TDA7294 + Power Transistors AMP (TDA7293 to come also) - diyAudio
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Old 13th February 2012, 12:09 AM   #1
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Default TDA7294 + Power Transistors AMP (TDA7293 to come also)

I was asked to post my home AMP from a fellow user on talk.maemo.org so here it is

This is the classic TDA7294 AMP with LOTS more Power then normal, this is with using Power Transistors at the output stage, it is a simple Addon to make, it just requires a SYNC resistor and the feedback to be moved to the output after the Power Transistors.
So to make this AMP you can just start with the TDA7294 with one change, just need to "move" the feedback so you can connect it to the Output after the Power Transistors, in all the AMPS i have made with the TDA7294 the 6.8Ohm has been spot on when using the 2SC5200 & 2SA1943, if you use other transistors you may need to experiment with another value for the SYNC resistor.
Things to do when SYNC it is to listen to it, things to listen to are from very low volume (FROM a clean source) and go slowely up in volume, the POINT here is that it should just get louder like a normal amplifier would, if the SYNC is off then a normal thing will be that at audio peaks (like drums & bass) it will sound like someone is kicking your speakers because the Transistors kick in at a wrong volume then the amp is playing, believe me you will hear it, this needs to be corrected by changing the resistor else you will have an amp that only sounds good at very low volume and medium to high volume.

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:
Click the image to open in full size.
NOTE: 6.8Ohm resistor is a 5W

Hole Print "Design": (Would like to make proper boards...)
Click the image to open in full size.

Pictures:
Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

STATS:
Output Power: well lets just say that speakers that where 250/500W 2Ohm (RMS/MAX) where played to the max with NO DISTORTION AT ALL
I will call the output at 400W+ (MAX) and this is based on that the TDA itself adds ONLY 20-40W (because of the much higher driving Ohm), but the 5200/1943 are some GOOD POWERFULL transistors and going through the datasheet it will deliver peeks over 600W (short pulse pr Transistor), they supply 100W but this is FULL DC and there are no audio tracks to my knowledge that has that kind of "sound"
Driving Impedance: i have been using it for 2-8Ohm speakers, the lowest i have driven was 1.3Ohm but as with all AMPS if you know your Transistors you know how many watts you can pull out, this AMP will drive what ever you hook it up to, JUST one thing, when i was using my 1.3Ohm set it did introduce some "noise" (sounded like 80' AMP hiss), and at this point the SYNC resistor properly needs to be changed, i did not do this, i took the lazy way out and put some 1.8Ohm POWER Resistors in line with the speakers instead.

I have been using this AMP for +3 years, it is good for driving 2-8Ohm speakers with current config (6.8Ohm RES & 5200/1943)
The only thing i can really say is BUILD it, you will not be disappointed i can guaranty that, as long as you follow the "guide" it will be fine, i will how ever RECOMMEND that you use the same components (5200/1943) then you should not go wrong and it will play beautiful the first time it is hooked up, and also with these components it is VERY cheap to make (depending on suppler), where i buy my components i can make 1 channel (All components) for about 15$, it is as always the POWER SUPPLY that is going to set the price back.


Link to the original Thread http://talk.maemo.org/showthread.php?t=74341

Whats more to come, well more "stats", and the new AMP im building right now, it's the TDA7293 With Power Transistors x 4, for a nice POWERFULL BI-AMP system, but it can also be used as a 4.0 Surround AMP or a Bridged 2x 700W+, also more pictures etc.

This post will be updated again and again to meet questions and to add pictures, guides etc...

EDIT: 2014.03 - Now also on facebook https://www.facebook.com/groups/760434413975466/

Last edited by dr frost dk; 25th March 2014 at 08:57 PM.
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Old 13th February 2012, 12:32 AM   #2
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Reserved for TDA 7293 AMP that im building these days
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Old 13th February 2012, 11:34 AM   #3
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Reserved for additional info (also can't edit post 2????)
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Old 13th February 2012, 02:05 PM   #4
GloBug is offline GloBug  Canada
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I think you can only edit the first post.
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Old 13th February 2012, 02:46 PM   #5
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Location: Jackson,michigan
Very cool Project!
There have been a few discussions on whether or not some thing like this would work well.
Please post some more testing info when you have it available.
I am very interested in seeing some THD figures as well as driving loads in the 2 ohm or lower range.
I have been thinking about something like this possibly using something like 4 to 8 pairs of output devices.

Great Job !!!

jer
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Old 13th February 2012, 03:58 PM   #6
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Quote:
Originally Posted by geraldfryjr View Post
Very cool Project!
There have been a few discussions on whether or not some thing like this would work well.
Please post some more testing info when you have it available.
I am very interested in seeing some THD figures as well as driving loads in the 2 ohm or lower range.
I have been thinking about something like this possibly using something like 4 to 8 pairs of output devices.

Great Job !!!

jer
Thanks, well i can say in my XP (15+ years, 30+ DIY AMPS, DIY 100+ Speaker sets & 100+Normal Speaker sets) that this AMP is just awesome, unfortunately i don't have any equipment to test it to the full, but some info and will be added to post #1 along the way:
Output power (2Ohm) Beyond 400W, tested with speakers rated to 250/500 and they were played up to the limit WITHOUT ANY DISTORTION.
S/N is even better then stock (TDA7294), wear the speakers as headphones and you will barely hear any hiss (also no hum what so ever) and this is with speakers that have a SPL of 95+.
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Old 15th February 2012, 01:56 PM   #7
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Just want to show a few pics of the "micro" prints for the new TDA7293, again TDA7293 so don't use these for reference if your making a TDA7294.

And yes those are SMD resistors, i could not find any 1% metal film resistors on wieser-electronic so i opted to make a "challenge" again

Also all the connections are not made yet when i took the pictures.

Click the image to open in full size.

Click the image to open in full size.
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Old 15th February 2012, 03:14 PM   #8
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sorry!i can't see the schematic.
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Old 15th February 2012, 06:30 PM   #9
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First picture in Post #1, it is from my dropbox but should not give any problems, or do you mean that it is not like a normal schematic, then yes your right, but is should not be that hard to follow, numbers represent pin numbers on TDA7294.

Also try clicking on it if you mean it is not clear enough.
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Old 16th February 2012, 06:16 AM   #10
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Fellow Dane here...

Any plans on making proper PCB's? I'd be interested in buying some.
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