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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

AKSA's Lender Preamp with 40Vpp Output
AKSA's Lender Preamp with 40Vpp Output
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Old 17th February 2020, 12:24 AM   #1261
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Output
Quote:
Originally Posted by pinnocchio View Post
My friend is asking me if there’s other buffer amplifier that could work well with the AKSA Lender setup with 27dB gain and 40Vpp. He’s looking into class AB amplifier to replace the Mofo in hot summer days. If anyone knows it would be great. I only know Class A designs as buffer amps.

Thanks
Do
Hi Do,
So your question is there a 0dB gain power amp that’s Class AB, not Class A?

That’s an interesting question. I think take your favorite Class AB amp, remove the front end and VAS stage and put the Aksa Lender input to it. I have lots of discrete Class AB that could try this with. But why? The whole reason is to drive 0dB SE Class A output stages that don’t have any global feedback and the smooth no-crossover distortion characteristics that lacks high order harmonics. I have an Apex FX-8 Class AB that uses lateral FETs for the output so it will be inherently stable and less prone to thermal runaway. I might see if that can be rejiggered to bypass the input LTP and VAS and just apply the Aksa Lender to the output. Fnny, but I have taken that same amp and removed the output stage to make a slick +/-40V preamp.

Just setting the Aksa Lender with PCA daughterboards on low gain, say 12dB and driving a conventional Class AB LM3886 chipamp actually sounds very nice. It’s sort of an analog sound processor that forces the amp to be dominant second order distortion.

Here is just such a system - just an inexpensive $40 stereo LM3886 with built in PSU and DC protection relay - just added a 250VA 25v trafo.

AKSA's Lender Preamp with 40Vpp Output-aksa-lender-pca-lm3886-02-jpg

AKSA's Lender Preamp with 40Vpp Output-aksa-lender-pca-lm3886-01-jpg

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This is the PCA daughterboard:
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Attached Images
File Type: jpg Aksa-Lender-PCA-LM3886-01.jpg (424.6 KB, 245 views)
File Type: jpg Aksa-Lender-PCA-LM3886-02.jpg (392.0 KB, 151 views)
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Last edited by xrk971; 17th February 2020 at 12:50 AM.
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Old 17th February 2020, 03:51 AM   #1262
dliscomb is offline dliscomb  United States
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Where can I find the stools for that amp?


;-)
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Old 17th February 2020, 04:25 AM   #1263
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Output
You can't - these are unobtanium stools fashioned by magical elves out of an extinct fruit tree wood. Guaranteed to make the equipment sound better.
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Old 22nd February 2020, 04:40 AM   #1264
ggetzoff is offline ggetzoff  United States
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Quote:
Originally Posted by pinnocchio View Post
Here's a couple pictures in test. The volume pot will be replaced by TKD sinc ethis one is a 3$ cheapo pot.

Attachment 816929

Attachment 816928

Attachment 816930

Just missing the chassis. I have two builds in there (not showing both), one for a friend and one for me.

Do
Ah, yes, good, smart man....940C caps!
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Old 23rd February 2020, 03:40 AM   #1265
pinnocchio is offline pinnocchio  Canada
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Yeah, those 940C are really impressive!
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Old 23rd February 2020, 03:56 AM   #1266
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Output
Hi Do,
How is the preamp working out so far? Have you connected it to the MOFO yet?
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Old 23rd February 2020, 04:08 AM   #1267
pinnocchio is offline pinnocchio  Canada
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My friend connected it to his mofo but he’s getting one channel with really bad noise. I don’t know what it is since I’m not there. However, the preamp works perfectly with headphones and measure perfectly on both channels. Probably something from the selector board? I’ll check with him and see if we can troubleshoot this remotely.

Otherwise, sounds really good with headphones!

Do
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Old 23rd February 2020, 04:29 AM   #1268
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Output
Try swapping the RCA out and see if the noise persists in the same channel. Make sure that each side has a proper ground - that is, ground is not left floating.

I know that the selector board on the Yarra has isolated left and right channel grounds, so if you only connect ground on one side but not the other, it may leave a floating ground which picks up noise. I don't know if this is a problem on the Aksa Lender, but worth a try to look and see.
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