Hi,
no issue so far. The 4 output transistors are 100W types. So there´s plenty of headroom for bridging. You might think about reduced power suppy voltages as described for 4Ohm loading. IIRC 2x24V transformer for 120W@4R instead of 2x36V for 120W@8R. Which translates to +-32V DC instead of +-50V DC.
Output impedance of the amps is extremely low, so no issue here too.
You should think about a decent protection circuit though.
jauu
Calvin
no issue so far. The 4 output transistors are 100W types. So there´s plenty of headroom for bridging. You might think about reduced power suppy voltages as described for 4Ohm loading. IIRC 2x24V transformer for 120W@4R instead of 2x36V for 120W@8R. Which translates to +-32V DC instead of +-50V DC.
Output impedance of the amps is extremely low, so no issue here too.
You should think about a decent protection circuit though.
jauu
Calvin
I know this is an old thread but I've recently built an L12-2 based amp and am very pleased with the results 
The transformer is 300VA 2 x 35V and the power supply board is an 'F6 Universal' available from a number of eBay sellers based in China. It has a good spec and importantly, built in speaker protection.
The transformer is 300VA 2 x 35V and the power supply board is an 'F6 Universal' available from a number of eBay sellers based in China. It has a good spec and importantly, built in speaker protection.
For the small price difference and very good assembly of the L12s I received, there's not a lot of point to DIY assembly of these kits. To get picky, some would probably like to see more familiar, Japanese electrolytic cap. brands and fancier resistors for the output transistors. Maybe I'll do that when bored sometime but really, the supplied parts work fine and I have to agree with a few posts here saying it really sounds quite good.
Given that it's a low bias, CFP design and has all the usual signs of having a fatiguing sound, it's surprising to see LAPT Sanken output transistors and construction and listening performance like that of expensive audio products. For a cheap Ebay module product, this is great value - even the components and PCB are in a different class to other LJM designs.
A couple of comments for a nice build that seems to nicely complement the modules:
Run the power leads to the modules as short and direct as possible and with the rail lead pairs twisted tightly together for as far as they can be, since the tabs are well apart but these can be bent up and the single lead tails run along the PCB top edge, clear of the input stage. Short leads can be half the size of long ones and so, easier to twist and locate. Try to do the same with twisting the output and ground leads a little tighter and well clear of the input stage and rail supplies too.
Cooling - these run almost cold until the power increases above 5W or so and then they begin to heat up rapidly, like any other amplifier. I can't see any case cooling vents (perhaps there are some?) but while this is no issue when used as a 5W amplifier, I figure you have a 300VA transformer for a reason. That reason demands plenty of air flow and probably bigger heatsinks. I'm considering bigger 'sinks myself, as sinewave testing at 40W got them quite hot. Otherwise, a lower supply voltage and just a 50VA transformer would be safer if you don't plan on turning up the wick.
Given that it's a low bias, CFP design and has all the usual signs of having a fatiguing sound, it's surprising to see LAPT Sanken output transistors and construction and listening performance like that of expensive audio products. For a cheap Ebay module product, this is great value - even the components and PCB are in a different class to other LJM designs.
A couple of comments for a nice build that seems to nicely complement the modules:
Run the power leads to the modules as short and direct as possible and with the rail lead pairs twisted tightly together for as far as they can be, since the tabs are well apart but these can be bent up and the single lead tails run along the PCB top edge, clear of the input stage. Short leads can be half the size of long ones and so, easier to twist and locate. Try to do the same with twisting the output and ground leads a little tighter and well clear of the input stage and rail supplies too.
Cooling - these run almost cold until the power increases above 5W or so and then they begin to heat up rapidly, like any other amplifier. I can't see any case cooling vents (perhaps there are some?) but while this is no issue when used as a 5W amplifier, I figure you have a 300VA transformer for a reason. That reason demands plenty of air flow and probably bigger heatsinks. I'm considering bigger 'sinks myself, as sinewave testing at 40W got them quite hot. Otherwise, a lower supply voltage and just a 50VA transformer would be safer if you don't plan on turning up the wick.
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Ian, could you please translate this in English, for I do not know what is meant by it?
Thanks,
Edwin
Many thanks for the constructive comments. Agreed that the wiring looks a bit untidy and at some point when I've got nothing better to do I might re-wire as you suggest.
The case does have ventilation slots so there is airflow over the heatsinks which in turn are firmly attached to the base plate providing some additional dissipation. The amp barely gets warm during normal usage at comfortable listening levels but owing to my domestic circumstances I have to refrain from really turning up the wick. It's good to know there's plenty left in reserve if need be.
Regards
If you like trivia, you've come to the right place!
I was surprised at the range of US (and British) origins for AWOL, widely used in US war movies, electronic games etc.
This is classic: "Absent without official leave", being recorded in the US fashion, where every letter in the acronym must
be assigned to a distinct word.
Here's an electronics one: SOA v SOAR for Safe Operating Area of (typically) semiconductors.
I was surprised at the range of US (and British) origins for AWOL, widely used in US war movies, electronic games etc.
This is classic: "Absent without official leave", being recorded in the US fashion, where every letter in the acronym must
be assigned to a distinct word.
Here's an electronics one: SOA v SOAR for Safe Operating Area of (typically) semiconductors.