Hi Agressiva
1. Yes you may use IRFP240. Note though that this is rated at 150 watts where the IRFP450 is rated at 190 watts.
2. Yes you can put more output devices on to handle a 2 ohm load. Can you please tell me what voltage rails you intend to use or how much power you want into 2 ohms.
Good luck with your project, it would be great to see photos of your work.
Cheers
1. Yes you may use IRFP240. Note though that this is rated at 150 watts where the IRFP450 is rated at 190 watts.
2. Yes you can put more output devices on to handle a 2 ohm load. Can you please tell me what voltage rails you intend to use or how much power you want into 2 ohms.
Good luck with your project, it would be great to see photos of your work.
Cheers
rolandong said:
and with you.
I don't have plans for a higher power version for this amp. But you could just up the rails (a little bit) and substitute higher power output devices (or more).
Do you mean the other schematic I posted here ?
http://www.diyaudio.com/forums/showthread.php?postid=595571#post595571
Cheers
Hi quasi, tkts for replay ..
Well, i use a 63 + 63 EI trafo or 55 + 55 @ 1200va toroid
i think use 2 subwoofer keybass that have 4r impedance.
I think make 2x 350rms @ 4hom or 1x 700rms @ 2hom.
can i do this doubling the fets per rail ?
Cya
Well, i use a 63 + 63 EI trafo or 55 + 55 @ 1200va toroid
i think use 2 subwoofer keybass that have 4r impedance.
I think make 2x 350rms @ 4hom or 1x 700rms @ 2hom.
can i do this doubling the fets per rail ?
Cya
agressiva said:
The 55v 1200va toroid will give you DC rails of around +/- 75 volts. Power output will be just over 2 x 550 watts into 4 ohms RMS depending on the regulation of your toroid.
i.e. 55v - 1.5v(diode bridge) * 1.4 - 8v (FET loss) / 1.4 = 48 volts RMS available to the speaker = 578 watts across 4 ohms (in theory anyway).
Whoa .....
assembly
Hi quasi ..
finaly i ordered all parts to make my first mosfet power amp. 😀
Well, i have 2 questions:
1- can i use BC639 in place of 2sc 1845 ?
2- how many fets per rail i need to drive 2hom load ?
I ordered 8x irfp450 and think use 4 per rail.
regards ...
Hi quasi ..
finaly i ordered all parts to make my first mosfet power amp. 😀
Well, i have 2 questions:
1- can i use BC639 in place of 2sc 1845 ?
2- how many fets per rail i need to drive 2hom load ?
I ordered 8x irfp450 and think use 4 per rail.
regards ...
Please let me know what rails you will use or how much power you want into 2 ohms.
If you run the transformers you mentioned earlier then 4 FETS per rail will not be enough. I.e. if you run +/- 75 volt rails then you should use 8 FETS per rail and avoid doing sine-wave testing. Remember 75 volt rails will deliver around 1000 watts into 2 ohms.
The BC639 is not really suitable as an input transistor, though it will work. You should look for something classified as high voltage and low noise. Some transistors that come to mind are 2SC2546, 2SC2547 and 2SC1841. I will have a look for some more when I get home tonight (at work now).
If you use rails lower than 55 volts then a BC546 will be ok (different pinouts).
Cheers
P.S. We had a very nice Brazilian boy (man now) live with us while he attended school here. His name is Henrique de Siqueira. His family live in Goianesia.
If you run the transformers you mentioned earlier then 4 FETS per rail will not be enough. I.e. if you run +/- 75 volt rails then you should use 8 FETS per rail and avoid doing sine-wave testing. Remember 75 volt rails will deliver around 1000 watts into 2 ohms.
The BC639 is not really suitable as an input transistor, though it will work. You should look for something classified as high voltage and low noise. Some transistors that come to mind are 2SC2546, 2SC2547 and 2SC1841. I will have a look for some more when I get home tonight (at work now).
If you use rails lower than 55 volts then a BC546 will be ok (different pinouts).
Cheers
P.S. We had a very nice Brazilian boy (man now) live with us while he attended school here. His name is Henrique de Siqueira. His family live in Goianesia.
For high volt rails try ...
