Hi Masta & Quasi,
there's nothing wrong with the first post.
It tells one that a quasi complementary FET output stage power amplifier can produce 200W into 8r and with suitable scaling of the components can drive almost any load to any level. Just add PSU & devices. Lot's of flexibility.
What needs updating
there's nothing wrong with the first post.
It tells one that a quasi complementary FET output stage power amplifier can produce 200W into 8r and with suitable scaling of the components can drive almost any load to any level. Just add PSU & devices. Lot's of flexibility.
What needs updating
Vgs multiplier
I can't quite recall all of the discussions in the development of the amp, but my question is, 'was a Vgs multiplier thought of instead of the Vbe multiplier' as it appears in the final schematics?
One more question, 'Will not adding a buffer before the single bjt Vas stage improve sonics?'
I can't quite recall all of the discussions in the development of the amp, but my question is, 'was a Vgs multiplier thought of instead of the Vbe multiplier' as it appears in the final schematics?
One more question, 'Will not adding a buffer before the single bjt Vas stage improve sonics?'
Re: Vgs multiplier
There was some talk about using a fet as a Vgs multiplier, but that wasn't from me. My intention was always to use the configuration shown in the schematic.
Another stage could be added, but I'm not sure whether it would improve the amp much. My view is that every stage adds some noise. It is also possible to cascode the first two stages and this would improve the speed of the amp, but I don't like cascodes (zener referenced ones anyway). The amp is intended to be a bare minimum and flexible unit that is still very high in quality.
Cheers
Q
Samuel Jayaraj said:
There was some talk about using a fet as a Vgs multiplier, but that wasn't from me. My intention was always to use the configuration shown in the schematic.
Another stage could be added, but I'm not sure whether it would improve the amp much. My view is that every stage adds some noise. It is also possible to cascode the first two stages and this would improve the speed of the amp, but I don't like cascodes (zener referenced ones anyway). The amp is intended to be a bare minimum and flexible unit that is still very high in quality.
Cheers
Q
O.K. I'm going to try with a simple buffer before the Vas stage to improve impedance matching.
Just one more question; looking at the discussions in MikeB's symasym thread about noise in CCS, I wonder whether replacing the two diode drop CCS with a red LED/cap coupled for better thermal characteristics and ofcourse, redimensioning the resistors to set the currents, would further improve your already wonderful creation? Any thoughts?
Just one more question; looking at the discussions in MikeB's symasym thread about noise in CCS, I wonder whether replacing the two diode drop CCS with a red LED/cap coupled for better thermal characteristics and ofcourse, redimensioning the resistors to set the currents, would further improve your already wonderful creation? Any thoughts?
Hi AndrewT
The mos amp runs similar earthing and is very quiet.
The only change I have made with this part of the layout is to shift the 27K resistor providing the bias to D1 & D2 from the decoupled ground to direct ground. I have seen other layouts that do this so I thought I'd try it.
It would be very easy to leave the 10R resistor out and run a seperate gnd from the pad just under the 1K resistor. I'll make this an option.
Probably time now to start the new thread and leave this one devoted to mos amp.
Thanks for your input
Cheers
The mos amp runs similar earthing and is very quiet.
The only change I have made with this part of the layout is to shift the 27K resistor providing the bias to D1 & D2 from the decoupled ground to direct ground. I have seen other layouts that do this so I thought I'd try it.
It would be very easy to leave the 10R resistor out and run a seperate gnd from the pad just under the 1K resistor. I'll make this an option.
Probably time now to start the new thread and leave this one devoted to mos amp.
Thanks for your input
Cheers
Compared : this bipolar to mosfet amplifier : what is better to built : Sond qualitiy I mean subject sound qualitiy : Can you describe sifference using word (your ear)
So this bipolar is +/- 70V : This is more than 300W 8ohm : but when yousing mosfets you get less power arond 200W ?
So why usnig dual power supply ? 60V and 70V can I use only 70 V ?
Can you link the LAST GOOD revision of mosfet schematics : so are all problems solved : can I trustly star to build it
So this bipolar is +/- 70V : This is more than 300W 8ohm : but when yousing mosfets you get less power arond 200W ?
So why usnig dual power supply ? 60V and 70V can I use only 70 V ?
Can you link the LAST GOOD revision of mosfet schematics : so are all problems solved : can I trustly star to build it
From "Brother of Quasi"
It seems we are now talking about this amp...
The mosfet amp can be built for voltages up to +/- 85 volts using a 10 FET board. Please refer to the power selection guide in the PDF.
Performance figures are listed in the thread several pages back.
The development of the amp was a combination of my ideas plus those of other contributers to this thread. You can see the schematic evolve over time. All calculations were done manually as were the analysis.
Cheers
Q
It seems we are now talking about this amp...
medogrizli said:
Ok thanks: it seems great :
I see the pdf: it seems the power supply is not limited to +/-70V it can work at higher rates
So what are the characteristic of the amplifier input voltage THD etc ?
So how did the the development proseeded: did you use computer proframs for analyzing and calculation or you did all manually
The mosfet amp can be built for voltages up to +/- 85 volts using a 10 FET board. Please refer to the power selection guide in the PDF.
Performance figures are listed in the thread several pages back.
The development of the amp was a combination of my ideas plus those of other contributers to this thread. You can see the schematic evolve over time. All calculations were done manually as were the analysis.
Cheers
Q
Re: From "Brother of Quasi"
OK I should read this thread completely
I am interested
so are you electrical engenner or just ethusiast with lots of knowlede ? cause you did a great job
+/-85V : What is the limit : I think first two stages : otput mosfets can handle +/-250V
But if I have irfp460 i think I can buy them VERY CHEAPLY : cause I have friend seling lots of these for very little money?
Can I use those? or there should be some changement
quasi said:
OK I should read this thread completely
I am interested
so are you electrical engenner or just ethusiast with lots of knowlede ? cause you did a great job
+/-85V : What is the limit : I think first two stages : otput mosfets can handle +/-250V
But if I have irfp460 i think I can buy them VERY CHEAPLY : cause I have friend seling lots of these for very little money?
Can I use those? or there should be some changement
I am not an engineer, just a hobbyist. My profession is sales and marketing.....(the enemy of the engineer).
85 volts is the limit because of the output stage SOAR and the heat generated by the other stages of the amp. If 85 volts is to be used then the heatsink for the second and third stages must be larger.
You can use IRFP460 for both the 6 FET and 10 FET board.
Cheers
Q
85 volts is the limit because of the output stage SOAR and the heat generated by the other stages of the amp. If 85 volts is to be used then the heatsink for the second and third stages must be larger.
You can use IRFP460 for both the 6 FET and 10 FET board.
Cheers
Q
quasi said:
What is SOAR ? full world
So can you describe the difference in the schematics between N channell and P channel-Nchannel complemetary amplifier design: where is the difference
Hmm that is very good knowledge for sb who didnt learn anything about electronic in his study or school?
I wish AndrewT was here...
He usually helps out...
SOAR: Look here http://www.comdel.com/pages/rf/glossary.html
There are so many different schematics that it would take too long to describe the differences. It would be better if you did some research rather than ask direct questions. You will learn a lot more if you did the reading required because you would gather a lot more information along the way.
Cheers
Q
He usually helps out...
SOAR: Look here http://www.comdel.com/pages/rf/glossary.html
There are so many different schematics that it would take too long to describe the differences. It would be better if you did some research rather than ask direct questions. You will learn a lot more if you did the reading required because you would gather a lot more information along the way.
Cheers
Q