- Jan 9, 2020
There have been some reservations about my no-recommending of the 48V PSU, like this:
So here is my reasoning:
1) the amplifier triggered off itself after 1 minute of 100W/4ohm single channel test, as already mentioned in this thread. This is probably not so important, but
2) I have just made a temperature measurement on the heatsink, with the K-thermocouple. The box was partially closed. I have set the power to 50W/4ohm maximum when the signal reaches 0dBFS. Then I used Amy Winehouse / Our Day Will Come track, which has DR=7 and the track was played in a loop. Only one channel of the amp was driven. The average power was much less than 50W, due to music programme with DR=7. And again, only one channel. After opening, there is a smell of melting plastic.
View attachment 106465
After 12 minutes, the heatsink temperature was 60°C. An this amplifier is specified as 2x300W/10% THD .....
So this is my reasoning and recommendation, run the amp with 32V power supply.
Though I was running my A07 with a quality power brick, my amp wasn’t running hot (actually, after a loud listening session with the top off, the heatsink was just warm to the touch.) I was powering it with with a Mean Well 48V, 220W power brick (GMS 220B48).
however, based on your comments, I switched the 48V supply with another Mean Well brick I had in my collection, this time a 36 V, 160 W (GSTA136). Though this supply obviously has less peak wattage, I’m still getting great sound from the amp.
it seems any penalty of using the smaller supply appears minimal. Perhaps it will increase the longevity of the A07.
FWIW, I am running the A04 with the stock 32V brick.
I also the stock op amps for 1656’s in the A04 and LM4562s in the A07.
I have both amps hooked to a pair of Unifi UF5 floor standers via an MCM auto speaker switch.
Though I haven’t done any direct A-B comparison. I’m very pleased with both of these amps though I think the A04 is my favorite. It seems to be clearer, better dynamic range and, seemingly, low end response.
Though there is an incredible mod thread about A04 mods over on DIYAudio, I’ve decided to put the cases back on and leave well enough alone. These little amps simply sound phenomenal for the price, despite some apparent graphs to the contrary.
That said, for someone just getting into hi-fi, especially on a limited budget, I would wholeheartedly recommend either amp as great starting points. For $75 with a power brick, you just can’t go wrong. Add some decent bookshelf speakers, a DAC (dongle) and a cellphone loaded with music, $500 will buy an incredible listening system the quality of which I could have only of dreamed of when I was a college kid just getting into this hobby.