Hello,
I currently am using two ACA's fed by a nuTube B1, driving a pair of Paul Carmody designed Speedster speakers, which I've seen spec'd at 81db sensitivity.
Given the relative inefficiency of the speakers I think things could be improved with more power, but am wondering if the F6 would be sufficiently greater than the two ACAs.
I'm more or less a beginner building amps, so the F5 is probably beyond my capabilities, though I do have local resources who could help.
Appreciate anyone's input (as long as it's balanced ;-)
-- Thing
I currently am using two ACA's fed by a nuTube B1, driving a pair of Paul Carmody designed Speedster speakers, which I've seen spec'd at 81db sensitivity.
Given the relative inefficiency of the speakers I think things could be improved with more power, but am wondering if the F6 would be sufficiently greater than the two ACAs.
I'm more or less a beginner building amps, so the F5 is probably beyond my capabilities, though I do have local resources who could help.
Appreciate anyone's input (as long as it's balanced ;-)
-- Thing
Having built and modified both, I can say that the F6 is in a different category. It will do a much better job driving relatively inefficient speakers, especially if you can boost the power rails to a solid 24 Volts, or even a little higher. It is a simple board design that is easy to stuff with components. It will do best with a deeper chassis. Mine is in the equivalent of a 3.5U x 400mm deep, which has plenty of room for a good dual-mono power supply.
2pico and I have spent some time working on some worthwhile modifications to the F6. Here is the latest one that uses different output transistors to get a nice blend of harmonics to the output spectrum.
The LED mod to the bias circuit is one that I suggested and 2pico confirmed. It lets the F6 come up to proper temperature and stable bias current faster than the stock circuit. It simply replaces the 5.1V zener with three mini green LEDs in series.
Originally Posted by 2 picoDumbs
IRFP250 at Q1 (has to be IRFP250 not IRFP150)
IXTH64N10L2 at Q2
This will get you the sound.
LED Mod + R7/R4 around 3k - Lower noise, better regulation, and adds thermal compensation to the bias circuitry, compared with the stock zener.
Reduce R1 and R2 to 0.22 Ohms (lower if you want) - Not critically important if you have very good resistors, but it does provide some improvement.
Increasing R4 to between 20 Ohms to 23 Ohms - Improves everything a little
The LED mod to the bias circuit is one that I suggested and 2pico confirmed. It lets the F6 come up to proper temperature and stable bias current faster than the stock circuit. It simply replaces the 5.1V zener with three mini green LEDs in series.
Originally Posted by 2 picoDumbs
IRFP250 at Q1 (has to be IRFP250 not IRFP150)
IXTH64N10L2 at Q2
This will get you the sound.
LED Mod + R7/R4 around 3k - Lower noise, better regulation, and adds thermal compensation to the bias circuitry, compared with the stock zener.
Reduce R1 and R2 to 0.22 Ohms (lower if you want) - Not critically important if you have very good resistors, but it does provide some improvement.
Increasing R4 to between 20 Ohms to 23 Ohms - Improves everything a little
With the ACA monos (bridged/banaced) the Speedster impedance will definitely affect the end FR, tipping up the top.
An externally hosted image should be here but it was not working when we last tested it.
The lower Rout out of the F6 would make for a better match.
dave
I guess I'm easily convinced or you folks are very persuasive.
Ordered everything from the store. Just have to sort out the PSU BOM and then make a component order from Mouser.
What are thoughts on general need or utility of a soft start and/or speaker protection board with this amp? I got a 300VA transformer, if it matters.
Thanks!
-- Thing
Ordered everything from the store. Just have to sort out the PSU BOM and then make a component order from Mouser.
What are thoughts on general need or utility of a soft start and/or speaker protection board with this amp? I got a 300VA transformer, if it matters.
Thanks!
-- Thing
The F6 will be awesome with the Speedsters. I've used both the original amp camp, the aleph J and the F6 with the Speedsters and the F6 was the best match by far (until I tried the M2). lol