A simple question, if I want to use a 2 x 22 VAC transformer, which gives just a little under 2 x 30 VDC after rectification and I am using the Fairchild output FETs, can I then use the standard F5 circuit as is? Ofcourse I would have to reduce the bias somewhat to keep the cooling requirements within reason, but anything around 10-15 W Class A into 8 ohm is enough already as it is, just need a little more power in reserve. Should be getting about 40-45 W Class AB into 8 ohm.
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Hi.It is good to hear this.How does it sound?I think Kendeils are good for this amplifier.Great energy smooth sound.
With 2x22V secondary, the solution I would suggest is to add a power supply regulator like in Zen V3 :
http://www.passdiy.com/pdf/zen-ver3.pdf
> why don't we just terminate the AC mains instead of shorten the inputs, outputs?
We do that as well, but you still have a lot of energy stored in your power supply caps that needs diverting away from your speakers.
Patrick
http://www.passdiy.com/pdf/zen-ver3.pdf
> why don't we just terminate the AC mains instead of shorten the inputs, outputs?
We do that as well, but you still have a lot of energy stored in your power supply caps that needs diverting away from your speakers.
Patrick
The best amp so far. Next upgrade: adding 2 X 100 000uf kendeil. But for now, i'm more than satisfied with my f5, it give my cd a second life.
You could have a look at the answers to the same question last week.
Link to post: http://www.diyaudio.com/forums/pass-labs/121228-f5-power-amplifier-796.html#post2200904
You could have a look at the answers to the same question last week.
Link to post: http://www.diyaudio.com/forums/pass-labs/121228-f5-power-amplifier-796.html#post2200904
Thanks, but going for the higher supply voltage to get just a little more power into 8 ohm Class AB.
Are there any suitable higher voltage substitutes for the JFETs used in the standard F5?
There are no 1-on-1 substitutes.
Problem for complementary JFETs is the P-channel.
Complementary JFET pairs with a higher voltage rating than 25V are obsolete numbers, for instance NEC J44/K163 (40V/50V).
The K163 is easy to buy in sufficient numbers for as little as 50 $cents, the P-channel will be several dollars each.
And not drop-in replacements, transconductance is less than 50% compared to J74/K170.
Strangely enough, the basic F5 can be scaled from substandard to 100W full Class A in a quad bridged balanced mode and anything inbetween.
Yet cascoding seems more favorable.
Before I order anything I have just one question, whats the max supply voltage that a F5 cascoded and with dual pair of output mosfets can take, using the board from Cviller. I was personally hoping for something around 2 x 30-35 VDC, is that possible? Bias would ofcourse be adjusted to a total of 2.6 amp pr channel(0.65 amp pr FET) with a possible reduction or smallish increase depending on what I decide upon and what cooling there will be available.
Arent you limited by the max Gate-source voltage of the output FETs? +/-30V for the Fairchilds and +/- 20V for the IRFs, have I gotten that right?...or wrong...?
But then again, NP mention somewhere in this gigantian thread that 30 V, or even 35 V was possibly since the output FET's could handle it, but that might have been something I misunderstood.
(Im a FET noob)
Arent you limited by the max Gate-source voltage of the output FETs? +/-30V for the Fairchilds and +/- 20V for the IRFs, have I gotten that right?...or wrong...?
But then again, NP mention somewhere in this gigantian thread that 30 V, or even 35 V was possibly since the output FET's could handle it, but that might have been something I misunderstood.
(Im a FET noob)
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He does, but only for a few more days.
I'm moving back to dk, so I won't be able to sell boards while I'm moving.
Hope I have until tomorrow(monday), or tuesday.
I think you can use the 22VAC trafos without any problems, but I have not heard any reports about what is the highest possible voltage with cascodes and I haven't tried it myself. You need a large heatsink to run this beast though...
A tiny correction: the standard current is 1.3A through each device, but you might want to go for a lower current per device.
A tiny correction: the standard current is 1.3A through each device, but you might want to go for a lower current per device.