Really like the performance of the PA5, while sounding extremely clean it does have a bit of thinness in the midrange. Inspired by PA5 modification thread, I decided to try a little power supply tinkering on my recently acquired PA5 to see if sonic improvements could be made at low to moderate cost with simple, tried and true mods. First, let me say this is all done using a simple multimeter, soldering iron and my ears--no scope or APx analyzer, basically subjective. Unlike most amplifiers the power supply is separate with a fairly long (1m?) umbilical cord consisting of 2-wire 18AWG stranded wire. My first thought was to shorten the umbilical to lessen its added resistance in the power supply to the amp. I shortened it about 50% with a slight improvement in lower midrange solidity (worth doing). Next step was to replace the umbilical with one made of 14AWG UPOCC stranded copper using the same connector at the amp. This was a very nice improvement overall with a fuller sound--improved lower midrange fullness and punch (worth doing as I already had the wire). Sound is now quite good and I could easily have stopped right here.
Thought about replacing the connector at the amp end with a lower impedance one but there is not much room. If you want to try this, maybe get a small diameter connector that protrudes out from the chassis instead of inside.
Higher cost improvements: Next I wanted to add some very low ESR 50V or 63V caps (bypassed with WIMA polys) to the power supply output to improve the sound and this requires a larger box for the power supply. Found an easy to drill ABS box on Amazon for $10. Caps can be found on Amazon like these or even better some like these. I usually buy 10 to get a better price each and use them all in parallel for even better overall ESR. You will also need connection for DC and for AC. I like these. Had some 16 gauge tin plated copper buss wire on hand and wired it up. Another real nice sonic improvement that gives you that fuller lower midrange along with the superb transparency. But the cost is going up.
Even higher cost improvements: As you can see in the PA5 Modification thread there are some subjectively higher quality, higher current switching 36V supplies that could be used with the PA5. I first tried a Mean Well RPS-400-36 ($100), very well made and a good reputation in the DYI community. Put it in my ABS box and off I go. While the stock PA5 supply is 38V (mine was 38.25V) you can adjust the Mean Well (MW) up to 37.5V so output was close. Sonic performance was good, about the equal to the stock supply. For me it almost was a keeper as it provided a bit for confidence in longevity vs. the stock supply which looks from visual inspection to be built to a lower standard. problem was the Mean Well produced a high frequency whine heard from the speakers. It could only be heard from about 12" away, but I knew this would not sit well with me over time as the stock supply is dead quiet. Back goes the MW, so next I tried the 36V Recom Power switcher at 37.3V output. While physically smaller than the MW, this one has the transparency of the stock supply all the way down through a full midrange and is dead quiet. So definitely a keeper and costs less than the MW. Quite happy with the sound/performance. But what about a nice linear supply?
Even higher cost improvements: Had an empty power supply chassis sitting around that would be perfect for a very hefty 400W linear power supply. Nothing special simple design using a 28V Antek transformer, bridge rectified along with some low ESR caps on the output similar to the switcher mods. Output ended up being 39.3V (under load) which is little higher than the switchers but within safe use margin. On first listen I reduced the volume by 1 dB for a similar perspective as to what I had been recently hearing. Only been powering the PA5 a couple days, but first impression is sounds very similar to the Recom but maybe, just maybe it has slightly more body while providing a more analog feeling. May just be bias listening. Will give it some time and go back to the Recom to confirm or deny.
P.S.--I also have this switcher on order for comparison. Will stop then as project funds are currently depleted.
You will of course notice I have not mentioned bass performance. This is because I crossover my KEF LS50 Metas to servo-subs between 100-200Hz. My system is all digital files from PC to a Holo DAC upsampling with HQ Player.
I did not expect to start a thread so I didn't take any pix along the way. At the urging of member "daniboun" I have started this thread to see if anyone else had interest in this fun. If anything seems unclear--just ask.
Chris H.
Thought about replacing the connector at the amp end with a lower impedance one but there is not much room. If you want to try this, maybe get a small diameter connector that protrudes out from the chassis instead of inside.
Higher cost improvements: Next I wanted to add some very low ESR 50V or 63V caps (bypassed with WIMA polys) to the power supply output to improve the sound and this requires a larger box for the power supply. Found an easy to drill ABS box on Amazon for $10. Caps can be found on Amazon like these or even better some like these. I usually buy 10 to get a better price each and use them all in parallel for even better overall ESR. You will also need connection for DC and for AC. I like these. Had some 16 gauge tin plated copper buss wire on hand and wired it up. Another real nice sonic improvement that gives you that fuller lower midrange along with the superb transparency. But the cost is going up.
Even higher cost improvements: As you can see in the PA5 Modification thread there are some subjectively higher quality, higher current switching 36V supplies that could be used with the PA5. I first tried a Mean Well RPS-400-36 ($100), very well made and a good reputation in the DYI community. Put it in my ABS box and off I go. While the stock PA5 supply is 38V (mine was 38.25V) you can adjust the Mean Well (MW) up to 37.5V so output was close. Sonic performance was good, about the equal to the stock supply. For me it almost was a keeper as it provided a bit for confidence in longevity vs. the stock supply which looks from visual inspection to be built to a lower standard. problem was the Mean Well produced a high frequency whine heard from the speakers. It could only be heard from about 12" away, but I knew this would not sit well with me over time as the stock supply is dead quiet. Back goes the MW, so next I tried the 36V Recom Power switcher at 37.3V output. While physically smaller than the MW, this one has the transparency of the stock supply all the way down through a full midrange and is dead quiet. So definitely a keeper and costs less than the MW. Quite happy with the sound/performance. But what about a nice linear supply?
