Emitter resistor problem?
Hi All - i started building this setup but i ran into difficulty in sourcing for the 0.15 emitter resistors and could only find 0.27 resistors ,can this still work ?
Component list: (1x AMP)
1x 680 (680R) Resistor
1x 10K Resistor
3x 22K Resistor
1x 6.8 (6R8) 5W Resistor
2x 0.15 (0R15) 5W Resistor
2x 10uF 50V Capacitor
2x 22uF 50V Capacitor
1x 1uF 63V MKT/BiPolar Capacitor
1x TDA7294 Chip AMP
1x 2SA1943 PNP Transistor
1x 2SC5200 NPN Transistor
Schematic:
NOTE: 6.8Ohm resistor is a 5W
Hi All - i started building this setup but i ran into difficulty in sourcing for the 0.15 emitter resistors and could only find 0.27 resistors ,can this still work ?
Component list: (1x AMP)
1x 680 (680R) Resistor
1x 10K Resistor
3x 22K Resistor
1x 6.8 (6R8) 5W Resistor
2x 0.15 (0R15) 5W Resistor
2x 10uF 50V Capacitor
2x 22uF 50V Capacitor
1x 1uF 63V MKT/BiPolar Capacitor
1x TDA7294 Chip AMP
1x 2SA1943 PNP Transistor
1x 2SC5200 NPN Transistor
Schematic:
An externally hosted image should be here but it was not working when we last tested it.
NOTE: 6.8Ohm resistor is a 5W
yes everything up to 0.5Ohm will work (larger will also work), but remember the more Ohm the more heat/power is lost in the resistors, the 0.15 i use is because i have a "case" of them and want to keep all the amps i make the same 
Of course you can use to little and risk the chance of blown output transistors, but so far with 0.15Ohm i have played 2 OHM 500W speakers up to their limit without any problems.
Of course you can use to little and risk the chance of blown output transistors, but so far with 0.15Ohm i have played 2 OHM 500W speakers up to their limit without any problems.
Hey mashoni23, before the bridged amp I've built this one, here is the image of the finished module and the PCB layout, hope it helps. My output transistors aren't even the same one is japan and the other who knows, but it was hooked up and tested and sounded just fine.
An externally hosted image should be here but it was not working when we last tested it.
yes, if you find anyone better then the set i purpose or if you like me have a box/case of transistors go nuts, only thing to "fiddle" with in this "design" is the "sync" resistor, in this case the 6.8Ohm, if it sounds weird then change it to lower or higher value, BUT use a power resistor, i cannot guarantee that the amp will sound properly thou, but it should.
yes the 22K feedback should remain the same, and yes same "system" should work with other chipamps, i think i once saw a TDA2030 with extra transistors, of course that chip cant handle many volts and will need to be bridged to achieve just the slightest boost, unless you are running 1-2Ohm or build your own speakers with 0.1-0.5Ohm voice coil(s)
and what if i have several parallel 8ohm
speakers? Like 4x 8ohm parallel gives 2 ohm
load,that would get alot of output from a
7293 and single pair, and i could use lower
power drivers. Or 8x 8ohm speakers with
tda +2x bipolar pairs?
How is the stability of the setup with the extra transistors? Looks like an easy No BS way to have a big amp if you already have the power supply parts.
I'd like to parallel 4 or more pairs to an amp chip, and use 4.7 ohm for a bit more drive from the chip directly to the speaker before the other pairs turn on. With +/- 38V rails, you could get 100WRMS/4Ohm or 200WRMS/2ohm, or 400WRMS/1ohm, which would be ideal.
Lower ohms driving is plain better. It's not hard to get a power supply that can supply the current, You can wire several sets of speakers to simple L and R on your amp, and have speakers around the room. Good easy sound, no nonsense. Especially since speakers of different frequency response sound good together anyway..............
