EMI and temperature measurements of several amps

[jmanalo]

[quote]Originally posted by col_s
Also you need to consider that SMPS' can be pretty bad at putting junk onto the mains and (especially cheap ones) are also susceptible to being interfered with by mains noise. I would imagine that in some cases an SMPS and a switching amplifier could also be partners in crime, polluting each other with EMI junk. I guess additional filtering between the DC output of the SMPS and the amp would help.
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My experience on SMPS is a lot better than the transformer. I have two Redrocks SMPS powering four Truepath in one case, included in the same case are the two xo/equalizer (above the four truepath) for the Orion, the system is VERY QUIET. Will be added above the SMPS (same case) is the Buffalo DAC (hopefully this will not give me a problem).
FYI the XO for the Orions have given a lot of owners a problem about the hum and some other noise.

Joe

[V-bro]

[quote]quote:Originally posted by jmanalo

Originally posted by col_s
Also you need to consider that SMPS' can be pretty bad at putting junk onto the mains and (especially cheap ones) are also susceptible to being interfered with by mains noise. I would imagine that in some cases an SMPS and a switching amplifier could also be partners in crime, polluting each other with EMI junk. I guess additional filtering between the DC output of the SMPS and the amp would help.
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My experience on SMPS is lot better that the transformer. I have two Redrock

My experience is they are both very good when they're new, only a transformer is MUCH MUCH MUCH less prone to failure....

------X-max. can be several meters on any driver, too bad it can be done only once...------

[V-bro]

quote:Originally posted by pepolman

I'm running my Amp2 with the IRFP4321s at +/-66V - no problems. I've been running using 5.6 ohm gate resistors with no problems.
I haven't really pushed them hard but so far so good.

BTW the IRFP4321 and the IRFP4228 FETs look to be almost identical in specs.

Indeed VERY identical, one would suspect they are just named differently and the differences are due to tolerance from the other fet/different measurement setup/temperature?

5,6 ohms, yes it will probably make them (and the chip) run extremely cool. At the price of slightly higher distortion...

You could try smaller resistors...But then pay well attention to the chip temperature...

------X-max. can be several meters on any driver, too bad it can be done only once...------

[V-bro]

I just noticed there's no real saying where the peak is as there's no reference to the span of each box. I shall have another go later on with a much narrower band to check where the peak actually is.

It looks like it's somewhere around 600Khz after all....

And I'll see what happens if I add a heatsink...

I shall also hook up some other amps to see how they perform. Like AMP15, as this one uses the ready made fully encapsulated inductors...

And AMP4, AMP6, AMP9, AMP32, AMP11.....

Any other wishes?


------X-max. can be several meters on any driver, too bad it can be done only once...------

[kifysara]

Truepath ofc! Not ready made inductors but still pretty popular ! ;p

The 4228 does have a bit lower Qrr than the 4321 - not sure if it makes any difference though.

[V-bro]

Yes, let's see if this four layer board makes a difference....

The difference between 4228 and 4321 is so minimal that I doubt it's real...

------X-max. can be several meters on any driver, too bad it can be done only once...------

[V-bro]

Ok, some more measurement publishing![}]

I also had an IRAUDAMP7 visiting my desk that was borrowed to me by Abelma. So BIG thanks to him!

I also did some temperature measurements...which were rather revealing. Sorry to say about this specimen of IRAUDAMP7 that it doesn't hold very nice components and runs QUITE HOT. It is well designed and nicely built, although I must say that the solders around the fet pins don't look too good... But I dare not touch it...[:I]

Here are the pics:

IRAUDAMP7:




Here you can see that the design holds many tantal caps which are really poor quality devices. Probably this is done to make it more compact, a bad decision if you ask me...



It runs BLOODY hot, and the worst thing is that it does this around pretty vulnerable parts... I don't think this is a very durable design...



TRUEPATH: (not with original parts, this was the only one I had on the shelve right now...)

All WITH heatsinks:



Without heatsinks: (a remarkable difference indeed!)


As you can see it doesn't run nearly as hot as the IRAUDAMP7! Both have been tested on +/-50Vdc


AMP15: (I didn't have an appropriate heatsink, sorry...)



As you can see here the pre-regulator transistors run pretty hot, even with these little heatsinks. Nothing to worry about though when placed on a big heatsink...

The fets themselves DO run very cool:




AMP7: (this time with heatsink, again a remarkable difference!)


Here you can see that all that EMI isn't as dramatic as it seems, half a meter away it's virtually gone...



AMP4:


With heatsink:

Overall there's hardly any EMI, but there does seem to be a little "hot-spot":

Near the speaker cables it's gone though...


AMP32: (the ready made inductors do seem to do a VERY good job!)


With heatsink:



These were all the amps I had at hand in the past few days, stay tuned for the other amps to be measured!

I sure hope all you guys are enjoying this as it is rather a time consuming hobby to get all this photographed and posted![8D]


------X-max. can be several meters on any driver, too bad it can be done only once...------

[dweekie]

It's interesting to see the same peak on the Truepath and Amp7 but not the Amp15.

That IRS2092 board runs hot! I think it should mentioned that it is a board off ebay instead of a reference iraudamp.

Thanks for the interesting work

[V-bro]

Yes, I think the ready made inductors make a BIG BIG difference in EMI! Although I haven't tried AMP15 with heatsink yet... But AMP32 sure doesn't emit anything!

I sure think this is a poor IRS2092 design, I've seen the reference design uses normal electrolytic caps and the board is somewhat larger which will enhance dissipation. I sure don't think this board will run for many years....

Still I'm afraid it's also not as efficient as the Tripath amps, and I'm speaking of the whole board here. There are a lot of resistors running very hot on the bottom of the board. Also the pre-regulators run VERY hot. After ten minutes the whole board gave that funny smell if you know what I mean

I couldn't get (the above) Truepath to run any hotter than 35 degrees...Only the toroids ran up to 45 degrees after a while, still nothing shocking though... But I'd really have to try the original toroids in that respect.



------X-max. can be several meters on any driver, too bad it can be done only once...------

[V-bro]

I have digged into the matter some more and have discovered there are probably higher emission frequencies possible afterall. So I'm gonna do a very wide band test to see if there's anything more popping up than the below 1,6Mhz area...

Stay tuned....

------X-max. can be several meters on any driver, too bad it can be done only once...------