I'm very pleased with the sound of my ACA 1.6/8 (in stereo mode) even into my 85dB, nominal 6 ohm, speakers, but would like to build something a little bigger (but not another ACA), say 15 watts per channel, with more into a 4 ohm load. Hopefully also saving on enclosure size (important in my typically small UK room). Do any of the First Watt designs lend themselves to such a 'derating' without losing their sonic signature, and if so, how? Many thanks.
any of them, practically
say that nominal FW rail voltage is 24Vdc
do not go bellow 17-18Vdc, thinking of nature of mosfet intrinsic capacitances - with lesser voltage across device, they're going berserk
then Iq - you can freely cut it in half, if not going wild with volume
OK, building amps is fun ......... but - if you invest some effort in finding more efficient and sensitive speaks ....... pool of adequate amps is suddenly huge ......... and World is your Oyster then, just start building them
say that nominal FW rail voltage is 24Vdc
do not go bellow 17-18Vdc, thinking of nature of mosfet intrinsic capacitances - with lesser voltage across device, they're going berserk
then Iq - you can freely cut it in half, if not going wild with volume
OK, building amps is fun ......... but - if you invest some effort in finding more efficient and sensitive speaks ....... pool of adequate amps is suddenly huge ......... and World is your Oyster then, just start building them
I stuffed my F3 clone into a Mini Dissipante 3U/300 chassis with a base plate to support the trafo and PSU. It's a very tight fit and you need a special slim right-angle screwdriver and a lot of patience to get the screws which attach the faceplate to catch their threads. I'd built this amp first in a 4U Deluxe chassis before I moved it into this one.
The heat sinks get hot (2-3sec touch) but not hotter than the sinks on my ACA. I run it at a bias of 1.4A rather than the FW spec of 1.65A.
The heat sinks get hot (2-3sec touch) but not hotter than the sinks on my ACA. I run it at a bias of 1.4A rather than the FW spec of 1.65A.
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Increasing the power and current is not "derating" but is rather the opposite, and will need larger heat sinks,
and possibly more devices, larger box, larger power supply, etc.
as I understood it, OP wants something between ACA and "regular" FW amps, regarding both power and heat
so, that is derating from "regular" FW format
aha, M2 is a peach
hard to beat it, while just 60-ish W of heat per channel
M2 is still One to Rule them All
so, that is derating from "regular" FW format
aha, M2 is a peach
hard to beat it, while just 60-ish W of heat per channel
M2 is still One to Rule them All
easy
15Vac secondaries xformer, resulting in approx. 19Vdc rails
source resistors - 0R56 instead of 0R47; no big sacrifice in xconductance, Iq goes to 1A range
38W of heat per side
even 3U/300 Modushop will work as a charm
hell, even 2U/300 Mosushop will suffice
15Vac secondaries xformer, resulting in approx. 19Vdc rails
source resistors - 0R56 instead of 0R47; no big sacrifice in xconductance, Iq goes to 1A range
38W of heat per side
even 3U/300 Modushop will work as a charm
hell, even 2U/300 Mosushop will suffice