Just change R10 above to gain you want. Gain is equal to R10/1000 so 10k is 10x or 20dB etc. if you really want highest voltage swing for those amps like MoFo or F4 use 12k. For normal line level type preamp something like 3.9k of 4.7k is fine. It’s easy to change - mount on backside of PCB to leave exposed and easy to swap. I am currently running 6.8k as headphone amp to eek volume out of a low sensitivity headphone.
I have been listening to this preamp configured as a hot running headphone amp (HPA) for past couple of days. I have to say that it is a very impressive sounding amp. It has the resolution and articulation of a DC coupled amp. The smoothness of a SE Class A amp and the dynamics of a push pull amp. Overall a great balanced performer that does not disappoint. As a preamp or headphone amp the volume control is butter smooth. No grain or scratchy sounds as you adjust. Finally, absolutely no turn on or off pop or thumps. Just silence - no matter when or how you turn on or off (no delays or relays needed).
Interesting how putting the cover on (or letting it warm up) dropped the THD from 0.023% to 0.01% for 2.0Vpp into 43ohms.
If you notice how clean this FFT is, it shows that the internally mounted DC-DC step up added no noise even though directly under the main PCB.
Interesting how putting the cover on (or letting it warm up) dropped the THD from 0.023% to 0.01% for 2.0Vpp into 43ohms.
If you notice how clean this FFT is, it shows that the internally mounted DC-DC step up added no noise even though directly under the main PCB.
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Just wanted to share my AKSA Lender preamp project.
I’ve been on a mission to get my AKSA fired up..... SUCCESS!! She is paired up with my Big MoFo and playing sweet music right now
I can’t believe the low frequency information that I’m hearing, not that it’s emphasized, it just wasn’t there before. Still very early to ‘critical listen’ but this combo sounds excellent so far.
I’m running at 40.5vdc after the cap Mx.
Q4 and Q5 run pretty hot, is that ok? I bent up a couple of small heatsinks to help but as you know, it’s a real tight spot.
I’ve been on a mission to get my AKSA fired up..... SUCCESS!! She is paired up with my Big MoFo and playing sweet music right now
I can’t believe the low frequency information that I’m hearing, not that it’s emphasized, it just wasn’t there before. Still very early to ‘critical listen’ but this combo sounds excellent so far.
I’m running at 40.5vdc after the cap Mx.
Q4 and Q5 run pretty hot, is that ok? I bent up a couple of small heatsinks to help but as you know, it’s a real tight spot.
Attachments
Beautiful work, Vunce!
Input selector, stepped attenuator, nice chassis! Awesome to hear that it works. The MoFo and this pre is a great combo. I ran mine at 45v after the cap Mx. That seemed to work well with MoFo letting me get 11Wrms. You should also share result in MoFo thread.
Input selector, stepped attenuator, nice chassis! Awesome to hear that it works. The MoFo and this pre is a great combo. I ran mine at 45v after the cap Mx. That seemed to work well with MoFo letting me get 11Wrms. You should also share result in MoFo thread.
Vunce,
Brilliant, artisan work! I love the Al angle bracket, even rounded to take out of the sharp points, elegantly done. Very nice wiring of the selectors, and really well earthed. You could have done it all in a box three times smaller!
When I penned the preamp circuit I never expected it would be so good. Thank you for showing it to the world - you and XRK are best!
Hugh
Brilliant, artisan work! I love the Al angle bracket, even rounded to take out of the sharp points, elegantly done. Very nice wiring of the selectors, and really well earthed. You could have done it all in a box three times smaller!
When I penned the preamp circuit I never expected it would be so good. Thank you for showing it to the world - you and XRK are best!
Hugh
Thank you X and Hugh for your kind words and bringing this project to the DIY community!!
The ability to ‘tune’ the preamp boards to whatever amplifier is downstream is great. This potentially could be the only preamp I need. You can also successfully use it as a headphone amp as X has outlined, very versatile indeed.
Yes Hugh, I certainly could have used a smaller enclosure. But, I was originally going to install the power supply inside for a single chassis unit. In the end, I decided against it.
BTW, How does the rug rate, haha!
The ability to ‘tune’ the preamp boards to whatever amplifier is downstream is great. This potentially could be the only preamp I need. You can also successfully use it as a headphone amp as X has outlined, very versatile indeed.
Yes Hugh, I certainly could have used a smaller enclosure. But, I was originally going to install the power supply inside for a single chassis unit. In the end, I decided against it.
BTW, How does the rug rate, haha!
Hi Vunce,
Nice rug
I suppose you agreee no manly linear toroidal PSU is needed then? What are you using as the power supply for the DC step up?
I have found that the SMPS that comes with the Lepai T2020 amp (branded “Vonage”) is one of the cleanest smps ever. I have tried lesser laptop smps and they have small bumps at 60Hz and 120/180Hz. Still inaudible - but I know they are there.
Thank you for a quick and beautiful build.
Nice rug
I suppose you agreee no manly linear toroidal PSU is needed then? What are you using as the power supply for the DC step up?
