I have a pair of original AMP CAMPS both in stereo mode to drive my Linkwitz LX-minis, along with the Nelson's analog LX-mini crossover.
At 5w/channel @ 8-ohms, the original AMP CAMPS just don't have enough oomph.
I'm hopeful that the ACA MinMax at double the power 10w/channel @ 8-ohms in stereo will make this baby sing.
Thoughts ? Am I kidding myself ?
Hoping to find a pair of boards and transistors, the rest I can source . . .
TIA,
🙂 neil
At 5w/channel @ 8-ohms, the original AMP CAMPS just don't have enough oomph.
I'm hopeful that the ACA MinMax at double the power 10w/channel @ 8-ohms in stereo will make this baby sing.
Thoughts ? Am I kidding myself ?
Hoping to find a pair of boards and transistors, the rest I can source . . .
TIA,
🙂 neil
3dB increase is about all you'll get.
The ACA MinMax is special. Replaced the F4s in my system.
However, not sure they will have enough grunt. Linkwitz recommended 4x50W minimum.
The ACA MinMax is special. Replaced the F4s in my system.
However, not sure they will have enough grunt. Linkwitz recommended 4x50W minimum.
I just listened to a pair of LX Mini’s + OB subs (actually an LX Studio) in a small to moderate sized room this past weekend and was only 7.5 feet from each speaker. I was listening at 85-90dB at the listening position. I’ll be honest with you - It was a wonderful experience.
The LX Mini portion had 100-125W of power, so as a minimum I would recommend 50 watts for the tweeter and 50 watts for the midwoofer (4 ohm ratings).
5-10 watt amplifiers are too little.
The overall system sensitivity (even though it’s active) is only about 84-85dB. Give this system some juice and the rewards are grand. Think of an F5 as your minimum. They will provide you 50 watts/4 ohms at least for the midwoofer.
A possible choice is (4) F5M redux kits. When it hits 50 watts you will be in Class A(B) but the first 30 watts peak are in class A.
Best,
Anand.
Last edited:
I could not get decent volume levels with my CampAmp driving Harbeth HLP-3 speakers. I then build a MiniMax that was a little better. I was going to build a second MiniMax to run them in mono mode but they were not available. I ended up buying a Shitt Vidar used and it works great but I like the warmth of the MiniMax better.
The ACAmini has 14 dB gain (I'm assuming the MinMax is the same), and the Vidar has 26 dB gain. That's a big difference. Do you have anything to add some more gain to the system when the MinMax is in place (like an extra preamp)? The Vidar has lots more power available, so the MinMax might still run out of steam, but I think it's possible you just need a bit more voltage juice to your signal to get what you want. You could build FE2022 front ends, a separate ACP+, or get one of xrk's BTSB boards for adjustable gain to add in.
Edit: Your Harbeths are pretty inefficient, so you may just be limited to amps with over 20WPC and moderate gain structure for your system.
Edit: Your Harbeths are pretty inefficient, so you may just be limited to amps with over 20WPC and moderate gain structure for your system.
Last edited:
Yup, the Harbeth HLP-3 speakers are about 83dB sensitivity. I have a buddy of mine who has been listening to the AmpCamp and is quite pleased with it. However, he is listening to them on Klipsch Forte (99dB).
And as vonAh has said, make sure you address gain differences or else you start conflating power differences with gain differences.
If you do build ACAMinMax and run them mono, each monoblock (XLR input) will also have +6dB more gain than the single ended input version so that helps too in addition to the increase in power output.
Best,
Anand.
And as vonAh has said, make sure you address gain differences or else you start conflating power differences with gain differences.
If you do build ACAMinMax and run them mono, each monoblock (XLR input) will also have +6dB more gain than the single ended input version so that helps too in addition to the increase in power output.
Best,
Anand.
