Alright! Thanks Tungsten Audio for all your help! and Craigl59 it is so much fun that you are trying the same things!
So I tried it and...
It worked great with no issues, no noise or distortion, no clouds of smoke.
I only have one amp configured this way and only two smps, so I listened in mono, and listened to one channel in the stereo configuration, I then rewired and listened to that channel as parallel mono.
All of the benefits of running parallel mono and dual power supply are evident. The bass had more authority, heft, and definition. The midrange was more fleshed out. It sounded more effortless. I do think that if you have speakers that dip below 8ohms, which is most speakers then parallel mono is a clear win.
I'm going to pull apart the second amp and copy my second round of upgrades and wire for dual power supplies. I'll order a couple more meanwells. Quad power supplies into monoblocks!
Still thinking about whether to go FGH44N10 in Q2 as well, Tungsten, I know you said that was a personal preference, but could you predict what making that swap in Q2 would do?
So I tried it and...
It worked great with no issues, no noise or distortion, no clouds of smoke.
I only have one amp configured this way and only two smps, so I listened in mono, and listened to one channel in the stereo configuration, I then rewired and listened to that channel as parallel mono.
All of the benefits of running parallel mono and dual power supply are evident. The bass had more authority, heft, and definition. The midrange was more fleshed out. It sounded more effortless. I do think that if you have speakers that dip below 8ohms, which is most speakers then parallel mono is a clear win.
I'm going to pull apart the second amp and copy my second round of upgrades and wire for dual power supplies. I'll order a couple more meanwells. Quad power supplies into monoblocks!
Still thinking about whether to go FGH44N10 in Q2 as well, Tungsten, I know you said that was a personal preference, but could you predict what making that swap in Q2 would do?
I haven’t tried this. I know that the IRFP140 is a good part for the Q2 position, as I have used it here. This is an interactive current source. Not the full Aleph version, but pretty close. It is possible that the FQH44N10 might be too much of a good thing for use in a current source.
Something else: Go back and read Nelson’s articles on the Zen v4. He does talk about setting the degree of interaction between the current source and the signal driving device (Q1). The takeaway is that the ratio is a personal choice.
Last edited:
Cool thanks, I think the amp has struck such a nice balance. My guess is that the FQH44N10 is a little fuller/lusher and the 140 is lighter and airier. I think I will leave it as it is and save my extra 44N10's for a possible future F6 build.
I will read those articles too, thanks again!
I will read those articles too, thanks again!
Unfortunately, I have managed to fry my ACA. Was setting up the final installation so that I could switch between the ACA and a tube amp, and both amps were connected to the same speaker terminals. After turning OFF the ACA, ran the tube amp briefly and noted that the front LED lights on the ACA started to turn on -- even though the amp was off. So the current from the tube amp was passing from the speaker terminal through to the ACA and it was enough to damage something and create noise, now, whenever I turn on the ACA. Prior to this, the amp had been completely quiet.
So what do you think I blew? The mosfets? Any of the capacitors? Perhaps even the Meanwell smps? Your suggestions will be greatly appreciated. the amp has been superb and it will be necessary to fix whatever the damage is. Should have separated the two leads into the speaker as I have done for my other SS amp, but forget to do so. Very dumb.
So what do you think I blew? The mosfets? Any of the capacitors? Perhaps even the Meanwell smps? Your suggestions will be greatly appreciated. the amp has been superb and it will be necessary to fix whatever the damage is. Should have separated the two leads into the speaker as I have done for my other SS amp, but forget to do so. Very dumb.
I wonder if it is the output coupling caps being driven backwards. There is quite a bit of info on the ACA thread about troubleshooting, what a bummer!
I did reach out to Meanwell in regards to the dual-SMPS set-up. Their engineer said that the dual SMPS set up in stereo with the only connection being the ground sounds fine.
They would not recommend running parallel mono with dual SMPS. I am going to finish the upgrade on the second amp, Mosfet swap, and Vishay resistors. Then I'll compare the Dual SMPS stereo with single SMPS mono's...
or as the amp ran well in parallel, I may just throw caution to the wind and try the quad-SPMS monobock option... or I could try the 36v Meanwell idea by implementing R16 at 1k?
They would not recommend running parallel mono with dual SMPS. I am going to finish the upgrade on the second amp, Mosfet swap, and Vishay resistors. Then I'll compare the Dual SMPS stereo with single SMPS mono's...
or as the amp ran well in parallel, I may just throw caution to the wind and try the quad-SPMS monobock option... or I could try the 36v Meanwell idea by implementing R16 at 1k?