For high volt rails try these input transistors.
2SC2546, 2SC2547, 2SC1841, 2N5550, 2N5551, 2SC1845, 2SC2003, 2SC2784, 2SC2362, 2SC1775, 2SC2856, 2SD755, 2SD756.
These are lower noise and higher gain than the BC639.
Let me know what rails you are going to use. For higher power I can easily modify the board layout to take 6 / 8 FETS per rail if you prefer to use the PCB I designed and posted earlier.
Cheers
PS. The way I found the 2SC1845 was by showing the list above to a local electronics dealer. He went through his inventry and voila 20 odd 2SC1845's. These can be bought on the www for around $0.50 to $1.00 US.
For high volt rails try these input transistors.
2SC2546, 2SC2547, 2SC1841, 2N5550, 2N5551, 2SC1845, 2SC2003, 2SC2784, 2SC2362, 2SC1775, 2SC2856, 2SD755, 2SD756.
These are lower noise and higher gain than the BC639.
Let me know what rails you are going to use. For higher power I can easily modify the board layout to take 6 / 8 FETS per rail if you prefer to use the PCB I designed and posted earlier.
Cheers
PS. The way I found the 2SC1845 was by showing the list above to a local electronics dealer. He went through his inventry and voila 20 odd 2SC1845's. These can be bought on the www for around $0.50 to $1.00 US.
thanks quasitoday my amp is complete
and it sounds greati use 35-0-35 transformer and 4 irf 450
i have a little problem it that mje 350\340 are hot
please gide me
🙄
can i use BIPOLAR CAP 4700mfd to protect speakers
from dc volt
!thanks
ravirat4u said:
today my amp is complete
i use 35-0-35 transformer
Congratulations, thank you for using this design.
You should have DC rails of just over +/- 50 volts at idle
Transistors T6 & T7 will dissipate about 0.6 watts each. Transistors T9 & T10 will dissipate about 0.8 watts each
If these transistors do not have a heatsink then they will get very hot. If you used my layout then you can put all these transistors on a small common heatsink. If not then individual heatsinks need to be used.
You can but it is not ideal. Attached is a DC-detect cct you can use. It is a variation of one presented by a number of electronics magazines here in Australia.
Cheers
Hi Quasi,
I had a long look at your +/-90V rail design. I think it's very good.
I particularly liked the way you used both LTP outputs; this is a Siemens trick from some years back and it reputedly works very well. Your cascoding and conjoined current feed for the VAS is clever and innovative.
Congratulations!
Cheers,
Hugh
I had a long look at your +/-90V rail design. I think it's very good.
I particularly liked the way you used both LTP outputs; this is a Siemens trick from some years back and it reputedly works very well. Your cascoding and conjoined current feed for the VAS is clever and innovative.
Congratulations!
Cheers,
Hugh
Hugh, thank you sincerely for your compliments. In practice it does work well.
The thermal tracking for O/P bias is not perfect and tends to over-react a bit. A few components around the sensing transistor could moderate this.
But you know, I just have looked at the schematic and have found a component value error. Resistor on the emitter of T6 should be 47 ohms not 22.
Better go and post the correction
Thanks once again & Cheers
The thermal tracking for O/P bias is not perfect and tends to over-react a bit. A few components around the sensing transistor could moderate this.
But you know, I just have looked at the schematic and have found a component value error. Resistor on the emitter of T6 should be 47 ohms not 22.
Better go and post the correction
Thanks once again & Cheers
Hi Quasi,
looked at your PDF posting of the DC detect and isolate.
I managed to follow through the +ve DC offset to trigger the relay, but I cannot make sense of the -ve DC offset.
Does it also trigger the relay?
Similarly what if a large, legitimate negative signal precharges both your detecting caps, then what kind of delay is needed to discharge and then recharge the caps to allow an illegal +ve DC offset to trigger the relay?
looked at your PDF posting of the DC detect and isolate.
I managed to follow through the +ve DC offset to trigger the relay, but I cannot make sense of the -ve DC offset.
Does it also trigger the relay?
Similarly what if a large, legitimate negative signal precharges both your detecting caps, then what kind of delay is needed to discharge and then recharge the caps to allow an illegal +ve DC offset to trigger the relay?
