ie only low capacity caps are employed,hand-wiring.....) |
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| Ipanema |
OPA549 is unity gain stable. You can use it as monolitic F4. :D
Pinkmouse likes it a lot. He can give a better suggestion. |
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| juma |
I used it this way :
http://www.diyaudio.com/forums/show...948#post1029948
with impressive result.
This configuration (SuSy) alows for some distortion and class AB artefacts cancelation and sounds much better than single chip topology. Look for "Bivoj" thread where Pavel published some real life measurments with single-chip amp with OPA549. Regulated PS helps a lot. I used LT1083 fot that. |
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| pinkmouse |
| quote: | Originally posted by Ipanema
Pinkmouse likes it a lot. He can give a better suggestion. |
Indeed! :)
My favourite implementation is inverting, with gain of 8, and for general use, at least 6800uF on the rails, (you can go slightly less for mid/high only, and more for bass, if you're using an active crossover). With this setup you can use a 15-0-15 traffo, but if you want all the power available, you will need a preamp or buffer with about 2 x gain, (I use the OPA627 for preference), and increase the rails to about 30V. |
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| Upupa Epops |
| Ask PMA to audio quality of this amp... :whazzat: |
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| juma |
There is a way to make a better sounding single-chip-per-channel OPA549 implementation (picture in attachment). Its sound character is dominated by first IC (AD823 sounded very good to me, AD797 even better).
This version is inspired by Walt Jung's article "Composite Line Driver With Low Distortion" published in ELECTRONIC DESIGN ANALOG APPLICATIONS, Issue June 24, 1996. |
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| Ipanema |
| Is this a nested feedback design? |
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| Gcollier |
| quote: | Originally posted by Ipanema
Is this a nested feedback design? |
Looks that way to me :) I'll have to give this application a try, it works great for preamps.
I have been using the OPA549 in my "upstairs" audio system for some time now and am very happy with it. For optimal sound quality follow Pinkmouse's suggestions and keep the gain low and use a preamp. The OPA549 does not have the gain bandwith to provide peak performance when used at high gains, but can provide plenty of output current. Honestly having tried most of the common chips (4780, 3886, 3876, 3875, 1875, OPA541) I have absolutely no complaints about the OPA549 as long as it is used within it's limitations. If anyone is interested I can post the board files that I have been using, its a 2 sided design, non-inverted, can be used as either a stereo pair or paralelled. I originally built it as a sub amp, but it worked out very nicely when the wife asked for an amp to use upstairs...who was I to refuse :devilr: |
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| juma |
Hi Gcollier,
I used AD823 because it swings rail to rail (it has to give bigger part of total voltage gain), and it sounds very good. If you plan to lower the gain of OPA549 to 2x or even unity, it would be good to use an OpAmp with higher PS voltage capability (OPA552 endures +-30V) instead of AD823. Regulated PS improves the sound in this case also. I used a pair of LM338s as regulators for OPA549. |
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| PMA |
| The OPA549 is an outstanding crossover distortion generator, even far better than the LM chipamps. |
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| HIPCHECK |
I wonder what interest in a BPA pcb that would use the OPA549?
i have used the lm3886 and opa549, and would like to build a amp for my midbass speakers with the OPA549. I am not up to the chore of a scratch built pcb for the BPA.
If the interest is high i would be willing to donate parts to all people that would order a pcb. (IE Panasonic stacked films for bypass caps ecq-v, and Vishay/Dale smt 0.3R 2W 1% WSR resistors) in the amount of maybe 30 kits.
I would assume
4 resistors per amp? 8 for stereo? x 30 kits=320 resistors?
8 bypass caps per amp and 16 for stereo? x30 kits=480caps?
The pcb i would have interest in would be 2 OPA549 per pcb that could be used parralell or as stereo amps, and a driver pcb that used the drv134 buffered by a simple opamp, maybe opa134 etc. The pcb would be nice if it was setup for different cap size/options and the use of the supplied smt resistors and thru-hole.
Im no pro at any of this, actually im new to this hobby! but i have lurked around and have an idea of what i would like to see in this type of kit.
I have some of digi's drv pcbs and im building a prototype of this amp sometime soon, if work/life permits.
below is some food for thought!
http://www.diyaudio.com/forums/attachment.php?s=&postid=997110&stamp=1157327637
http://www.shine7.com/audio/bpa300.htm |
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| jaudio |
| This is a bridged parallel OPA549 amp. The amp will be an inverted amp with trimmers to dial out dc. Actually the amp can be set inverted or non inverted. The gain can be changed, by pull the resistor out of their sockets. I would like to set the gain for the OPA549 to 1 and use the OPA552 (also inverted) at the gain of 13.75 to drive the OPA549. |
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| jaudio |
| quote: | Originally posted by jaudio
This is a bridged parallel OPA549 amp. The amp will be an inverted amp with trimmers to dial out dc. Actually the amp can be set inverted or non inverted. The gain can be changed, by pull the resistor out of their sockets. I would like to set the gain for the OPA549 to 1 and use the OPA552 (also inverted) at the gain of 13.75 to drive the OPA549. |
If I go this route, the preamp will need to drive low impedance (around 1k). I was thinking a signal splitter, then send the +and - signal to a PGA2310, maybe an AD815 for an output buffer. |
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| Upupa Epops |
| To PMA : How you can see, not only in our country people like distortion... :D ...it is lost fight... :rolleyes: |
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| pinkmouse |
| quote: | Originally posted by Upupa Epops
...it is lost fight... :rolleyes: |
:D |
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| juma |
Yes it is. This sch. may not be what you are used to see, but Negative Feedback should always be in opposite phase (otherwise it would be called Positive Feedback). ;) |
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| Gcollier |
Here is the board design that I have been using for a while now. I am currently running these as two seperate channels, but the board is set up to run the OPA549 in parallel by simply jumpering the central red traces for in and out. This is the textboox non-inverting design. I could modify this fairly easily to accomodate different types/sizes of caps. There is a common supply for the amps, I get zero hum running these as stereo using this layout. Currently it is set up for the "home" etcher who doesn't have the ability to do plated through holes, a few of the traces could be removed if the boards were fabricated. A simple bridging board and two of these modules coulm make for a fairly high powered amp.
I'll see about opening the top of my current amp to show you all the guts (when the wife isn't looking...she just loves when I rip my "finished" projects apart ;) )
G.
| quote: | Originally posted by HIPCHECK
I wonder what interest in a BPA pcb that would use the OPA549?
...The pcb i would have interest in would be 2 OPA549 per pcb that could be used parralell or as stereo amps, and a driver pcb that used the drv134 buffered by a simple opamp, maybe opa134 etc. The pcb would be nice if it was setup for different cap size/options and the use of the supplied smt resistors and thru-hole.
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| Leolabs |
| If the OPA549 still be used at gain of x20,besides bandwidth problem,what else???? |
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| Gcollier |
| A BPA configuration can avoid that issue since you could run each side with a gain of 10 and have an overall gain of 20...if that is what you desire. |
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