Yes, there has been seveal questions for real power full amps.AMT-freak said:
And we have had some diffilculties to give a good answer.
Sometimes you can need something extra.
I am a long time, 20 years, prescriptor of Elektor.
So I have that article of PA300.
It is a tremendous Amp. not only for PA,
but for Hifi.
I wouldn't say it is easy to build. No beginners project.
But it is well documented and tested. With some figures!
In bridge version it should be a real KILLER.
halo - not in need for a kill - but who knows ...
Ooops, I've just editet my post to remove a stupid mistake, and now everyone can see it because Halo quoted me 
Swapping inverting and non-inverting input of the opamp for bridging two channels will NOT work as it is within the feedback loop. Use an external phase splitter instead.
Halo, you are right of course. It is not as easy to build as, say, an LED flasher, but certainly one of the most simple amplifiers with that much output power. Definitely not a beginner's project, though.
/AMT-Freak - likes peace as much as halo
Swapping inverting and non-inverting input of the opamp for bridging two channels will NOT work as it is within the feedback loop. Use an external phase splitter instead.
Halo, you are right of course. It is not as easy to build as, say, an LED flasher, but certainly one of the most simple amplifiers with that much output power. Definitely not a beginner's project, though.
/AMT-Freak - likes peace as much as halo
I am too quick t post.AMT-freak said:
Yes, it is simple for so much power.
But the difficulty is more in the practical building
of the amplifier. With so much power you have to be
careful with small details. Much current will flow!
At high voltage supply.
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The heart of the amp is the good old NE5534 OPamp.
It shows that this OP have data enough to get
HiFi in a PowerAmp.
halo - Loves NE5534 - Don't you say no bad about it!
Attachments
Oliver/AMT-freak,
Thanks for the schematic. Yes, I have built the PA-300. It is a good but not a great amplifier.
First, a suggestion: I have used TLE2141 in place of the NE5534 and found the resolution of the amp to be much better. The mid-frequencies come forward with the replaced chip. Also the voltage to the input stage can be increased to +-20volts for more headroom and dynamic range than the more normal +-15volts required for the NE5534. (Other opamps like OP27, OPA604 did not sound as good in this position).
Secondly, some questions:
1. If you have heard/built the Leach Low TIM Amp/Leach SuperAmp, how would you compare the sound of the PA600 to this?
2. Is this design, as is, capable of driving 2ohm loads continuously?
3. By today's standards, won't replacement of the output stage with MJ21193/21194 be a better choice?
4. Would it be possible to post a rough idea of the original PCB design?
Thanks,
Thanks for the schematic. Yes, I have built the PA-300. It is a good but not a great amplifier.
First, a suggestion: I have used TLE2141 in place of the NE5534 and found the resolution of the amp to be much better. The mid-frequencies come forward with the replaced chip. Also the voltage to the input stage can be increased to +-20volts for more headroom and dynamic range than the more normal +-15volts required for the NE5534. (Other opamps like OP27, OPA604 did not sound as good in this position).
Secondly, some questions:
1. If you have heard/built the Leach Low TIM Amp/Leach SuperAmp, how would you compare the sound of the PA600 to this?
2. Is this design, as is, capable of driving 2ohm loads continuously?
3. By today's standards, won't replacement of the output stage with MJ21193/21194 be a better choice?
4. Would it be possible to post a rough idea of the original PCB design?
Thanks,
Hi Samuel,
I agree to your suggestions. I also tried different opamps and found them to have more influence on sound than I expected. I posted the schematic mostly for DJing or use as a subwoofer amplifier. The amps I'm currently using in my PA system are fully discrete designs and much more complicated.
1. I haven't heard the "Leach SuperAmp"
2. No. 2 Ohm is really low. To be able to drive full rated power continously into 2 Ohms, you'll need a bigger power supply and you have to add some more complementary pairs to be on the safe side.
3. The design is from 1990, so yes, you could improve things by updating some of the components. You might have to modify the compensation capacitors in the feedback network, as Yugaaa mentioned.
4. The original design was a small PCB, containing only the driver circuit. An extra board contained the protection circuit. The rest (power supply & output stage) was wired p2p. On the original PCB, T102 and T104..T107 were mounted to a common small heatsink for better thermal stability. Signal and power ground were separated. Component placement was - as you would expect - close to the schematic. I did a similar design, but my older PCB files got lost at the last computer crash, sorry...
