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#3,481
kunkurus said:
I knew my Yamaha had 0.06% THD. A 0.00014% THD amplifier shoud be several times better than a 0.06% THD one, not marginaly better, isn't it?
Click to expand...
The problem is 0.06% THD is already too small to "hear" so you won't hear any difference between that and 0.00014%. Some fine tube amps are closer to 1% THD. There's WAY too much focus on THD, especially expressed as a %. Now, if those numbers referred to 3rd order harmonic distortion, not total, and 3rd order distortion is all there was, there MIGHT be a chance to hear the difference. But even that seems unlikely to me. Of course, I haven't heard such a thing so I'm only surmising.
 
#3,482
Carlp said:
The problem is 0.06% THD
Click to expand...

The problem is really that single number THD is not much more useful than useless.

You have to step back one step and look at the spectrum. The details that get lost when this is collapased also loses all the important stuff.

dave
 
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#3,483
My third build using Apex Microtechnology power op-amps. This one with the high power PA04 MOSFET chip since the amp was built to drive four subs. The design has 4 channels in a dual, 2 channel configuration, with two power supplies. One side puts out 2 x 140W into 4R when both channels are driven just below clipping. The PA04 chip is capable of 400W according to the data sheet, but I certainly don’t need 4 x 400W at home, and I wanted to get it all in a 19” 2RU case anyway.
The case is made mostly from recovered e-waste with the aluminum panels from an old Apple G5 Mac and the heat sinks from industrial servo drives. The extruded brackets, handles and feet were all that was purchased for the case.
Been listening for a while now and very pleased with the results. Thanks for looking.
 

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#3,484
Carlp said:
The problem is 0.06% THD is already too small to "hear" so you won't hear any difference between that and 0.00014%
Click to expand...
Well I can detect in an AB test a 7th harmonic of 100Hz at -65dB down, which is 0.056%, and my hearing's not that great. The commonly accepted limit is 0.01% as being undetectable for human ears (for THD - IMD is more complex). Detectability may not be quite the same as hearing a difference listening to random source material.

One issue with IMD is that ultrasonic tones can inter-modulate to produce audible tones across the most sensitive range of human hearing - electronically synthesised music can be a source of this - I've often thought about this but haven't heard of any thorough investigation of the issue.
 
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#3,491
Hi

Many years ago I had built a stereo LM3886 amp and since my brother in law literally fell in love with it, I gave it to him for his birthday.

I caught the bug to build another one so I bought the amps board ready built (based on the open source PCB layout by member 00940) in swap/meet, got the enclosure from a friend, read some stuff and then decided to buy a 200VA, +/- 20Vac, etc…. Filtering capacitors are 15000uF per rail. Rails (no load) is +/-27Vdc. I then ordered a label for the unit (trophy guys on eBay)
So everything is new except for the recycle enclosure 😀

This amp is playing very nicely and has guts when needed.

Below are some pictures and where I took

BR
Eric
IMG_3338.jpegIMG_3339.jpegIMG_3018.jpeg
IMG_3341.png
 
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#3,496
My latest and most hideous creation!
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This was a throw together made in haste combining some experiments in construction with what ever was lying around. The idea was to make a bluetooth amplifier for my basement while I build stuff.
It is a hodge podge of scrap parts and old projects that have been sitting around along with a couple of experiments.
The result is a deliciously ugly success. The high vis yellow should hopefully accidents!

Full build details here:
https://www.diyaudio.com/community/...ogether-for-the-basement.416216/#post-7763788
 
#3,497
Nice. My build (LM3886) was very similar, even down to the heat sink! In a re-purposed chassis too. I left it unpainted and made a wooden front but otherwise it's remarkably similar. I posted mine here somewhere, quite a few years ago I think.

Oh, and mine didn't have BT, but I see that I have a board or two and some power boards that would work lying around awaiting a project. Perhaps I should add that to mine too!
 
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