Lme49830

[nickarsow]

Dear DIY audio professionals,
Has anyone a good designed SMD PCB for LME49830 ?
Thanks in advance with best regards
Nick Arsow ( info@interlux-bg.com , www.interlux-bg.com )

[pacificblue]

What's wrong with the one from AN-1850? Gerber files can be downloaded from National

[peranders]

Not that I know of... smd is nice

[nickarsow]

The National's PCB is awful.
In the meantime I found one PERFECT design in a russian forum - the amp is called "BLACK CLONE" and the link is http://www.vegalab.ru/forum/showthre...t=18407&page=3
Thanks for replies
Best regards to all
Nick

[SpittinLLama]

Nick, can you elaborate more on why you consider the National PCB awful? I'd really like to know specifics that you dislike about it. Just not right for your design?

Thanks,
-TH

[nickarsow]

Hi SpittinLLama,
When I design PCBs ,my design looks like pharmacy - hope you know what does it means! The National's PCB is a little chaos. More I like
to use SMD components where possible.
That's why I like compact and brain made PCBs.
Regards
Nick

[Segran]

Hi Spittin Llama and other pro's, I have a LME49830/MOSFET PCB layout (sorry nickarsow, it's not SMD...) to which I would like to get some feed-back. This is supposed to be the final version, I have made improvements to the signal ground and feed-back loop compared to the previous prototypes.

Thanks in advance!

[Segran]

Here's the schematic to go with the layout. The layout is used both for LME49810 and 49830 with MOSFET/BJT's. That's why R12, J3, D6, D7 are present on the PCB, but not used with LME4930/MOSFET's.

I have found C14 and C15 in the Leach type feedback RC-net to cause more distortion (THD, THD+N and IMD) so they are not to be mounted. Anyone else that have made the same experience, or is it due to an "inferior" PCB layout?

I have made some measurements using Arta (great stuff) and my Asus Xonar Essence STX sound card (also great stuff - dynamic range >124dB, 0,0003%THD+N on Line out, 118dB and 0,0002%THD+N on Line in, measured using AP!).

In the MOSFET version I get 0,00067%THD, and 0,00055%THD on the BJT, measured at 110W@7R0 (that's due to my 2x48VDC suplly as opposed to the 60VDC in the schematic. IMD also slightly better on the BJT version.

However, the odd harmonics is higher on the BJT, which probably explains why I (and several others) deem the MOSFET to sound more pleasant to the ear in spite of the measured data.

[nickarsow]

Dear Sergan,
Thanks for your reply. Now I'm working on a LME49830 module - a separate module which could be suited for any amplifier design.
It contains 1 lme49830 with a heat sink , a preamp lme49710 , surrounding SMD components and some capacitors at power pins.
The module will have 2 rows of pins - 10pins and 15pins.
The problem I'm thinking on is how to realise the groundon the module , because it has just an analogue groung.
Could I use top and bottom poligon copper for the analogue ground?
Best regards
Nick

[Segran]

The problem I'm thinking on is how to realise the groundon the module , because it has just an analogue groung.

I'm sure there are more experienced guys around thsi forum to give you better answers than me!

If you look at my schematics you will notice that I use different ground symbols for analog Signal GND and PWR GND, including decoupling cap's.

The two "grounds" are joined by R31, it's stated 82R but could be anthing in the range from 10 to 100R. The important thing is to keep the two grounds separate all the way to your Star ground point (teh ONE and ONLY). I use separate ground wires for Signal GND and PWR GND.

BTW, since you will have a lower voltage supply for the LME49710, you have to give some thougt to how you connect the GND leads from the two DC supplies - again only connected to the Star GND point. Just a piece of advice, this had me going in circles for weeks until I found my wrong doings!