Appropriate gain for the use case is the key. Anand's friend can get away with smaller output amps with super efficient speakers. 99 dB is LOUD in any home. I used my OG ACA Mini (the 'experimental' board 
) for years in a bedroom system with passive volume control and Fostex FF125WK speakers, never going full-out. My main rig rarely goes over 80 dB. Naturally, others want BIG sound in their systems and use bigger amps with lots of gain and power. All is fair game, just don't lose your hearing. 
) for years in a bedroom system with passive volume control and Fostex FF125WK speakers, never going full-out. My main rig rarely goes over 80 dB. Naturally, others want BIG sound in their systems and use bigger amps with lots of gain and power. All is fair game, just don't lose your hearing. 
Glad to see interest in the MinMax, unfortunately it's bittersweet. There are currently no plans to restock these kits on the diyAudio store or my site. I have 5 pairs of Rev 1 (purple) boards left that I can offer with transistors, but that's my entire stock of boards.
I also have the 15000uF caps, binding posts for the ACA chassis, alumina thermal pads, and a handful of other parts that could be included if helpful. Thoughts?
F5m Redux and ACA Redux kits are currently in stock, but I will be out of the country for some time and kit making will not continue while I'm gone since this is a one man operation. I may have someone to fulfill orders from remaining stock, then pause or close the site, TBD.
I also have the 15000uF caps, binding posts for the ACA chassis, alumina thermal pads, and a handful of other parts that could be included if helpful. Thoughts?
F5m Redux and ACA Redux kits are currently in stock, but I will be out of the country for some time and kit making will not continue while I'm gone since this is a one man operation. I may have someone to fulfill orders from remaining stock, then pause or close the site, TBD.
Thanks again Nelson.
The LXmini will need more oomph, so I'm looking into F5m Redux.
I don't there is enough surface-area in the ACA chassis for a F5m Redux without a fan somewhere . . .
However, I have other ideas for the rev 1 (purple) boards w/transistors, pads, caps, etc. Basically an "essentials" kit for the MiniMax for those with the ACA chassis.
🙂 neil
Last edited:
I would not recommend an F5m in an ACA chassis, my kits come with enough heatsink and fan that they run cool, though in an unconventional form factor. Here's a link to the thread and my store page.
The remaining MinMax boards are all spoken for. Going through my DMs now...
Hi, has anyone tried MOSFET pairs with different gfs ratios than the IRF140/IRF9140 or IRF520/9520 pairs that came kitted with the MinMax/ACA Mini? I asked a similar question in the ACA Mini thread but want to revisit it here as I have some MinMax boards in my hot little hands (with thanks to the Nelsons!).
The FQP3N30/3P20 pair is apparently popular in a DIY headphone amp and I've been curious about them for a while but the gfs of these devices is way lower than the Harris IRF520/9520 pair. This list is all stuff I have on hand, there are of course many more options. Thoughts?
The FQP3N30/3P20 pair is apparently popular in a DIY headphone amp and I've been curious about them for a while but the gfs of these devices is way lower than the Harris IRF520/9520 pair. This list is all stuff I have on hand, there are of course many more options. Thoughts?
| Pair or singlet | gfs values n/p and ratio | predicted harmonic profile |
| IRFP140/IRFP9140 (Infineon/Vishay) | 11/6.2 = 1.77 | negative phase 2nd (given) |
| IRF520/9520 (Harris) | 4.1/2 = 2.05 | negative phase 2nd (given) |
| IRFP240/IRFP9140 | 6.9/6.2 = 1.11 | minimal distortion? |
| IRFP250/IRFP9140 | 12/6.2 = 1.93 | negative phase 2nd? |
| IRFP150/IRFP9140 | 13/6.2 = 2.09 | negative phase 2nd? |
| FQA9P25 | 6.1 | (more or less a sub for the 9140?) |
| IRFP048 | 20 (!) | Probably ridiculous amounts of negative 2nd paired with these P-channel parts (60V part may not be long happy at 36V?) |
| FQP3N30/3P20 | 1.75/1.23 = 1.42 | minimal negative phase 2nd? low gain? |