View Full Version : EMI and temperature measurements of several amps
Hi, I'm doing some EMI measurements on the AMP7 right now.
Now I'm in no way familiar with the procedures that are normally used to do this kind of stuff so if you want to know something in particular or have any hints or guidelines please tell me...:)
I am using a Rhode&Schwarz FS300 spectrum analizer with a 9cm long antenna connected to the input. (I know the formula is roughly (300/f)/4 times 0,8 should give the length of the antenna in meters, but I think this length should pick up EMI well enough if there is any) I have set the center frequency as 800Khz and the band I'm measuring in reaches from 9Khz to 1,6Mhz.
I have tested the amp at idle and with 1Khz tone connected. At idle I get some readings (800Khz) when I place the antenna real close (within 15cm of the board) The board is not shielded at all, just playing openly on my desk. When I move the antenna outside the 15cm radius the signal disappears almost instantly...
Have a look:
The setup:
http://www.snapdrive.net/files/361770/AMP7/SNC10176.JPG
The amp: (with IRFP4228 and all parts chosen by me, the stock version will be somewhat different)
http://www.snapdrive.net/files/361770/AMP7/SNC10181.JPG
Pretty close up (aprox 20cm from the amp, you can see the speaker cable right under the antenna. We may conclude that the output filter works:))
http://www.snapdrive.net/files/361770/AMP7/SNC10177.JPG
With the antenna poking right into the amp: (1cm away from the toroids, here we can see a clear 800Khz peak)
http://www.snapdrive.net/files/361770/AMP7/SNC10179.JPG
With the 1Khz tone at 10cm distance:
http://www.snapdrive.net/files/361770/AMP7/SNC10180.JPG
At 12cm running at idle:
http://www.snapdrive.net/files/361770/AMP7/SNC10178.JPG
I hope you guys find it interesting [^]
Next up is THD measurements...
------X-max. can be several meters on any driver, too bad it can be done only once...------
Yep, it is interesting :)
longitude
12-Mar-09, 03:02
V-bro,
I know you have several other 41hz amps in hand,
I hope you plan to do the same measurements with them too.
I really like to see the result.:D
Hi guys, yes I sure will!
To make some people happy (and try them out myself)I'm planning research on designing aircore inductors that show no (or low) leakage...
Funny detail by the way that big yellow 200W dummyload resistor there on my desk was driven pretty hot while the amp (with IRFP4228) was hardly breaking a sweat (1khz sine wave, aprox 1A current draw per rail but driving just one channel...). The amp was playing without heatsink!
I have used a Fluke IR thermometer gun and measured the fets and chip being 33 degrees celsius for the fets, 40 degrees for the chip. 2,2ohm Rg resistors driving the gates, BYV27-400 discharge diodes.
------X-max. can be several meters on any driver, too bad it can be done only once...------
It's good that there is not much EMI radiated from the board itself, but I wonder if the EMI would increase if you had a heatsink attached, as heatsinks can act like antennas. Also things like chassis and wiring also create antennas. You need two things to create radiated EMI: some noise and an antenna (eg. a wire, a pcb trace, a heatsink).
Thanks Colin, I'll try that!
------X-max. can be several meters on any driver, too bad it can be done only once...------
what's your supply voltage? my very old amp2 can't run for more than a few secs without a heatsink on the fets even when idle. ran it at +/-47V.
Just to let you know my experience with Truepath. I have two Truepath modules and one Redrocks SMPS in on full Aluminum Case (so lots of cables/antennas connected to it). When I switch on the amp my wireless mouse and keyboard loses connection (the cordless access point is just laying next to the amp). I actually have to move the access point very close (about 50cm) to the mouse and keyboard to make it work again. My understanding is that these cordless desktops work in the 2.4 GHz range. Could it be that there is much more EMI radiation in this frequency range? Maybe we should build our amps according to Tripath Application Note AN17 (DOS AND DONTS WHEN DESIGNING FOR EMI COMPLIANCE) to avoid this kind of problems?
