L'Amp: A simple SIT Amp

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#2,541
Oh, I forgot to attach this:
 

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#2,543
SandroN said:
Plasnu, this is important data. Do you have more data for 2sk82? I need to know:

-Max total power dissipation
-Max junction temperature

Thanks
Click to expand...

Im sorry that I missed your post.

Here is the link of the Japanese site.

The author says that the data is from the original SONY confidential papers. He also comments on the graphs and the ranking notes on the original papers. Try Google translate. 😉

2sk82 spec 6/28/'76

http://vmorita.com/sugarabotto/sub05/sub05.html#_8
 
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#2,545
gadut said:
I'm using 2SK82, no idea for other type.

Just power up with sef bias 1ch and it sings lovely, mid and high is special eventhough low bass not as strong as AJ but i'm happy now (my previous result is dull with separate bias). my Alpair10 is being delivered from singapore, SIT + FR seems good couple 🙂

using 25V toroid, I get Vds 29V and 7V bias, a little
higher.Rs is veryyy hott,around 105°C which means I should get 4R with huge heatsink.

I only play for 30minutes but Cout is very hot and it's inside oil blown out, really bad,I should have used cheap cap for first try. I think that I put it on wrong direction where + is connected to SITsource and - to speaker - terminal.

Tomorrow wil try again with - to SITsource, I got many nichicon kg 4700uf for testing
Click to expand...

What will be the result after you change the polarity?
 
#2,546
I'm little confused with the powersupply voltages. What voltage are we aiming for for the main feed, and is it essential to have the second power feed (ie: the 15V feed on the diagram). Sorry I am very new to this project and want to get my head around powersupply requirements so I can keep an eye out for suitable transformers. Got my 2SJ28's on the way! thanks
 
#2,547
Slimecity, there are several variations on this amp.
Provide a post number or link to your schematic.
The main voltage supply drives the SIT, +35v for example and the -12v bias' the SIT.

Also, the 2sk82 requires the voltages to be reversed.
 
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#2,548
Thanks vdi.

The powersupply query I had related to the diagram on page 1 of this post. I am sourcing some C-core transformers that put out 0-35VAC and are rated at 418W max. Assume these will do the trick?

I have also read a bit of this thread and yep, realise the 2SJ28s will need the bias voltage reversed from that that is in the circuit descriptn for the 2SK82's.

Will it be no problem having seperate powersupplies for both the large and the small DC supply voltages I assume? My main transformers that I am sourcing only have the one tap....

thanks for ur help!
 
#2,549
slimecity said:
Thanks vdi.

The powersupply query I had related to the diagram on page 1 of this post. I am sourcing some C-core transformers that put out 0-35VAC and are rated at 418W max. Assume these will do the trick?

I have also read a bit of this thread and yep, realise the 2SJ28s will need the bias voltage reversed from that that is in the circuit descriptn for the 2SK82's.

Will it be no problem having seperate powersupplies for both the large and the small DC supply voltages I assume? My main transformers that I am sourcing only have the one tap....

thanks for ur help!
Click to expand...

400+ Watts should cover it.

Aside from the SIT, the caps and any polarized parts need to be reversed. Find a proven schematic using the 2sj28 or redraw it and post it so the wizards can give their blessing.
I know I've seen one hand drawn.

Seperate supplies are fine.

Vince
 
#2,551
Cheers again vdi. I just bought my large transformers....

There is a post around page 201 of this thread which basically sets out the circuit diagram that is on page 1 of this thread, but just has hand-drawn changes made to show the reversed bias voltage required for the 2SJ28.

This is a longterm project for me, so plenty of time to sort this out!
 
#2,552
What kind of current do you need for the biasing supply - around 500mA? Or 1amp or more?

How crucial is the lighbulb voltage? - having read a few posts here, do I really need to get 110VAC bulbs? We have 240V mains supply here and I cant imagine any lightbulbs would arrive here in NZ in one piece!

thanks
 
#2,553
slimecity said:
What kind of current do you need for the biasing supply - around 500mA? Or 1amp or more?

How crucial is the lighbulb voltage? - having read a few posts here, do I really need to get 110VAC bulbs? We have 240V mains supply here and I cant imagine any lightbulbs would arrive here in NZ in one piece!

thanks
Click to expand...

You can find lot's of responses to your questions in original Mr Rothacher L'Amp article part 1.

We need for two light bulbs configuration 300W/120V one part and resistance range around 11~13 Ohm for two bulbs together
other configurations search response in article ....you can experiment with huge 600w~800W/12 Ohm resistor
or equivalent resistors who probably need to be atached with heatsink if specified light bulb's is difficult to get.

I luv beauty of light bulb glow so nice :cheers:
 
#2,557
eLarson said:
Sadly, it can't be watched in the US:
"This video contains content from SME, who has blocked it in your country on copyright grounds."
Click to expand...

Few screen captures for show Mr Rothacher L'Amp beauty mono blocks build.
Hope photos help in your diy project realisation. Thanks Audiohobby.com
 

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#2,559
So my 2 x 2SJ28s have arrived from circuitdiy. I see that u guys put these thru the curve tracer - do I need to do that or is that something you guys do generally for entertainment? Ie: I dont have a scope, yet.....

I have my large power transformers but have a question re: the 193V choke version - I think I want to build this version rather than any version using a large resistor, and the lightbulb version will present its own issues.

So on that topic - I know that the Hammond 193V is in the schematic - however I have seen pics here of pple who have used a 159ZL Hammond choke (2.5mH/10A). IS there some flexibility here to what one to use? The 193V is about 3x the cost of the 159ZL choke - I know at some point however you just need to "suck it up" and invest the requisite $$$$$.

thanks!
 
#2,560
Some people use curve tracing to confirm proper operation of the devices.
This is especially important if the devices came from less well-established
sources where provenance is uncertain. One also may want to design around
the particular parameters of a device at hand, and curve tracing usually
gets you these parameters.

I highly recommend this video by Mike as an example of tracing and some
calculation of parameters:

Frankentracer: $20 SIT Curve Tracer Part One | Audiohobby.com

On your second question, the 159ZL will not give you anything resembling
full range; the inductance is too low. Others might be using it as a power
supply choke. (I guess loading with the 159ZL will give you something like
a tweeter amp.)

Mike details an inductor loaded version here:

http://www.diyaudio.com/forums/diyaudio-com-articles/202480-l-amp-simple-sit-amp-part-deux.html
 
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