More about CPU coolers with LM3886
By the way, rljones.
There is more people using your idea of mounting the LM3886 with small CPU heatsinks + fans, and seems to work fine (the only problem I see is noise, but a little bit of experimenting with their speeds and temperature can help).
Have a look at:
http://www.pablin.com.ar/electron/circuito/audio/amp50/
Regards
By the way, rljones.
There is more people using your idea of mounting the LM3886 with small CPU heatsinks + fans, and seems to work fine (the only problem I see is noise, but a little bit of experimenting with their speeds and temperature can help).
Have a look at:
http://www.pablin.com.ar/electron/circuito/audio/amp50/
Regards
Cheapskates unite
Hi guys (and any gals...?)
Thank you rljones for saving me a heap of trouble. I was going to embark on the suggested design in the Nat Semi app note, but it makes sense to design it the way you propose. Please add me to the list of people who want details of the circuit board you design!
The heatsink idea also blew me away. I have been grappling with finding a nice looking, decent sized heatsink that wasn't going to cost me a fortune: a cpu cooler will be far smaller, neater, and cheaper!
The one thing that hasn't been mentioned in this thread is the fact that National Semi kindly GIVE AWAY these amp chips in quantities of FIVE at a time.
Just go to http://www.national.com/pf/LM/LM3886.html, and click on the order samples button, and away you go. This is particularly nice of them, considering that our local parts supplier, Jaycar, wants us to pay AU $20 retail each for them!
Now all I need is to find a manufacturer who will give me some samples of some 10,000 uF 50V+ electros, and another manufacturer who will sample me a few 500va toroidal trannies......
Cheers from Oz!
Hi guys (and any gals...?)
Thank you rljones for saving me a heap of trouble. I was going to embark on the suggested design in the Nat Semi app note, but it makes sense to design it the way you propose. Please add me to the list of people who want details of the circuit board you design!
The heatsink idea also blew me away. I have been grappling with finding a nice looking, decent sized heatsink that wasn't going to cost me a fortune: a cpu cooler will be far smaller, neater, and cheaper!
The one thing that hasn't been mentioned in this thread is the fact that National Semi kindly GIVE AWAY these amp chips in quantities of FIVE at a time.
Just go to http://www.national.com/pf/LM/LM3886.html, and click on the order samples button, and away you go. This is particularly nice of them, considering that our local parts supplier, Jaycar, wants us to pay AU $20 retail each for them!
Now all I need is to find a manufacturer who will give me some samples of some 10,000 uF 50V+ electros, and another manufacturer who will sample me a few 500va toroidal trannies......
Cheers from Oz!
Re: Cheapskates unite
Thanks,
Paul
Samples are intended for manufacturers who may be ordering production quantities. If DIYers abuse this previlege it will disappear. Please be reasonable when requesting samples. I refrain from doing it unless there is no other way I can get the parts.Paulmcv said:
Thanks,
Paul
I agree with paulb.
I ordered some samples before and now I work for a big company and we appreciate a lot the possibility of obtaining free samples because it accelerate the development process a lot.
I think it is not bad for companies that DIYers use free samples, as it was in my case. Now we buy a lot of the products I tried before at home.
But please be responsible, and ask for them only in case you don't have other way to find them.
Regards.
(let's continue with the issue of this thread: LM3886 amps
I ordered some samples before and now I work for a big company and we appreciate a lot the possibility of obtaining free samples because it accelerate the development process a lot.
I think it is not bad for companies that DIYers use free samples, as it was in my case. Now we buy a lot of the products I tried before at home.
But please be responsible, and ask for them only in case you don't have other way to find them.
Regards.
(let's continue with the issue of this thread: LM3886 amps
Hey guys calm down!
I'm not ordering commercial quantities of the things!
If they are happy to give away samples and courier them across the globe, then thanks heaps! They have decided that they are a big enough company to support it.
I agree: abuse it and you lose it.
I have ordered the parts, I will make an amp, and I'm sure I'll need to do some tweaking with the layout etc etc. before I'm happy with it.
If a friend asks me to build one for them, no worries. A $20 amp module is a small part of the total price to build it, when you add in the cost of the toroidal transformer, filter caps, and a half decent case to put it in.
If it sounds like sh*%te, I won't order or buy the part again.
The same can be said about op amps. I've been designing a pcb for the mixer project as described in http://sound.westhost.com/project30.htm , and have also been following the threads here regarding which particular chip/fet/tranny/diode/piece of string sounds good or sounds bad.
It is interesting to come across a chip that sounds good on paper, and do the exercise of getting one. You will often hear the following conversation: "Yes sir, we can get those for you. It will take six to eight weeks, minimum order of 2500 and they cost $xxxx each...." If they don't do samples, I don't get to audition the chip.