"djk" mentioned in the original thread that even the article in "Elrad" from 1990 wasn't the origin of the circuit. Interestingly, it seems to have been available commercially. Read his post here:
http://www.diyaudio.com/forums/showthread.php?postid=123662#post123662
I agree to your suggestions. I also tried different opamps and found them to have more influence on sound than I expected. I posted the schematic mostly for DJing or use as a subwoofer amplifier. The amps I'm currently using in my PA system are fully discrete designs and much more complicated.
1. I haven't heard the "Leach SuperAmp"
2. No. 2 Ohm is really low. To be able to drive full rated power continously into 2 Ohms, you'll need a bigger power supply and you have to add some more complementary pairs to be on the safe side.
3. The design is from 1990, so yes, you could improve things by updating some of the components. You might have to modify the compensation capacitors in the feedback network, as Yugaaa mentioned.
4. The original design was a small PCB, containing only the driver circuit. An extra board contained the protection circuit. The rest (power supply & output stage) was wired p2p. On the original PCB, T102 and T104..T107 were mounted to a common small heatsink for better thermal stability. Signal and power ground were separated. Component placement was - as you would expect - close to the schematic. I did a similar design, but my older PCB files got lost at the last computer crash, sorry...
"djk" mentioned in the original thread that even the article in "Elrad" from 1990 wasn't the origin of the circuit. Interestingly, it seems to have been available commercially. Read his post here:
http://www.diyaudio.com/forums/showthread.php?postid=123662#post123662
Crap that you lost youre PCB:s in the crash I would have loved them with the new design on the safety circuits. I've built the PA300 som years ago and it just doesn't have enough for bigger woofers it goes into clipping way too soon.
Crap I would have loved to build that amp.
Thanks for schematic anyway very helpful
Patrik
Crap I would have loved to build that amp.
Thanks for schematic anyway very helpful
Patrik
I won't build any more of these, so motivation to re-make a PCB layout is somewhat limited... And I wouldn't have time until April anyway. If you don't want to wait that long, hm, maybe someone else volunteers? I know there are great PCB experts here
SlaitH, do you have a 8 Ohm sub? Have you tried bridging two PA300 channels? Then you'd have around 500W instead of 160W...
SlaitH, do you have a 8 Ohm sub? Have you tried bridging two PA300 channels? Then you'd have around 500W instead of 160W...
Yep did that and it worked just fine actually.
I made my own op based inverter with a realy for switching the output. Works just fine, but at this time i've got the thing in a 19" rack box, but i think i'm gonna redo it and put the transformer, rectifier, capacitors and softstart in a separate box.
Maybe not for the sound so much as the more simple thing to carry At this time it's weight is about 19 Kilos. And i'm gonna redo a little with the passive cooling, new cables stuff like that. Just got to get around to it.
Been looking for Passive Coolers for a nice price but I just can't find any good ones here.
Not building them anymore eh?? ...Found a better solution??
Thanks anyway
/Patrik
I made my own op based inverter with a realy for switching the output. Works just fine, but at this time i've got the thing in a 19" rack box, but i think i'm gonna redo it and put the transformer, rectifier, capacitors and softstart in a separate box.
Maybe not for the sound so much as the more simple thing to carry
At this time it's weight is about 19 Kilos. And i'm gonna redo a little with the passive cooling, new cables stuff like that. Just got to get around to it.Been looking for Passive Coolers for a nice price but I just can't find any good ones here.
Not building them anymore eh?? ...Found a better solution??
Thanks anyway
/Patrik
Hey AMT-freak,
How about the cooling? I've got two huge heatsinks already, but I just think things can't be huge enough in a 400W-amplifier. My first plan was to build a PA-300, and that's what I bought them for. They are 300*100*40 mm and they can sink about 0,4 K/W, but I don't know what effect four 80mm-fan's will have on that. The fans will be there anyway, because of the compact design. That is, relatively compact, the whole thing will just fit into a 3 unity's high 19"-case, which is quite big. Well, that is my story, please tell me what you would recommend on the cooling subject. I'm also thinking of building four PA-300's to brige them, you can read about that in the PA-300 thread.
Thanks, Robert.
