Put simply, you can't just put in an n-channel device instead of a p-channel one. They work the opposite way round, so if you just put an n-channel one in it will be fully turned on at idle and blow the amplifier up.
The modifications required are not trivial and will not be able to be accomplished using the existing PCB as will not be space for the necessary additional components and the heatsinking required.
Just build something that is right in the first place. What you propose is like a 17 year old boy wanting to convert an Opel Corsa to rear wheel drive
The modifications required are not trivial and will not be able to be accomplished using the existing PCB as will not be space for the necessary additional components and the heatsinking required.
Just build something that is right in the first place. What you propose is like a 17 year old boy wanting to convert an Opel Corsa to rear wheel drive
Hi Richie,...
"The modifications required are not trivial and will not be able to be accomplished using the existing PCB as will not be space for the necessary additional components and the heatsinking required."
I think you have me missunderstood
I dont like using existing PCB, i need information and help about necessary additional components to upgrade Schematic and design new sample PCB with N channel devices
regards
from Germany
"The modifications required are not trivial and will not be able to be accomplished using the existing PCB as will not be space for the necessary additional components and the heatsinking required."
I think you have me missunderstood
I dont like using existing PCB, i need information and help about necessary additional components to upgrade Schematic and design new sample PCB with N channel devices
regards
from Germany
OK!!!! I am lost! You don't know if the original circuit meets your goals! Yet you have not tested it into 2 ohms, correct? Maybe it will exceed your goals.! If it does, you don't need 300V P channel devices, correct?
You have also stated that the original circuit has little output bias applied to it, correct? Well IMHO I don't think that there is anyone on the forum that will tell you that a low biased mosfet output stage is in a very linear state.
Operate the devices you have at their most linear operating point and you and the circuit win's!!!!!!!!!!! That is, with that device, and with that circuit topology.
Your design priorities don't seem to be well thought out. Only a very "expensive" unit will deliver what you want for PA use. Producing +6dB with a compressed signal with bass boost also will require current and voltage limitations of the output stage, or a monster amp!!!!!!!!!!!!! Let me repeat MONSTER
amp!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
None of the above factors will be effected by polarity or type of device. If you will drive the unit into clipping on a regular basis, I.E. PA use, you should be looking at how the amp clips, not what of devices are used into clipping. Believe me, with PA use, there will be clipping.
IMO you would like an audio welder. Welders have duty cycles. Gig's do not. Whatever your final solution is, it will have to be built bullet proof and never shut down under any conditions, except for maybe a direct lighting strike!
I hope that my comment's above are not as confusing as what you are trying to accomplish here.
Thanks, Don
You have also stated that the original circuit has little output bias applied to it, correct? Well IMHO I don't think that there is anyone on the forum that will tell you that a low biased mosfet output stage is in a very linear state.
Operate the devices you have at their most linear operating point and you and the circuit win's!!!!!!!!!!! That is, with that device, and with that circuit topology.
Your design priorities don't seem to be well thought out. Only a very "expensive" unit will deliver what you want for PA use. Producing +6dB with a compressed signal with bass boost also will require current and voltage limitations of the output stage, or a monster amp!!!!!!!!!!!!! Let me repeat MONSTER
amp!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
None of the above factors will be effected by polarity or type of device. If you will drive the unit into clipping on a regular basis, I.E. PA use, you should be looking at how the amp clips, not what of devices are used into clipping. Believe me, with PA use, there will be clipping.
IMO you would like an audio welder. Welders have duty cycles. Gig's do not. Whatever your final solution is, it will have to be built bullet proof and never shut down under any conditions, except for maybe a direct lighting strike!
I hope that my comment's above are not as confusing as what you are trying to accomplish here.
Thanks, Don
Hello Don S
thanks for your posting
I think you have me missunderstood.
I want use this amp with higher Rails +/- 130 - 150 V such as many China BJT Class AB PA Amps with Toshiba 2 SA 1293 and 2 SC 5200 out put Devices.
My Problem is to get P Mosfet Devices with 250 V so its easy to take N Devices for this Rails but i need help to add additional components.
Mangnatec www. magnatec-uk.com can offer me BUZ 903DP and BUZ 908 DP with 250 V 16 A and 250W but the devices so expensive about 15 EUR pcs., so its not possibile to use in PA Amp
I can get similar only N Devices from IRF for 1 to 2 EUR but i have no idea about changes and additional components in Mosfet circuit.
Another option in my Mosfet Amps is to design new PCB with 2 Amplifier +/- 90 - 95 V on each PCB and Bridge for High Output Power but the cost is expensiver because i need 32 Devices IRFP 9240 and IRFP 240 for 1 Channel Bridge PCB
I think the output Power will be 2000 W @ 4 OHM
thanks for your posting
I think you have me missunderstood.
I want use this amp with higher Rails +/- 130 - 150 V such as many China BJT Class AB PA Amps with Toshiba 2 SA 1293 and 2 SC 5200 out put Devices.
My Problem is to get P Mosfet Devices with 250 V so its easy to take N Devices for this Rails but i need help to add additional components.
Mangnatec www. magnatec-uk.com can offer me BUZ 903DP and BUZ 908 DP with 250 V 16 A and 250W but the devices so expensive about 15 EUR pcs., so its not possibile to use in PA Amp
I can get similar only N Devices from IRF for 1 to 2 EUR but i have no idea about changes and additional components in Mosfet circuit.
