"The Wire AMP" Class A/AB Power Amplifier based on the LME49830 with Lateral Mosfets

Stammheim · 2017-03-06 8:40 pm

Andrew, it's not about clipping, but the negative amplitude desreases faster, that the positive increases.
Please also notice the voltage:
+33.2V vs -27.6V

So the negative is first clipping, keeping increasing the input signal the positive amplitude is still increasing, before it gets clipping.

It's like the sine would be moved into the negative field, while increasing the input signal.

multisync · 2017-03-06 8:57 pm

Have a look at the gates and see if the LME chip is clipping. My LME supply voltage is +/-10 volts higher than the fet supply voltage. On my setup the output fets clip before the lme chip does. When clipping occurs are the power supply voltages symmetrical? Are you driving a load?

Stammheim · 2017-03-06 9:24 pm

Great hint, thanks!
Oh man, a lot of work to remove the amps.
Yes, a 4R / 300W resistor is connected.

Yes, both voltages are symmetrical, ok with a difference of 50mV.
LME and Mosfets are connected to the same PS for now.

Stammheim · 2017-03-18 7:44 pm

Guys, does anybody know, where to get the LME49830 these days??
There are some available on eBay from UK, but I'm not sure they are original IC's.

Thanks,

Stammheim

multisync · 2017-03-18 8:59 pm

I bought 10 from an eBay seller. I haven't tried them yet. No other chip plant makes the LME parts so fakes are kind of hard to produce. Think of all the opamp manufactures. It would be easy to buy a cheap opamp and rebrand them. How many folks test an opamp Specs? Same thing about Transistors. National/TI only made 3 lme 49810, 11, 30 parts. No high voltage or low voltage or low or high distortion parts, just the 3 variations. Unless you are buying a piece of plastic with wires coming out, they are probably OK.

scottjoplin · 2017-03-18 9:23 pm

Stammheim said:
Guys, does anybody know, where to get the LME49830 these days??
There are some available on eBay from UK, but I'm not sure they are original IC's.

Thanks,

Stammheim

I bought a couple from RS Components recently

Stammheim · 2017-03-18 9:51 pm

Not available at RS anymore...

scottjoplin · 2017-03-18 9:56 pm

Yes, sorry about that, I've just looked, I must have been lucky, bought them a few months ago. It is a real bugger, they seem to have become very hard to get very quickly. Don't know what to suggest I'm afraid but the ones on Ebay are probably fine

Stammheim · 2017-03-18 10:14 pm

What a pity... all that good TI-parts...
The Alfet-Mosfet's are also not available anymore. By the way... I've got some of the ECW-Mosfet's, but which are the best Lateral Mosfet's these days?
Yes, I think I'll give the eBay-LME's a try...

scottjoplin · 2017-03-18 10:25 pm

Exicon? Hitachi? I'm going to have to wrap my amps in cotton wool!....I have 4 amps lme49830's driving original 1980's Hitachi Lateral Fets...I'm afraid to use them now!

IanAS · 2017-03-19 1:39 am

Stammheim said:
The Alfet-Mosfet's are also not available anymore.

http://uk.rs-online.com/web/c/semico...397,4294964938

The 8 Amp 200V TO247 are mostly in stock.

AndrewT · 2017-03-19 10:31 am

At RS prices that makes my 100pairs worth £2167.20
I must have bought them at the right time.

astx · 2017-03-19 11:33 am

Stammheim said:
What a pity... all that good TI-parts...
The Alfet-Mosfet's are also not available anymore. By the way... I've got some of the ECW-Mosfet's, but which are the best Lateral Mosfet's these days?
Yes, I think I'll give the eBay-LME's a try...

Have some LME49830 on stock...send me a pm if you still need them.
My LME49830 project used 3 pairs IRFP240/IRFP9240 and the result is pretty good. Have a look here: SA2012 - 4 channel V-MOSFET amplifier 4 x 180W@8R
Have some amplifier PCB spares lying around too - pm me.

BR, Toni

scottjoplin · 2017-03-19 12:21 pm

Hi astx. Had a look at your link, stunning build by Tiroler. I notice he's used huge sinks for the LME, mine aren't anywhere near that big. Mine are running at +/-60V, they are hot to the touch, can hold back of my finger on, I'm guessing about 60C. What do you think? I'm a little paranoid now since these chips are obsolete.

AndrewT · 2017-03-19 12:38 pm

I commented on the small space left for the chip sink and how close it was to the adjacent capacitors.

The chip should be kept cold to warm, never hot.

Because of the lack of space, the very small PCB has limited itself (for reliability) to lower supply rail voltages.

scottjoplin · 2017-03-19 12:51 pm

Judging by the size and design of my sinks I'm guessing they are around 10C/W. There is plenty of space around them in a well ventilated case. I have another pair running at +/-36V with smaller sinks running much cooler

astx · 2017-03-19 3:42 pm

scottjoplin said:
Hi astx. Had a look at your link, stunning build by Tiroler. I notice he's used huge sinks for the LME, mine aren't anywhere near that big. Mine are running at +/-60V, they are hot to the touch, can hold back of my finger on, I'm guessing about 60C. What do you think? I'm a little paranoid now since these chips are obsolete.

Yes - "Tiroler" has shown an outstanding metal work! Very professional!

I have designed the SA2012 to use SK481/75 from Fischer Elektronik.
If you can touch your LME49830 heatsink some seconds, you are save. Otherwise better the cooling for a longer chip life. Don't forget the electrolytic capacitors in the near of the heatsink. Excess heat lowers their lifetime ...

BR, Toni

scottjoplin · 2017-03-19 9:53 pm

Thanks, that's put my mind at rest. Just checked data sheet, my sink should be ok. Still...I'm tempted to drop the chip voltage a bit, I don't need that much power.

Stammheim · 2017-04-06 9:17 pm

Hi guys,

after the Mosfet's got burnt I also replaced the LME-IC and measured the output of the LME49830 WITHOUT the Mosfets using a sine signal. The negative amplitude looks like it is clipping (flat amplitude), so I made a short clip of it, while increasing and decreasing the singal voltage.

What is strange is that both new amps show the same behaviour, unfortunatelly I cannot compare with other amps anymore.
Please could you watch my clip and give me a hint??

https://youtu.be/pAG_khKDSxk

Both channels are connected, so Pout and Nout are visible and are equal btw...

aive · 2017-04-06 9:25 pm

Stammheim said:
Hi guys,

after the Mosfet's got burnt I also replaced the LME-IC and measured the output of the LME49830 WITHOUT the Mosfets using a sine signal. The negative amplitude looks like it is clipping, so I made a short clip of it.
What is strange is that both new amps show the same behaviour, unfortunatelly I cannot compare with other amps anymore.
Please could you watch my cliß and give me a hint??

https://youtu.be/pAG_khKDSxk

Does the "clipping" go away when you reduce volume?

Measured your rails to confirm both are same (+,-)?

"The Wire AMP" Class A/AB Power Amplifier based on the LME49830 with Lateral Mosfets

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