Hi Andrew T,
Yes I should have posted a description.
Two 33K resistors and the two 22uF capacitors form a low (very low) pass filter .
A sustained positive voltage will turn on Q3. This turns Q4 off which turns off Q5 and the relay.
A sustained negative voltage causes Q1 to turn on. This turns on Q2 which turns Q4 off etc.
A very large negative or positive “music” swing could indeed trip the circuit; this could be a good or bad thing depending on the point of view.
The trip timing is dependant on the input voltage applied plus the value of the capacitors and resistors in the low pass filter. Increasing these values slows the reaction time and increases the restoration time.
As a bonus the 330K resistor and the 470uF capacitor provides a speaker connection delay (de-thump).
Yes I should have posted a description.
Two 33K resistors and the two 22uF capacitors form a low (very low) pass filter .
A sustained positive voltage will turn on Q3. This turns Q4 off which turns off Q5 and the relay.
A sustained negative voltage causes Q1 to turn on. This turns on Q2 which turns Q4 off etc.
A very large negative or positive “music” swing could indeed trip the circuit; this could be a good or bad thing depending on the point of view.
The trip timing is dependant on the input voltage applied plus the value of the capacitors and resistors in the low pass filter. Increasing these values slows the reaction time and increases the restoration time.
As a bonus the 330K resistor and the 470uF capacitor provides a speaker connection delay (de-thump).
Hi quasi
I am using a small common heatsink, today I replace it with medium size heatsink but still have some heat on it I think it is common.
Thank you for dc detector circuit using a relay
Using op amps and transistors I made DC and temperature protection circuit and that works well
Still I want to make a circuit with out a relay in the output
Can NP capacitors solve this, I read in qsc manuals that they use capacitors in short circuit Scheme in the output
what I want to know that if we use caps in the output Can we eliminate short circuit and DC problems effectively🙄
Today I am going to upgrade my amp with 2morefets
If we want more high power then mje 350/40 work well
or replace with mje 15032/33 please suggest me
thank you for every thing
I am using a small common heatsink, today I replace it with medium size heatsink but still have some heat on it I think it is common.
Thank you for dc detector circuit using a relay
Using op amps and transistors I made DC and temperature protection circuit and that works well
Still I want to make a circuit with out a relay in the output
Can NP capacitors solve this, I read in qsc manuals that they use capacitors in short circuit Scheme in the output
what I want to know that if we use caps in the output Can we eliminate short circuit and DC problems effectively🙄
Today I am going to upgrade my amp with 2morefets
If we want more high power then mje 350/40 work well
or replace with mje 15032/33 please suggest me
thank you for every thing
Hi Ravirat4u,
The MJE350/340's will run quite warm. My measure is if you can keep your finger on the heatsink without pain then things are ok.
As far as an output capacitor is concerned it could offer some protection against short circuit depending on it's value. But this is only because the capacitor exhibits an impedance. In practical terms I doubt it would offer enough protection under music conditions (though it would offer some).
If you like I will explore short cct options for the design.
If you add more FETs you can drive into lower impedance speakers and get more power. Because this amp uses FET outputs you will not need to upgrade the MJE340/350's.
Cheers
The MJE350/340's will run quite warm. My measure is if you can keep your finger on the heatsink without pain then things are ok.
As far as an output capacitor is concerned it could offer some protection against short circuit depending on it's value. But this is only because the capacitor exhibits an impedance. In practical terms I doubt it would offer enough protection under music conditions (though it would offer some).
If you like I will explore short cct options for the design.
If you add more FETs you can drive into lower impedance speakers and get more power. Because this amp uses FET outputs you will not need to upgrade the MJE340/350's.
Cheers
Hi quasi
Adding 2 more fets and with +-63v now I'm feeling the
power
Thank U 4 such a project that really works well
🙂 
Regards,
Ravi
Adding 2 more fets and with +-63v now I'm feeling the
power
Thank U 4 such a project that really works well
🙂
Regards,
Ravi
Well done again Ravi. Did you use the layout I posted or did you design your own. If you designed your own I would very much like to see it. Photo's too if you're able to.
Cheers
Cheers