Cheers
Ivo
quote:Originally posted by djQUAN
what's your supply voltage? my very old amp2 can't run for more than a few secs without a heatsink on the fets even when idle. ran it at +/-47V.
+/-61Vdc :)
Get some other fets!
quote:Originally posted by ivo
Just to let you know my experience with Truepath. I have two Truepath modules and one Redrocks SMPS in on full Aluminum Case (so lots of cables/antennas connected to it). When I switch on the amp my wireless mouse and keyboard loses connection (the cordless access point is just laying next to the amp). I actually have to move the access point very close (about 50cm) to the mouse and keyboard to make it work again. My understanding is that these cordless desktops work in the 2.4 GHz range. Could it be that there is much more EMI radiation in this frequency range? Maybe we should build our amps according to Tripath Application Note AN17 (DOS AND DONTS WHEN DESIGNING FOR EMI COMPLIANCE) to avoid this kind of problems?
Cheers
Ivo
Like Colin said it's possible for the emission to leave through wires/casing/heatsink... You can perhaps solve this problem very simple...
I don't think there's more EMI from the amp at 2,4Ghz It's possible that there's some other problem....
------X-max. can be several meters on any driver, too bad it can be done only once...------
quote:I don't think there's more EMI from the amp at 2,4Ghz It's possible that there's some other problem....
Well, Im not quite sure. I had another experience with an AMP4. Operated without 240V mains-filter I had some interference on a TV-Set 2 rooms away! So I have to believe that EMI traveled over the power cord to the mains. TV receiver operates between 500 and 800Mhz. So Im pretty sure that these Amps radiate EMI at these high frequencies, but dont ask my why;)
Cheers
ivo
The interference may be triggered at a level my spectrum analizer hardly distinguishes from static...
But it is also very important that you place some ferrite beads on the in/out going cables, keep the distances of cables VERY short and make sure they hit some kind of filtering as quick as possible.
I see many build where enormous wire lengths go unshielded through the case and to the outside world. That's really asking for problems...
------X-max. can be several meters on any driver, too bad it can be done only once...------
Hi,
Nice to see some measurements on this!!
Question is what it "means" in reality and
how it compares to other equipment.
There are some Tripath App notes on the Downloads section
of the support site on this.
Tripath recomended using casings with vent opening
slots no larger than 3x25 mm.
The thick insulator pads used for AMP7/Truepath
have a benefit in that they minimize coupling to
the heat sink.
Using lower gate drive resistor values mean faster
switching, probably more EMI and possibly lower
distortion.
Small caps, 1000pF or so on between connectors
and chassis on speaker cables are a possibility.
The 800kHz are high-ish. You could probably
swap the capacitors on the feedback to a bit higher
values, to lower the idle switching to around 600kHz
which you should get with the nominal 330pF-390pF.
quote:Originally posted by ivo
Well, Im not quite sure. I had another experience with an AMP4. Operated without 240V mains-filter I had some interference on a TV-Set 2 rooms away! So I have to believe that EMI traveled over the power cord to the mains. TV receiver operates between 500 and 800Mhz. So Im pretty sure that these Amps radiate EMI at these high frequencies, but dont ask my why;)
Cheers
ivo
Ivo, I think it is most likely that the interference did travel over the power line, not through air. The frequency of the EMI does not need to be at the RF frequency of the antenna of the interfered device. It's more likely that lower frequency interference entered the device through its power supply and interfered with other circuitry. You're television's display, for example, probably operates below 100Hz.
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.
longitude
13-Mar-09, 03:35
quote:Originally posted by V-bro
quote:Originally posted by ivo
Just to let you know my experience with Truepath. I have two Truepath modules and one Redrocks SMPS in on full Aluminum Case (so lots of cables/antennas connected to it). When I switch on the amp my wireless mouse and keyboard loses connection (the cordless access point is just laying next to the amp). I actually have to move the access point very close (about 50cm) to the mouse and keyboard to make it work again. My understanding is that these cordless desktops work in the 2.4 GHz range. Could it be that there is much more EMI radiation in this frequency range? Maybe we should build our amps according to Tripath Application Note AN17 (DOS AND DONTS WHEN DESIGNING FOR EMI COMPLIANCE) to avoid this kind of problems?
