TDA7294 + Power Transistors AMP (TDA7293 to come also) - Page 12 - diyAudio
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Old 24th May 2013, 09:32 PM   #111
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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.
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Old 24th May 2013, 09:35 PM   #112
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and the feedback loop takes care of the biasing?
And yes i have lots of things to try.
Like this same with some other chipamps and
transistors.
Thanks!
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Old 24th May 2013, 09:52 PM   #113
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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)
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Old 25th May 2013, 01:17 AM   #114
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Quote:
Originally Posted by dr frost dk View Post
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?
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Old 25th May 2013, 07:42 AM   #115
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The amp is 2 ohm stable with one pair of the transistor set i purpose, if you use others you need to look to the schematic, and also test it., 8x 8Ohm in parallel would give 1 Ohm then you need 2x Pairs to be totally certain, and of course a BIG power supply.
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Old 26th May 2013, 03:37 AM   #116
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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.
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Last edited by EWorkshop1708; 26th May 2013 at 03:41 AM.
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Old 26th May 2013, 09:56 AM   #117
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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.
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Old 27th May 2013, 03:18 PM   #118
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Pictures:
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Are the Transistors and IC's insulated from the heatsink?from the images above i don't see if they are..

Last edited by mashoni23; 27th May 2013 at 03:29 PM. Reason: to remove additional messages
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Old 27th May 2013, 04:43 PM   #119
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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.
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Old 29th May 2013, 02:17 PM   #120
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Quote:
Originally Posted by dr frost dk View Post
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.
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
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