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Old 7th November 2012, 09:44 PM   #61
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If you are only using 8Ohm then 2x won't do anything more then 1x Power Transistors, however if you make a 4x AMP with a inverting opamp on 2x Channels and thereby bridging that AMP to 2x then 2x Power Transistors (PR. AMP) will give you a 4 Ohm stable AMP capable of driving ALOT of power, can't say how much but in peak/max i will saw way over 1000W, RMS sound yield 400W+

Would be nice for someone that has testing equipment to build this and give the exact numbers.

Again as posted before, the 7294 + Power Transistors as i posted in Post #1 will drive speakers with 250/500 (RMS/MAX) to the limit WITHOUT distortion, even at near breaking point for the speakers the sound is just clear because of the power handling of the Transistor set and the fact that the TDA7294 is only pulling 8Ohm (2Ohm speaker + 6.8Ohm "balance" resistor) so the TDA7294 is never really near it's limit at any time no matter if you are pulling 8Ohm or 0.25Ohm
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Old 7th November 2012, 09:55 PM   #62
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Quote:
Originally Posted by dr frost dk View Post
If you are only using 8Ohm then 2x won't do anything more then 1x Power Transistors, however if you make a 4x AMP with a inverting opamp on 2x Channels and thereby bridging that AMP to 2x then 2x Power Transistors (PR. AMP) will give you a 4 Ohm stable AMP capable of driving ALOT of power, can't say how much but in peak/max i will saw way over 1000W, RMS sound yield 400W+

Would be nice for someone that has testing equipment to build this and give the exact numbers.

Again as posted before, the 7294 + Power Transistors as i posted in Post #1 will drive speakers with 250/500 (RMS/MAX) to the limit WITHOUT distortion, even at near breaking point for the speakers the sound is just clear because of the power handling of the Transistor set and the fact that the TDA7294 is only pulling 8Ohm (2Ohm speaker + 6.8Ohm "balance" resistor) so the TDA7294 is never really near it's limit at any time no matter if you are pulling 8Ohm or 0.25Ohm
correct me if im wrong but for driving 8ohm speakers i need to make two TDA7294 boards each with two pairs of power transistors. then i need to bridge them using inverting op amp on one chanel thus giving me an bridge capable of driving 8ohm speakers?

Anyway i also have 4Ohm 300w rms speakers and to drive them its enough only to have single tda7294 with 2x power transistors (comes to 2xNPN and 2xPNP) ?

P.S. would it be enough to use tda7294 + 4x/6x/8x power transistor couples to drive 8Ohm's?
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Last edited by ozracing; 7th November 2012 at 10:00 PM. Reason: idea
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Old 7th November 2012, 10:15 PM   #63
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For 2 to 8Ohm speakers just use TDA7294 with 1x set of Power Transistors, it is 2 Ohm stable, for driving speakers with less then 2 Ohm you will need:
1 Ohm = 2x Power Transistors - Max Power about 800W
0.5 Ohm = 4x ~~ - ~~ 1600W
0.25 Ohm = 8x ~~ - ~~ 3200W
Last but most obvious you need a power supply big enough for the application.

Again for 2-8Ohm 1x set is enough, even for 4-8Ohm bridged 1x set is enough just remember it is now only 4Ohm stable, just power output in 4Ohm is very high (this i have tested with easily putting a 700W woofer to it's max), more then 1x set will provide more A to speakers but should make no difference when driving 2-8Ohm

Hope im making myself clear, not the best of explaining things....

I think i better get on the whole youtube thing and post a video some day with this amp maxing out a pretty powerfull woofer, also need to put my electro ciao on there......

