Newbee build: PA03 amp (LM4780)

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It took me some time to hook the PA03 to my main stereo set because I had no earthed wall socket near my audio set. It's fixed now but it was a hell of a job to thread the earth wire through the existing pipes in the wall.
In my previous contribution I told you something about my first and favorable listening impressions using the PA03 in my spare audio set in the loft room. But for me a more daunting test was to hook it up to my main audio system.

For years and years I had it all. You name it, tape and cassette recorder, record player, cd player, tuner, pre and power amp. Then in the upcoming tide of streaming audio I decided that perhaps less could be more and almost overnight I changed my set drastically.

Now it's consists of:
- Synology NAS with Flac files running LMS (Logitech Media Server);
- wired network connection;
- PC Engines Alix 3d2 system board running Voyage linux with Squeezelite, a headless player for LMS;
- ODAC by NwAvGuy;
- Power amp Pioneer M-73 a 21 kg Japanese beast. Switchable between class A/AB operation (25W/125W);
- Music and volume control by the Ipeng app on IOS;
- Quad 2805 electrostatic speakers.

My power amp is the reason why I decided to build another one. It is a very well built amp in Japanese Urushi style from the early nineties. But for some time now I am no longer at ease with its musical presentation. What's more, given its age it is probably time for a full recap and I have decided I won't do that.

Okay to make a long story short I have listened carefully to this amp and have collected some impressions I like to share with you. It's nothing scientific, no ABX test, no double blinds so take my observations with a grain of salt, better still take a handful. :)

The other day when I had the house to myself I moved my chair in the sweet spot of my beloved Quads and listened to several songs. A piece of paper with me to take some notes. The files I played were mostly in hires formats.

My listening took place at low to moderate sound levels. In general I found this amp having a smooth velvety sound character without being deficient in the presentation of mid and high frequencies. I think some people would associate its sound with valve based audio amplifiers. Bass seems tight and well controlled. In the midrange where the Quads are very sensitive the PA03 is clean and without apparent distortion. Despite the smoothness there were a few tracks where I had doubts about (some excess ??) brightness. Could well be recording related !! Sound stage was very well defined stretching from left to right and with a lot of depth information.

For instance the 1992 version of The Rythm Divine by Yello and Shirley Bassey. I was impressed by the way her strong voice stood out, powerful and crystal clear.
Then Diana Krall with Baby Baby All The Time (24 bits). Her vocal cords almost touchable. Piano sounding very delicate and refined.
Donald Fagen's Maxine (1982) in 24 bits flac, vocals prominent, razor sharp with a nice bite, very clean sounding.
Then an oldie, Summertime from Porky and Bess by Ella Fitzgerald and Louis Armstrong (24 bits). Louis' trumpet has a nice sting and the vocals are very convincing.
I listened for hours on end. Outside it was stormy and inside I enjoyed this diminutive amp very much.
Another one Stan Getz and Charly Bird with Samba Triste a recording made in 1962. Despite the age of the recording I am able to hear the airstream in Stan Getz' saxophone and I almost hear the moist in the mouthpiece. Very relaxing presentation.

Is this an amp for everyone ? If you are used to ear-shattering levels in big rooms with inefficient speakers it is not for you. But I think that for a lot of people this amp could well be the last amp they ever want and given its quality and relatively low build cost it is a very rewarding and fun thing to build.
 
Hi clog,

Nice review and assessment of your experience with the PA03. Until I built my PA03, I didn't hear much basic difference in most amps. Perhaps I 'haven't 'arrived' at that ultimate audiophile nirvana of having every component in my chain able to flawlessly recreate the illusion of a recording - be it studio or live.

That was UNTIL my PA03! I instantly heard a BIG difference in sound from the PA03. It was more than sublte. It's hard to properly articulate other than simply the 'presence' and utter 'aliveness' of the sound. I felt as if a veil had been lifted and the music sprang forth with more life. My real test came from recordings using acoustic instruments rather than ones produced electronically. For some reason I always hear a slight harshness with electronicly produced music. Not so with acoustic. One exception may be the pop recording of Adele and her recent 25 CD. A pure joy to listen to. Very easy on the ears. That is a very well produced and engineered CD.

The one thing I still want to do is add a subwoofer to my stereo test rig. This for sure will add a dramatic impact of bass information while still allowing the mids and highs to flow effortlessly to my ears with a smooth presentation.

