Lightspeed building Henry ! Very neat as usual.
Seems that's it's your PSU V2.x. Super Regulator, but which one ?
Congrats 🙂
Seems that's it's your PSU V2.x. Super Regulator, but which one ?
Congrats 🙂
Thanks. That's another one of my Super Regulator supply boards. I've built four of them so far, and there's one more in circulation that a friend built up. The only difference is that I set this one up for +-24V and used the next-taller size of heatsinks (50mm vs 38mm), hopefully to run slightly cooler. Oh, and I bought 3900uF filter caps instead of the 2200uF ones in my earlier boards. Ripple on the raw supply is very low, like 100mV.
These supplies typically dissipate 1-1.5W per pass transistor in my amps. At the high end of that range, the 38mm heatsinks are perfectly fine in open air, but the temperature is just around the threshold of pain if you hold a finger on them too long. They get hotter inside a box, of course.
I used 2x22V transformers and the regulator input voltage is about 33V under load, FWIW.
I threw a scope probe on the supply rail with music playing and saw absolutely nothing that looked like signal. That's doesn't mean much because scopes, especially old digital ones, are pretty low-resolution. But I have a hard time believing the supply is adding anything. You can speculate why a less tightly-regulated supply might sound better. But I have no insight into that, technically speaking.
These supplies typically dissipate 1-1.5W per pass transistor in my amps. At the high end of that range, the 38mm heatsinks are perfectly fine in open air, but the temperature is just around the threshold of pain if you hold a finger on them too long. They get hotter inside a box, of course.
I used 2x22V transformers and the regulator input voltage is about 33V under load, FWIW.
I threw a scope probe on the supply rail with music playing and saw absolutely nothing that looked like signal. That's doesn't mean much because scopes, especially old digital ones, are pretty low-resolution. But I have a hard time believing the supply is adding anything. You can speculate why a less tightly-regulated supply might sound better. But I have no insight into that, technically speaking.
LOL, what you see in the picture is the whole system. Well, except for the music server. Topping E30 DAC, USB input, driven by Ropieee on a Raspberry Pi 3B. Server is Roon Core running in an Ubuntu VM on my FreeBSD-based (TrueNAS) storage server. I don't bother with ethernet, just use wifi and it seems fine. Headphones are Sennheiser HD560S.
I wanna say, you have to be a gosh-darned fricking computer genius to set up and maintain the software bits of a system like this. Definitely not for the faint of heart or computer-illiterate.
So, not reference-grade equipment by any means, if you believe in all that (which I know you do). But it is what it is. So far I haven't been able to convince myself that dropping five or ten thousand dollars to upgrade my gear would bring me more than incremental improvements. But you never know.
So, I think I'm prepared to write a first evaluation of this amp in its current configuration. The usual caveats about my mid-fi equipment, my sorry ears, lack of audiophile creds, component break-in, and so on, apply. Much of this will echo earlier comments.
I gotta apologize in advance -- this is gonna be a whole bunch of audiophile hooey. But I feel obliged. You have been warned.
First off, this is a very good amp. You could confidently build it and probably be set for life with headphone amps if you're so inclined. On the other hand, I would say the same thing about A1 and A2, though there are differences between them.
The first impression I have of this amp is that it's "polite." By that, I mean you can crank it very loud and it never gets shouty or painful. This is the biggest difference I hear between the A3 and my other amps, including the Topping A30 Pro. With the other amps, upper midrange can sound a little forward. I wouldn't quite call it "congestion" because you can hear through it and still pick out the individual sounds. I want to use the word "intermodulation," but I think I know what that sounds like and it's not what I hear. It's more like the brighter sounds augment one another and it becomes a little overpowering, making you want to turn the volume down. What I don't know is if if this is just faithful reproduction of what's on the recording, and as rendered by my headphones (which have a reputation for being a little bright -- though I do use EQ on them), or if it's something the other amps are adding.
On the other hand, the A3 doesn't sound rolled-off on top or veiled. I won't reference particular tracks. Let's just say that brass instruments have plenty of bite, percussion is percussive, you can hear the rosin on the violin bows, the spit coming out of Ella's mouth -- you know, the audiophile stuff. Somehow, the amplifier manages to tame the top end without apparently losing anything.
It's a subtle tradeoff. I don't know how my particular implementation compares to the production amplifier, but let's assume they are similar. Then, the A3/HPA-1 manages to deliver the goods, but in a way that makes you want to listen to it for extended sessions, and you don't get tired and want to rest your ears. What I don't know is if it's too polite. I'll have to spend more time with it. I'm not sure it matters, but that's my inner skeptic talking.
Bass is solid, but not exceptionally deep, i.e., I don't jump up and down screaming, "This is a bass MONSTER." It's perfectly fine bass, comparable to my other amps. The Topping is my current bass king. It's hard to quantify, but I'd say the Topping has a 10% advantage here.