But again you only need more Transistors the LOWER Ohm you need to drive, or if you need 2Ohm stable in bridge
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Old 7th November 2012, 10:24 PM   #64
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Quote:
Originally Posted by dr frost dk View Post
For 2 to 8Ohm speakers just use TDA7294 with 1x set of Power Transistors, it is 2 Ohm stable, for driving speakers with less then 2 Ohm you will need:
1 Ohm = 2x Power Transistors - Max Power about 800W
0.5 Ohm = 4x ~~ - ~~ 1600W
0.25 Ohm = 8x ~~ - ~~ 3200W
Last but most obvious you need a power supply big enough for the application.

Again for 2-8Ohm 1x set is enough, even for 4-8Ohm bridged 1x set is enough just remember it is now only 4Ohm stable, just power output in 4Ohm is very high (this i have tested with easily putting a 700W woofer to it's max), more then 1x set will provide more A to speakers but should make no difference when driving 2-8Ohm

Hope im making myself clear, not the best of explaining things....

I think i better get on the whole youtube thing and post a video some day with this amp maxing out a pretty powerfull woofer, also need to put my electro ciao on there......

But again you only need more Transistors the LOWER Ohm you need to drive, or if you need 2Ohm stable in bridge
Thanks for explaining. I still have some stuff that needs explaining but first i need to build the amp and test it out
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Old 16th November 2012, 11:09 PM   #65
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Sorry for double post but i cant edit my last post.
Anyway made proper schematics and board layout in EAGLE 6.2.0
Could any one check for mistakes and etc. for me it looks ok.
Added up to 4x transistors for just in case situation

connectors:
Audio in: 1.In 2.Gnd
Power: 1.+Vss 2.Gnd 3.-Vee
Speaker: 1. Out 2.Gnd


P.S. adding used libraries too.

lbr.zip

TDA7294+power transistors.zip
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Last edited by ozracing; 16th November 2012 at 11:14 PM.
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Old 13th December 2012, 03:49 AM   #66
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hi gud day
im interested on this add on.i just want to ask if i can use the power supply seen in the attached schematic.i've done that project(the one in schematic) and i want to try the add on.
any advice?
tia
Attached Files
File Type: pdf tda7294_caraudio_schematic.pdf (32.1 KB, 392 views)
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Old 29th April 2013, 05:58 PM   #67
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Location: uruapan, michoacan, mexico
hi dr frost! just wanted to ask you, does it work with tda 7293?

thanks
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Old 29th April 2013, 06:05 PM   #68
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yes if you change it alittle, if you want to use the 7293 use this schematic
Click the image to open in full size.

There are just a little change to pin 6 & 12 & 14, so DO ONLY use this for the 7293 and it will work, i know this since i build and tested it.

And sorry for the GIANT absence from the forums, i been very busy in the last LONG time, i will have to complete my 4x 7293 for my TV project
http://www.facebook.com/media/set/?s...1&l=0b484a5e9d

Last edited by dr frost dk; 29th April 2013 at 06:10 PM.
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Old 29th April 2013, 06:29 PM   #69
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Join Date: Jun 2004
Location: uruapan, michoacan, mexico
dont want to abuse, may ask your opinion?
what result from undervolt?
my xfrmer is 25-0-25 125 va
want to squeeze the max out of the PS,
and about to use parallel 2 chip, which
i think is more like your design?
i already have the bipolars from scratch.
I wish your TV project goes allright and everything OK!

martinnez
uruapan michoacan
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Old 29th April 2013, 07:25 PM   #70
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you may have to "experiment" with the 6.8Ohm resistor if it sounds "off", if you use dual set transistors with that voltage it will be 0.5-1.0 Ohm stable so you can get alot of power if your speakers are at 1 ohm, but you will still be limited to 125va from you "input" power.
If you mean bridge to get higher power at higher Ohm then you need to try it out your self, i have never attempted to bridge my amp in the usual way as described in the TDA729x schematic, BUT it works just fine with an inverted input on one channel by using an opamp.

EDIT: and the TV is almost done, just need to build a Subwoofer that will occupy almost all space in the top of the TV.
and make a parallel port transistor power drive to the motor in the "foot" so it can be turned via the computer
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