LME49830 with 2SK1530 / 2SJ201 from ebay

[mantabernd]

Hello!

I've got the schematic of the following amp sold in ebay.

LME49830+K1530/J201 300W Mono Power Amplfier Board | eBay

Can someone tell me the values of T10, T11, R1_1, R1_2 and Rt?

I think it's a very interesting circuit and I'd like to build it.

Best regards
Bernhard

 

[AndrewT]

T10 & T11 are likely to be small signal transistors, To92 or sot23.
R1-1 & R2-1 will probably be low value metal film.
Rt is that 3/8" VR next to the 830 heatsink.

Having got the schematic from the Vendor, don't you feel morally obliged to buy the PCB from them as well?

 

[mantabernd]

Hello Andrew!

I asked the seller if I can have the schematic and he sent it to me. No don't feel morally obliged because I'm only interessted in the design. I don't want to build an exact copy of this amp.

I want to understand how it works and with this schematic, the app. note 1850 of texas and some other shematics I will design my own Poweramp using LME49830 and 2SK1530/2SJ201.

So what does T10/T11 in the feedback path? What is the advantage to put them in? Could I use BF469/470 for it?

What does 3/8" VR mean? My english is not sooo good ...

regards and thanks
Bernhard

 

[AndrewT]

T10 & T10 are not "in the feedback path". they are protection devices to limit the output current if you abuse the amplifier.
bc5xxb will do here, you do not need anything fancy. These transistors should never trigger and thus never affect the audio signal, if you set up the protection circuit correctly and never abuse the amplifier.

I reckon the Vbe across protection transistors should be <400mV when the amplifier is passing highest output to lowest specified load.
I further believe that there must be a mechanism that allows additional current to pass to a reactive load such as a speaker. This additional transient current could be +100% of the DC current limit set by the resistive component values in the protection circuit. The schematic omits reactive components and thus cannot allow a valid output current to pass to a speaker load. The schematic as shown is not complete.

The little blue box next to the heatsink is the VR. It looks to me to be a 3/8" size box.

 

[mantabernd]

Wow you're a real amplifier-guru

Hmm I'm not sure if its complete, but now I know what T10 and T11 do - thank you for this!!

Ah you mean the trimmer, ok know I understood.

Do you also know something about the clipping led? The original datasheet says that Pin 1 isn't connected and here they use Pin 1 together with a Clipping led?

If I have time this weekend I will build my first prototype of my LME49830. Hope it wont fire up^^

 

[mantabernd]

Hi,

i built this Amp with just one pair of Mosfets and without the extra Transistors T1 and T6 which are only needed for more than two pairs of Mosfets.

My problem is that I don't really understand the function of T10 and T11. I testet the amp with and without this "protection circuit" but nothing changed. What does the OSE wire of the LME49830 do? Even if I disconnect it, the amp sounds good and everything is fine. No oscillation or other problems. Isn't it the sense and purpose of T10, T11 and the OSE Wire to avoid clipping?

I used BC639/BC640 for T10/T11 and 100 ohms for T1_1 and T2_1.

Thanks, regards.
Bernhard

 

[bobodioulasso]

This schematic is for LME49810, not for LME49830.
Look at presence of clip flag pin.

 

[panson_hk]

The guy simply changed a LME49180 based schematic to LME49830! The output device symbols are BJT NPN and PNP, but marked 2SK.2KJ. This schematic has been used universally in many eBay items.

The output sense Ose pin of LME49810 is connected to the emitter join of T10 and T11. It is definitely wrong. T10 and T11 won't function at all. Baker clamp of 49810 won't too.