Good news. The noise was actually the result of a loose RCA connection and, so, am back on track. Have reconfigured the speaker terminals through a knife switch so that this can't happen again. Will be getting the second ACA parts this week and, hopefully, the case next week. Sorry for the above, but it is interesting that current sent to the shared speaker lead could cause the ACA to faux "turn on."
Great news!
Are you going to try the parallel monoblocks with dual-smps?
I ran one amp into on speaker for a while yesterday and the results were really good. I'm working up the second amp up now, but need to order another couple of meanwells to really try it out...
Are you going to try the parallel monoblocks with dual-smps?
I ran one amp into on speaker for a while yesterday and the results were really good. I'm working up the second amp up now, but need to order another couple of meanwells to really try it out...
Zj27: Have been able to order the double-pole front switch mentioned above and will have several of them tomorrow. This will allow for both smps to be turned on by the same, front switch. Now this also raises the question of using that back switch to move between the stereo version and the parallel mono one. Your advantages noted above make this attractive. Can you describe how you are wiring the back panel speaker terminals for parallel operation? Is it the same as the inline manual describes? Would think that it would not be ideal to share an active, as opposed to chassis, ground. Perhaps that is what the Meanwell engineer meant?
Cool, can you let me know the part number and where you ordered the switch.
For the parallel operation, with the switch out of the picture and being used as a power switch, I just tied the positives of both the rca inputs and followed the speaker wiring on the 1.8 wirng instructions, using a short piece of wire to link the - speaker posts(which are really positive)
I had zero issues running in parallel mono this way, like TA said maybe the cap on the dc in is helping.
I have both power supplies connected to the same ground wire on the back panel.
It works great in parallel mono with dual-smps and sounded great, I'm not smart enough to understand how the SMPS could interact with each other, Meanwell wasn't too sure about it after looking at the wiring diagrams that I sent them. They might just not like to see any connection beyond the ground with their psu's as a rule.
I also think that running parallel mono, either with a single or dual smps would be really advantageous into your 4ohm DI's
I've run it for an hour with no problems, so I'm just trying to decide if I want to order some more power supplies.
For the parallel operation, with the switch out of the picture and being used as a power switch, I just tied the positives of both the rca inputs and followed the speaker wiring on the 1.8 wirng instructions, using a short piece of wire to link the - speaker posts(which are really positive)
I had zero issues running in parallel mono this way, like TA said maybe the cap on the dc in is helping.
I have both power supplies connected to the same ground wire on the back panel.
It works great in parallel mono with dual-smps and sounded great, I'm not smart enough to understand how the SMPS could interact with each other, Meanwell wasn't too sure about it after looking at the wiring diagrams that I sent them. They might just not like to see any connection beyond the ground with their psu's as a rule.
I also think that running parallel mono, either with a single or dual smps would be really advantageous into your 4ohm DI's
I've run it for an hour with no problems, so I'm just trying to decide if I want to order some more power supplies.
Yes, an hour, and then I got bored of listening to one speaker, switched back to stereo and start modding amp #2 so I can try the dual-smps monoblock config in stereo.
Zj27: Ordered the switch as was mentioned in a post above as: RR81231121 EG5661-ND
SWITCH ROCKER DPST 10A 125V from DigiKey. Shipment has been delayed and will not have it until next week. At that time will check it with the new parts from DIY and make sure it will fit into the front panel.
SWITCH ROCKER DPST 10A 125V from DigiKey. Shipment has been delayed and will not have it until next week. At that time will check it with the new parts from DIY and make sure it will fit into the front panel.
Zj27: Have decided right now that the stereo multi-smps approach is the best for my system. It has more than enough volume with phono pre and digital feeds and the cassette decks I switch between are a mixed bag -- the Nakamichi and Denon decks have plenty of oomph and the others are close.
SO, since I don't need any more volume, and am delighted with the clear and powerful soundstage the ACA is producing, will stick with this and am building a second, identical ACA for my other stereo system (both use DIs).
Have 2 thoughts for the parallel approach. Since the same audio waveform is being sent to two PCBs, it seems best that they behave exactly the same if their amplified output is going to be joined. To do this, I am assuming you will readjust the Voltage trimpots for the specific speaker each is sharing (on mine, the two speakers required differing voltage adjustments and I assume this is because of the specific load). Different from stereo to mono, right?
And, second, would very much like to hear your assessment as to the stereo soundstage when the parallel mono approach is used. Is it as clear as the single-PCB approach? In particular, this is the lack I am noticing with my Emotiva XPA-1 High-bias amp. The voicing is not nearly as clear as the ACA and while the overall volume can be much louder, the "natural volume" as created by the ACA is far superior.
