X-Amp (LME49830 + Exicon Lateral Mosfets)

[danfo098]

Hello forum, it's been a while...

I just wanted to share my latest project with you.

It's a LME49830 based amplifier with Exicon lateral mosfets as output devices.

The schematic:
http://www.diyprojects.se/X-Amp/X-Amp.pdf

The BOM:
http://www.diyprojects.se/X-Amp/X-Amp_BOM.pdf

And the layout in its current state:


All comments are welcome.

[panson_hk]

Nice! Is it a two-layer board? High-current path is so close to the input jack. Will it be a problem?

You don't need G-S voltage clamp protection?

[danfo098]

Hi panson and thank you.

I haven't done any routing yet and haven't decided on how many layers it will be but it will be four or six layers. I want complete layers for GND, V+ and V- and if I can do the routing on one side I'll go with four otherwise six.

I'll try to squeeze the psu connectors as close together to the right as possible later. It might be a problem but hopefully not.

Why is the G-S overvoltage protection not needed, I mean isn't it always good practise to use them.
And what about esd protection for when "fiddling" with the amp?

[AndrewT]

2layer PCB is sufficient.
Ground Planes and Power Planes are not required for audio signals.

[Sebastiaan]

Originally Posted by AndrewT

2layer PCB is sufficient.
Ground Planes and Power Planes are not required for audio signals.

Dear Andrew,

I tend to agree with you, but my vision about this has changed since last saturday, when I followed one of the most interesting AES audio courses in a long time. Given by Mr. Bruno Putzey (Hypex) and Mr. Guido Tent (Tentlabs).

And they where totally disagree with star grounding. Their vision is, even for low bandwidth audio signal's one should think RF. We learned in this course that ground-planes don't have to be bad at all, you just must know how to design them. Thinking in current circles and loops, and carefully place components. Basically the same way of thinking when you design star-grounds, however star grounds are more forgiving.

The idea of star-ground is more a left over from old ways of thinking, and ground-planes do scare the hell out of some people (it also fear them ) But once good implemented I believe that ground-planes must be superior also for audio. For any audio designer, I think it is really worth it to invest a lot of time in this to master it.

I've seen them successfully implemented here by forum members (I remember a BPA300 design). Jeff Rowland does it successfully. Just to mention some examples.

With kind regards,
Bas

[danfo098]

Red squadron...

[riktw]

holycow they look awesome
is it possible to buy 2 PCB's?

[danfo098]

Hi riktw,

I have 10 PCB's right now but unfortunately all are claimed for (2 by me). I haven't assembled and tested the design yet so I don't even know if it works yet, however I don't see any reasons why it shouldn't.

Another thing is that the PCB's are quite expensive, 50 USD per PCB. It's a 2.4mm thick 6 layer design with 70um copper on all layers and gold plating.

When I have assembled and tested the amp I'll get back with the results, waiting for components right now.

If more forum members are interested I'll order another batch of PCB's and sell them but I at least want to test it first.

[carlmart]

Great design. Congratulations!

Pity you didn't implement any DC servo for it, or DC protection.

Perhaps something like this might be used:

Untitled Document

I found this quite recently and thought it to be a clever idea.

If you add an input switch and an LDR attenuator at the input, you would have a very high quality integrated amp.

Are there any US sources for the MOSFETs?


Carlos

[danfo098]

Hi Carlos and thank you.

Actually I'm working on a DC-offset protection board and
also a soft start board which I will use for this project. However there will
be no DC servo.

Input switch and attenuator will be a separate preamplifier project. Didn't know about the LDR attenuator it looks interesting.

I don't know if there are any US sources for the MOSFETs maybe some other forum member know?