AKSA's Lender Preamp with 40Vpp Output

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#1,323
Streamer build

TBH, I hadn't really thought about it until now.
After making the MoFo, it made sense to move on to the pre amp.

I mean; my AKSA-Lender still isn't done, needing a case and the proper voltage.



In any case, it made sense to try for the next stage.
I'll start that investigation when the preamp has a proper enclosure.


Kind regards,
drew
 
#1,325
I have power supply questions. The end goal for The AKSA lender is to drive an F4. But in the meantime, It will be driving an F5 Turbo biased to 80 class A watts/channel.

The boards I have are marked T141 and T142, and I recall reading *somewhere* about using Talema transormers. I even recall looking for them a couple years back, but somehow, I've gotten lost.....

And, the BOM does not identify either T141 or T142.

could someone point me in the right direction please?
 
#1,327
BigE said:
The boards I have are marked T141 and T142, and I recall reading *somewhere* about using Talema transormers. I even recall looking for them a couple years back, but somehow, I've gotten lost.....

And, the BOM does not identify either T141 or T142.

could someone point me in the right direction please?
Click to expand...

The AKSA Lender Preamp doesn’t have provisions for onboard transformers.
The Yarra preamp uses a pair of Talema Trafos, 15va or 25va, 60mm x 60mm size. Example: Blocked
 
#1,330
Lost

I am at a loss. I have built the preamp but I am getting wicked amounts of dc at turn on, something like 12v at the output. This then declines into the millivolt range over 30 seconds or so. If left on long enough it warms up and the output dc drops to a steady 1mv or less.

Where do I begin to look for the cause of this?
 
#1,331
I haven't read through all the 133 preceding pages.
Is the pcb layout essential? Will using a veroboard (or p-t-p) be ok?

V3 is the power supply? Unipolar 100V?
Where can I find the schematic for that?

646627d1511075484-aksas-lender-preamp-40vpp-output-aksa-lender-preamp-hv-v2-0-schematic-jpg
 
#1,334
xrk971 said:
No schematic- you need to make your own. I use DC/DC converter and CLC filter and cap Mx filter followed by CRCRC filter. That’s provided in the design.
Click to expand...

thanks for that. I've started to read the 133 pages. There's are plenty of info dispersed within those pages. I didn't think those buck converters were quiet enough for us in the golden ear crowd, but happy to be proved wrong.
 
#1,336
Well it finally happened, after 50 years of building electronic stuff I put a electrolytic capacitor in backwards, didn’t hurt anything as I slowly ramped power up watching an amp meter. Not to look a gift horse in the mouth ( not sure where that saying came from) I would have caught it if the polarity marking had not been covered by the capacitor ( hint hint). Also my pre amp boards powered up with no smoke however do not work. I verified no solder bridges or cold joints and I always verify resistors to 5 digits ( critical positions buy extra and match). I did measure and match the bc560c for hfe but did not verify rest of semiconductors. Since both boards act the same I suspect I may have sourced some fakes.

Bill
 
#1,338
0dB gain amplifiers like MoFo, F4, LuFo, etc... need a preamplifier that swings big voltage like the Aksa Lender to drive them properly.
You are correct that an amplifier with 26-28dB of gain built in would not require this much oomph.
 
#1,339
Nelson Pass mentioned he felt full range speakers benefited being driven by a current buffer as opposed to standard amp. Since I happen to have a pair of stereo F4 amps and a pair of Frugal horns I thought I would see for myself. Once you have listened to a full range speaker there is a purity to them.
 
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