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Project Gallery: Class A Amp (Audio '77) a77-p1-1.jpg (15514 bytes)

a77-p1-2.jpg (18038 bytes)

a77-p1-3.jpg (32910 bytes)

a77-p1-4.jpg (33841 bytes)

Dear Mr. Pass.

This is how I've done it.
It started two years ago. After another DIY-project had blown off for the second time, I wanted to build something a bit more reliable, without compromising the sonic performance I wanted.
A friend of min showed me this old article of yours, from –77, and when I saw your name, I was reminded of Threshold, so I reckoned it was more than worth a try.

Pic1: I don't like bolts, nuts and screws to be visible, partly because of the WAF (Wife Acceptance Factor), but also because I'm a sucker for details. 

Pic2: As you can see, I had to use a fan, not as much because of the heat generated by the output transistors, as for the power-supply.

Some of my friends doubted, that 20 Watts would be enough, because my loudspeakers are not the most efficient ones. Small two-way system, with a sensivity of only 85dB/W. I was glad to disappoint their concerns.

The amplifier play with great ease and clarity, and is quiet, when asked to be. No hum or other kind of distractions. I LOVE IT.

Pic3: Here you see the reason for using the fan.
I just “had” to make a voltage regulator, and because I`ve made it as an emitter-follower, it has a somewhat high drop-out voltage, and subsequently gets hot. But, there`s NO ripple.

To get rid of the fan, and some of the heat, I`m working on a low drop-out, high current voltage regulator, to replace this one.

Pic4: I guess it speaks for it self.

Thank you, Mr. Pass, not only for this little wonder, but also for this opportunity to share.


Regards

Ole Hoffmeyer Lund

contact info:

help@passdiy.com

webmaster@passdiy.com