LM4702 or LME49810 work in class A mode to drive the output stages in class A/AB

[rhythmsandy]

hey guys i got the LME49810 module 500W in 4 ohm but the document says that it can be biased even in class A but according to nelson to calculate how much power out is mainly on Bias current like if its 1A of Bias then the peak is 2Amp so the power out peak is 2x2x8 ohm = 32W and in RMS its around 22.63W but the datasheet never says about going beyond 1A. Now since the amplifier has about 10 output devices I think I can try biasing this in Class A but I dont think LME49810 can be made to run in class A...

 

[rhythmsandy]

My schematic for 49811 is more or less identical to the data sheet schematic. Here is an example with ThermalTrak output devices (http://www.pansonaudio.com/Compact498xx_files/lme49810_compact_amp rev2p1.pdf).

Do you familiar with a SPICE program such as LTspice? You can analysis an output stage to determine how many pairs of power devices are needed for 800W, 8 R. Note you need to consider real speaker reactive impedance. Pay attention to beta droop.

The picture shows an output stage (triple EF) with six pairs output devices in LTspice.

Regarding differences between 49810 and 49811. I can't really hear any difference in my system (including my ears). However, bias tuning is easier for 49811.

I don't think you can use 498xx to make a 800 W, 8R amp "directly". The max supply voltage of the chips is +/- 100 V. For 800W, 8R, you need higher than +/-100 V. You may consider bridge mode.

panson can you send the thermaltrack large image version that you have attached in the previous post...

 

[bobodioulasso]

How many threads will you open for the same purpose?

 

[rhythmsandy]

im not getting the right answer and couldnt find it in the datasheet aswell...

 

[panson_hk]

hey guys i got the LME49810 module 500W in 4 ohm but the document says that it can be biased even in class A but according to nelson to calculate how much power out is mainly on Bias current like if its 1A of Bias then the peak is 2Amp so the power out peak is 2x2x8 ohm = 32W and in RMS its around 22.63W but the datasheet never says about going beyond 1A. Now since the amplifier has about 10 output devices I think I can try biasing this in Class A but I dont think LME49810 can be made to run in class A...

Do you want Class A bias for 500 W, 4 Ohm?

 

[rhythmsandy]

The module is rated at 500W in 4 ohm in class AB

Im thinking to use that module to switch to class A if possible with lme49810..

 

[palstanturhin]

I don't think no-one quite understands what you mean?
Your module most sertainly is at class-A at low powers. And will 'switch' to class B at higher powers.
There is no point in hipower Class-A because you will not get any better sound quality by doing so.
More than 10-20w in class A is a total waste of energy - unless you want to heat up your house with it???

 

[rhythmsandy]

Here is my LME49810 with Class A biased output THD vs freq for 10 W into 8 Ohm.

but why generally people prefer lme49811? when it comes to class A

 

[andreivlad1999]

Probably they have golden ears. I have tested LME49810 and LME49811 in the same audio chain(including my ears) and I did not heard any difference.

 

[bobodioulasso]

LME49810 incorporates a driver stage. LME49811 does'nt. LME49810 + darlington = LME49811 + triple.
This driver stage works in classAB.