Well I started tearing into my non-working monocrap hybrid amp. The component quality is so-so. The solder work and some obvious production repairs are total crap.
The power amp uses a LM18751 chip per channel on a decent sized heat sink. These are pretty good chips that can put out a clean 20 watts into 8 or 4 ohms. The real limiting factor is the pcb layout, power supply, and supporting component quality. I suspect the power supply is marginal. I'll tear into that next and post some photos of the guts later.
Right now my plan is to gut it and transplant a 50wpc amp board and power supply. No need for the tubes (eek! did I really say that?), but I'll leave them there with their filaments hooked up to glow.
I know I promised puctures, just haven't had time to upload them from my phone. I have gutted the amp case. I cut out a rear window in the plastic top box where the original transformer was hiding. I cut a piece of perf steel, painted it black, and hot glued it inside the window. The TDA amp board will reside inside that top box so it needed some ventilation.
The amp board has no need for addition gain, so I totally am removing the tubes and covering that up with a thin painted piece of aluminum. I'm saving those nice looking chrome plated tube cages for a preamp project that actually uses tubes
I am retrofitting the controls on a machine at work and was able to save a 24Vdc, 5 amp, switching power supply from the trash. That will take up 75% of the lower amp case's space.
BTW, the gloss black (plastic) side panels are simply glued on and could easily be removed and replaced by some DIY beautiful hardwood pieces if some felt like jazzing up the look of their amp. I'm sticking with the stock ones until I mess up and put a big ugly scatch in one.
Comments
https://www.monoprice.com/product?p_id=16159
https://www.monoprice.com/product?p_id=16051
https://www.monoprice.com/Product?p_id=16154
Ebay = 400$
Monoprice bundle = 299$
Just headphone = 199$
Just amp - 69$
Total = 268$
The power amp uses a LM18751 chip per channel on a decent sized heat sink. These are pretty good chips that can put out a clean 20 watts into 8 or 4 ohms. The real limiting factor is the pcb layout, power supply, and supporting component quality. I suspect the power supply is marginal. I'll tear into that next and post some photos of the guts later.
Right now my plan is to gut it and transplant a 50wpc amp board and power supply. No need for the tubes (eek! did I really say that?), but I'll leave them there with their filaments hooked up to glow.