After a week of listening, I am hooked on the ACA and it has become the main amp in my system. Am setting up my speakers so they can use either the ACA or a 300B SET amp and this will serve all my listening needs.
Keep these units coming, DIY!
SO, since I don't need any more volume, and am delighted with the clear and powerful soundstage the ACA is producing, will stick with this and am building a second, identical ACA for my other stereo system (both use DIs).
Have 2 thoughts for the parallel approach. Since the same audio waveform is being sent to two PCBs, it seems best that they behave exactly the same if their amplified output is going to be joined. To do this, I am assuming you will readjust the Voltage trimpots for the specific speaker each is sharing (on mine, the two speakers required differing voltage adjustments and I assume this is because of the specific load). Different from stereo to mono, right?
And, second, would very much like to hear your assessment as to the stereo soundstage when the parallel mono approach is used. Is it as clear as the single-PCB approach? In particular, this is the lack I am noticing with my Emotiva XPA-1 High-bias amp. The voicing is not nearly as clear as the ACA and while the overall volume can be much louder, the "natural volume" as created by the ACA is far superior.
After a week of listening, I am hooked on the ACA and it has become the main amp in my system. Am setting up my speakers so they can use either the ACA or a 300B SET amp and this will serve all my listening needs.
Keep these units coming, DIY!
Craigl59, so I was upgrading my other amp and accidentally snipped the wrong transistors... luckily I had some FQH4410N's so I'm trying them in Q1 and Q2. I have them in single smps parallel monoblocks. I do think that having the FQH in Q2 sounds a little warmer with a very wide spacious soundstage, very liquid.
I am thinking that a single stereo ACA with dual smps is pretty amazing, and maybe every bit as good as monoblocks. I am going to run these for a while as I have hardwired them internally for parallel mono... but... I may follow your lead and do two dual-smps stereo amps if I set up a stereo in my new office.
BTW it is so cool to know that this amp can run the Teckton Double Impacts, so cool, would love to try their speakers someday, maybe the Lore's or DI monitors?
There is a certain openness to the dual-smps stereo unit, something I can't put my finger on.
I think that your analysis of using the dual-smps in parallel mono is probably correct, and along with the feedback from Meanwell I think I will table that idea for the time being as there is nothing lacking in performance either the dual-smps stereo amp, or single-smps monoblocks.
Thanks again for all of the advice, upgrades, and help in this forum. These amps are now light years ahead of where they were in stock form!
I am thinking that a single stereo ACA with dual smps is pretty amazing, and maybe every bit as good as monoblocks. I am going to run these for a while as I have hardwired them internally for parallel mono... but... I may follow your lead and do two dual-smps stereo amps if I set up a stereo in my new office.
BTW it is so cool to know that this amp can run the Teckton Double Impacts, so cool, would love to try their speakers someday, maybe the Lore's or DI monitors?
There is a certain openness to the dual-smps stereo unit, something I can't put my finger on.
I think that your analysis of using the dual-smps in parallel mono is probably correct, and along with the feedback from Meanwell I think I will table that idea for the time being as there is nothing lacking in performance either the dual-smps stereo amp, or single-smps monoblocks.
Thanks again for all of the advice, upgrades, and help in this forum. These amps are now light years ahead of where they were in stock form!
Zj27: Yes, your comment about a "certain openness" is right on the mark. Someone used to very "full" and powerful amps might find our MS ACA version light. But if you listen to good feeds, you notice that the accuracy for the voice/instrument "size" is exactly correct and sits in the soundstage with perfection. This tightness creates a LOT of space in the soundstage and helps create your "certain openness."
Shipment of the cases from Italy is being delayed by summer vacation and, so, it will be a while before I can duplicate and refine my first attempt. But in the meantime, am listening every day to the MS ACA and finding it grows on you quickly and infectiously.
Must point out that my listening room is very large, roughly 25' X 30' with arched ceilings and two large rooms opening directly into this space. With the DIs, am effortlessly achieving listening levels in the mid-90s -- again, as mentioned above, much louder than I normally listen. So much so that I have been noticing occasional ringing in the ears afterwards and must cut back. The synergy between the MS ACA and the DIs is remarkable.
Shipment of the cases from Italy is being delayed by summer vacation and, so, it will be a while before I can duplicate and refine my first attempt. But in the meantime, am listening every day to the MS ACA and finding it grows on you quickly and infectiously.