Cheers
Ivo
Like Colin said it's possible for the emission to leave through wires/casing/heatsink... You can perhaps solve this problem very simple...
I don't think there's more EMI from the amp at 2,4Ghz It's possible that there's some other problem....
------X-max. can be several meters on any driver, too bad it can be done only once...------
I have amp4 with Meanwell SMPS and my mouse/keyboard are also at 2.4GHz, never have any problem.
The amp and smps are in metal case.
I have done a MAAAAJOR wireless job for television by creating a talking suitcase, I've posted about this before. It had all kinds of 433/830Mhz and 2,4Ghz equipment and an AMP6 all very near to eachother in the suitcase and I had no problems whatsoever....
------X-max. can be several meters on any driver, too bad it can be done only once...------
quote:Originally posted by V-bro
quote:Originally posted by djQUAN
what's your supply voltage? my very old amp2 can't run for more than a few secs without a heatsink on the fets even when idle. ran it at +/-47V.
+/-61Vdc :)
Get some other fets!
I would if I can find sources. [xx(] it still works quite well though so no need to fix something that isn't broken. [B)]
Mail me your adress, as soon as I've got some IRFP4321 I'll send you a couple...
------X-max. can be several meters on any driver, too bad it can be done only once...------
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.
[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.
---------------------------------------------------------------------
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
quote:Originally posted by 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.
--------------------------------------------------------------------
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...------
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...------
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...------
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.
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...------
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:
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120478k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120479k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120480k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120481k.JPG
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...
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120488k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120490k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120491k.JPG
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...
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120500k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120478k.JPG
TRUEPATH: (not with original parts, this was the only one I had on the shelve right now...)
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120501k.JPG
All WITH heatsinks:
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120502k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120503k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120504k.JPG
Without heatsinks: (a remarkable difference indeed!)
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120505k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120506k.JPG
As you can see it doesn't run nearly as hot as the IRAUDAMP7! Both have been tested on +/-50Vdc
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120507k.JPG
AMP15: (I didn't have an appropriate heatsink, sorry...)
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120511k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120512k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120514k.JPG
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...
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120517k.JPG
The fets themselves DO run very cool:
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120520k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120521k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120522k.JPG
AMP7: (this time with heatsink, again a remarkable difference!)
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120523k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120524k.JPG
Here you can see that all that EMI isn't as dramatic as it seems, half a meter away it's virtually gone...
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120528k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120529k.JPG
AMP4:
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120530k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120531k.JPG
With heatsink:
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120532k.JPG
Overall there's hardly any EMI, but there does seem to be a little "hot-spot":
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120535k.JPG
Near the speaker cables it's gone though...
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120536k.JPG
AMP32: (the ready made inductors do seem to do a VERY good job!)
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120537k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120538k.JPG
With heatsink:
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120539k.JPG
http://www.snapdrive.net/files/361770/EMI%20and%20TEMP%20measurements/P1120542k.JPG
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...------
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 :)
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 :D
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...------
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...------
V-bro,
In my experience on switch-mode power supplies and similar devices (D-class amplifiers), the most problematic frequency range where the EMI really kicks up is between 50 and 200 MHz. I suggest that you measure at least that frequency range. The best way to measure EMI has been to measure the ground noise voltage, since that creates common mode emissions, and are notoriously difficult to get rid of once created. So best way to suppress them is not to create them.
