mosfets said:Without validating or checking the schematic for errors, in general I would say this design as it is could deliver 600 watts into 4 ohms. But I'm just making generalizations.
The pdf clearly states 1200 watts.
nigelwright7557 said:The pdf clearly states 1200 watts.
The oracle has spoken.
w
netuddki said:Hi!
if you see errors please tell me!
Have you tried it out in a simulator? Linear Technologies offers a free simulator from their web site. BTW the circuit does look nice. I'm not certain if I have ever seen a VAS stage quite like this one. I may try to simulate for my own curiosity.
This is nothing too fancy, no real need to simulate it. The input stage is super classical and the VAS is just a cascoded one, cascoded with a mosfet, ok, more usually it is a bjt. Actually a bjt would be certainly better for cascoding from a pure technical point of view. Anyway, this has been done before and will be done later... To me it is another non inventive design... With a miscalculated power max as a cherry on the cake.
Nevertheless I am quite sure it would perform pretty well, like all of his kind.
Regards
Nevertheless I am quite sure it would perform pretty well, like all of his kind.
Regards
The max power is given by (max voltage)square/R/2 in a push-pull power amp as far as I know electronic. But you may think what you want...
The max voltage is less than the PSU because it lowers when loaded and the output transistors are not perfect shortcut at full power. This is the theory, after, it could be even less power if the fanning is so insufficient that the output transistor blow away before the theorical max.
Sorry but I think I am pretty right on that one! Even with more transistors, 80v will only get you that far!
The max voltage is less than the PSU because it lowers when loaded and the output transistors are not perfect shortcut at full power. This is the theory, after, it could be even less power if the fanning is so insufficient that the output transistor blow away before the theorical max.
Sorry but I think I am pretty right on that one! Even with more transistors, 80v will only get you that far!
Of course it depends on the load!!!
Let s say you have 8 ohms and run 3 amps at peak to reach a peak of 24v and your power supply is 24v, you clip. At 4 ohms you can run run twice the current in there before it clips. And when you go too low in load the peak current is so high that you blow up the transistor...
I am a little surprised by your assertion...
Let s say you have 8 ohms and run 3 amps at peak to reach a peak of 24v and your power supply is 24v, you clip. At 4 ohms you can run run twice the current in there before it clips. And when you go too low in load the peak current is so high that you blow up the transistor...
I am a little surprised by your assertion...
darian said:I am a little surprised by your assertion...
I know! It is a moot point and has been well discussed on many, many threads here @ diyaudio. With “traditional” designs such as this one, you would need some where near _+ 100 volt rails to get near 1000 watts into 4 ohms and to support it further an oversized transformer and very large capacitor bank would be required. Furthermore looking into the SOAR ratings of output devices, a great number of parallel outputs would be required. Of course these things really are not required; anyone can do as they please. But to truly support large claims of output power, large amounts of reinforcement are required. Cooling these great beasts is another topic all together. It’s all wonderful stuff to me. I think Glen Kleinschmidt made a spread sheet for calculating similar scenario’s but I’m not certain and can not find it.
“from the net” circuit looks nice and I will simulate it in the next week or so when I spare some time. I wish I could get my head around PCB layout software like Eagle and such, as I would really like to be able to try such designs at home at my own free will. I have spent many hours on Eagle and I almost always end up with very bad results.
Oh well…
Well, I didn t see the cooling as a limiting factor here as we were discussing the schematic at first. I guess it would need some serious cooling for sure, like big fans and a fan forced funnel cooling. But I don t think it would be that hard to achieve a sufficient cooling since the power mosfets are very rugged. 4 oms is low enough anyway, I don t think it s very safe to go down to 2 for any amp unless it s vastely oversized in every aspect.
netuddki said:the pcb is coming soon! almost done!
Give me a nice PCB layout and I will be happy to do a trial test and set up for feed back.
Is there anyway to crank up the rails without blowing this amp up? I'd like to get it as close to the original claim of 1200 watts. Perhaps we can get there afterall?
It will blow up!
Input pair resistors will blow up, fry, ...
Those guys have VCE of 120V... you are feeding them with 80+80 = 160V...
Use these:
MPSA42 http://www.onsemi.com/pub_link/Collateral/MPSA42-D.PDF and MPSA92 http://www.onsemi.com/pub_link/Collateral/MPSA92-D.PDF
Solving this, let's continue...
1st, change those fets from VAS. Use HV bjt's there.
2nd, put a 2k2 resistor in // with the bias pot, just to be sure you don't get any surprise!...
3rd, if you plan to use 4Ohm load, put more pairs at output. BTW, witch are the output devices?
4th, the overall gain is far high!... you must work a little on those FB resistors...
5th, output is unprotected! Output mosfets will blow before you can blink your eyes. Put protection diodes from output to rails and some inductance before speaker output.
6th, be carefull with pcb design.
7th... 600W...700W... no more than that...
8th, distorsion will be very high!...
9th, I'll stop here...
Input pair resistors will blow up, fry, ...
Those guys have VCE of 120V... you are feeding them with 80+80 = 160V...
Use these:
MPSA42 http://www.onsemi.com/pub_link/Collateral/MPSA42-D.PDF and MPSA92 http://www.onsemi.com/pub_link/Collateral/MPSA92-D.PDF
Solving this, let's continue...
1st, change those fets from VAS. Use HV bjt's there.
2nd, put a 2k2 resistor in // with the bias pot, just to be sure you don't get any surprise!...
3rd, if you plan to use 4Ohm load, put more pairs at output. BTW, witch are the output devices?
4th, the overall gain is far high!... you must work a little on those FB resistors...
5th, output is unprotected! Output mosfets will blow before you can blink your eyes. Put protection diodes from output to rails and some inductance before speaker output.
6th, be carefull with pcb design.
7th... 600W...700W... no more than that...
8th, distorsion will be very high!...
9th, I'll stop here...
Hi Everybody,
First let me say that this is interesting design. Might just work but with designs just floating around on the net you should be carefull, might have some flaws.
With double die laterals in the output it could be able to do maybe 700 or watts. No problem with driving them, T11 and 12 will do it very nicely. I dont see a problem with the mosfet cascodes either, will work. Others have used mosfet cascode before with no problems. The voltage I agree is a bit high for those input transistors. Who is the designer of this?? Simm it and iron the problems out, could possible sound pretty good.
First let me say that this is interesting design. Might just work but with designs just floating around on the net you should be carefull, might have some flaws.
With double die laterals in the output it could be able to do maybe 700 or watts. No problem with driving them, T11 and 12 will do it very nicely. I dont see a problem with the mosfet cascodes either, will work. Others have used mosfet cascode before with no problems. The voltage I agree is a bit high for those input transistors. Who is the designer of this?? Simm it and iron the problems out, could possible sound pretty good.
homemodder said:Hi Everybody,
Who is the designer of this??
Hi, homemodder,
This design is from Anthony E Holton aka The Saint here.
It's a working design, but what I said before, still stands.
I never use LTP's with VCE lower that 1.2x the rail voltage sum...
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