Even higher cost improvements: Had an empty power supply chassis sitting around that would be perfect for a very hefty 400W linear power supply. Nothing special simple design using a 28V Antek transformer, bridge rectified along with some low ESR caps on the output similar to the switcher mods. Output ended up being 39.3V (under load) which is little higher than the switchers but within safe use margin. On first listen I reduced the volume by 1 dB for a similar perspective as to what I had been recently hearing. Only been powering the PA5 a couple days, but first impression is sounds very similar to the Recom but maybe, just maybe it has slightly more body while providing a more analog feeling. May just be bias listening. Will give it some time and go back to the Recom to confirm or deny.
P.S.--I also have this switcher on order for comparison. Will stop then as project funds are currently depleted.
You will of course notice I have not mentioned bass performance. This is because I crossover my KEF LS50 Metas to servo-subs between 100-200Hz. My system is all digital files from PC to a Holo DAC upsampling with HQ Player.
I did not expect to start a thread so I didn't take any pix along the way. At the urging of member "daniboun" I have started this thread to see if anyone else had interest in this fun. If anything seems unclear--just ask.
Chris H.
Thanks Chris ) Really interesting )
Seems that the Recom Power should be a good choice and its Small factor format makes it easy to integrate in a small case.
For the moment, I am still enjoying my Connex SMPS 300RS and sounds absolutely clean !
As soon as my A-DP 400 36 PSU with active PFC is ready, will share my impressions. (will set it @ 40V / 10A)
PS : I asked Amir (ASR) if he could test the performance of the PA5 with the Connex SMPS300 RS since he has one under his elbow) Still waiting his response... fingers X )
Seems that the Recom Power should be a good choice and its Small factor format makes it easy to integrate in a small case.
For the moment, I am still enjoying my Connex SMPS 300RS and sounds absolutely clean !
As soon as my A-DP 400 36 PSU with active PFC is ready, will share my impressions. (will set it @ 40V / 10A)
PS : I asked Amir (ASR) if he could test the performance of the PA5 with the Connex SMPS300 RS since he has one under his elbow) Still waiting his response... fingers X )
Let me know if anything I wrote needs clarification or expansion of explanation.
My prediction for Amir will show it is a clean supply, just like the stock supply and therefor (by default) one will not "sound better" than another--though I disagree. I used to be obsessive about getting a flat frequency in my system, since getting the resolute PA5 I have gone beyond that and am obsessed with getting the right harmonic balance of a particular instrument. These clean power supplies give me the tools to do that.
Chris H.
My prediction for Amir will show it is a clean supply, just like the stock supply and therefor (by default) one will not "sound better" than another--though I disagree. I used to be obsessive about getting a flat frequency in my system, since getting the resolute PA5 I have gone beyond that and am obsessed with getting the right harmonic balance of a particular instrument. These clean power supplies give me the tools to do that.
Chris H.
Bad news! Left my PA5 on overnight to help burn-in the new linear power supply--next day it was dead. I replaced the power supply with stock and it powered up, just unfortunately no sound. I will pay around with it, but heed this warning to keep power supply below 38.5V. I have achieved my overall object of determining if these new ultra low noise amps will improve my listening experience. Yes, they do. It was a costly lesson , but will now save up for a stereo Purifi Eigentakt and be done.
Chris H.
Chris H.
Yes. With all else in the chain the same, the thinness was not there using my Bryston amps. After tweaking a power supply for my F5, my experience is that power supply impedance, capacitors and wiring all make a sonic difference. Shortening the length of cables to lower impedance, adding low ESR capacitors with poly bypass and using UPOCC wire all make a noticeable improvement in sonics.
Chris H.
Chris H.
After reading thoughts from daniboun, I decided to also try the Connex SMPS300RS. I ordered on AliExpress and received around 30 days later 
. I built the supply in a new black box the same way as my other supply for comparison. Fired it up today and it sounds excellent. So far the Connex and the Recom sound very similar. I'll give the Connex 30 days of listening and then go back to the Recom for final thoughts. If you are considering this DIY both options are excellent.
Chris H.
. I built the supply in a new black box the same way as my other supply for comparison. Fired it up today and it sounds excellent. So far the Connex and the Recom sound very similar. I'll give the Connex 30 days of listening and then go back to the Recom for final thoughts. If you are considering this DIY both options are excellent.Chris H.
After reading thoughts from daniboun, I decided to also try the Connex SMPS300RS. I ordered on AliExpress and received around 30 days later
Chris H.
Nice, thanks for the feedback. Could you share some pictures too ?
Any further thoughts on the Connex vs Recom?After reading thoughts from daniboun, I decided to also try the Connex SMPS300RS. I ordered on AliExpress and received around 30 days later
Chris H.
Listened to the Connex for a couple months, was totally satisfied and really saw no need to switch back. Went on vacation for 8 days and powered down the music system. Upon return, I thought this would be a good time to try the Recom again with fresh ears. They both sound excellent (certainly better than the stock supply). I listen to string quartet, violin and cello duo, pianos trios, along with other acoustic performances. To my ears the Recom is slightly preferred with a little better soundstage depth and a better sense of clarity--as though there is simply less between you and the recorded performance.
Chris H.
Chris H.
Just wanted to follow up on previous posts. I did purchase a pair of Purifi Eigentakt 1ET-400A mono amps from VTV ($679 each). After comparing to my modified PA5, the Purifi certainly come out on top. The tonal balance is similar with the Monos having greater authority in the bass and mids. They just sound completely in control of my LS50 Metas. The highs also sound slightly more extended with better low level retrieval (cymbal shimmer lasts longer as do recording hall reflections). They are dead quiet and provide a complete black silence when the sounds stop. Yes, the Monos cost 3 times more, but for me are worth it. YMMV
BPT
BPT