My first discrete amp build

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#41
NanoFarad said:

JLH 1969 CLASS-A​

Although it's not much difficult for me to build a good class-ab amplifier but i always wanted to start my discrete amp journey by building a class-A amplifier. So i made one, a zeroboard/ experimental version of John linsley hood Class-A. I used all cheapo components, so nothing special. For input tr i used 2n3906, for driver/phase splitter old faithful bd139 (sorted for higher gain) & for outputs venerable 2n3055 as sacrificial rat :innocent:

For capacitors 0.47uf mkt as input, 470uf for bootstrap+feedback and 3300uf as output cap. For power supply i used a 125va transformer with 17vAC secondary(34vCT), a CRC filter made of 4×4700uf & 0.33R 5W wirewound resistor and for rectification 6A6 type discrete diodes.

Supply voltage(unloaded)--22vDC
Supply voltage(loaded)--19vDC
Quiescent current--1.1ampere

The result is impressive, i mean i like the sound. Probably the distinction isn't hugh in comparison with lm3886 but there a 'difference'! I mean very revealing sonic qualities, excellent midrange. I don't know why some people say this amp isn't good at low end(uncontrolled bass etc), this is totally false. With little bass boost it sounds really amazing. But one thing i want to mention that this amplifier is quite sensitive to radio frequencies. Although there is no noise at all when input disconnected.


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JLH 1969 Class A is a very fun project.
It is refreshingly simple.
And the result is surely satisfactory.
So, I can very well understand why you built it.

By the way, there is a thread with 1000s of post about that amplifier.
 
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#43
lineup said:
By the way, there is a thread with 1000s of post about that amplifier.
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I know and fully aware of it. I just tried to avoid that gigantic thread by starting a fresh one. Anyway it is not only about JLH. I would like to build other Class-A amps too & post here in this thread.

EDIT: i want to request forum members please don't make this thread as JLH specific. It is NOT.

Thank you
 
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#44
adason said:
'Sure' means that someone on the page that i linked already measured 45 watts out of jlh amp with two pairs of outputs.
You are saying its impossible.
So authors of that page are wrong, or you.
This needs to be explained.
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Where was it written that this is not possible?
I wrote that I am skeptical in terms to such of practical implementation ...

You probably have a poor understanding of the design features of amplifiers, if you think so.
 
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