The A3 has a "warm" tone. I noticed this when I was running it with the HP supply. The Super Regulator has dried it up a good amount. I don't find myself focusing on this aspect of the sound the way I did before. It sounds like the mid bass is just a bit accentuated. This, in turn, fills in the sound a little, and generally it's a pleasant thing.
The spatial/ambient qualities are a little hard to describe. Sometimes, I think it sounds a bit flat with that warm aura, and then all of a sudden a sound will pop out and I think, wow, that's pretty amazing. The amp projects a nice, fat soundstage with good depth. It's just not in-your-face holographic sound. Maybe you could say it's "natural" and "unpretentious."
I don't want to get carried away here and start making stuff up. To summarize, very nice amp, easy to listen to. No audible grain or distortion, never etched or hard. Plenty of detail, but not in a conspicuous way. Fun presentation, holds your attention. Probably a little on the euphonic side, but not obtrusively so.
Final words: Same as my first experiment a couple of weeks ago, the more I listen to this amp, the better it sounds. Is it warming up? Breaking in? Or is my brain adjusting? Does any of this really matter? Anyway, I know I'm not the only one who's surprised this design hasn't gotten more traction in the community. It's not especially hard or expensive to build. I would prefer that everyone builds an A2, so I can be a world-famous audio designer. But the HPA-1/A3 is definitely worth trying. If anyone is interested in the design files, or actual PC boards (I have three more in the closet), let me know.
I gotta apologize in advance -- this is gonna be a whole bunch of audiophile hooey. But I feel obliged. You have been warned.
First off, this is a very good amp. You could confidently build it and probably be set for life with headphone amps if you're so inclined. On the other hand, I would say the same thing about A1 and A2, though there are differences between them.
The first impression I have of this amp is that it's "polite." By that, I mean you can crank it very loud and it never gets shouty or painful. This is the biggest difference I hear between the A3 and my other amps, including the Topping A30 Pro. With the other amps, upper midrange can sound a little forward. I wouldn't quite call it "congestion" because you can hear through it and still pick out the individual sounds. I want to use the word "intermodulation," but I think I know what that sounds like and it's not what I hear. It's more like the brighter sounds augment one another and it becomes a little overpowering, making you want to turn the volume down. What I don't know is if if this is just faithful reproduction of what's on the recording, and as rendered by my headphones (which have a reputation for being a little bright -- though I do use EQ on them), or if it's something the other amps are adding.
On the other hand, the A3 doesn't sound rolled-off on top or veiled. I won't reference particular tracks. Let's just say that brass instruments have plenty of bite, percussion is percussive, you can hear the rosin on the violin bows, the spit coming out of Ella's mouth -- you know, the audiophile stuff. Somehow, the amplifier manages to tame the top end without apparently losing anything.
It's a subtle tradeoff. I don't know how my particular implementation compares to the production amplifier, but let's assume they are similar. Then, the A3/HPA-1 manages to deliver the goods, but in a way that makes you want to listen to it for extended sessions, and you don't get tired and want to rest your ears. What I don't know is if it's too polite. I'll have to spend more time with it. I'm not sure it matters, but that's my inner skeptic talking.
Bass is solid, but not exceptionally deep, i.e., I don't jump up and down screaming, "This is a bass MONSTER." It's perfectly fine bass, comparable to my other amps. The Topping is my current bass king. It's hard to quantify, but I'd say the Topping has a 10% advantage here.
The A3 has a "warm" tone. I noticed this when I was running it with the HP supply. The Super Regulator has dried it up a good amount. I don't find myself focusing on this aspect of the sound the way I did before. It sounds like the mid bass is just a bit accentuated. This, in turn, fills in the sound a little, and generally it's a pleasant thing.
The spatial/ambient qualities are a little hard to describe. Sometimes, I think it sounds a bit flat with that warm aura, and then all of a sudden a sound will pop out and I think, wow, that's pretty amazing. The amp projects a nice, fat soundstage with good depth. It's just not in-your-face holographic sound. Maybe you could say it's "natural" and "unpretentious."
I don't want to get carried away here and start making stuff up. To summarize, very nice amp, easy to listen to. No audible grain or distortion, never etched or hard. Plenty of detail, but not in a conspicuous way. Fun presentation, holds your attention. Probably a little on the euphonic side, but not obtrusively so.
Final words: Same as my first experiment a couple of weeks ago, the more I listen to this amp, the better it sounds. Is it warming up? Breaking in? Or is my brain adjusting? Does any of this really matter? Anyway, I know I'm not the only one who's surprised this design hasn't gotten more traction in the community. It's not especially hard or expensive to build. I would prefer that everyone builds an A2, so I can be a world-famous audio designer. But the HPA-1/A3 is definitely worth trying. If anyone is interested in the design files, or actual PC boards (I have three more in the closet), let me know.
