That is all super interesting.
Running the ACA with FQH44N10 in Q1 and Q2 is just a little too thick sounding and rounded off up high for me either in stereo or mono (in mono the bass weight and depth is insane but out of scale with everything else), the mids and vocals are so liquid, but I am losing some air...
So I am going to go back to IRFP140 in Q2 and run parallel mono I will do one last comparison with dual-smps stereo. I think that works the best in this room, I think in a larger room with more room to breathe, like yours Craig, it would handle the bass better.
It is amazing that this can progress from upgrading to system-matching and personal preference, I think I am at the equivalent of "tube-rolling" at this stage. I hope my boards can handle one more careful desolder...
The Infenion part is out of stock everywhere is the Vishay IRFP140 comparable/better/worse?
Running the ACA with FQH44N10 in Q1 and Q2 is just a little too thick sounding and rounded off up high for me either in stereo or mono (in mono the bass weight and depth is insane but out of scale with everything else), the mids and vocals are so liquid, but I am losing some air...
So I am going to go back to IRFP140 in Q2 and run parallel mono I will do one last comparison with dual-smps stereo. I think that works the best in this room, I think in a larger room with more room to breathe, like yours Craig, it would handle the bass better.
It is amazing that this can progress from upgrading to system-matching and personal preference, I think I am at the equivalent of "tube-rolling" at this stage. I hope my boards can handle one more careful desolder...
The Infenion part is out of stock everywhere is the Vishay IRFP140 comparable/better/worse?
Ok, I stand corrected, The dual-smps, with FQH44N10 at Q1+Q2 is special.
Had a friend over that had last heard the stock amp and his jaw it the floor hearing the upgraded amp. Great news is now I have two great stereo amps! I'm going to look into building a pream and speakers next for my office. Thanks Craig for inspiring me to try this set-up. Tunsgsten, again thanks, wow this was fun, and it sounds so good!
Had a friend over that had last heard the stock amp and his jaw it the floor hearing the upgraded amp. Great news is now I have two great stereo amps! I'm going to look into building a pream and speakers next for my office. Thanks Craig for inspiring me to try this set-up. Tunsgsten, again thanks, wow this was fun, and it sounds so good!
Switch news and a belated THANKS to rhthatcher above for his listing the RR81231121 Digi-Key dual pole as a way to handle two sources.
These switches arrived yesterday and have been carefully measured/compared with the DIY switch. They are exactly the same as regards circumference (19.8mm) and front outer housing (23mm). The only difference is the spring clips that are 4mm on the DIY switch and wider at 5mm on the RR81231121. Am hoping this will cause no seating problems. Do not have the case (August Euro holiday) and, so, cannot be 100% sure but they seem fine. Checked the two pole operation, performance at 24 volts, 5 amps and both operate fine. The wire holes on the back bracket are small by comparison to the DIY switch but two 24awg wires will just fit into them
SO this switch will allow turning on the MS ACA (=multi-smps ACA) with a single push and avoid the need for the second switch on the back of the unit -- that can be repurposed for, perhaps, parallel mono operation.
These switches arrived yesterday and have been carefully measured/compared with the DIY switch. They are exactly the same as regards circumference (19.8mm) and front outer housing (23mm). The only difference is the spring clips that are 4mm on the DIY switch and wider at 5mm on the RR81231121. Am hoping this will cause no seating problems. Do not have the case (August Euro holiday) and, so, cannot be 100% sure but they seem fine. Checked the two pole operation, performance at 24 volts, 5 amps and both operate fine. The wire holes on the back bracket are small by comparison to the DIY switch but two 24awg wires will just fit into them
SO this switch will allow turning on the MS ACA (=multi-smps ACA) with a single push and avoid the need for the second switch on the back of the unit -- that can be repurposed for, perhaps, parallel mono operation.
So, back when I used to mod CD players I used to use Black Gate caps in the output and it always made a big difference.
I see that Black Gates arent' made anymore but there are these Audio Note Kasei. Has anyone tried these as an output coupling cap?
4700uF 16Vdc KAISEI Snap-In, Audio Note Electrolytic Capacitor
I see that Black Gates arent' made anymore but there are these Audio Note Kasei. Has anyone tried these as an output coupling cap?
4700uF 16Vdc KAISEI Snap-In, Audio Note Electrolytic Capacitor
My stereo amp with the dual 24v smps is running great. I think I am going to try the 36v supply on my other amp with the 1k at r16.
I don't currently have R16 installed, can anyone snap a pick of this that has cut the trace and installed this on a V1.6 board?
Zj27: Am interested in this possibility as well. Think that there was another pcb board created that had this design and was being sold much earlier in this thread. Have gotten the M2X boards for a longterm 25-watt build and am wondering about power supplies there. Could the 36v Meanwells be used with the M2x boards using the Class A daughterboard? Say, one for each circuit pair?