I don't know if you have read my story on the diyaudio already, but here is a quick replay:
I had severe EMI-problems on my TA0104-based Tripath, until I re-designed the board. This is a ground noise comparison between those two designs, older 2-layer one has about 40 dB more EMI-potential than the 4-layer design with one contiguous ground plane next to top layer. Any kind of ground splitting was not used (even recommended by Tripath), because I have seen it causing more trouble than good in more than one instance. Just placing components properly and having ground plane very close to the signal itself yields to good results:
http://koti.mbnet.fi/jahonen/Audio/DIY/Tripath-TA0104/Tripath_TA0104_GroundNoiseComparison.png
The 900 MHz peaks are from local GSM base station. Note also that this measurement was near signal input GND, and in 2-layer design, the grounds were isolated as recommended by Tripath. Still the solid ground plane beats it hands down. The graph was measured by connecting short circuited coaxial cable to the PCB ground. This way, the common mode currents show up as voltage in the coaxial ground resistance. Not that EMI is now very low (I could remove all common mode filtering from the IO), that also improved the audio noise levels considerable.
Regards,
Janne
Very interesting Jahonen! Looks like I gotta do some more measuring indeed!
I will attend to it if there's some more time. I now first have to weld some new panels in my car and repair the brakes before it can pass the annual test.... Cars, man they can sure be money and time consuming!
------X-max. can be several meters on any driver, too bad it can be done only once...------
quote:Originally posted by V-bro
Cars, man they can sure be money and time consuming!
------X-max. can be several meters on any driver, too bad it can be done only once...------
.....unlike audio amplifiers [:p]
***It's so easy, everyone should be doing it***
scott.endler@verizon.net
27-Oct-09, 12:14
Did you see my air core toroids. They still leak a little more than my type 2 cores but are much better than my solenoidal coils which pollute an AM radio up to 20 feet away. They sound fantastic too. Much better than the same wire and value T106-2 core.
.
http://www.41hz.com/Forums/photo_gallery.asp?action=displayimage&photo=610&loc=/gallery/scott.endler@verizon.net/airtoroidextrasmalljpg.jpg
.
I would post the photo here but am new to the board and can't make it work.
Scott
Hi Scott
How much inductance those air core inductors? 11 uH ? I tried something similar and almost that size, but I did not reach the 11uH, maximum 4 uH with one layer ! The size of the air toroid (Not totally air, it is a wood ring!) d=10 mm, Dext= 60 mm , Dint=40 mm.
Abel
scott.endler@verizon.net
28-Oct-09, 04:45
I am testing filters with 6uH on each of the bridged legs. My coils are more like 14mm d *109mm inside circumference. 80mm od and 62 turns. I am also building a cotton faced Litz wire version at 22mm d to try. The solid core version sound really amazing. Great parts in your filter is the key to class AB beating sound from your class D. No solenoidal air cores allowed though. They blast out wicked amounts of EMI that will drown out an AM radio in the next room.
Scott
Scott, I believe the problem with posting the photo is the '@' symbol in your account.
This breaks the html link to the jpg you posted in the photo gallery here:
http://www.41hz.com/Forums/photo_gallery.asp?action=displayimage&photo=610&loc=/gallery/scott.endler-verizon.net/airtoroidextrasmalljpg.jpg
Replace the - with the @ symbol in the link above.
***It's so easy, everyone should be doing it***
Scott
I do like the litz wire better than solid, please try and forward your opinion. I am testing an air core but in solenoidal design, so far, I do not have any issue with EMI. The amplifier is right on the top of the radio tuner and a lcd tv. Not problem in FM listening, but, I did not tried with AM..I will. Also, when I am using my wifi phones, not problem neither. I have to find more time to do more test and post my experience here and on others topics. Rgds
This kind of aircore I've been planning to create a while ago. A toroidal construction to prevent the EMI from leaking too much...
I'm planning to make a pair for a Truepath real soon and compare the emission on the spectrum analizer.
------X-max. can be several meters on any driver, too bad it can be done only once...------
scott.endler@verizon.net
28-Oct-09, 11:09
quote:Originally posted by abelma
Scott
I do like the litz wire better than solid, please try and forward your opinion. I am testing an air core but in solenoidal design, so far, I do not have any issue with EMI. The amplifier is right on the top of the radio tuner and a lcd tv. Not problem in FM listening, but, I did not tried with AM..I will. Also, when I am using my wifi phones, not problem neither. I have to find more time to do more test and post my experience here and on others topics. Rgds
The noise is easy to find. Tune your AM radio to the switching frequency or 2nd or 3rd harmonic. You will hear a thunderous roar from your solenoidal coils. They are narrow band though and low in frequency compared to modern digital equipment so you probably won't get into trouble with the authorities unless one of your neighbors happens to listen to an adjacent station.