How about the cooling? I've got two huge heatsinks already, but I just think things can't be huge enough in a 400W-amplifier. My first plan was to build a PA-300, and that's what I bought them for. They are 300*100*40 mm and they can sink about 0,4 K/W, but I don't know what effect four 80mm-fan's will have on that. The fans will be there anyway, because of the compact design. That is, relatively compact, the whole thing will just fit into a 3 unity's high 19"-case, which is quite big. Well, that is my story, please tell me what you would recommend on the cooling subject. I'm also thinking of building four PA-300's to brige them, you can read about that in the PA-300 thread.
Thanks, Robert.
AMT-freak: Actually I could wait that long, but I don't want to put you thru the agony of making a PCB layout
But if you feel up to it you are more than welcome to try.
Prior: I used this box for my stereo PA-300.
But for Cooling the amp the fins were a little to small so i added one fan on each side and it worked just fine. Looks like crap and i have a ringing in the Coolers
But I mainly use it at partys to power some subs i have so it works for that.
I'm gonna rebuild it in a while.
Some tips: make sure you use a realy for high amps for the speaker out.
(I was sleeping one time playing loud music, when i woke up one channel had gone into DC protection.) Why??
One of the transistor got shorted and broke, when the current flowed in it welded the relay shut so it couldn't open up. Strange thing that a 12" sub doesn't take 120Volts DC and about 20 Amps.
RESULT: 3 new transistor 15$ one new subwoofer 120$.
and that wasn't the only time that happened because of the realys. So use big realys.
/Patrik
But if you feel up to it you are more than welcome to try.
Prior: I used this box for my stereo PA-300.
But for Cooling the amp the fins were a little to small so i added one fan on each side and it worked just fine. Looks like crap and i have a ringing in the Coolers
But I mainly use it at partys to power some subs i have so it works for that.
I'm gonna rebuild it in a while.
Some tips: make sure you use a realy for high amps for the speaker out.
(I was sleeping one time playing loud music, when i woke up one channel had gone into DC protection.) Why??
One of the transistor got shorted and broke, when the current flowed in it welded the relay shut so it couldn't open up. Strange thing that a 12" sub doesn't take 120Volts DC and about 20 Amps.
RESULT: 3 new transistor 15$ one new subwoofer 120$.
and that wasn't the only time that happened because of the realys. So use big realys.
/Patrik
Attachments
In the PDF above I described how I solved the cooling problem. it was done similarly in the original article.
I used four crappy and cheap heatsinks, about 300mm x 100mm x 30mm with vertical fins and mounted them as the four side walls of a "tunnel" using L-shaped bars. Then I mounted 3 devices on each heatsink and a big powerful fan at the front side. Using a fan increases efficiency of a heatsink so much that you can really use those tiny heatsinks even for continious full output power.
If you want to use the amp at home and don't like the idea of a fan making background noise, you can rely on the fact that you probably don't need continious full output power. It's a class AB design after all Have a look at the photos in the original article of PA-300. The heatsink shown there is at the limit, but definitely enough for home use.
I used four crappy and cheap heatsinks, about 300mm x 100mm x 30mm with vertical fins and mounted them as the four side walls of a "tunnel" using L-shaped bars. Then I mounted 3 devices on each heatsink and a big powerful fan at the front side. Using a fan increases efficiency of a heatsink so much that you can really use those tiny heatsinks even for continious full output power.
If you want to use the amp at home and don't like the idea of a fan making background noise, you can rely on the fact that you probably don't need continious full output power. It's a class AB design after all
Have a look at the photos in the original article of PA-300. The heatsink shown there is at the limit, but definitely enough for home use.hacknet: I was reffering to my overpowered power supply.
since I have a 800VA transformer and at least 40 000uF thru the filtering.
Then you can imagine the current spike when this shorts thru the speaker to ground.... See what i mean?
Okay maybe not 20 amps but enough to beat the crap out of my subs.
I didn't want to buy new heatsinks since the box I got had them already mounted, but I soon came to realize they were a little to small.
So now when I rebuild the amp i'm gonna get some bigger coolers.
since I have a 800VA transformer and at least 40 000uF thru the filtering.
Then you can imagine the current spike when this shorts thru the speaker to ground.... See what i mean?
Okay maybe not 20 amps but enough to beat the crap out of my subs.
I didn't want to buy new heatsinks since the box I got had them already mounted, but I soon came to realize they were a little to small.
So now when I rebuild the amp i'm gonna get some bigger coolers.