Philip,
Your preamp has enough output voltage to run the F5 well. It will work with your speakers.
Your preamp has enough output voltage to run the F5 well. It will work with your speakers.
@AudioSan
try this to check what your speakers need
A Test. How much Voltage (power) do your speakers need?
cheers
A.
try this to check what your speakers need
A Test. How much Voltage (power) do your speakers need?
cheers
A.
Iam a fan of the f5 (it's my main amp) but 4 ohms and low sensitivity with a low gain preamp? F5 would not be my first choice unless you listen less than 80db or so and never listen loud.
It's not my speakers. And not my question. I just pointed out the calculation mistake.
A quick test is just hook a cd player with 2Vrms output directly to the amp, and decide whether that sounds:
1) Bloody loud
2) Aaah just in the ball park
3) Aaah bastard that would put a bloody baby to sleep.
At 2.8V peak output of the cd player you'll be seeing 2.8V x 6 dynamic peaks out of the amp which will be under clipping of the amp.
My family starts complaining at anything over 15W rms (that's dynamic peaks not average) on 87dB speakers.
If you have 4 Ohm speakers, the F5 sounds better with less source resistance on the Fets anything under 0.2 Ohms is a decent improvement, or just remove all together. You'll need to go through the biasing procedure again (back it off first)
1) Bloody loud
2) Aaah just in the ball park
3) Aaah bastard that would put a bloody baby to sleep.
At 2.8V peak output of the cd player you'll be seeing 2.8V x 6 dynamic peaks out of the amp which will be under clipping of the amp.
My family starts complaining at anything over 15W rms (that's dynamic peaks not average) on 87dB speakers.
If you have 4 Ohm speakers, the F5 sounds better with less source resistance on the Fets anything under 0.2 Ohms is a decent improvement, or just remove all together. You'll need to go through the biasing procedure again (back it off first)
Indeed; I missed that. Which means one needs to double all my power figures.
Cheers,
Jeff.
ok, fine! thanks to all. So I will just give it a try and see if I get happy with the volume 😉
Just in case, two more questions:
- how do i actually notice if I am in the clipping area of the F5? I really don't want to blow up the amp...
- the louder I listen to music, the more power I need, thus more heat is produced? so even if I am not in the area of clipping, it might not be a cosy area for the amp with respect to the heat? (It a really really warm summer here in Austria...). Or is the main heat produced due to the bias current which is constant?
thanks, philip
Just in case, two more questions:
- how do i actually notice if I am in the clipping area of the F5? I really don't want to blow up the amp...
- the louder I listen to music, the more power I need, thus more heat is produced? so even if I am not in the area of clipping, it might not be a cosy area for the amp with respect to the heat? (It a really really warm summer here in Austria...). Or is the main heat produced due to the bias current which is constant?
thanks, philip
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a class amps ....... louder you play , more heat is transferred from amp to speakers
so , that's no amp , more like refrigerator
so , that's no amp , more like refrigerator
You can't blow up the amp with current limiters in place, it's never too hot in NZ similar I imagine to Austria in climate.
I should have read the manual once again before asking... thanks for the hint!
That's a bit lower in efficiency than would probably be ideal for the F5 in stock form. The 25 wpc RMS is what it will do in class A and that doesn't change based on impedance. The original design will push 10 amp according to the owner's manual, which is well over 50 watts, but it won't do it for long, and that's well outside of class A. The F5 Turbo would be better suited to the demands of your speakers, but that's not to say a standard F5 won't sound great, just not loud.
i can imagine that, that's why I was asking how I can notice when I am close to this area. Anyway, I think i will just try and see how loud it will be
The best way to tell if you're overdriving the amp is by temperature. Once the outputs start pushing current outside the class A envelope they'll heat up. You're going to end up getting some heating because there's always going to be peak transients that push the amp outside class A, but if it's operating there consistently you're going to find that it gets too hot to touch. I'd say heatsink temps over 60 would be cause for concern. My build sees heat sink temps a bit over 57C and that usually means the outputs themselves are running in the low 80's which is about as hot as I really ever want to get them.
Class A power doesn't change based on impedance??? yes it do. a 25W@8ohm device only do 12.5W@4ohm.
But F5 is a push pull class A/B it will swich to class A/B when pushed beound it's class A current range.
Wait... I misread your reply to me. The F5 isn't a current source amp. It's voltage source. It doesn't reduce it's power into lower impedance. Amps like the F4 and J2 do that. The F5 much different than them. The actual class A envelope on an F5 is 50 watts peak. It's explained in the F5 and F5 Turbo articles as well as Burning Amp 2016.
they all reduce there class A power with lower impedance. But the F5 is a push pull amp. so it goes into class A/B when the current demand is higher then the class A current.
Even that is not 100% accurate.
If you bias the F5 at 2A then Class A power into 4 Ohms will be slightly higher.
It will depend on your biasing point.