I was building a discrete amp with similar specs, it took forever to build, then my house got burned down, lost nearly all my onsemi parts and everything else, and I salvaged the burned 1500VA Toroid core, to rewrap with new coils to rebuild again! I'm so over taking forever to design an amp, I just want to use a chipamp driving transistors now to get big power. Just a stereo amp with 2x200 or 400w would be great. An amp I could build over the weekend with just a few rows of nice transistors driven from a chip amp would be nice.
I'd like to parallel 4 or more pairs to an amp chip, and use 4.7 ohm for a bit more drive from the chip directly to the speaker before the other pairs turn on. With +/- 38V rails, you could get 100WRMS/4Ohm or 200WRMS/2ohm, or 400WRMS/1ohm, which would be ideal.
Lower ohms driving is plain better. It's not hard to get a power supply that can supply the current, You can wire several sets of speakers to simple L and R on your amp, and have speakers around the room. Good easy sound, no nonsense. Especially since speakers of different frequency response sound good together anyway..............
I was building a discrete amp with similar specs, it took forever to build, then my house got burned down, lost nearly all my onsemi parts and everything else, and I salvaged the burned 1500VA Toroid core, to rewrap with new coils to rebuild again! I'm so over taking forever to design an amp, I just want to use a chipamp driving transistors now to get big power. Just a stereo amp with 2x200 or 400w would be great. An amp I could build over the weekend with just a few rows of nice transistors driven from a chip amp would be nice.
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First the 6.8Ohm is for sync and can't see you can get more efficiency or what ever you are trying to archive, but since i have been messing around with this amp for so long i can say the when driving lower then 2 Ohm you might need to change it to a lower or higher value, again this is as stated in the beginning of the thread, the 6.8Ohm resistor is KEY to this amp working.
Also having build 100' of speaker sets in ALL configs i will agree with you that lower OHM is always better for so many reasons, a weird thing is the BIG basses/woofers sound better in the above bass area when connected in parallel.
The good thing with this amp is the sound, there are no nonsense there at all, and how easy and fast you can build it, before this amp i was also building amps from the "bottom up", but i always wanted a more easy approach and it came in this way, would be nice if they would make a 2013 version with even more voltage handling.
But of course the Class D amps are getting better and sound very good, like the ULTRA simple but low power VMA2012 2*3W Class D Audio Amplifier Module - Free Shipping - DealExtreme, i use this little amp for so many things because it runs on a single LiPo battery.
Also having build 100' of speaker sets in ALL configs i will agree with you that lower OHM is always better for so many reasons, a weird thing is the BIG basses/woofers sound better in the above bass area when connected in parallel.
The good thing with this amp is the sound, there are no nonsense there at all, and how easy and fast you can build it, before this amp i was also building amps from the "bottom up", but i always wanted a more easy approach and it came in this way, would be nice if they would make a 2013 version with even more voltage handling.
But of course the Class D amps are getting better and sound very good, like the ULTRA simple but low power VMA2012 2*3W Class D Audio Amplifier Module - Free Shipping - DealExtreme, i use this little amp for so many things because it runs on a single LiPo battery.
Pictures:
Are the Transistors and IC's insulated from the heatsink?from the images above i don't see if they are..
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Are the Transistors and IC's insulated from the heatsink?from the images above i don't see if they are..
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YES you MUST DO THIS, if you don't the whole thing will just burn up, also you will have LIVE heatsink's, if you can't get more then 80W out of your amp then that's why.
My amp in the pictures has 2x LONG strips of insulation instead of the normal pads, this is just because of the compactness of it.
My amp in the pictures has 2x LONG strips of insulation instead of the normal pads, this is just because of the compactness of it.
I think this is what i did, but the Transistors (uninsulated) were on another heatsink and the TDA(uninsulated) on another heatsink there were no "sparks" or "noise" i guess the transistors died a silent death coz the TDA is working fine.By the way i did use the same schematic as you had uploaded,so i was concerned why i was not enjoying the +400watt power output
LOL