Optimizing TDA7294 Output

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Can't go through the entire thread. But I thought I should share this .Moderators kindly remove the post of the schema is already discussed. There are a couple of Russian designers who has done extensive work on tda 7294 series chips. Unfortunately,they are all in Russian and a regular Google search like tda 7294 doess not yield those pages..
1.Search for TDA 7294 LINCOR MF1 .The Russian pages can be translated and read in English. The schema is a mixed voltage and current feedback ,and uses a F shaped feedback loop. The. Author ,whose pen name is LINCOR, gives explanation and explains how he tried to achieve near flat response across frequently spectrum without resonance peak boom. There is a printable PDF layout and the construction is very easy ,even for novice.Now, most importantly,how does it sound..? Having used this amplifier for about one year, I can vouch for its sonic quality. Subjectively, the music is very fluid and easy to listen. No listener fatigue , A special word on the deep, yet controlled bass. One has to build and listen to believe... Considering the cost and simplicity to build,this could make one fine amplifier...
2. Search for tda 7294 audiokiller. Another Russian, with the pen name audio killer,has a entire page dedicated to tda 7294 . He also proposes mixed feedback topology and gives software for calculating feedback resistor for tweaking.. Really a different dimension for these chip amps..I will try to copy the link tomorrow.
 
Hi all people..!!

Can a Chip amp , like TDA7293, TDA7294, LM3886 , obtain a sound quality like a discrete amplifier ( Bipolar , Mosfet , Darlington ) ?

Santiago

I have designed chip amps and class ab and d amps and cant tell the difference between them.
The only one that sounded a touch better was a hybrid TDA7294/12AU7 valve amp.
 
Finally hybrid FB. Finally real output optimization.
tnvijay, thank you!
However, i have even simpler plan. First, i didn't discover anything new. I am convinced such design exist for long time, but is not discussed publicly.
I do not like inverting amplifiers, that is why i go this way.
So:
Pick whatever kit you can/wish, with non inverting amp. Any chip, or even discrete, depending on your knowledge. Get it working as is. Optionally replace input and FB shunt caps to get better low end response. In my case with TDA7293 i throw 4.7u at input and 220u at FB shunt. Don't bother with other parts in FB.
When it works stable, pick some low value resistor and put it between speaker and ground. My speakers happen to be 6-7 ohm effective, so i paralleled 2x0.47ohm/2w. Idea is to achieve just a little bigger current FB amplification (calculated) compared to existing voltage FB. Say, +1, +2 more. For real 8ohm speakers this resistor should be something like 2x0.47 in parallel, with one more 0.47 in series to them. Some experimenting is needed, because no one knows real impedance of the speakers.
Pick a cap, say, equal to voltage shunt FB cap and place it between speaker/resistor junction and - input of your amplifier.
That is all! Magic is here! You have non-inverting hybrid FB.
If you wish, you can calculate and further optimize this design. I will not put calculations here because they are pretty complex and will not give a lot to mass users.
How it sound? Different! I like it. No, to be more correct: because of this hybrid now i hate my multi-thousand euro sound system, built and optimized over the years. For me it sounds better even compared to valve amps.
How it measures? Most likely very bad! O-scope 'audiophiles' definitely will not like it. But i use my ears for listening and scope for other things.
With this simple addition almost any amp can be 'fixed', virtually for free.
 
Finally hybrid FB. Finally real output optimization.
tnvijay, thank you!
However, i have even simpler plan. First, i didn't discover anything new. I am convinced such design exist for long time, but is not discussed publicly.
I do not like inverting amplifiers, that is why i go this way.
So:
Pick whatever kit you can/wish, with non inverting amp. Any chip, or even discrete, depending on your knowledge. Get it working as is. Optionally replace input and FB shunt caps to get better low end response. In my case with TDA7293 i throw 4.7u at input and 220u at FB shunt. Don't bother with other parts in FB.
When it works stable, pick some low value resistor and put it between speaker and ground. My speakers happen to be 6-7 ohm effective, so i paralleled 2x0.47ohm/2w. Idea is to achieve just a little bigger current FB amplification (calculated) compared to existing voltage FB. Say, +1, +2 more. For real 8ohm speakers this resistor should be something like 2x0.47 in parallel, with one more 0.47 in series to them. Some experimenting is needed, because no one knows real impedance of the speakers.
Pick a cap, say, equal to voltage shunt FB cap and place it between speaker/resistor junction and - input of your amplifier.
That is all! Magic is here! You have non-inverting hybrid FB.
If you wish, you can calculate and further optimize this design. I will not put calculations here because they are pretty complex and will not give a lot to mass users.
How it sound? Different! I like it. No, to be more correct: because of this hybrid now i hate my multi-thousand euro sound system, built and optimized over the years. For me it sounds better even compared to valve amps.
How it measures? Most likely very bad! O-scope 'audiophiles' definitely will not like it. But i use my ears for listening and scope for other things.
With this simple addition almost any amp can be 'fixed', virtually for free.

