Looks good, but the part numbers on the circuit are hard to read. Could you give us a large version?
The placing of the compensation caps around the pre-drivers is not something that is seen everyday, but if it works then it works. 😉
The placing of the compensation caps around the pre-drivers is not something that is seen everyday, but if it works then it works. 😉
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Without them i had a small sub millivolt oscillation in the simulation.
Heres a larger version of the schematic, the output transistors are MJW21195 and MJW21196 but i don't have simulation models for these yet.
http://i.imgur.com/xJHfp.png
Heres a larger version of the schematic, the output transistors are MJW21195 and MJW21196 but i don't have simulation models for these yet.
http://i.imgur.com/xJHfp.png
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Be carfull with the power simulation.
You have to devide the power by 2.828 (2x 1.414) if you want to have the rms power, LTspice is using maximum voltages and maximum currents.
You have to devide the power by 2.828 (2x 1.414) if you want to have the rms power, LTspice is using maximum voltages and maximum currents.
Yes i know and my power supply is rated at 500VA so 300W RMS is the max practical output power if even that.
This amp will clip due to your transformer running out of gas. If you had an +800VA you would be looking more at 560 watt "rms" into 4 Ω resistive load.
Atleast it clips before the SOA of the outputs is exceeded. And i will never ever reach anywhere near clipping anyways, any of my amps are lucky to make it past 5 watts as i live in a apartment.
I don't use a sub in my system so this build is only for fun, just like all my other projects.
I don't use a sub in my system so this build is only for fun, just like all my other projects.
So i finally put the output stage together, and i havent yet finished building the frontend and drive as i havent decided the topology just yet, so i took a board i already had from another half scrapped project for a test.
A pic of the test setup: http://i.imgur.com/vNPAy.jpg
Im feeding it 2x50VDC from the 500VA transformer and four 22000µF 63V caps, a quick power test reveals around 100 watts rms into 8.2 ohms(a buncha 25ohm 50w power resistors in series/parallel) I dident have enough soundcard level to get up to clipping here.
4.1 ohms(doubled the amount of resistors in parallel) was roughly 200W rms and again not enough level to reach clipping.
2 ohms(all resistors in parallel) revealed abour 338W rms, here i was able to reach clipping due to psu sag, and since the volume control on a sound card is a bit coarse(next step up
= clipping), this figure is not accurate and could be anything from 330W to 400W rms.
A real load (three 4ohm subwoofers in parallel) is no problem for this amp despite the 1.33ohm dc resistance, it takes it like a champ and shakes the building doing so, scope shows peaks exceeding 40 volts, suggesting over 1200 watts peak, so this is by far the most powerful amp i ever built.
The power transistors are five pairs of MJW21195/21196 with MJE15030/15031 for drivers.
PS: all above testes were made with a 50Hz sine to mitigate any bandwidth issues with using a non true rms meter.
A pic of the test setup: http://i.imgur.com/vNPAy.jpg
Im feeding it 2x50VDC from the 500VA transformer and four 22000µF 63V caps, a quick power test reveals around 100 watts rms into 8.2 ohms(a buncha 25ohm 50w power resistors in series/parallel) I dident have enough soundcard level to get up to clipping here.
4.1 ohms(doubled the amount of resistors in parallel) was roughly 200W rms and again not enough level to reach clipping.
2 ohms(all resistors in parallel) revealed abour 338W rms, here i was able to reach clipping due to psu sag, and since the volume control on a sound card is a bit coarse(next step up
= clipping), this figure is not accurate and could be anything from 330W to 400W rms.
A real load (three 4ohm subwoofers in parallel) is no problem for this amp despite the 1.33ohm dc resistance, it takes it like a champ and shakes the building doing so, scope shows peaks exceeding 40 volts, suggesting over 1200 watts peak, so this is by far the most powerful amp i ever built.
The power transistors are five pairs of MJW21195/21196 with MJE15030/15031 for drivers.
PS: all above testes were made with a 50Hz sine to mitigate any bandwidth issues with using a non true rms meter.
I've decided to double the amount of output transistors from 5 pairs to 10 pairs just because i can and kinda want to, so i've ordered more MJW21195/96's from onsemi.
Today i brought this amp up to the hjighest voltage psu i have, a 500VA rated transformer with 2x48VAC out, this gives me 2x67VDC for the amp.
Into 4 ohms i got 40VAC RMS out which translate to ~390 watts RMS.
Into 2 ohms i got 35.5VAC RMS out which translates to ~630 watts RMS.
That 500VA transformer is obviosly slightly underrated, judging from this amp output, i'd say that transformer is closer to 800-1200VA.
For these tests i used a 100Hz sine wave to mitigate the bandwidth limitations of my DMM which is not a true RMS meter.
The oscilloscope showed peaks of 60V on the output at clipping into 4 ohms and peaks of ~55V at clipping into 2 ohms.
Into 4 ohms i got 40VAC RMS out which translate to ~390 watts RMS.
Into 2 ohms i got 35.5VAC RMS out which translates to ~630 watts RMS.
That 500VA transformer is obviosly slightly underrated, judging from this amp output, i'd say that transformer is closer to 800-1200VA.
For these tests i used a 100Hz sine wave to mitigate the bandwidth limitations of my DMM which is not a true RMS meter.
The oscilloscope showed peaks of 60V on the output at clipping into 4 ohms and peaks of ~55V at clipping into 2 ohms.
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I custom made it back when i had a job at a transformer manufacturer, so it dident cost me anything.
40Vac is exactly 400W into 4r0.
35.5Vac is ~-1dBV ref 4r0.
This tells you the amp is struggling to deliver current into your 2r0 test load.
Aim for <0.6dBV loss into half your intended speaker impedance.
post3:
r9 is passing ~3mA
r33 is passing ~4mA
q25 is starved
There is something seriously wrong here.
I think that r9<<r33 and that r10<r9
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