Hybrid ZEN Amplifier + LM317 = Efficient and simple

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Ready for the factory...

PCB_AMP-LM317-IRF150_2025-02-10 (1).png
 
This looks very professional!
I haven't tried so far to design a pcb, and maybe it's pretty obvious that I'm not a very tech guy. But I like to build and test what I built.
So, for my construction I've got so far: my CD audio's 1 khz signal produces about 0.6 volts output. My amp which has a R2/R1 ratio of 0.83 gives (full output) gives about 5 volts RMS. The amplifier has R5/R6: 3K3 and 330 ohm. Does this mean that my 8 ohm speaker outputs more than 3 watts ? From a 20.4 volt supply? I'm asking this because these findings contradict Diego's tables. Any reason for that ?
 

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In my bench tests, I have used around 20 Vdc for the power supply (due to the limited heatsink), so I can measure around 12 Vpp over the load without appreciable clipping. I have reached close to 16 Vpp, but with obvious cuts.

The table I uploaded includes an additional margin of safety so that the distortion profiles remain adequate for what it was designed for (single-ended character throughout its excursion, with predetermined cadence in its distortion profile and predominance of H2 over the higher ones). ). It is a more conservative table in terms of power expectations.

The voltage drop that I considered for the LM317 plus the voltage drop in one of the power resistors was 3.75 V, while for the mosfet (plus the voltage drop in one of the power resistors) was 5.3 V.

Your measurements are within expectations, considering what I clarified in the text I quote.

Be happy with the power thus achieved per channel. It is a more than acceptable value and sufficient for a desktop amplifier. The power dissipated is not that extreme at that supply voltage. I congratulate you and enjoy it, which truly surprises with the naturalness of reproduction transmitted to the speaker.

Cheers
 
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Thank you Diego for your excellent design, kind words and advice. It really is a very pleasant sounding piece, very stable thermally, at max power I can keep my hand on it indefinitely. ( My heatsink is not a giant one - 125x50x35mm... and even with a switching laptop supply, there's no hum neither any noticeable noise produced by the speaker.
Moreover, max power is quite ear deafening in my rather small room... think a neighbour also noticed this...
I have yet to conduct any THD measurements but from what I see (oscope), sinewave looks very clean.

Wish you all the very best,

Radu
 
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This looks very professional!
I haven't tried so far to design a pcb, and maybe it's pretty obvious that I'm not a very tech guy. But I like to build and test what I built.
So, for my construction I've got so far: my CD audio's 1 khz signal produces about 0.6 volts output. My amp which has a R2/R1 ratio of 0.83 gives (full output) gives about 5 volts RMS. The amplifier has R5/R6: 3K3 and 330 ohm. Does this mean that my 8 ohm speaker outputs more than 3 watts ? From a 20.4 volt supply? I'm asking this because these findings contradict Diego's tables. Any reason for that ?
hi radumar1

with single supply 20.4 volt its normal that you get "just" 5Vrms. 20.4 volt shoould be split in half then you loos some voltage on your outputs and then you get about 7Vpeak. thats fine for this amp.
chris
 
hi radumar1

with single supply 20.4 volt its normal that you get "just" 5Vrms. 20.4 volt shoould be split in half then you loos some voltage on your outputs and then you get about 7Vpeak. thats fine for this amp.
chris
Chris, Hi

Thanks for your message. I actually do not 'complain' for the 5 volt RMS output: this is pretty loud for my small environment... some neighbours could also confirm this 🤯
Anyway, this was intended to serve as a desktop amplifier, as Diego said.

Bests,
Radu
 
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