Thanks . I am a self taught electronic hobbyist.To Understand your design principle,can you post a schematic, for ex with a TDA2050 ?
 
Here is schematic with generic amp. Things in red represent what is added. Math is near approximation, giving satisfactory result and starting point for fine tuning.
Starting image was pick from random internet site.
 

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Thanks! And, then we have these (attached).

We're not likely to see any "in the wild" because this is DIY and they're likely to get modded (no matter how nice they are if not modded). Therefore, the normal usage for these is the solid place to start that was not provided by the datasheet.

The under-volted 45W example will image better (used along with 20-0-20 and 22+22 transformers). At the expected voltage (printed on the schematic) and with the assumption of excellent compact (I mean tiny!) layout and route the gain divider's resistors most directly (rather than most decoratively), then the cermet trimmer is set to 780R but can be fiddled to support different applications, including different voltages and other modding. Of the two schematics presented below, the lower voltage example has higher resolution. Sounds like a hi-fi.

However, the #1 most popular mod for amplifiers is a push for power build. So, I generated a second schematic showing the higher rails and different gain setting involved (used along with 25-0-25 and 28+28 transformers). Note the cheap little 680R film resistor has not performed optimally as a base stopper; however, if you replace that with a cermet trimmer, you can dial it to 730R. Also, the series elements are high efficiency MBR1645 schottkies, which have smallest voltage drop but still work just barely well enough to secure the excellent power decoupling necessary for clear audio.
Some of the imaging/3d/realism quality of the undervolted 45W example isn't accomplished by the higher power 65W example, and that's the cost of 20 more watts, which won't boost the speaker output by so much as 1.5db--certainly not worth the compromise, except for people who equate watts with quality. That is actually popular. The higher power version (with higher voltage rails), has a pretty tone and will certainly work well enough to rock the house for a party and for woofer amplifiers as well. Sounds like a party amp.
Hi Daniel
first of all, thanks for sharing, I want to build this amp. my transformer is double 24volt. want to make a 3 way system, wonder that can I use two of these in bridge mode for woofer? do you recommend this topology for your schematic? or should I change it?
thank you
 
When you got authentic chips, no pcb, just direct solder component on chip. It would sing nice n clean.
Following @Daniel documentation, this chip '93 would sounding almost as 1k priced commercial amp.

When you got fake chip. No matter using whatever pcb layout, it would be problematic.
Mostly are rebranded or relabel from tda7926, it almost impossible to go further more than 18vac transformer.

Buying from highly reputable seller is mandatory. ��
Buying from unknown seller, with difference between 0.5 to 1 bucks,
will make high dissapoint.
 
Hello, I apologize - I know this might not be the best place to ask , but is anyone familiar with this chip amp?

TPA3118 PBTL Mono Digital Amplifier Board 1X60W 12V 24V POWER AMP .

I can't find how many amps the power supply, (12v - 24v) is supposed to be for this amplifier - I tried emailing the seller but hasn't responded -- does anyone know?

Here is a link to eway - - Thank you for any help!


2PCS TPA3118 PBTL Mono Digital Amplifier Board 1X60W 12V 24V POWER AMP Car | eBay
 
Hi hellcon


This is a chip amp but the technology is class D chip. so please use the Class D forum and search with "TPA3118 mono"....then you will get a lot of information.


the TPA3118 is a chip which need a single supply with max 26V. its better to use it not on its max--so use 24V then its fine.


chris
 

Just a heads up for anyone that finds the board on pcbway for this design the holes for the 7294 and R7 weren't big enough and there doesn't seem to be big enough pads around them to try to enlarge them with a small drill bit.

I've been trying to find a top notch TDA7294 board for quite some time. I guess I'm going to have to see if I can grasp design software at some point. I almost ordered these from Japan https://www.jauce.com/auction/f346319466 but the total looks a bit high
 
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