So sorry, guys. I didn't mean to start an abuse thread.
I agree with ssanmor; let's continue with the issue of this thread: LM3886 amps.
BTW, I have built an amp using a similar chip previously, and they work really well. I can put it in bridge mode for when my wife can't hear herself singing enough, and it still cranks it out. However, when these amps clip, or go out of their SOA, they sound *bad!* Somewhat like a lightning crack..... I've yet to quantify actual power output, because I'd like to know whether it's the power supply that can't keep up, or the chip doesn't like the roughly 6ohm load I sometimes use.....
Perhaps it's my wife's singing....
I'm not ordering commercial quantities of the things!
If they are happy to give away samples and courier them across the globe, then thanks heaps! They have decided that they are a big enough company to support it.
I agree: abuse it and you lose it.
I have ordered the parts, I will make an amp, and I'm sure I'll need to do some tweaking with the layout etc etc. before I'm happy with it.
If a friend asks me to build one for them, no worries. A $20 amp module is a small part of the total price to build it, when you add in the cost of the toroidal transformer, filter caps, and a half decent case to put it in.
If it sounds like sh*%te, I won't order or buy the part again.
The same can be said about op amps. I've been designing a pcb for the mixer project as described in http://sound.westhost.com/project30.htm , and have also been following the threads here regarding which particular chip/fet/tranny/diode/piece of string sounds good or sounds bad.
It is interesting to come across a chip that sounds good on paper, and do the exercise of getting one. You will often hear the following conversation: "Yes sir, we can get those for you. It will take six to eight weeks, minimum order of 2500 and they cost $xxxx each...." If they don't do samples, I don't get to audition the chip.
So sorry, guys. I didn't mean to start an abuse thread.
I agree with ssanmor; let's continue with the issue of this thread: LM3886 amps.
BTW, I have built an amp using a similar chip previously, and they work really well. I can put it in bridge mode for when my wife can't hear herself singing enough, and it still cranks it out. However, when these amps clip, or go out of their SOA, they sound *bad!* Somewhat like a lightning crack..... I've yet to quantify actual power output, because I'd like to know whether it's the power supply that can't keep up, or the chip doesn't like the roughly 6ohm load I sometimes use.....
Perhaps it's my wife's singing....
lm3886 price is good
the price can be checked at www.national.com - i paid 3US$ quantity of 20. I think quantity of 1 is around 6$US$
the price can be checked at www.national.com - i paid 3US$ quantity of 20. I think quantity of 1 is around 6$US$
hello, did the schematic of rljones ever come to light? If it was emailed, can I have someone forward it to me please?
Also, I would rather use the isolated TF version of the LM3886 if it is only marginally worse than the T with insulating washer. Can anyone confirm if the TF version is OK in practice? (also for the 50W solo chip amps)
Grant
Also, I would rather use the isolated TF version of the LM3886 if it is only marginally worse than the T with insulating washer. Can anyone confirm if the TF version is OK in practice? (also for the 50W solo chip amps)
Grant
Just referring to Rachel's request in the very first post here: paralleling is not going to improve damping factor because of the series resistors. Neither will bridging help because then both internal output resistances are effeciviely in series.
Paralleling and/or bridging helps distortion though by keeping the load on the individual amp down.
Paralleling and/or bridging helps distortion though by keeping the load on the individual amp down.
Ok, I have just found it and imported it from Protel.
My car amp had 6 inverting LM3886 amplifiers, all of them wired the same way, just as in the datasheet typical app. diagram.
I combined 4 of them in parallel-bridge and other two were for the mids/highs, independently connected in stereo.
For the bridge/parallel, simply group 4 channels in two pairs. All of the channels had 0.1 series output resistors.
Join the output of the 2 channels forming the first pair, and do the same with the second pair.
Both amps in the first pair are driven by the same input signal, the amps in the other pair are both driven by an inverted version of the input signal (generated by an external inverting unity-gain opamp). Then connect the speaker between the output of the first pair and the output of the second one.
I hope you can get it clear enogh from this explanation ;-)
My car amp had 6 inverting LM3886 amplifiers, all of them wired the same way, just as in the datasheet typical app. diagram.
I combined 4 of them in parallel-bridge and other two were for the mids/highs, independently connected in stereo.
For the bridge/parallel, simply group 4 channels in two pairs. All of the channels had 0.1 series output resistors.
Join the output of the 2 channels forming the first pair, and do the same with the second pair.
Both amps in the first pair are driven by the same input signal, the amps in the other pair are both driven by an inverted version of the input signal (generated by an external inverting unity-gain opamp). Then connect the speaker between the output of the first pair and the output of the second one.
I hope you can get it clear enogh from this explanation ;-)
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