AKSA's Lender Preamp with 40Vpp Output

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#541
xrk971 said:
I have a DCG3 but this Aksa Lender Preamp specializes in higher output swing while maintaining a nice harmonic distortion profile and low THD. The DCG3 is a great Preamp design. My subjective opinion is that the soundstage and imaging on the Aksa Lender is better - wider and more depth. I feel that a BJT, especially the 2SA1837 is more resolving and refined compared to an IRF9610 as an output device. Having the output transistor emitter drive the output node (as in Aksa Lender output topology) is more accurate than having the drain of a mosfet drive the output node and rely on feedback to make it accurate again. Perhaps Vunce can chime in on his experience?
Click to expand...

Thanks X, that's nice to know.
 
#554
xrk971 said:
It’s in this post on GB thread. Need to drop Vcc to 24v though to manage heat output. Headphones don’t need huge swing. I have not tried 2SA1837 at lower bias and higher voltage yet.

http://www.diyaudio.com/forums/grou...der-preamp-40vpp-ouput-gb-28.html#post5311833

So first thing to try is swapping KSA1381 for 2SA1837 leave everything the same. Then try changing R15 to 22ohms and R14 to 4.7ohms. That should double bias from previous.
Click to expand...

X, et all;
I changed R15 to 22 Ohms and R14 to 4.7 Ohms, and am planning to install the 2SA1837's now. Do the 2SA1837's and or the DN2540's need heatsinks?

I have some small clip on sinks I was planning to use if need be.

This is pre-amp use, not headphone amp fwiw.

I'm close to wrapping up the component build phase, then I'll slap it on a prototype board and give it a listen. Need to build a stepped attenuator too, can't forget that.


Do you know if there are any connectors for X141, X142, etc. that are available at Mouser or Digikey (domestic US)? Would prefer to use some easy connectors there instead of soldering until I put it in a proper case.

Cheers,
Gable
 
#555
The connectors are somewhere in this thread. And yes available at Mouser. Make sure you get the through hole version. I don’t have part number off top of my head.

You can cheat and use standard 0.100in or 2.5mm pitch PCB header pins - the ones you can break off to size. Use two rows and put mating female header sockets (2pin) on top at diagonal. Middle two are input ad outer two are outputs. They all share a common ground - the star ground hub is at these pins. That’s what I am doing now in lieu of proper part.

You should add a heatsink to the DN2540 and 2SA1837. They will be a bit warm at the higher bias of circa 34mA and 45v/2 that is 750mW ea. Definitely at headphone amp bias they are hot.
 
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#556
xrk971 said:
The connectors are somewhere in this thread. And yes available at Mouser. Make sure you get the through hole version. I don’t have part number off top of my head.

You can cheat and use standard 0.100in or 2.5mm pitch PCB header pins - the ones you can break off to size. Use two rows and put mating female header sockets (2pin) on top at diagonal. Middle two are input ad outer two are outputs. They all share a common ground - the star ground hub is at these pins. That’s what I am doing now in lieu of proper part.

You should add a heatsink to the DN2540 and 2SA1837. They will be a bit warm at the higher bias of circa 34mA and 45v/2 that is 750mW ea. Definitely at headphone amp bias they are hot.
Click to expand...

I will add the heatsinks to those, thanks X!!
 
#557
#558
Hi Gable,

I just went back to try the RCA jacks I got from ebay again. They DO fit! I was trying to put them in the wrong side of the board before. DOH! I'm going to blame that on sleep deprivation.

On the connectors you are looking for, are you talking about the X111 and X112 8-pin to connect the main board to the RCA board? X141 and X142 are 2-pin connectors for power and led. Anyway, here's what I sourced from Mouser. I verified that they are the trough-hole and they fit on the board.

TE Connectivity 2178710-8 - Header

TE Connectivity / AMP 2205062-2 - Cable
 
#559
jwjarch said:
Hi Gable,

I just went back to try the RCA jacks I got from ebay again. They DO fit! I was trying to put them in the wrong side of the board before. DOH! I'm going to blame that on sleep deprivation.

On the connectors you are looking for, are you talking about the X111 and X112 8-pin to connect the main board to the RCA board? X141 and X142 are 2-pin connectors for power and led. Anyway, here's what I sourced from Mouser. I verified that they are the trough-hole and they fit on the board.

TE Connectivity 2178710-8 - Header

TE Connectivity / AMP 2205062-2 - Cable
Click to expand...

Haha, glad you got the RCA's figured out!

I have the 8 pin cable and the 8 pin connector is on the way. I think I need to review which connectors I think I need again when I get back in front of the board.

Cheers,
Gable
 
#560
In case you wonder how to fit the heatsinks. As the 1837 needs to mount in the backside of the DB, it works perfectly.

657047d1516059914-aksas-lender-preamp-40vpp-ouput-gb-aksa-lender-hpa-amp-cores-2-jpg
 
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