Scott
quote:Originally posted by scott.endler@verizon.net
quote:Originally posted by abelma
Scott
I do like the litz wire better than solid, please try and forward your opinion. I am testing an air core but in solenoidal design, so far, I do not have any issue with EMI. The amplifier is right on the top of the radio tuner and a lcd tv. Not problem in FM listening, but, I did not tried with AM..I will. Also, when I am using my wifi phones, not problem neither. I have to find more time to do more test and post my experience here and on others topics. Rgds
The noise is easy to find. Tune your AM radio to the switching frequency or 2nd or 3rd harmonic. You will hear a thunderous roar from your solenoidal coils. They are narrow band though and low in frequency compared to modern digital equipment so you probably won't get into trouble with the authorities unless one of your neighbors happens to listen to an adjacent station.
Scott
My Am radio has a minimum tuning freq of 500 Khz. The filter of the truepath is designed to be a filter of second order of 100 Khz. I dont have now connected the Truepath, but to understand better. The 2nd and 3rd harmonic, where will be situated on the truepath?
scott.endler@verizon.net
28-Oct-09, 21:45
Tune around the switching frequency of 650kHz. Try also around 1300kHz.
Scott
Audiocats
30-Oct-09, 21:23
This is very very interesting!
Scott, how does the toroid-type aircore sound comparing to the spool-type aircore (solenoidal style?)?
(EMI radiation can be shielded in some ways, I suppose)
Not having the pro instruments to measure the Emi, neither the knowledge, I think , tuning the Am radio, it is a good way to test the EMI impact on amps and their modifications.
Thanks for the idea Scott!
Hang in there guys, I have two Truepath boards built up except for the toroids and I have wound two toroidal aircores to try out. Plus I have a Rhode and Schwarz spectrum analizer! :) I shall son set it up for a broad bandwidth emission test (200Khz to 100Mhz?)
I plan on comparing the aircores with the standard cores. And of course do a sound check... Hopefully I can find the time to do it in the next few days...
------X-max. can be several meters on any driver, too bad it can be done only once...------
scott.endler@verizon.net
31-Oct-09, 01:19
quote:Originally posted by Audiocats
This is very very interesting!
Scott, how does the toroid-type aircore sound comparing to the spool-type aircore (solenoidal style?)?
(EMI radiation can be shielded in some ways, I suppose)
The air core toroids actualy sound much better than the solenoidal air cores but are also made of better wire. 14ga. Belden for the toroids, 20ga. wire unwound from a cheap inductor for the solenoid. The air toroids with Dayton foil caps sound amazing. No excuses for being Class D. This amp now has explosive dynamics like I have never heard via a switch mode supply. I also have some 14ga. Litz wire air toroids completed that I should get a chance to listen to this weekend along with the same wire on Ferroxcube cores.
Scott
It's a pity this thread is in the AMP7/AMP15 section, it really belongs somewhere more 'general'...
Anyways I'm planning on winding some aircore inductors as a test for an AMP4. I'm building a batch of AMP4 at the moment so I can make nice comparisons.
For an AMP4 the story is different of course because it is a bridged power stage, but I was thinking it can be solved. And the solution is also a space saving one! :) I am planning on using a dual strand of copper wire and wind a toroidal aircore with it. Then the four ends of wire have to be connected in a way that the signal is generating a field that is magnetically in phase in the 'core'. This is of course not so hard...
Funny thing is that it'll look like a single ended amp with just two toroids, while it'll in fact have four!:)
What do you guys think?
------X-max. can be several meters on any driver, too bad it can be done only once...------
scott.endler@verizon.net
31-Oct-09, 20:25
quote:Originally posted by V-bro
It's a pity this thread is in the AMP7/AMP15 section, it really belongs somewhere more 'general'...
