LME49810 - a new cousin for LM4702

[AndrewT]

Originally posted by kesee
According to specs LME49810 and MOSFETs pair ( SK1058/J162) can handle supply voltage safely up to +_100V and 200V respectively.

Hi,
the 1058 & 162 are 160Vds devices.
The absolute maximum supply rail voltage is +-80Vdc.
This may occur when the mains is at maximum tolerance and when the amp bias is turned down and/or one of the amps is disconnected (fused).
The maximum working voltage for the supply rails when mains is at nominal supply voltage and the bias is set correctly will be about +-73Vdc and that leaves some leaway for the exceptional conditions.

Fets generally require a driving voltage that is significantly above the source voltage. This results in less power from the amplifier when all stages are supplied from the same common rails.
This "lost" power can be released by running the voltage amp stage from higher supply rails as you suggested. The normal overhead adopted to get good power delivery is about 5V to 7V above the output supply rail voltage.
The 4702 can be run from this higher voltage supply but if you run it higher than necessary you gain nothing extra and the chip has to dissipate more heat. This may activate the protection circuits in the chip earlier than if running cold.

[kesee]

Hi Andrew,

So you are suggesting to have +_60V at the chip stage an to have +_50V at the MOSFET stage will give the best results?


Initially I am building a Sub woofer amp to drive my PC sound cards sub output. Now I am very much interested to build a complete true audio amp and listen to my LP collection

[AndrewT]

Hi,
35Vac will give near 50Vdc.
Add on a 5Vac transformer and bridge rectify that 40Vac to give 58Vdc.
These would be near ideal for 100W into 8r0 or 200W into 4r0 if the PSU and amplifier are designed for this loading.

If you want to try regulating the chip supply then use a 9Vac transformer giving about 62Vdc. Regulate this down to 56Vdc.

These two schemes are best done with dual secondary transformers. Using a single rectifier on each winding allows all the PSU stages to remain separate and then connect the zero volt star together. This is the more flexible arrangement if you decide to regulate and also minimises power amp ripple in the HV low current supply.

[kesee]

Hi Andrew,

Got it thanks

Regards KC

[kesee]

Originally posted by AndrewT
[
If you want to try regulating the chip supply then use a 9Vac transformer giving about 62Vdc. Regulate this down to 56Vdc.

These two schemes are best done with dual secondary transformers. Using a single rectifier on each winding allows all the PSU stages to remain separate and then connect the zero volt star together. [/B]

Hi Andrew,
Do you have any scamatic for the chip amp regulated PSU for +_ 55-60V

Regards KC

[AndrewT]

There are dozens here

[kesee]

Originally posted by AndrewT
There are dozens here

Hi Andrew,

Would like to share with us
it will be a great help to me

Regards

[paokakis]

Thanks everybody, you have been very helpfull. I'll post again when I have some results to share. thanks again!

[kesee]

This is my board and it not final.
anybody care to comment on this welcome and appreciated.

Regards KC

[gmphadte]

U need filter caps near the output fets.

If u want to fix a heatsink for the LME, make space for it.
Keep symmetry at the output coil and connect the feedback resistor at the coil.

Gajanan Phadte