Wow! I can't believe this. I take a 3 hour drive and then walk my dog, and come back to see all this! This is the most action any of my threads have ever gotten. And I missed it! That's the good news. The bad news is that it was hijacked by a band of marauding Steps aficionados. And then, just as I geT to page two.... the forum goes down. How does it all end? And then I fall asleep after I write this into notepad and my laptop won't wake up and I have to slam it down. Ah... but I saved the note pad file before I fell asleep. Gotcha Dell!
Seriously, though, don't worry about the hijack because this is an interesting subject and I think I'm all alone in the wilderness on the brick idea. Except that one guy that posted those images that got me started on that....
A couple things since my name kept popping up. I did test my Millet with a Steps and a Tread and they did measure (in RMAA) identically. My Tread is in a brick but fed by a wall wart so it was very isolated from the amp. The Steps had the standard Amveco toroidal (24V/25KVA) and was in it's own Hammond case. It has upgraded MUR820 rectifiers and an LM338 regulator. It would be capable of some serious power output if the reg were bolted to a boat anchor.
RMAA basically runs a most likely not very stressful set of signals through the amp, looking for noise, channel separation, THD and IMD. By not very stressful, I mean that it probably does not push the amp very hard. I don't think their methodology is well documented but I have listened to the test signals in my headphones- it is a very modest signal level. That tells me that the Tread is very adequate at basic noise rejection. It does not tell me what the more limited cap reservoir is or is not capable of, or any of the other upgraded parts such as the discrete diode bridge. When you consider the PSU caps, you also have to consider that some amps have so much on board reservoir capacity that the PSU probably doesn't need any at all beyond what is required to smooth the ripple enough to make the regulator happy. Some people put so much capacitance in their amps that they blow up their PSUs just firing the amp up.
One thing that I did play with (extensively) was power supply placement. Here I used my M3, which is my inherently quietest amp. It is really quiet- like -100db noise. See AMB's RMAA results- mine were very similar although he edged me out on most of his measurements. I found that placing my Steps (encased in a Hammond) directly side by side with the M3 (also encased in it's own larger Hammond) added a fairly significant set of bumps (60Hz and harmonics) to the RMAA noise graph and it did affect the overall noise score. Moving it about a foot or two away cleared that up.
I did further testing with my Tread and my portable Pimeta (because the Pimeta is in a Serpac H65 and therefore totally unshielded and exposed, same with the Tread in a plastic project box). I laid the Tread directly on top of the Pimeta (and vice versa) and side by side. The transformer wart was several feet away. I was not able to adversely affect the RMAA noise results by any position of the Tread and Pimeta, and from that I concluded that the Tread board itself does not emanate any measurable noise. When I laid the wart on the Pimeta, the numbers went into the crapper, of course.
Sometime later I made a statement in a thread to the affect that I would never put a Steps in the same case as an amp. I got a little heat for that statement and in some contexts it might have been deserved. At the time I was thinking about my M3, which has such spectacular test numbers. My thinking was... why go to all the effort and expense to build an amp with such fantastic measurable specs, and then stick a trannie next to it and add big 60 Hz (and harmonic) humps to it's noise charts? The fact that I personally never heard any noise from the Steps when it was kissing the M3 had nothing to do with it. It is a philosophical thing with me. I see guys extolling the virtues of their $20/ft pure silver wire (whose benefits cannot be measured as far as I know); that is not my thing, but something that is clearly measurable is of great interest to me. Beyond that, half the fun of building an M3 is to see if AMB really made up all those numbers and RMAA charts out of thin air
Ssshhhh.... (whispering) I put my Steps on top of my M3 whenever desk space is tight. I have never heard any of the noise that RMAA is showing me. I just wouldn't imprison it next to my M3. Make sense? Function over form.
One thing to add here: it was pointed out to me that my tests of the Steps/M3 were using aluminum (from the cases) as shielding. An integrated amp/psu would normally have a steel plate shielding the psu (if it's done right). Therefore, my test results might not agree with tests done on well built integrated amp/psu with a steel shield plate. Most of the images I have seen here of integrated units, WERE NOT shielded, though. Something to consider if you are designing such an amp.
Maybe that will help vixr with his question.
Nate: you have piqued my interest enough that I am going to play with my Millet and compare PSU's again. Even better, the M3, assuming it doesn't shut down the Tread regulator. It would be easier, by the way, to remove capacitance from the Steps and compare to a Tread, rather than try to rig up some sort of air wired bank on the Tread. Some people think monolithic bridges sound bad and discretes sound better. Personally I don't buy that because any difference is noise (correct me if I am wrong here - do wimpy little monolithic bridges suffer from voltage or current sag when they are pushed dynamically?). See also Tangent's test results using his LNMP hi gain amp. His noise level tests of a Steps and Tread are virtually identical. If there is a difference in the sound quality, I don't think it is noise related.
The reason I asked Nate about the blind testing is that when I look at my Steps in it's nice 6.3x4x2 Hammond case, with it's relatively big cooling tower on the reg, and then look at my wimpy little Tread in it's plastic RatShack make believe brick, I have a hard time believing the Tread can keep up with the Steps. It's a psychological thing that has nothing to do with objective numbers. I would LOVE to see some serious blind testing.
Clutz: Good points; I am going to address some of these in another post.
Regards,
Neil