Anyways I'm planning on winding some aircore inductors as a test for an AMP4. I'm building a batch of AMP4 at the moment so I can make nice comparisons.
For an AMP4 the story is different of course because it is a bridged power stage, but I was thinking it can be solved. And the solution is also a space saving one! :) I am planning on using a dual strand of copper wire and wind a toroidal aircore with it. Then the four ends of wire have to be connected in a way that the signal is generating a field that is magnetically in phase in the 'core'. This is of course not so hard...
Funny thing is that it'll look like a single ended amp with just two toroids, while it'll in fact have four!:)
What do you guys think?
------X-max. can be several meters on any driver, too bad it can be done only once...------
I had thought about that too as my amps are bridged/balanced as well but didn't know if it would work. Another benefit would be if the switching wave would be perfectly inverted when the audio outputs are run in from opposite ends to become in phase so as not to cancel. The switching wave would be highly attenuated right there, reducing the requirements of the filter drastically but it might be too much power to magnetically "short" resulting in smoke in the coil or shorting the amp's outputs? Now that I think of it, I'm sure Tripath would have tried it if it could work.
Scott
It will work, believe me. The AMP32 has dual chokes on the outputs as well... Look at the Firenze audio aircore chokes (solenoid though, not toroidal), these use the same trick...
Tripath has stepped past more opportunities to improve than I had first thought....
------X-max. can be several meters on any driver, too bad it can be done only once...------
http://firenzeaudio.50webs.com/tech_dual.htm
------X-max. can be several meters on any driver, too bad it can be done only once...------
Audiocats
31-Oct-09, 23:33
I think the amp32 coke blocks have two individual pot-core inductors in each block, each inductor is independant.
quote:Originally posted by Audiocats
I think the amp32 coke blocks have two individual pot-core inductors in each block, each inductor is independant.
Ok, but still when two signals are fed through two windings on a single core (air, ferrite, iron core...it doesn't matter) in the same magnetic flux phase both signals should be filtered equally to my understanding. The signal to be filtered shows the exact same pattern on the positive and negative output only in counter phase, so of course care should be taken to get them in phase magnetically.
I shall do some experiments on this next week...
------X-max. can be several meters on any driver, too bad it can be done only once...------
scott.endler@verizon.net
01-Nov-09, 01:25
The space saving is one thing but the other question is does the 650kHz switching wave come out balanced between the two legs as the audio does or does it have the same phase on both legs, as this would create another whole set of considerations to the reversed direction, bi-filar coil concept. It should be easy to see which is true on a two channel scope.
Scott
I've got a four channel scope so don't worry about it, I'll make the measurements...
I'm afraid the bifilar concept indeed is not an option due to the massive energy that'll be dissipated in the coil. This would probably become dreadfully hot...
Then the other considerations would probably involve the question what will happen if both switching frequencies are induced in phase? Would we be creating terrible EMI?
------X-max. can be several meters on any driver, too bad it can be done only once...------
Hi Scott
Which material core are You using to wind the "air" core. Plastic? Wood?
thx
quote:Originally posted by Scratchy
Scott, I believe the problem with posting the photo is the '@' symbol in your account.
This breaks the html link to the jpg you posted in the photo gallery here:
http://www.41hz.com/Forums/photo_gallery.asp?action=displayimage&photo=610&loc=/gallery/scott.endler-verizon.net/airtoroidextrasmalljpg.jpg
Replace the - with the @ symbol in the link above.
***It's so easy, everyone should be doing it***
I used a shaft to fit in my drill, then wound around it, applied super glue and glue activator (which makes it rockhard in two seconds) and took it off... No core at all!
------X-max. can be several meters on any driver, too bad it can be done only once...------
scott.endler@verizon.net
04-Nov-09, 19:08
There isn't any core in the finished air toroid. I wind on a wooden dowel and slide the cylindrical coil off and shape it around into a toroid.
