Hybrid ZEN Amplifier + LM317 = Efficient and simple

[Vunce]

You’re right, no reason not to go that route either. Probably will come down to the best way I can add the additional parts to an existing pcb. Macgyver it!😂

 

[EUVL]

It takes away any potential issues with current sharing between 3x 317s.

And of course can also use a single 338.
Easy enough to try on circuit if one might be better than the other.


Patrick

 

[EUVL]

Was there gerbers for a pcb layout for this amp shared here?

www.diyaudio.com/community/threads/hybrid-zen-amplifier-lm317-efficient-and-simple.402477/post-7468997

We are all blind .....
You might want to have wider tracks for the high current part though.

And another one :
www.diyaudio.com/community/threads/hybrid-zen-amplifier-lm317-efficient-and-simple.402477/post-7474567


Patrick

 

[homeswinghome]

Hello,

The input impedance of this design seems quite low (less than 500Ohms? maybe I am wrong?). Which source is recommended?

Christian

 

[Julian RO]

This is why the relatively low input impedance should not be a problem, as many outputs are capable of handling 32 ohms with ease (whereas this amplifier has an input impedance of around 350 ohms).

 

[Julian RO]

Hi, yes, I built it.

Radu, how hot are the power resistors?

 

[radumar1]

Hi
The 5W power resistors reach around 38 Celsius, the main heatsink around 35 and temperature measured at the body of LM317 is around 45. About 50-53 Celsius for the Mosfet. Hope this helps
Bests

 

[Julian RO]

Ok, thanks.
I asked you to optimize the PCB redesign.

 

[radumar1]

Ref temperatures, please note that I use a rather modest voltage laptop supply producing 20.4 volts. I have yet to run proper tests, but I reckon around 1.5 watts is the amp's RMS current power output.

 

[Julian RO]

Yes, I understand.

 

[Julian RO]

Ready for the factory...

 

[Julian RO]

I forgot a diode...
🤣 😎

 

[Julian RO]

Ready to go...
Anyone who wants PCB should send me a private message.
7 EUR pcs , shipping included EU.

 

[radumar1]

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 ?

 

[diegomj1973]

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

 

[radumar1]

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

 

[Kokanee]

@ Julian RO,

Nice design. Are you planning on sharing gerbers for non designers living across the pond ?

MM

 

[chermann]

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

 

[Julian RO]

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• Julian RO

 

[radumar1]

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