Another option in my Mosfet Amps is to design new PCB with 2 Amplifier +/- 90 - 95 V on each PCB and Bridge for High Output Power but the cost is expensiver because i need 32 Devices IRFP 9240 and IRFP 240 for 1 Channel Bridge PCB
I think the output Power will be 2000 W @ 4 OHM
Dorian, I don't mean to sound rude but you certainly have no idea of what you want and what you are proposing. Making a bullet-proof amp for PA use, and that into a 2 ohm load, is no mean task. Forget about burning all that cash. I have way too much experience with unstable, high power amps using IRF N-channel devices - in other words, don't learn the hard way like I did. You could have a look at Quasi's designs but in my opinion, there are some unresolved issues with rail voltages higher than +-63volts.
Do a wise thing and buy yourself a QSC amp, perhaps an RMX1850HD, for use into 2 ohm loads.
Do a wise thing and buy yourself a QSC amp, perhaps an RMX1850HD, for use into 2 ohm loads.
Mosfet amps more natural than BJT amps but BJT Amps are much more cheaper and easier to produce
But QSC amp, perhaps an RMX1850HD, for use into 2 ohm loads
its not a good idea. The sound is not so good
In Germany very popular for PA is
QSA Class D Digital Amp
Model NX 7.0 and NX 5.0
2 x 3000 W @ 2 Ohms only 9kg
about 650 EUR equal. to 850 USD
Note: QSA is not QSC, QSA is another Company
But QSC amp, perhaps an RMX1850HD, for use into 2 ohm loads
its not a good idea. The sound is not so good
In Germany very popular for PA is
QSA Class D Digital Amp
Model NX 7.0 and NX 5.0
2 x 3000 W @ 2 Ohms only 9kg
about 650 EUR equal. to 850 USD
Note: QSA is not QSC, QSA is another Company
Attachments
Hello richie00boy
"The number of output devices is the same for if you used grounded load topology for a given power."
Please can you explain me grounded load topology for a given power, i dont have study it
Im very interested, in Germany we have much trading companies but i cant nobody ask for technical details
"The number of output devices is the same for if you used grounded load topology for a given power."
Please can you explain me grounded load topology for a given power, i dont have study it
Im very interested, in Germany we have much trading companies but i cant nobody ask for technical details
bridging or not
Hi,
8pair of 250W devices can do 1000W into 2ohm @ 45degree phase angle.
Two of these amps in bridge mode will do 2000W into 4ohm and each will require 1.5kVA 50+50Vac transformer with +-60mF @ 80Vdc or 100Vdc rating.
A single amp putting out 2000W into 4ohm @ 45degree phase angle will require a 3kVA 100+100Vac transformer also with +-60mF @150Vdc rating. It too needs 16pair of 250W devices to meet that medium severity loading.
I would be tempted to try the low voltage version but not into a 2ohm speaker.
I would go for 500W into 4ohm and stretch the design to allow 60degree phase angle loading, this needing just 5pair of 250W devices, 800VA, 50+50Vac, +-40mF @ 80Vdc rating
Hi,
8pair of 250W devices can do 1000W into 2ohm @ 45degree phase angle.
Two of these amps in bridge mode will do 2000W into 4ohm and each will require 1.5kVA 50+50Vac transformer with +-60mF @ 80Vdc or 100Vdc rating.
A single amp putting out 2000W into 4ohm @ 45degree phase angle will require a 3kVA 100+100Vac transformer also with +-60mF @150Vdc rating. It too needs 16pair of 250W devices to meet that medium severity loading.
I would be tempted to try the low voltage version but not into a 2ohm speaker.
I would go for 500W into 4ohm and stretch the design to allow 60degree phase angle loading, this needing just 5pair of 250W devices, 800VA, 50+50Vac, +-40mF @ 80Vdc rating
MOS fet N High Voltage High Power PA Amp
Hello
i get some feedback for changes and add additional devices in Mosfet Schematic for N Channel Mosfet Amp.
I will design and order PCB but it takes up to 3 weeks to get 2 PCBs
for test and development.
The Rail is +/- 90 V.
After Mosfet N Amp working stable i want improve schematic Mosfet N Amp for +/- 140 V Rails and test.
Im very glad who can to help me finished design
Hello
i get some feedback for changes and add additional devices in Mosfet Schematic for N Channel Mosfet Amp.
I will design and order PCB but it takes up to 3 weeks to get 2 PCBs
for test and development.
The Rail is +/- 90 V.
After Mosfet N Amp working stable i want improve schematic Mosfet N Amp for +/- 140 V Rails and test.
Im very glad who can to help me finished design
"The positive rail output FETs have a zener on the gate."
So do the negative ones.
The zeners should have a forward biased diode in series with them to isolate the zener junction capacitance (very non-linear), and there should be a current limiting resistor between the drivers and the diode stacks.
I doubt the Baxandall diode does much at it needs to be more like 3.3V to make the base voltages equal on the driver transistors.
So do the negative ones.
The zeners should have a forward biased diode in series with them to isolate the zener junction capacitance (very non-linear), and there should be a current limiting resistor between the drivers and the diode stacks.
I doubt the Baxandall diode does much at it needs to be more like 3.3V to make the base voltages equal on the driver transistors.
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