You guys have been doing an awesome job with your ACA builds. 
If you’re thinking about building a 25W amp next, it’s probably time to commit to using linear power supplies. The M2x is a great amp that runs on +/– 23V. The front end uses an Edcor signal transformer as the gain stage, and supports several alternate buffer circuits to drive the transformer. It’s a fun amp to tinker with.
One of the tricks with this amp is finding a good way to isolate the signal transformer from the much larger one in the power supply. The Edcor is susceptible to picking up electric and magnetic fields. This isn’t a huge deal, but if you’re used to an absolutely silent background, that’s not going to happen without some extra work. Most find it sufficient to use a shielded toroidal power transformer and apply some copper shielding around the Edcor.
You’ll forget about all that once you get to hear what a 25W N. Pass amp sounds like.
If you’re thinking about building a 25W amp next, it’s probably time to commit to using linear power supplies. The M2x is a great amp that runs on +/– 23V. The front end uses an Edcor signal transformer as the gain stage, and supports several alternate buffer circuits to drive the transformer. It’s a fun amp to tinker with.
One of the tricks with this amp is finding a good way to isolate the signal transformer from the much larger one in the power supply. The Edcor is susceptible to picking up electric and magnetic fields. This isn’t a huge deal, but if you’re used to an absolutely silent background, that’s not going to happen without some extra work. Most find it sufficient to use a shielded toroidal power transformer and apply some copper shielding around the Edcor.
You’ll forget about all that once you get to hear what a 25W N. Pass amp sounds like.
Here’s a premium ACA project I’m almost done with. I tested amp 1 on my bench test speakers, and it sings. I need to set the voltages on amp 2. I also played around with “tripod” feet…. I’m going to go with 4.
There’s a CLC filter board in there which is inspired by the P channel vfet filter, except doubled.
A pair of the boards is on the way to a friend and ACA user who will comment on the differences he hears.
I have extra CLC boards. I’m thinking of doing a group buy with boards and a kit of all the required parts. Any interest? I can run the cost numbers. I will also make a nice “how-to” doc to retrofit existing amps. It should be very straightforward.
There’s a CLC filter board in there which is inspired by the P channel vfet filter, except doubled.
A pair of the boards is on the way to a friend and ACA user who will comment on the differences he hears.
I have extra CLC boards. I’m thinking of doing a group buy with boards and a kit of all the required parts. Any interest? I can run the cost numbers. I will also make a nice “how-to” doc to retrofit existing amps. It should be very straightforward.
Attachments
rhthatcher: I would be very interested in purchasing a set of boards and parts (or two, I have two amps), that seems really cool. I have experimented with a cap on the DC and just that had positive results so I'd be really interested in trying the next step
TungstenAudio: I think that a 25w Pass amp with Linear supplies will be the next step. Looking at the F6. I may really try the 36v Meanwell on my other ACA. Besides R16 at 1K is there anything else I should be on the lookout for, more heat?
Craig: Thanks again for inspiring me to try the ms aca, so great, wanted to let you know that a good friend just ordered a pair of Double Impacts, so I may have a chance to bring my amp down and hear what you are hearing on them.
TungstenAudio: I think that a 25w Pass amp with Linear supplies will be the next step. Looking at the F6. I may really try the 36v Meanwell on my other ACA. Besides R16 at 1K is there anything else I should be on the lookout for, more heat?
Craig: Thanks again for inspiring me to try the ms aca, so great, wanted to let you know that a good friend just ordered a pair of Double Impacts, so I may have a chance to bring my amp down and hear what you are hearing on them.
Zj27: The F6 is, of course, another very fine amplifier. I built mine with a somewhat higher voltage dual-mono PSU. And FQH44N10 all around.
rthatcher: That dual channel CLC filter board looks very nice. Would also be a good choice for those wanting to try something a little extra in their P-type VFET amps.
rthatcher: That dual channel CLC filter board looks very nice. Would also be a good choice for those wanting to try something a little extra in their P-type VFET amps.
TA: Understand the advantages of a linear PSU and have long selected gear with such. Have been reading various threads and, frankly, am having trouble working through the relationships of ripple, capacitance, etc. Would need to order a pre-existing package to make it work for me. Any suggestions? Is the ACA PSU shown in rhthatcher's premium build available as a kit? Can you use a 24 volt Meanwell just to get started with the M2X? Know these are simple questions, but am at that stage. Could not locate the CLC filter in rhthatcher's pictures but am unsure what to look for.
