Hey X. I just put the AKSA Lender back in to service after a while of listening to an F7 clone with the WHAMMY and most recently the B1 Korg. I have to say it put a huge smile on my face and brought me back to when I first built it. Back then it was with an Alpha 20W but the sound is still great if not better than I remember. The stage is big, on the warm side of neutral, yet still detailed. I built mine with some 2sa1837’s as well. Maybe that has something to do with the sound. 
It’s making me more excited to finally get the Yarra put together. Just got my Mouser order yesterday. Thanks again Hugh, X, and JPS for getting this pre out to the DIY community. I’m going to keep it in my system for a while, at least until the Yarra is ready.
It’s making me more excited to finally get the Yarra put together. Just got my Mouser order yesterday. Thanks again Hugh, X, and JPS for getting this pre out to the DIY community. I’m going to keep it in my system for a while, at least until the Yarra is ready.
Here is a clip of the AKSA Lender Pre in action. One of these days I’ll make the recording with a decent mic. This is off my iPhone 11.
First Watt F7 Clone with AKSA Lender Preamp a la diyAudio.com - YouTube
First Watt F7 Clone with AKSA Lender Preamp a la diyAudio.com - YouTube
Thanks X! Yep, that's the new basement. ~1,500 square feet of unfinished space right now. We may start finishing soon though. I have plans for a 13'x17.5' dedicated listening room/home theater. For now, YES, the insulation really does help the reflections. It's actually a pretty decent listening experience.
I got hooked on OB sound a while back and I've been experimenting ever since. If you remember I had the dual 3fe25 mini-k's over the OB 15 H-Frames. Those sounded great. I've recently upgraded to the Lii Audio Crystal 10's for the full range. They're incredible. Not a budget speaker though, that's for sure.
I got hooked on OB sound a while back and I've been experimenting ever since. If you remember I had the dual 3fe25 mini-k's over the OB 15 H-Frames. Those sounded great. I've recently upgraded to the Lii Audio Crystal 10's for the full range. They're incredible. Not a budget speaker though, that's for sure.
Testing my AKSA's Lender...
I have finished the PCBs for my preamp, but don't have everything to put it together yet (chassis and mechanicals, mostly). I thought to try a 19V laptop supply in place of my intended 48v, if only to see if any signals are getting through.
Tested with my smartphone providing a 1khz test tone, volume on max, and driving a small 8R speaker.
I didn't expect anything huge for sound, but what I got was 'scratchy', and very faint; adjusting R1021 (ALPS RK09L12B) to anything below ~75% became inaudible. I use the same phone plugged directly into my MOFO all the time with great results.
Power at the daughterboards comes in at 19.2V.
Unfortunately, I don't have an o-scope, so I can't get a picture of the output.
Can anyone suggest some test points and values to look for? I realize this is scant information, but I'm at a loss about what details to provide.
Kind regards,
Drew
I have finished the PCBs for my preamp, but don't have everything to put it together yet (chassis and mechanicals, mostly). I thought to try a 19V laptop supply in place of my intended 48v, if only to see if any signals are getting through.
Tested with my smartphone providing a 1khz test tone, volume on max, and driving a small 8R speaker.
I didn't expect anything huge for sound, but what I got was 'scratchy', and very faint; adjusting R1021 (ALPS RK09L12B) to anything below ~75% became inaudible. I use the same phone plugged directly into my MOFO all the time with great results.
Power at the daughterboards comes in at 19.2V.
Unfortunately, I don't have an o-scope, so I can't get a picture of the output.
Can anyone suggest some test points and values to look for? I realize this is scant information, but I'm at a loss about what details to provide.
Kind regards,
Drew
Hi Drew,
Feeding the ALP such a low voltage power source is not how this design was intended to work. You can confirm the mother board psu functionality with the daughter boards removed. But, as far as sound quality testing, it needs proper input voltage (+48vdc) for the components/transistors to work as designed.
Feeding the ALP such a low voltage power source is not how this design was intended to work. You can confirm the mother board psu functionality with the daughter boards removed. But, as far as sound quality testing, it needs proper input voltage (+48vdc) for the components/transistors to work as designed.
To follow up, Vunce, the schematic indicates "<= +63VDC".
I didn't see a mention in earlier posts indicating the minimum voltage that would be reasonable for this design, but now that I think about it, there should be some floor below which the transistors (both FET and BJT) won't function well.
Kind regards,
Drew
I didn't see a mention in earlier posts indicating the minimum voltage that would be reasonable for this design, but now that I think about it, there should be some floor below which the transistors (both FET and BJT) won't function well.
