Sorry, but you are either trolling or clueless. I have speakers with a nearly 100Db sensitivity and a Purifi based amplifier - no hiss at all even if I put my ear as close as possible to the drivers.
-
WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!
Noisy Purifi amplifiers
- Thread starter vco1
- Start date
Sorry, but you are either trolling or clueless. I have speakers with a nearly 100Db sensitivity and a Purifi based amplifier - no hiss at all even if I put my ear as close as possible to the drivers.
When I looked at the build I could not believe they had the mains run so close to the amplifier module. What were they thinking.
That's a shortcut to knowledge.
So this is how they look inside. Don't know how to try to improve them.
AUDIOPHONICS MPA-M400ET Mono Class D Amplifier Purifi 1x400W 4 Ohm - Audiophonics
Class D mono power amplifier based on a PURIFI 1ET400A module and a HYPEX SMPS600A400 power supply.www.audiophonics.fr
View attachment 160349
I would start by rerouting the thick cable bundle going first "north" (in the picture") then west, and replacing the mains cable with a shielded one.
Technology has progressed. Assembly can stil be poor.
That's middle of the road sensitive, they shouldn't be overly prone to amp noise?
This one is the cheapest assembled stereo Purifi around, AFAIK.
Would be curious to see true measurements of it.
ta240
Major Contributor
- Joined
- Nov 7, 2019
- Messages
- 1,511
- Likes
- 3,009
And obviously not audible from your normal listening position...
Your going-down a "rabbit hole" trying to reduce noise that you can't (normally) hear. But of course, less efficient speakers would help.
......
Isn't a lot of what is discussed here the journey down that rabbit hole of looking to reduce things that already are at levels that they can't be heard at all, let alone 'normally'?
- Joined
- Aug 14, 2018
- Messages
- 2,827
- Likes
- 8,340
My guess would be the internal cable routing, but that's just a guess. I have the stereo version of the Audiophonics amp - the HPA-400whatever model. It has audible low-level hum from one channel - but only when there are no inputs connected to the amp. With an input connected I have to put my ear within 2-3 inches of the speaker to hear anything, and even then I have to focus in order to consistently hear it.
The amp is so quiet that it has spoiled me for noise: as soon as I turn on the components connected to the amp, I can hear their self-noise through the speakers (although that too is inaudible from a foot away).
When I first got the Audiophonics amp, it was the first time I was able to clearly distinguish the noise floor of my amp from that of my source components, and with the noise floor lowered so much I was surprised to discover that there was some difference in the noise level depending on which plug/outlet I used for my various different components. Swapping them around among the wall plug, a power strip, and my DC blocker's plugs produced different combinations of improvement or deterioration in hiss and hum (though all of it was low-level and the differences I would guess were in the 3dB or less range).
My Purifi-based NAD C298 is as silent as the grave.
Sometimes noise is a weird thing with these amplifiers. As tmtomh has said, these modules can be so transparent that one actually hears the self noise of the upstream stuff. Example: before building my Purifi/Neurochrome based amp, I had Apollon Audio monoblocks. I tried both Sonic Imagery and Sparkos discrete opamps in the buffers and with the latter I could hear some extremely faint crackle from the speakers, and only when certain equipment was active at home. Not with the Sonic Imagery. So the NC500 modules allowed one to listen the ability of these opamps to reject power supply or EMI/RF noise (and with very sensitive speakers in very close proximity only). My current build has proper distancing between mains, SMPS and linear supplies on one side, and audio circuitry. Dead as a grave, to quote MaxBuck.
D
Deleted member 27948
Guest
The feedback in self-oscillating Class D is deep - nevertheless, any first order of astatism feedback loop takes a derivative of distortions thus the hiss is essential. Its level / audibility is a separate issue. The hearing abilities of people are different. If you don't hear anything ... alas, it only means that YOU don't hear anything.
Are you talking about the 500khz (or 600khz, whatever) oscillation? Yes it is there. Can you hear that? Good for you, but I have my doubts. Can it intermodulate with the signal? Yes of course. Can the results further intermodulate through the feedback loop? Yes. What will be the resulting noise level?
Of course I can only hear what is in the audio range and with a driver that has a sensitivity of 108db/w/m, but with the ear glued. Just 1W at that distance would probably perforate my drum.
But you do not have to trust me. Look at the noise level in the audible range. The module alone has an output noise of 11.5μV (A weighted). I have no idea how sensitive must be a driver to make that audible, but I can tell you I doubt it can be built….
Bob from Florida
Major Contributor
- Joined
- Aug 20, 2020
- Messages
- 1,331
- Likes
- 1,230
Two choices. Live with it or get different amps. I would return them and get something different. If you ever get more efficient speakers it will get worse.
maty
Major Contributor
AUDIOPHONICS MPA-M400ET Mono Class D Amplifier Purifi 1x400W 4 Ohm - Audiophonics
Class D mono power amplifier based on a PURIFI 1ET400A module and a HYPEX SMPS600A400 power supply.
Poor cables placement and implementation -> noise
Excellent
So - trigger input routed directly over and in contact with the SMPS flyback transformer, then over the amplifier module. AND the PSU wiring routed directly over and in contact with the output filter inductor and capacitors.
Not exactly optimal.
Not exactly optimal.
What brand/model of Purifi amp do you have? Whoops-didn't read far enough. Sorry you're hearing hiss-my VTV, even when the Freya+ is full volume w/ no program material playing is dead silent when my ear is 2-3 inches away from the tweeter on the F208's.
Hello,
I have some NC400 amps and with my horn (high efficiency) speakers there is no noise at all at one foot from the speakers. Really have to wonder at some who buy from suppliers who cram power supply and amps into the smallest box possible, with terrible routing of the wiring and then complain that things aren't perfect and badmouth all of class D.
A larger box lets you separate things, route the wiring much better and keeps things cooler as well. Saving a couple of bucks going for the smallest box possible is just silly at best. IHMO. When done perfectly, it may work, but much tougher to get right.
There are good and bad implementations of pretty much any amp design on the planet.
Greg
I have some NC400 amps and with my horn (high efficiency) speakers there is no noise at all at one foot from the speakers. Really have to wonder at some who buy from suppliers who cram power supply and amps into the smallest box possible, with terrible routing of the wiring and then complain that things aren't perfect and badmouth all of class D.
A larger box lets you separate things, route the wiring much better and keeps things cooler as well. Saving a couple of bucks going for the smallest box possible is just silly at best. IHMO. When done perfectly, it may work, but much tougher to get right.
There are good and bad implementations of pretty much any amp design on the planet.
Greg
Bravo for using an obscure general engineering term to explain linear feedback but completely ignoring the level/audibility of hiss, which is the subject!
A good example on how to derail a thread.
Similar threads
