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F5 Power Amplifier

So far, First Watt has made a few different amplifiers: Very different amplifiers.

Quite a few people have asked me for a regular sort of amplifier, you know the kind you plug like any other, with some voltage gain and a real damping factor.
Amplifiers that have low distortion and noise, and will drive a 4 ohm load.

The last time people asked for that they got the Aleph J, which satisfied most of those requirements. Single-ended Class A, the Aleph J is an easy-going design which is happy driving 8 ohm loads with a warm, relaxed presentation.

By way of contrast, I present the F5 (taa-daa!), a push-pull Class A amplifier, utilizing JFETs and MOSFETs in a very simple two stage complementary circuit – a little bit like a complementary version of the Aleph J. But like all the other First Watt amps so far – this one is different.

In many ways, it’s an ordinary topology - the basic circuit is found in numerous preamp circuits and the odd power amplifier (Check out the Profet amp from Selectronics). But the F5 is the product of numerous decisions that set it apart.

It has very wide bandwidth, DC to > 1 MHz.

No capacitors anywhere in the circuit. (except in the power supply, of course!)

It has a high input impedance – 100 Kohms, and a high damping factor (~40)

The distortion is very low, between .001% and .005% at 1 watt.

It will drive low impedances.

It’s very quiet, about 60 microvolts or so.

Did I mention that it sounds terrific?

Download F5 Manual


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