Scott
Audiocats
09-Nov-09, 02:54
any updates?
my own Litz vs. solid test done on an amp3(both on ferrite core):
litz gives better micro details, better bass definition (amazing for bass guitar tracks), but the sound is not as "full bodied" as the solid core wires. Solid core also give more bass slam, though it might have something to do with the solid core I use is twice as thick as the litz.
scott.endler@verizon.net
09-Nov-09, 05:01
I was surprised by the sound of my 14ga. litz wire. I expected it to be more transparent and detailed but it wasn't. Slightly opaque. I actually removed it from the Ferroxcube cores where I had used it with the cotton facing removed to see if the solid core would sound better on them as well and it did. There's a photo of the Litz air toroid in the gallery. I can't post links to photos until I can figure out how to change my user name from my email address. The photo of the little Ferroxcube cores is up as well. The Ferroxcubes sound pretty good. More detailed than the T106-2 cores. More detailed than the solid core wound air toroids but not quite as fleshed out and musical. A little edgy. Funny thing about them, you can hear the music playing in the coils! with a dummy load plugged into the speaker connectors. That 14ga Belden wire is so stiff I can hardly bend it around those little cores by yanking as hard as I can, yet, something is vibrating loudly enough to tell which song is playing! Crazy. The air toroids don't even do that and there is nothing holding them steady. I will try potting the Ferroxcubes in hot glue to see if this will tame the micro-phonics and maybe some of the slight edgy tendency. There is also still some leakage of noise and music into my AM radio. The T106-2 cores did it. The Ferroxcube cores do it. The air toroids a bit more. The only cores that were truly devoid of EMI were the little shielded bobbins that came with the amp but sounded not so great. I have also ordered some Coilcraft SER2900 inductors to try next.
.
Scott
Audiocats
12-Nov-09, 08:06
quote:Originally posted by scott.endler@verizon.net
. I actually removed it from the Ferroxcube cores where I had used it with the cotton facing removed to see if the solid core would sound better on them as well and it did.
.
Scott
sorry I am a little confused...the solid on Ferroxcube is actually better than the Litz(without cotton) on the Frroxcube?
Since the solid will vibrate on the Ferroxcube, I assume the litz will too, but the litz is flexible so the vibration is "muffled", do you think that might be the cause of the "opaque-ness"?
scott.endler@verizon.net
12-Nov-09, 13:08
quote:Originally posted by Audiocats
quote:Originally posted by scott.endler@verizon.net
. I actually removed it from the Ferroxcube cores where I had used it with the cotton facing removed to see if the solid core would sound better on them as well and it did.
.
Scott
sorry I am a little confused...the solid on Ferroxcube is actually better than the Litz(without cotton) on the Frroxcube?
Since the solid will vibrate on the Ferroxcube, I assume the litz will too, but the litz is flexible so the vibration is "muffled", do you think that might be the cause of the "opaque-ness"?
The sonic attributes of either wire were consistently prevalent with both winding designs. In the case of the air core toroids and on the Ferroxcube cores, The Litz wire was a little less transparent. Logic and theory filled me with anticipation of the possible advantages as I tracked down a US source for the Litz wire, and even while winding it onto the cores with the cotton facing removed I appreciated the ease of it's flexible construction but in practice I like the sound of the solid wire better. I am actually disappointed, as winding with the Belden 14ga can put a hurting on your fingers. It is very stiff. I am shocked at the amount of audible resonation I hear from the Ferroxcubes considering the hardness of that wire. I have ordered some cheaper solid core wire in 14ga and 18ga to play with and will try potting the Ferroxcubes in hot glue to see if that will tame the microphonics and reduce the slightly aggressive edge to the sound. I wish I could get some of the larger TN26 cores as they are rated for twice the current. I also have received some Coilcraft SER2900 coils to try. Only 4 turns on the 10uH shielded bobbin. They are rated at 28amps for -10% induction and 20A RMS for 20 degree temp rise. I wonder what they will sound like for $3 apiece ready made.