Must point out that my listening room is very large, roughly 25' X 30' with arched ceilings and two large rooms opening directly into this space. With the DIs, am effortlessly achieving listening levels in the mid-90s -- again, as mentioned above, much louder than I normally listen. So much so that I have been noticing occasional ringing in the ears afterwards and must cut back. The synergy between the MS ACA and the DIs is remarkable.
Oh man you have me looking at the Tekton website every day, I am super intrigued.
Tungsten Audio: You were totally right again that the choice between a 140 or FQH44 is a completely personal preference. I also think you were on the money that using the FQH in Q2 could potentially be "too much of a good thing"
Having the FQH in Q1 and Q2 and then also running parallel monoblock gives you insane bass, like someone dropped a sub in your room bass, like Charlie Haden is in the room bass, like you are inside Charlie Haden's bass bass. It is deep and solid and well-articulated. The highs are extended but very smooth and grain-free, this is part of what I think makes it play loud better.
So, in terms of tuning the amp, is this awesome, or is it like TA said "too much of a good thing?" Two option in tuning is to drop 140's back in at Q2. Or, follow Craig's lead and run a dual-smps single stereo unit with FQH at Q1 and Q2.
The added heft and scale are amazing on my Klipsch RP600m's, anyone who thinks they are bright, thin, and lack bass, needs to come to hear these now. Obviously, Craig with the Tekton Double Impacts does not need the additional heft of parallel mono.
The great takeaway is that you can have a single stereo unit with dual-smps that sounds awesome and not need to buy or build two units.
This has been so fun to experiment with, but school is starting up, and I have a great new job teaching at a great new school (for me) so I am going to try to keep these bolted together for now....
Tungsten Audio: You were totally right again that the choice between a 140 or FQH44 is a completely personal preference. I also think you were on the money that using the FQH in Q2 could potentially be "too much of a good thing"
Having the FQH in Q1 and Q2 and then also running parallel monoblock gives you insane bass, like someone dropped a sub in your room bass, like Charlie Haden is in the room bass, like you are inside Charlie Haden's bass bass. It is deep and solid and well-articulated. The highs are extended but very smooth and grain-free, this is part of what I think makes it play loud better.
So, in terms of tuning the amp, is this awesome, or is it like TA said "too much of a good thing?" Two option in tuning is to drop 140's back in at Q2. Or, follow Craig's lead and run a dual-smps single stereo unit with FQH at Q1 and Q2.
The added heft and scale are amazing on my Klipsch RP600m's, anyone who thinks they are bright, thin, and lack bass, needs to come to hear these now. Obviously, Craig with the Tekton Double Impacts does not need the additional heft of parallel mono.
The great takeaway is that you can have a single stereo unit with dual-smps that sounds awesome and not need to buy or build two units.
This has been so fun to experiment with, but school is starting up, and I have a great new job teaching at a great new school (for me) so I am going to try to keep these bolted together for now....
Have decided with my listening today that one of the reasons for the superb soundstage must be the fact that you custom set the voltage for each speaker to the same value -- then, this match presents the original mix more faithfully.
None of my other amps have this custom alignment capability. Is it handled by some automatic process in the retail amp world? Or is it generalized to a specific resistance value? Would this be why a number of tube amps offer separate speaker posts for 4 or 8 ohm speakers? Apologize for my ignorance.
As noted above, my MS ACA will not set the voltage off of the 2nd pole of Q1 (to ground) unless it is hooked up to a speaker. Otherwise, it rises to 10 volts or so then just starts going downwards. Am also assuming it is not healthy to do this without connecting some load. Could find no description in the online build guides of the load necessity but only the simple voltage adjustment procedure.
A specific reason why the MS ACA soundstage is so powerful has to do with its handling of depth. Studios do this with volume "pushback" and L/R blend. On the MS ACA, you can clearly hear wind, brass, and percussion sections/soloists in their correct position and this contributes to the overall sense of a natural, live recreation.
Got the DIY parts for the 2nd build today but will be waiting another 3-4 weeks for the Italian chassis. Am going to build the PCBs then put all away until September. Measured, btw, the on/off button and it appears to be close to the RR81231121 noted above (double pole). Circumference of right around 19.8mm. Should work but will know next week when the 1121s arrive.
None of my other amps have this custom alignment capability. Is it handled by some automatic process in the retail amp world? Or is it generalized to a specific resistance value? Would this be why a number of tube amps offer separate speaker posts for 4 or 8 ohm speakers? Apologize for my ignorance.