Kind regards,
Drew
That’s correct what Vunce said. This preamp was designed to be powered by 48v (and as high as 55v) as designed. I have found the best performance at 48v (at the daughterboards). To do that, you need to give it about 48v plus 4v or 52v due to the voltage drop at the built in capacitance multiplier which has a 3.5v to 4v dropout.
The way I did this was to use a DC/DC step up power supply and fed that with a 12v 1000mA Class 2 linear wall wart adapter (from old school wired or wireless routers). For some reason, feeding a DCDC step up with a SMPS was noisier.
The DCDC step up has a pot and this lets you precisely adjust the voltage at the daughterboards to be 48v. Actually 48.2v was the perfect Goldilocks setting for ideal harmonic profile.
You may find that a 48v Meanwell or other SMPS has a small adjustment pot near the output for trimming the voltage. Usually the 48v units can be adjusted up to 50.2v or so. 46v is ok still.
But not 19v at the daughterboard.
The schematic shows that the simulation of the resistor setpoints are made for 48v. Besides, this was supposed to swing 40Vpp to drive 25w into 8ohms for 0dB gain power amp stages.
The way I did this was to use a DC/DC step up power supply and fed that with a 12v 1000mA Class 2 linear wall wart adapter (from old school wired or wireless routers). For some reason, feeding a DCDC step up with a SMPS was noisier.
The DCDC step up has a pot and this lets you precisely adjust the voltage at the daughterboards to be 48v. Actually 48.2v was the perfect Goldilocks setting for ideal harmonic profile.
You may find that a 48v Meanwell or other SMPS has a small adjustment pot near the output for trimming the voltage. Usually the 48v units can be adjusted up to 50.2v or so. 46v is ok still.
But not 19v at the daughterboard.
The schematic shows that the simulation of the resistor setpoints are made for 48v. Besides, this was supposed to swing 40Vpp to drive 25w into 8ohms for 0dB gain power amp stages.
Hi Rolandong,
I am unsure what you mean. The schematic for the daughterboard design specifies "V+ < +63VDC" and "AGND", but I don't see an indication for a negative rail. The motherboard's main responsibility is to power the daughterboards. (It also organizes the input and output signal paths, but only to attentuate them for volume control.)
The motherboard receives power from a CLC filter, and the input to the CLC filter is indicated as "V+ SMPS".
Am I missing something?
Kind regards,
Drew
Ebay for BC560C NOS BC560C PNP Transistor OnSemi On Semiconductor X10 | eBay
Mouser for KSC1845 https://www.mouser.com/ProductDetai...rchild/KSC1845FTA?qs=UMEuL5FsraDCmxWozTypUA==
Mouser for KSC1845 https://www.mouser.com/ProductDetai...rchild/KSC1845FTA?qs=UMEuL5FsraDCmxWozTypUA==
AKSA-Lender + MOFO + Mini Karlsonators
I finally screwed up the courage and hooked up my preamp today (TH daughterboards). I'm using a Meanwell rat-tail providing 48V/1.25A, so my source voltage to the daughterboards is ~43V. Still waiting for the step-up converter to properly power it up to 48V.
I had tested voltages around, and found I had incorrectly installed R3 and R4a, and so had to rectify that.
So happy with the sound. My Chromebook is streaming Miles Davis, Cannonball Adderly, and John Coltrane and the sound is awesome.
Again, huge thanks to Hugh Dean (AKSA) for the design, xrk971 for the implementation, JPS64 for the layout, and everyone else here for their patience and dedication to these excellent designs.
Now I only have to build my own streamer, and I'll have a 100% home-built system!
Kind regards and happy soundwaves,
Drew
I finally screwed up the courage and hooked up my preamp today (TH daughterboards). I'm using a Meanwell rat-tail providing 48V/1.25A, so my source voltage to the daughterboards is ~43V. Still waiting for the step-up converter to properly power it up to 48V.
I had tested voltages around, and found I had incorrectly installed R3 and R4a, and so had to rectify that.
So happy with the sound. My Chromebook is streaming Miles Davis, Cannonball Adderly, and John Coltrane and the sound is awesome.
Again, huge thanks to Hugh Dean (AKSA) for the design, xrk971 for the implementation, JPS64 for the layout, and everyone else here for their patience and dedication to these excellent designs.
Now I only have to build my own streamer, and I'll have a 100% home-built system!
Kind regards and happy soundwaves,
Drew
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