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

[rhythmsandy]

does the chip itself works in class A?

 

[AndrewT]

The output stages are Push-Pull. They will be biased to operate in ClassAB.

 

[panson_hk]

I am told LME49811 output is Class A biased.

 

[rhythmsandy]

can I just replace the lme49810 with lme49811?

 

[AndrewT]

Icc is typically around 14mA to 17mA.
Max output is stated as 9mA.
For a ClassA output this would imply an output bias of ~5mA.
Certainly ClassA is possible for the 811.

There is comment from a few years ago on the lme series from the design team.

 

[panson_hk]

do you have a driver for the output stage and how much output power of your design?

 

[rhythmsandy]

im thinking of going with 5200 1943 pairs..
Im considering class AB output stage in one config and
one in class A...

class A 100W ( im interested to go with scanspeak drivers for bass and mids from wavecor )
class AB 500W in 8 ohms ( I have PA subwoofers with me from Eighteen sound )

thinking of going with lme49811

 

[panson_hk]

class a 100w! are you serious! no typo?

you need triple EF output for 500 W.

 

[rhythmsandy]

i know 100w its pretty huge... just a thought but even if 30w can serve my purpose im still fine.. like hiraga but what about the lme chips did u try them in class A?

when it comes to class AB i have seen some amp modules based on 49810 which have 5 pairs of EF and still deliver 300W in 8 ohms im looking something double to that..

the question is..
a pair of 2SA1930 and 2SC5171 can drive how many EF pairs?

 

[panson_hk]

Yes, I did try LME498xx with Class A output stage for 20 to 30 W.

I would use A1930/C5171 as pre-driver and a pair with higher current rating as driver. Which output devices do you plane to use?

I believe you seen such 49810 amp module in eBay using C5200/A1943. Right?

 

[rhythmsandy]

hi panson Ive seen an amp from nnexelectronic.com and even on ebay with the above drivers... I have even seen hiraga 30w super class A with a pair of c5200/a1943.

so whats your suggestion for class AB how to achieve like 800w in 8 ohms
for class A may be 60w is also fine...

so how many pairs i can drive using the predrivers A1930/C5171? for class AB..

 

[panson_hk]

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

 

[rhythmsandy]

hi panson I have few questions to you...

1. Did u find difference between 49810 and 49811? was that a decent difference?
2. I got polystyrenes as in put its like veil taken out i found much difference just like that if there is difference then it would be great to use lme49811 instead of 810

3. Do you have a schematic of lme49811 to look at?

 

[rhythmsandy]

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

very impressive distortion figures... nice man...

 

[panson_hk]

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.

 

[AndrewT]

The 1943/5200 has a cold SOA that has dropped to ~30W @ 100Vce.
That is the sort of voltage you would need to get 500W into 8r0. (89.4Vpk)

 

[rhythmsandy]

how are companies like Dynacord making with just 6 pairs they are achieving 1200watts into 4 ohms ive seen the schematic they have just 6 pairs I really suspect the ratings aswell? example Dynacord L2400
technically if the ratings are about 1200watts x 2 then the psu should be about 5kw which they dont have they are the size of 625va x 2 trafos i really dont understand how they can achieve these power outputs...

 

[AndrewT]

probably by not using ClassAB

 

[panson_hk]

SL2400 (newer model) is Class H.

 

[rhythmsandy]

yeah it seems class B