Class D 200 Wrms with 2 mosfet cheap

stewin

Member
thanks silvio for the fast reply,
will the ne5532 be fast enough to generate the triangle wave required for the switching devices?
also i had tried the 2n5551 and 5401 instead of bc 337 and 327 , but they cause the output fets to heatup too much.
 

Silvio

Active member
Regarding the NE5532A (from Texas instruments) it is claimed to go up to 10Mhz. This should be fast enough for the 240Khz you may be needing.
I would like to understand why are the output fets heat up with a particular transistor. Is it the waveform produced, the noise, bias, gain, output swing, amplitude etc? Understanding why will help you cure the problem using different transistors I guess. As I can see you surely need a complimentary pair not to say matched for your need. These need to work together and have the same symmetry in their outputs.
 
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stewin

Member
Regarding the NE5532A (from Texas instruments) it is claimed to go up to 10Mhz. This should be fast enough for the 240Khz you may be needing.
I would like to understand why are the output fets heat up with a particular transistor. Is it the waveform produced, the noise, bias, gain, output swing, amplitude etc? Understanding why will help you cure the problem using different transistors I guess. As I can see you surely need a complimentary pair not to say matched for your need. These need to work together and have the same symmetry in their outputs.
thanks silvio , the tl074/84 is a very sensitive area . if i put chinese tl074/84 they don't work but consumes a lot of current. same as the bc337/327 they have to be genuine parts .
if ne5532 will work , maybe i can give them a try and hoping it will not be too choosy as the tl074/84. by the way which other transistors have similar parameters as bc327/337 .can a1020 and c2655 be used?
 

Silvio

Active member
hi silvio . will this below quad opamp work??
mc33179
Hi Stewin, I called a friend of mine and asked about your choice of ICs. He mentioned a few and told me that they are direct replacement for each other. He also told me that it would be better to use 2 dual op-amps instead of a quad one for the reason to minimize cross talk. His experience is rather dealing with pre amplifiers rather than class d. Your particular use may be somewhat different as here you only need to generate the triangular wave form for the base frequency of the amplifier. I am listing a few iCs for you whom are directly replaceable with each other regarding input, output and supply pins.

4560, 4558, 072, 5532, 1458 and MC33178. These are all dual op-amps but I guess you can find the quad version of some of these as well.

Checking about the MC33178/9 I guess this will also do the job for you. Finally if you try any of these ICs mentioned see that the waveform produced is what you are looking for as they may differ slightly from one another in this particular use. You will only know when you try them out.
 

stewin

Member
hello all , i have made my latest version of this amp , i opted for a through hole ic due to challenges in getting a geniune tl074/84 smd . imagine the smd also have issue :(,
A not original ic works fine in preamp,eq, crossovers etc , but can't work well in this class d amp ,
with this amplifier it works but the amp produces a lot of hf . but when i use a good geniune ic the hf noise reduces and the amp does not draw a lot of current
but a geniune tl074/84 works with no issues at all .

here is my project and pcb files . have fun fam :D:D
 

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Silvio

Active member
If I am correct it seems that you opted for 4 X 200w mono amplifiers. I guess that is a very versatile setup. It can take 4 X 15 inch speakers whenever needed and having a total of 800w power. I seen this made in pro amplifiers. A common heatsink for every two amps will make a good stack and can fit in a 2U box. My guess having 4 separate volume controls and 4 separate preamps which can make a bridged pair thus either having a stereo unit with bridged amps or 4 mono. This will need 4 separate inputs and 4 separate outputs.

One last note. Have you tried a band pass filter for reducing HF noise in the input? Are you using an smps to drive these amplifiers? Some carful screening maybe also passing a grounded trace between the signal traces may help you out. Just some ideas that cropped up for you.
 
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stewin

Member
If I am correct it seems that you opted for 4 X 200w mono amplifiers. I guess that is a very versatile setup. It can take 4 X 15 inch speakers whenever needed and having a total of 800w power. I seen this made in pro amplifiers. A common heatsink for every two amps will make a good stack and can fit in a 2U box. My guess having 4 separate volume controls and 4 separate preamps which can make a bridged pair thus either having a stereo unit with bridged amps or 4 mono. This will need 4 separate inputs and 4 separate outputs.

One last note. Have you tried a band pass filter for reducing HF noise in the input? Are you using an smps to drive these amplifiers? Some carful screening maybe also passing a grounded trace between the signal traces may help you out. Just some ideas that cropped up for you.
thanks silvio for the reply. this amp is robust and works flawless without any hf noise and comfortably handles 2ohms load per channel with +/-49volts . the only issue is that you have to use geniune tl074/84 and bc327 and bc337 if you use counterfeit the amp will draw alot of current and it will produce nasty hf noise at output

by the way silvio can lm324 work instead of tl074?
 
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Silvio

Active member
Quote: By the way Silvio can lm324 work instead of tl074?

Well seeing that the amp is that sensitive you only need to try it out to see if it works. The pinouts of the LM324 are the same as TLO74.
 
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