Scott
Audiocats
13-Nov-09, 01:59
Just curious...what brand is that litz wire? is it made by belden also?
scott.endler@verizon.net
13-Nov-09, 02:34
quote:Originally posted by Audiocats
Just curious...what brand is that litz wire? is it made by belden also?
Here is the listing from which I bought the Litz wire.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItemVersion&item=350264672277&view=all&tid=180737879022
Scott
Audiocats
13-Nov-09, 17:33
"item info no longer available"....
scott.endler@verizon.net
13-Nov-09, 19:16
quote:Originally posted by Audiocats
"item info no longer available"....
It was this wire.
http://cgi.ebay.com/50-ft-New-England-Elect-Wire-Type-2-Litz-Wire-AWG-14_W0QQitemZ350267514776QQcmdZViewItemQQptZLH_Defa ultDomain_0?hash=item518d921f98
Scott
Audiocats
14-Nov-09, 06:44
thanks so much Scott, so the industrial strength New England wire is still not clear enough for highend audio....
You have just saved me a bunch money! I was gonna buy some 11~14 awg type-2 litz wire to try some air cores. Now I know the solid is probably a better way to go...
however, I have compared the 41hz Litz (the 1mm equiv. red wire that came with the T106 cores) and 0.5mm solid on my Amp3 test rig; the 1mm Litz is made up of 15x 30awg magnet wires, it gives a wider sound stage, and is expressing details more clearly than the 0.5mm (24awg) solid. Maybe the individual wire size should not be smaller than a certain gauge, for T amp application?
scott.endler@verizon.net
14-Nov-09, 14:17
quote:Originally posted by Audiocats
thanks so much Scott, so the industrial strength New England wire is still not clear enough for highend audio....
You have just saved me a bunch money! I was gonna buy some 11~14 awg type-2 litz wire to try some air cores. Now I know the solid is probably a better way to go...
however, I have compared the 41hz Litz (the 1mm equiv. red wire that came with the T106 cores) and 0.5mm solid on my Amp3 test rig; the 1mm Litz is made up of 15x 30awg magnet wires, it gives a wider sound stage, and is expressing details more clearly than the 0.5mm (24awg) solid. Maybe the individual wire size should not be smaller than a certain gauge, for T amp application?
The wire I have is made up from 40ga strands so that is one difference to what 41Hz uses. A much bigger improvement would be the Ferroxcube cores If you could get any of those.
Scott
Hi Scott,
Just saw your post at diyaudio.com. Great title for a fine subject. I'll cross-post it here if you don't mind: http://www.diyaudio.com/forums/class-d/143669-sure-electronics-new-tripath-board-tc2000-tp2050-80.html#post1997912
Guys, have a look!
scott.endler@verizon.net
01-Dec-09, 19:14
Yeah. The new cylindrical air cores seem to be acceptably quiet regarding emissions and will make a huge improvement in any class D amp.
Scott
A quick question, you're at around 7.5 uH ... in an amp where the stock coils are around what value? 11 uH?
scott.endler@verizon.net
01-Dec-09, 20:40
Tripath used 12uH. Sure had a different filter that came with tiny 22uH shielded bobbins. I am using 7.5uH with a pair of .47uf shunts and a .22uf differential cap.
Scott
I like the way your experiments lack any kind of scientific approach, actually many break-through ideas have been created this way! Somehow you can spend a million years to try to theoreticize whatever will happen, but like taking the wrong turn just one meter away from the right one in practise may make you end up miles off. This is what often happens when you discard the unforeseen factor in calculations.
I'm not implying that calculation and theory are useless, but the real test in the pudding is in the tasting...
That said I have had a response earlier on in this thread which I found rather interesting. The one from Jahonen on page two. I still have to attend to doing some broadband EMI measuring. Just testing what happens in the AM band according to his experience would not be enough...
Then some inband measurements of the output response would also be quite interesting with the air cores...
I already have a pair of aircores ready for the test, but I just lack the time to perform them...
------For first power-up testing don't have the large power supply caps installed yet!!!------
Powered by vBulletin® Version 4.2.0 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.