Zj27: The wait for the DIs used to be very long. Has Eric caught up? How long will your friend be waiting? Pass along my information about damping the back port -- it is necessary. And let him know that the speaker takes weeks to settle in. The initial sound can be slightly bright depending upon the room. Placement is critical for good soundstage and I toe them in so that their angle converges 1 foot in front of my nose in the listening chair. Tell your friend that when they are properly setup, you will NEVER hear the speakers -- only a full panoramic soundstage. And I use 2 awg welding cable (!) for speaker wire in order to preserve the high damping factor of my Emotiva XPA1. The effect is dramatic on the soundstage -- the more damping, the more air and space. My MS ACA amp is connected by 10 awg Belden cable and sounds fine. Since the damping is minimal with the ACA, cannot fathom why the soundstage is so clear and the voices so tightly defined.
BTW, my MS ACA makes no thump when turned on and a very minor one at turn-off. Have found this sound is a pleasing confirmation of the turn-off and have no desire to remove it.
Zj27: The wait for the DIs used to be very long. Has Eric caught up? How long will your friend be waiting? Pass along my information about damping the back port -- it is necessary. And let him know that the speaker takes weeks to settle in. The initial sound can be slightly bright depending upon the room. Placement is critical for good soundstage and I toe them in so that their angle converges 1 foot in front of my nose in the listening chair. Tell your friend that when they are properly setup, you will NEVER hear the speakers -- only a full panoramic soundstage. And I use 2 awg welding cable (!) for speaker wire in order to preserve the high damping factor of my Emotiva XPA1. The effect is dramatic on the soundstage -- the more damping, the more air and space. My MS ACA amp is connected by 10 awg Belden cable and sounds fine. Since the damping is minimal with the ACA, cannot fathom why the soundstage is so clear and the voices so tightly defined.
BTW, my MS ACA makes no thump when turned on and a very minor one at turn-off. Have found this sound is a pleasing confirmation of the turn-off and have no desire to remove it.
A linear PSU can seem daunting at first, but they are actually fairly straightforward. The diyAudio store sells a "Universal Power Supply" PCB that is an easy way to get started. Especially when one follows 6L6's build guide. The next step after that is a CRCRC supply, which can also be found in PCB form, or crafted by point-to-point wiring. The upper end would be a Capacitance Multiplier or even a regulated PSU, both of which are somewhat more complex, and still have PCBs available. I used a pair of dual-rail SLB CapMx supplies in my F6, and a pair of CRCRC supplies in my Aleph J. Both did a very fine job, given some attention to detail.
You need a bipolar 24V power supply, so if you are talking about the ACA 24 volt Meanwell that is sold as part of the ACA, I don't think you can use it, no. Also, you may need more than 5A.
I may be wrong,
Rafa.
You are not wrong 
I don't even recommend 'stacking' the Meanwell SMPS to get +/– 24V. (This is especially problematic, as these SMPS are non-isolated.) The larger 25W amps need a better power reserve than can be achieved with a pair of 120W switching supplies. Linear with a sufficiently large set of reservoir capacitors is the way to go.
I don't even recommend 'stacking' the Meanwell SMPS to get +/– 24V. (This is especially problematic, as these SMPS are non-isolated.) The larger 25W amps need a better power reserve than can be achieved with a pair of 120W switching supplies. Linear with a sufficiently large set of reservoir capacitors is the way to go.
TA: considering the transformer/noise issues with the M2X this suggests an outboard PSU might be better. Thoughts? Have read 6L6's fine build guide on the Universal Power Supply several times and it is mostly clear. Need to check on the voltage and how to set that unit up for the +/- 23 volts needs.
BTW, have been ordering components for the M2X and finding almost all are back-ordered and some by many months. Called up Edcor about the transformer and although they stated 8 weeks delay on the website, their rep said maybe a week. Their shipping costs are very high.
BTW, have been ordering components for the M2X and finding almost all are back-ordered and some by many months. Called up Edcor about the transformer and although they stated 8 weeks delay on the website, their rep said maybe a week. Their shipping costs are very high.
Given my recent experience with the VFET amp, I would also consider building an external PSU for the M2x. The Edcor used in that design seems a little more susceptible to external interference than the Jensen which is used in the F6.
Edcor (the company) has been good so far at delivering transformers within about three weeks. I think they prefer to under-promise and over-deliver. The M2x is a fairly simple design (F6 is even simpler), so I might expect that there are alternate parts that would be suitable, and available.
Edcor (the company) has been good so far at delivering transformers within about three weeks. I think they prefer to under-promise and over-deliver. The M2x is a fairly simple design (F6 is even simpler), so I might expect that there are alternate parts that would be suitable, and available.
Buy fifteen pieces of the Edcor PC600-15K. You'll need them for the M2x, and for the VFET-clone Front End boards, and to give away / sell to other diyAudio members who didn't have the foresight to buy lots of Edcors before they needed them.
The shipping cost, amortized across 15 units, is significantly less chapsome.
The shipping cost, amortized across 15 units, is significantly less chapsome.