As noted above, my MS ACA will not set the voltage off of the 2nd pole of Q1 (to ground) unless it is hooked up to a speaker. Otherwise, it rises to 10 volts or so then just starts going downwards. Am also assuming it is not healthy to do this without connecting some load. Could find no description in the online build guides of the load necessity but only the simple voltage adjustment procedure.
A specific reason why the MS ACA soundstage is so powerful has to do with its handling of depth. Studios do this with volume "pushback" and L/R blend. On the MS ACA, you can clearly hear wind, brass, and percussion sections/soloists in their correct position and this contributes to the overall sense of a natural, live recreation.
Got the DIY parts for the 2nd build today but will be waiting another 3-4 weeks for the Italian chassis. Am going to build the PCBs then put all away until September. Measured, btw, the on/off button and it appears to be close to the RR81231121 noted above (double pole). Circumference of right around 19.8mm. Should work but will know next week when the 1121s arrive.
The parallel mono amps with the FQH44N10's in Q1 and Q2, well the bass was too much, there is a perfect balance with it in dual-smps stereo... maybe it sounds a little more open on top with a IRPF140 in Q2, but the liquid midrange and highs, and the depth in the bass with FQH44N10's in both places is pretty special (just not in parallel mono, it was like hitting a loudness button)
Craig, I think I will follow your lead and have two stereo amps, I may do the second one with the 140's in Q2, choices... How does the ACA compare with your 300B amp
I would love to try the Elekit 300b next, it is so expensive though.
Craig, I think I will follow your lead and have two stereo amps, I may do the second one with the 140's in Q2, choices... How does the ACA compare with your 300B amp
I would love to try the Elekit 300b next, it is so expensive though.
Zj27: MS ACA and 300B SET Tube monoblocks are completely different. The SET tubes have the typical "ringing" of the harmonic structure and the overall damping is poor. My set has 10 watts each block and is plenty loud enough -- rate the tubes at "10" loudness value and the MS ACA is about a 6-7. OK soundstage but nothing at all like the ACA.
The quality I have always gone to the 300B for is the tonality (= timbral accuracy). It is superb on time variant instruments such as violins or pianos. The "middle part" of the tone is rendered continuously and accurately and, so, certain instruments that suffer in digital rendition, are much more pleasant with 300B: pipe organs, choirs, strings, and others. And cassette play is preferred on the 300Bs.
Tonality on the MS ACA is complicated. The overall accuracy is good or very good. With the soundstage and dynamic superiority, tonality is rendered well enough to make all natural and extremely listenable -- so far I rank listenability far above the 300Bs. But you cannot analyze the timbre with the same degree of accuracy as you can with the 300B.
BTW, my 300B monoblocks came from Shenzhen, China and were Nobsounds only attempt at a high-end offering. Even then, they were reasonable and were marketed on Amazon for about a month. When Nobsound found out how much money they were losing shipping to America, they stopped their Amazon offering. The two monoblocks, with J&J tubes, retailed for around $1200 and they paid over $600 to ship them to me by expedited UPS. But they came in about 6 days. Still available through their site on the internet, I believe, but am not sure they still have the quality German and European components that were initially advertised and fulfilled. Building a 300B tube amplifier would be an excellent endeavor. Have ordered the M2X PCBs and am going to start working towards that design after the second MS ACA is done.
The quality I have always gone to the 300B for is the tonality (= timbral accuracy). It is superb on time variant instruments such as violins or pianos. The "middle part" of the tone is rendered continuously and accurately and, so, certain instruments that suffer in digital rendition, are much more pleasant with 300B: pipe organs, choirs, strings, and others. And cassette play is preferred on the 300Bs.
Tonality on the MS ACA is complicated. The overall accuracy is good or very good. With the soundstage and dynamic superiority, tonality is rendered well enough to make all natural and extremely listenable -- so far I rank listenability far above the 300Bs. But you cannot analyze the timbre with the same degree of accuracy as you can with the 300B.
BTW, my 300B monoblocks came from Shenzhen, China and were Nobsounds only attempt at a high-end offering. Even then, they were reasonable and were marketed on Amazon for about a month. When Nobsound found out how much money they were losing shipping to America, they stopped their Amazon offering. The two monoblocks, with J&J tubes, retailed for around $1200 and they paid over $600 to ship them to me by expedited UPS. But they came in about 6 days. Still available through their site on the internet, I believe, but am not sure they still have the quality German and European components that were initially advertised and fulfilled. Building a 300B tube amplifier would be an excellent endeavor. Have ordered the M2X PCBs and am going to start working towards that design after the second MS ACA is done.
Last edited: