Wattage of Pass F5

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I get your point. I feel Alpeh4 is little too much for my place. It will turn out be a furnace generating about 600 to 800 watts of heat continously.

My place has 9 months of summer to 3 months of winter. Is there any other design which will get me 50 W class A.

Thanks
Pandu


Do the CViller cascode dual output version, this version can deliver 50watts /ch ....
 
Just searched for "F5 power" to check my calcs, and came across this; some good info.

I would just like to see if some of my thoughts/calculations are right. This is what I calculate:

Regarding the power of an F5, I calculate about 100W into 8ohms. This is assuming 40Vp-p output (a best-guess with +/- 25v rails). This gives P=Vrms^2/R=((20*sqrt(2))^2)/8=20^2*(2/8)=400/4=100w (if that notation makes any sense!). You can bias as you wish - or really has heat permits. The manual says bias to 25w, but I'm seeing this Class A power as "arbitrary" - is that right?

EDIT: At 100W, that calculates to 5Ap-p current output, so there is no current limit before 100W.

The same cannot be said for a Single Ended Class A. In that case, the MOSFETs are biased to their mid-operating point. The power of the amp is then its Class A power only.

So if the Aleph 4 is SE, and 100W Class A, and the F5 is 100W Class A/B (25W Class A), they both have basically the same "driving" ability.

This assumes massive PSUs which don't limit anything. Have I made any massive errors here?

Having completed my own F5 amp, I would say it is good - very good. I'm not being down on it here, but I would say that it sounds like a very solid, well designed amp. Its not "out of this world", but I suppose what I would expect for a £2k transistor amp - and that was about its retail. Clearly, I'm pretty chuffed for the £400 outlay, but I do prefer my Sugden - the mid range has just a slightly more correct timbre to the instruments, and doesn't really loose anywhere else.

Of course, the main temptation now is to try another First Watt variation!
 
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Can you please explain why its only 25W Class AB into 8Ω? The Class A figures you give seem to add up to my calcs, but I cannot see how you arrived at the class AB figures. What am I missing?

Also, why do you say that the F5 is 1.3A bias? The comercial version was set to that, but as far as I can see, it will be a valid design at less than that (and maybe a bit more if you can keep the MOSFETS cool).

Just curious!
 
The amplitude of the output voltage to be considered is not 40v peak to peak but 20 volts peak.
Redo your maths starting from that
or
P= V peak*V peak/2R(load)
Depending on the output devices used you can increase the bias to 1.6A or even a bit more, though, for doubling the bias, better to double the output devices.
 
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Maybe this will prove useful to someone, I dunno.

I listened to a friend's recently-acquired homebrew F5 yesterday, feeding a pair of Altec 605's in custom-built 620 cabs. He has a high-end set of sources and power line conditioning (he doesn't filter the power to his amps though). The F5 sounded fantastic. He prefers it to his 2A3 and Dynaco MkIII clones. He likes the extra headroom that 25 watts offers, saying something akin to "the F5 brings the Altecs to life." He also prefers the class A s/s sound to tubes because of the clearer presentation. I have to agree with him, and I'm a huge tubes fan. He has a number of other systems and he often listens to tubes, so he's no reactionary anti-tube bigot. It's just that the F5 with the Altecs sounds best to him (and damn good to me).

So, the original question was if the F5 can handle less efficient speakers. I don't know; it probably can in some circumstances, but I doubt it would sound its best. The F5 sounds great with Altecs, and that's surely worth something, as those drivers are very revealing. More important to me is that the F5 is capable of making something akin to magic, not just reproducing music. I could listen to that combo all day.

Damn, I wish I had the room and the money! :D
 
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