Thanks for the answers. Far from trying to work the chips too hard, I am just doing due diligence before designing a product for potential sale. I'll take whatever I can SAFELY get - stupid not to.
I will, of course, blow a few up in the course of testing: just hoping someone could save me some smoke.
BTW, I caught the suggestion from an earlier post that the super-cheap eBay items may be using down spec chips. Sorry for repeating it if it isn't true.
I will, of course, blow a few up in the course of testing: just hoping someone could save me some smoke.
BTW, I caught the suggestion from an earlier post that the super-cheap eBay items may be using down spec chips. Sorry for repeating it if it isn't true.
Why would you put 19v through an 18 v chip? Have you checked the voltage of your laptop ps?
Would Destroyer recommend 19v for his $200 amp? I have no idea what the voltage is of his ps kit.
A brief period of irrational exuberance when the ebay package arrived, thinking "hey it's only 1V over, maybe it will work, and it's only $6!".
I'm now using a simple regulator to drop the SMPS voltage down to 16V with excellent results on the two replacements I ordered shortly after my Homer Simpson moment.
That chip doesn't have the same core. When the tonality/stability and decoupling needs are different, the chip cores are not related.
Nichicon KG off the board for bass is really nice.
I think recent advances in sources are starting to expose the FC for being lower than purposed audio grade caps.
In your build you mention wiring a large 10000uf KG off the board - is this in parallel with the pair of 470uf FG on the board, or instead of the pair of 470s?
Parallel. The 470uf caps are closer and provide a form of decoupling noise because the inductance is much less so long as the leads and tracings are shorter. Also they're smaller and presumably a little faster. Daniel, despite his claim I can't understand, also likes having a couple 470uf FG caps on the board. But I did testing and found bass is better with more capacitance.
The chip is current limited so keeping voltage high helps maintain all the output you can get. Keeping that voltage up is much easier with large capacitance. The one I recommended is simply one that doesn't color sound as much as most tend to do. They've become my favorite for power sections since they aren't outrageously expensive, but remain undetectable in sound.
So far I'm zero for four with these guys. First one was my fault for flipping +/- power input. Second one I'm not sure what happened, but the output appears to be pure DC (?) as on power-up my drivers are immediately "sucked in" to their max excursion.
Third and fourth were from the same 5-pack from ebay. They were basically modded according to Destroyer's build guides 1 and 2, respectively. Both sounded very noticeably distorted. I'm not talking nuanced imperfections, but blatant "static" mixed in with the music.
To be fair, I haven't tested any from the 5-pack in stock form. Before I spend more time on these, does my description sound like I screwed up the mods, or maybe a bad TDA7297 chip? Or something else?
Third and fourth were from the same 5-pack from ebay. They were basically modded according to Destroyer's build guides 1 and 2, respectively. Both sounded very noticeably distorted. I'm not talking nuanced imperfections, but blatant "static" mixed in with the music.
To be fair, I haven't tested any from the 5-pack in stock form. Before I spend more time on these, does my description sound like I screwed up the mods, or maybe a bad TDA7297 chip? Or something else?
My approach to the mods was to test the amp in totally stock form, and make sure it was working at 100%
I had my PS on a switch, and it I did not get the green LED immediately, I cut power.
Never smoked on due to power.
I did the caps one at a time, and checked after each one.
On one, I got the pad too hot and it separated from the board, my bad.
I have used both paste and wire solder in the mods, and for this kind of work, I find that the lower temperature paste solder worked best with my technique.
Shotgunning in all the parts at once seems like the most likely course to failure.
The one in my Son's room is still playing great. I think I still owe photos to the thread. as the Amp/Passive Pre is missing feet, I have to open it again anyway, so will try and do it then.
YMMV
Dave
I had my PS on a switch, and it I did not get the green LED immediately, I cut power.
Never smoked on due to power.
I did the caps one at a time, and checked after each one.
On one, I got the pad too hot and it separated from the board, my bad.
I have used both paste and wire solder in the mods, and for this kind of work, I find that the lower temperature paste solder worked best with my technique.
Shotgunning in all the parts at once seems like the most likely course to failure.
The one in my Son's room is still playing great. I think I still owe photos to the thread. as the Amp/Passive Pre is missing feet, I have to open it again anyway, so will try and do it then.
YMMV
Dave
Post pictures and we can check if you made any mistakes. Also let us know what power supply you're using.
Lots of people have done the mods without any problems.
Last edited:
An audiophile is either born with super sensitive hearing or it was arrived at by years of training.
Without the above you will probably not notice any difference when a few components are changed.
Ah, the bad tda chip, they only seem go bad for the modders trying to squeeze more out of them than they were designed for.
Really? How do you come to that conclusion? Most modders are doing 12v. They go bad at the voltages they're spec'd for with zero relationship to load. They handle complicated loads with grace as far as I can tell.
You seem rather interested in the aspect of encouraging people not to do modifications.
I hooked up my non-chinese version up to the Totem Elements Metal speakers. It sounded awesome. It had no trouble driving them what-so-ever. This review specifically says to put a big mother-ffer on them, but so what? You don't have too! It sounded better than the McIntosh MC302/452 (can't recall which one it is). It didn't have the power to hurt your ears as badly playing a stupid ear-drum-assault demo, but it easily pushed them to as loud as you'd want to listen. It's slightly hard to define the bass differences because one is much more articulate and the digital source was awful.
Would 2-3A be sufficient for this amplifier? I found a deal on a linear Lab PSU, it's 13,8v 2-3A. With my Maxim Class D, I got a good improvement in bass control and dynamics by going from a wall wart 15v 3A SMPS to a laptop brick 12v 5A SMPS, but am willing to give the linear PSU a try.
Last edited:
For the most part, I agree. The stock amp sounds amazing. I just wish my ears would stop ringing 24/7. I'm sure the stock amp would sound even better.
However, for someone wanting to learn how a simple DC circuit works, these mods provide an inexpensive learning experience.
Replacing the diode with a jumper gets you an extra .7 volts, but you can quickly find out that you are also losing reversed polarity protection.
Some of these amps come with 16V power caps. 18 volts may be a little much?
Replacing the .22 uF signal cap with a 1.0 uF cap may or may not make a big difference, but one can learn at what frequency each value is 3 dB down at 30k...the input impedance of the chip.
Still, the biggest improvement, if you are running the amp at full volume with a preamp, is the power supply. The bricks would hiss through my
Klipsch, but a battery or Astron is dead silent.
Cheers
Mike