Ok, my first post in this thread. I have been reading and admiring, but not posting 
I'm using EQ APO for active XO in PC, and started testing that by using some surround amps as DAC and to drive each speaker, after that, one surround amp has been used as multichannel volume control, and I tested various commercial amps to drive the speakers. After that I started purchasing some DIY-kits and evaluating the sound from them, changing some output transistors, playing with bias and lately some measurements too. (LJM L12-2, LJM MX50SE, LJM MX50x2, NAP250 clone, Zerozone PASS AlephMini, ZeroZone JLH1969).
Speakers are Based on Troels Gravesen's Vifa C17 project, but tweeters have been upgraded, and passive filters disconnected except for some full range amp evaluation. A pair of sealed 10" subwoofers are also 'in the system', but not used at the moment.
I liked the LJM MX50SE driving 8ohm bass, so I decided to build a 4ch amp and have one amp for each C17 woofer.
I liked the PASS too, but managed to destroy the boards when modifying them, so I tried the JLH as a replacement. That will drive the tweeters, even if I feel it would be at it's best for midrange or maybe a fullrange driver.
The 4xMX50SE is based on a surround receiver parts + protection board, PS-board and amps from ebay. Running at +-37V. I was worried about hum etc, but it's really silent. Oak plank replaced the Sony front.
The JLH is more 'true diy'. Frame from oak, with some bits and pieces holding it together Dual mono with two 19,5V laptop bricks. Some CLC/CRC filtering on the supply. Taken apart now for some 'tuning' to improve cooling, maybe add some overtemp protection etc. No 'inside picture' of this one atm.
/Sam
I'm using EQ APO for active XO in PC, and started testing that by using some surround amps as DAC and to drive each speaker, after that, one surround amp has been used as multichannel volume control, and I tested various commercial amps to drive the speakers. After that I started purchasing some DIY-kits and evaluating the sound from them, changing some output transistors, playing with bias and lately some measurements too. (LJM L12-2, LJM MX50SE, LJM MX50x2, NAP250 clone, Zerozone PASS AlephMini, ZeroZone JLH1969).
Speakers are Based on Troels Gravesen's Vifa C17 project, but tweeters have been upgraded, and passive filters disconnected except for some full range amp evaluation. A pair of sealed 10" subwoofers are also 'in the system', but not used at the moment.
I liked the LJM MX50SE driving 8ohm bass, so I decided to build a 4ch amp and have one amp for each C17 woofer.
I liked the PASS too, but managed to destroy the boards when modifying them, so I tried the JLH as a replacement. That will drive the tweeters, even if I feel it would be at it's best for midrange or maybe a fullrange driver.
The 4xMX50SE is based on a surround receiver parts + protection board, PS-board and amps from ebay. Running at +-37V. I was worried about hum etc, but it's really silent. Oak plank replaced the Sony front.
The JLH is more 'true diy'. Frame from oak, with some bits and pieces holding it together
Dual mono with two 19,5V laptop bricks. Some CLC/CRC filtering on the supply. Taken apart now for some 'tuning' to improve cooling, maybe add some overtemp protection etc. No 'inside picture' of this one atm./Sam
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Do you mean those torroidal ones? They have another function in digital amplifiers. The output coil is wound around the output resistor, which is an usual approach.
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Is this little fan all there is in there?
Where are the vents located to get air in and out?
With those modules 100% "indoors" in that big case, and with all the heatsinks having their fins aimed at the floor, the airflow is definitely not convective in nature and the only way to cool this off somewhat more efficiently is to heavily ventilate, in a forced manner.
Would cool far better with all the heatsink aimed in a way to have all their fins vertical, to use more natural convection. Having their fins in the "outdoors" would also be better than keeping all that totally enclosed.
I totally agree with your observation. Yes, these are little fans running very quietly providing some air currents as relaying on natural convection would not work well. I did extensive testing and IR filming to be sure the design trade-of is not impacting performance negatively. Mind you there is very little idle heat coming of the amplifier modules. Even with a modest load, which turns out to be quite uncomfortably loud, these modules barely reach 30 degrees C. Air vents are on the bottom and top of the case.
The shown schematic has a fatal error - a short to GND for upper mosfet switch.
TD1800 schematic corrected
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an integrated amp with the now obsolete LME49810
Had bought some of the last LME49810's on sale , got around to building an amp a few weeks back. The output stage on 2 pairs of NJW1302/3281 per amp. Transformer's a 25-0-25 500VA. A tight fight in the chasis, locally made sheet metal chasis wiht an aluminium face plate. The aluminium face plate is machined from 10mm aluminium bar stock , needs a bit more finishing on the edges.
Had bought some of the last LME49810's on sale , got around to building an amp a few weeks back. The output stage on 2 pairs of NJW1302/3281 per amp. Transformer's a 25-0-25 500VA. A tight fight in the chasis, locally made sheet metal chasis wiht an aluminium face plate. The aluminium face plate is machined from 10mm aluminium bar stock , needs a bit more finishing on the edges.