Congratulations! Sounds like another winner and something complementary to your other HPAs. There's a lot to be said for a non-fatiguing amp that engages and encourages a long listening session. Will this amp get it's own enclosure and a place next to the others on the hifi shelf, or are the boards destined for the "completed projects" box? Maybe too early to tell, but this is often the real test of whether it works for you!
What I've been doing is packaging up my Kicad files and Gerbers and putting them on Dropbox so people can download them. This way, there's less chance the boards end up on eBay. I'll do that by tomorrow and send you a PM. I am currently on Kicad 5. I understand Kicad 6 packages component libraries in with the project files to make them more portable. Now that the A3 is working, I need to do the upgrade, which will take some work. If all you want to do is send off the Gerbers to a board house, then you can use the existing ones as-is.
It's worth reading the original HPA-1 thread, though there isn't much detailed build info there: https://www.diyaudio.com/community/threads/pass-hpa-1-what-do-we-know.300060/
Mine isn't the only interpretation of this project, but I would be wiling to help people out who want to try my version.
Jeff's design uses all KSA992/KSA1845 transistors for the BJTs. I switched most of them to BC550/560s. I have no idea what transistors the original HPA-1 uses, aside from the input and output stage FETs. The BC-series transistors are obsolete, but plenty of genuine ones are available on eBay. I bought several hundred of them.
If you want to use the official Pass-style supply, you'll have to roll your own, or wait for my board design which will come eventually.
I would consider starting a separate build thread, since this thread covers a lot of ground. Is anyone interested in that?
I'll probably build a nice chassis for the amp once the Toroidy transformer comes. It's going to be a rack-width enclosure, definitely not something for the executive desktop.
I got going on subjective testing yesterday and wound up confused and unsure of myself like last time. I want to hear this subjective stuff for myself, but it's hard and I don't have a reference-grade system for evaluation. I can't justify plopping down the cash for an exotic DAC and headphones, so people can always say, "The problem is your ancillary equipment."
I tried comparing the A2 and the A3 last night. Depending on your attitude, the difference is either huge, or very subtle. The A2 is a very good amplifier. But so is the Topping. I know some people hate amps like that. The high-feedback amps deliver see-through transparency at the expense of sounding a little over-detailed and sometimes hard on the ears. The A3 holds back slightly but maybe leaves you wanting more. With extended listening, the ears adapt and both amplifiers sound nice.
The A3 probably wants to be more transparent. It seems like a tasteful compromise, but I bet it can be improved.
TBH, you don't need better sound than this to enjoy listening to music. People will draw the line differently, but esoteric sound quality is a niche pursuit. It's like people who are into fine watches, and spend their time examining the hands and dials with loupes. It's interesting, but can make you neurotic. A tiny imperfection you can only see under magnification can either ruin your whole life, or make no difference whatsoever. I want this to stay fun. I don't want to get carried away and lose my objectivity and sense of proportion.
I'm not saying the power supplies won't make a perceptible difference. I just don't have any evidence that the Super Regulator is putting a signal on the rails that affects the sound. It could be that the amp sounds better with a less stiffly-regulated supply. Or, it's quite possible whatever artifacts there may be are invisible to a low-resolution instrument like my scope.
Its possible to measure audio on power rails with an AP. Sometimes something shows up. Of course could also be as Scott Wurcer suggested, that looking at things like distortion residuals after a notch and makeup gain LNA can be give different insights than spectral analysis. For example, a pic of a dac output residual posted by Scott is attached.
Attachments
The regulator has non-zero output impedance so there has to be residual signal on the rails. The residual will depend on the design of the regulator. The question is whether or not it matters to the listener, and I don't know how to tell that from a graph.
Yup. Hey, speaking of killing the fun with better equipment I guess having an APx555 would pretty much ruin the hobby? 🙂
This amp definitely needs at least an hour, preferably two, to "wake up" from a cold start. It sounds unexceptional when cold.
Same thing with my Aragon 8008 that powers the Sound Lab ESLs. Nothing unusual for designs that don't rely on large amounts of negative feedback.
I want to blame my ears, but it's like a switch flips and the lights turn on after two hours. I don't hear this with my other amps.
Edit: According to Nichicon, the lifespan of an electrolytic capacitor running continuously 24 hours a day is like five years.
Edit: According to Nichicon, the lifespan of an electrolytic capacitor running continuously 24 hours a day is like five years.
I'm listening to the A2 right now. I gave it a good warm-up. I think when cold, the A2 is a little too analytical. It's sounding good now and not at all bothering my ears. The warm A3 opens up nicely and creates a bigger soundstage and is a little more dynamic, less controlled. I reserve the right to revise my opinion.