I have found that the SMPS that comes with the Lepai T2020 amp (branded “Vonage”) is one of the cleanest smps ever. I have tried lesser laptop smps and they have small bumps at 60Hz and 120/180Hz. Still inaudible - but I know they are there.
Thank you for a quick and beautiful build.
X,
I must admit, if I didn’t build the MoFo first and get such good results with the smps, cap Mx and crc, I was going the trafo/linear route. These two projects have opened up a new set of options for me.
I’m using s Toshiba 15v laptop smps for the AKSA and a pair of MeanWell 24v smps for the MoFo.
I was actually doing my research and planning to build either an Aleph J or F5 when I stumbled across the Build this MoFo thread. Now, I’m thinking if I can implement this type of smps based supply for one of those amps.
I must admit, if I didn’t build the MoFo first and get such good results with the smps, cap Mx and crc, I was going the trafo/linear route. These two projects have opened up a new set of options for me.
I’m using s Toshiba 15v laptop smps for the AKSA and a pair of MeanWell 24v smps for the MoFo.
I was actually doing my research and planning to build either an Aleph J or F5 when I stumbled across the Build this MoFo thread. Now, I’m thinking if I can implement this type of smps based supply for one of those amps.
Right, out your meanwells in series and you have +/-24v good enough for any Pass amp. You can add a cap Mx of course and Prasi has an excellent dual rail stereo cap Mx that fits on a 100mm square PCB. Even just that used with a trafo can get you a much more compact PSU without the CRC cap bank.
The MoFo is driving a pair of modified Klipsch Forte’s. I was using an
Aragon 18K MkII prior to the completion of my AKSA and that combo sounded good but just didn’t have the slam or volume to satisfy me. When I replaced the Aragon with the AKSA Lender preamp a large transformation happened. It was like a shot of steroids was injected into the system! Very wide soundstage, the ‘capture effect’ was back (that’s one I’m walking through the room and just have to stop and listen), major increase in the available volume. But, the most surprising change is an increase of low frequency information I’m hearing/feeling. It’s hard to explain, I hear/feel music now that sort of comes up from the floor? Weird, I know.
All in all, I’m extremely happy with the AKSA Lender/MoFo combo!
Aragon 18K MkII prior to the completion of my AKSA and that combo sounded good but just didn’t have the slam or volume to satisfy me. When I replaced the Aragon with the AKSA Lender preamp a large transformation happened. It was like a shot of steroids was injected into the system! Very wide soundstage, the ‘capture effect’ was back (that’s one I’m walking through the room and just have to stop and listen), major increase in the available volume. But, the most surprising change is an increase of low frequency information I’m hearing/feeling. It’s hard to explain, I hear/feel music now that sort of comes up from the floor? Weird, I know.
All in all, I’m extremely happy with the AKSA Lender/MoFo combo!
Hi Vunce,
Forte’s are 99dB sensitive so you got plenty of volume even with an 11Wrms amp. Nice.
With an 8.2uF input cap the F3 is 0.4Hz so even 2 octaves above is 1.6Hz. So your response is probably close to flat to 2Hz on the bottom. If your source material has infrasonic content and your speakers can handle it you are probably get 20Hz stuff from the speakers.
Did you ever post photos of your MoFo? Would be nice to see the whole setup with the Aksa Lender, MoFo and the Forte’s. You did a really nice job on the preamp. Super high quality work - thanks for taking the time to make it work and look good. Top of the line coupling caps too.
Forte’s are 99dB sensitive so you got plenty of volume even with an 11Wrms amp. Nice.
With an 8.2uF input cap the F3 is 0.4Hz so even 2 octaves above is 1.6Hz. So your response is probably close to flat to 2Hz on the bottom. If your source material has infrasonic content and your speakers can handle it you are probably get 20Hz stuff from the speakers.
Did you ever post photos of your MoFo? Would be nice to see the whole setup with the Aksa Lender, MoFo and the Forte’s. You did a really nice job on the preamp. Super high quality work - thanks for taking the time to make it work and look good. Top of the line coupling caps too.
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Great looking build Vunce, looks very boutique!
I'm looking forward to seeing how your MoFo build ended up as well. I was thinking about the Mundorf EVO's for both this preamp and the MoFo, since they are a bit cheaper option than other Mundorfs.
I have a few projects in the pipeline before I get to this and the MoFo, but really appreciate you and X sharing your builds for all of us to use as inspiration!
I'm looking forward to seeing how your MoFo build ended up as well. I was thinking about the Mundorf EVO's for both this preamp and the MoFo, since they are a bit cheaper option than other Mundorfs.
I have a few projects in the pipeline before I get to this and the MoFo, but really appreciate you and X sharing your builds for all of us to use as inspiration!
Thanks gtose
When you get to build them, I’m sure you’ll enjoy the combination. Efficient speakers are a plus. I like the Mundorf EVO oils, good price/performance and their size is manageable. I posted pics of my MoFo on the ‘Build This MoFo’ thread.
When you get to build them, I’m sure you’ll enjoy the combination. Efficient speakers are a plus. I like the Mundorf EVO oils, good price/performance and their size is manageable. I posted pics of my MoFo on the ‘Build This MoFo’ thread.