For now, this is my amp of choice and the one that has earned a permanent spot in my test rig at the moment while I experiment with other gear, DACs and subs. I'm glad your experience has been a positive one with the PA03. I'm seriously thinking of building another one for a yet-to-be-put- together system in our living room that will be using some vintage HPM-100 speakers. :)

Rick
 
The main attraction of the "ultimate audiophile nirvana" is that you'll never reach it. :):)
I see that you share my opinion of the PA03. At the same time I'm still wondering if my extremely positive opinion of this amp isn't some kind of expectation bias. You know: lots of work on your own build then perhaps your brain is fooling you into believing that your creation is the ultimate in hifi. Basic psychology. On the other hand yesterday my brother came over to listen to this amp. We listened to the hires version of "Within" a track of the latest Daft Punk album. I tell you I never heard my set performing the way it did.

Btw This satisfying result made me curious about thomchr's modulus86 and parallel86.
On a dutch diyaudio site they just completed the design of a comparable composite amp based on the LM3886.
 
Hi all

After following this thread and seeing the nice builds here I got the courage to order the PA03 today as I'm a total beginner in this area. So as this is my first post ever on this forum and it will be my first amp build I felt I had to leave a comment :).

Next step is to get a multimeter, soldering station and the components once I get the BOM from Per-Anders. Can't wait to get started!
 
The PA03 is just a chipamp that is properly implemented. That makes the build fairly straight forward, if you follow the instructions. What you don't understand, ask rather than guess.

With a good PCB and normal commercial quality components it will work very well.
You don't need any "special" components.
Don't spend a lot of money on an expensive DMM. Buy a cheap one that reads down to 200mVac full scale reading. It allows a resolution of 0.1mVac and is plenty good enough to get you started.
After you have learned how to use that and what it's limitations are, you can decide what instrumentation you need to add to your arsenal.

But 63/37 eutectic solder. don't buy 60/40 and especially don't buy lead free.

After a while you may decide to buy a different leaded eutectic.
63/36 plus 1% copper (Multicore "Savbit") or plus 1% silver are both good and all three have their place on your workbench. There is also 62/36/2% copper

I don't have 1%/2% copper, but I do have 1% silver, but it rarely gets used. It's more an ornament on the shelf.
 
siha, If you look at my first post you'll notice I'm a beginner too but with some help here I managed to get it done. Listen to the experts here like AndrewT !! Check every component, check every step you take and check it again. Read the posts in this thread because you might find something useful for your build. And I tell you, this amp is going to amaze you.
 
Thank you guys for your answers.

But 63/37 eutectic solder. don't buy 60/40 and especially don't buy lead free.

How critical is it to use 63/37 eutectic solder? I've found it's difficult to find that one in regular shops (at least in Sweden). However, Mouser has it but it's not that cheap.

One thing that gets me confused right now is the different configuration modes that are described in sjostromaudio.com for this amplifier. I don't know what mode (Balanced, non-inverted and inverted) I should go with. When to use what, why and what are the advantages and disadvantages?
@clog: What mode did you use and why?

Regards
Siha
 
@clog: What mode did you use and why?
If you bought one board the non-inverted mode is recommended for the signal input of the PA03 as a stereo power amplifier. That is what I did.
If you bought more than one board you can bridge them. To connect for bridged mode one of the channels goes in non-inverting mode and the other in inverting mode.
The jumpering of the board is a little bit confusing. Carefully read the Build Guide, PerAnders website and the schematic. It took me some time to come to grips with the subject.
 
Ok here´s a few from me. Hope it´s ok to put them in your thread:)
To my build i choose a standing heatsink, have one more kit to build and my intentions is to build my own chassis as slim as possible and have to monos.
Maybe i can mill down the heatsinks from todays 15cm to 10cm so i can have even smaller chassis!? The heatsink after a few hours is barely warm and the heatsink now is maybe little oversized:)
 

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Why not, good tip! You think it´s enough to cool the 4780 and the 2 regs with only 7,5 cm high heatsink? Maybe it´s easy to calculate?
look up the 3886 datasheet.
It shows how to predict the heatsink size required to allow the chipamp to operate at a maximum of 150°C
I recommend you double their heatsink size to allow all normal music and audio operation at very much lower temperatures.

eg if the datasheet says to use 3.0C/W then use 1.5C/W for one channel.
For two channels I would then use a 0.75C/W.

But a 4780 is two channels on a single heatsink interface. It needs a bit more cooling because of the interface area limitation.
Try the basic quadrupling (doubling for reduced temp and doubling for two channels) and see how your 74mm high heatsink compares.