Hello Plott,
I think that behaviour you describe isn't very unususal after turn-off. The M2X has the auto-bias in the outputstage.
I have the experience with complementary outputstages, that after switch off the two halves of the circuit (n-channel and
p-channel side) do not 'deload' in the same time. This is in my opinion why you see that large offset. I think, this is nothing
I would be afraid about.
I have this behaviour in most/all of my preamps and poweramps - during turn-off..
Most important is , that after turn on, your DC-offset at poweramp-speaker-output will stabilize anywhere below 50mV.
Below 10mV is better - but not strictly necessary. And those heavy-weight-classA-amps need some time to warm up
heavy aluminum-heatsinks...
And you have a speaker-protection installed. Nothing bad should happen. Although there are critical persons out there,
which will say. hopefully the relays in the protection circuit will be fast enough...
Cheers
Dirk
I think that behaviour you describe isn't very unususal after turn-off. The M2X has the auto-bias in the outputstage.
I have the experience with complementary outputstages, that after switch off the two halves of the circuit (n-channel and
p-channel side) do not 'deload' in the same time. This is in my opinion why you see that large offset. I think, this is nothing
I would be afraid about.
I have this behaviour in most/all of my preamps and poweramps - during turn-off..
Most important is , that after turn on, your DC-offset at poweramp-speaker-output will stabilize anywhere below 50mV.
Below 10mV is better - but not strictly necessary. And those heavy-weight-classA-amps need some time to warm up
heavy aluminum-heatsinks...
And you have a speaker-protection installed. Nothing bad should happen. Although there are critical persons out there,
which will say. hopefully the relays in the protection circuit will be fast enough...
Cheers
Dirk
to be honest, I don't know that I have checked this happening. I have speaker protection on my build so it takes 3-4 seconds to active on turn-on and disconnects the speakers immediately on turn-off. I would think that is an odd behavior, especially since the other channel operates differently.Nobody?
I will add that I have never had a "false" protection activation, either on start-up or shut down. So if you are getting high DC at start-up too, that does not sound normal to me.
Ho hum.
I'm seeking thoughts about dealing with the hum in my M2X, which is significant enough to be heard from the listening position, and is present in both channels.
Background and configuration:
I've swapped boards from side to side, twisted every wire, swapped the Ishikawa input buffer boards side to side, moved wires with an insulated stick, doublechecked my soldering (I'm getting really good!), put output ground to PSU ground instead of amp board ground, turned off other computers, monitors, LED lights, equipment, run it all off of an isolation transformer (the ultimate two-prong adaptor!), made a copper-foil tape isolation cover out of card-stock and two layers based on Pferrel's post here , spun around three times while clucking like a chicken, moved the major PSU components around in many layouts, etc.
None of these have had an effect. I really expected the Antek transformer shield and the foil cover to make a difference, but not in the least. In short, I've run out of things to try and am looking for inspiration. I have read through this and another multipage thread (which I now cannot find, of course) and have read through the hifisonix presentation on the hum topic.
My M2X just hums. I love the sound of the M2X, but the hum is so present. I want to get it gone. Thoughts?
Edited to add: Yes, I know the input RCAs are on the opposite side of the back panel and that they are floating. When testing, they are shorted and moving them around has no effect on the hum. I've also shorted them to chassis ground, to each other. sigh
I'm seeking thoughts about dealing with the hum in my M2X, which is significant enough to be heard from the listening position, and is present in both channels.
Background and configuration:
- M2x with Ishikawa front end boards
- 4U300 chassis (I had in 5U400, with less, but still quite audible, hum and want that 5U for something else
- This 4U chassis kept the full PSU, bridges, trafo, etc. from the (no hum! silent!) F4; I basically just swapped in the M2X amp boards
- On the 5U chassis, the DC offset would swing 30-40 mV even fully warmed up. In the 4U, is stays within a couple of mV when warm. Weird.
- Antek 4218, shielded with Antek case (see picture)
- Star chassis ground:
- transformer
- mains
- PSU lifted by a CL-60 ICL thermistor
- Twisty, twisty, twisty wires
- Have monolithic diode bridges and the DIY universal PSU
- Shielded RCA cables on input
I've swapped boards from side to side, twisted every wire, swapped the Ishikawa input buffer boards side to side, moved wires with an insulated stick, doublechecked my soldering (I'm getting really good!), put output ground to PSU ground instead of amp board ground, turned off other computers, monitors, LED lights, equipment, run it all off of an isolation transformer (the ultimate two-prong adaptor!), made a copper-foil tape isolation cover out of card-stock and two layers based on Pferrel's post here , spun around three times while clucking like a chicken, moved the major PSU components around in many layouts, etc.
None of these have had an effect. I really expected the Antek transformer shield and the foil cover to make a difference, but not in the least. In short, I've run out of things to try and am looking for inspiration. I have read through this and another multipage thread (which I now cannot find, of course) and have read through the hifisonix presentation on the hum topic.
My M2X just hums. I love the sound of the M2X, but the hum is so present. I want to get it gone. Thoughts?
Edited to add: Yes, I know the input RCAs are on the opposite side of the back panel and that they are floating. When testing, they are shorted and moving them around has no effect on the hum. I've also shorted them to chassis ground, to each other. sigh
Attachments
I haven't messed with the M2X but I suspect that the Edcor is just very sensitive to "B" field (magnetic) flux line interference. A little bit of thin metal, braid, or foil on something might help in situations with an EM wave that is "E" field in nature, but that's not going to help with magnetic flux in close proximity. I would want lots and lots of distance between the two transformers (Edcor and Antek) in an amp like that to start with, and that chassis is just awfully tight on space...
Thanks; yes, it takes 3-4 seconds for turn on and the speakers will be separated immediately after turn off, so that's fine.
I also made measurements in both channels at many places and the values were almost identical, so no issues with the boards detected. That's why I think it was a one-time voltage swing above the sensitivity of the protection
Hi Plott,
Beautiful amp you have there!
Granted that my M2X is in a 5U chassis, I do not have (knock on wood) issues with hum even if the Edcor on both channels has no shield. I believe you have enough space that it will not require a shield also.
In your case, may I suggest to try the following:
Beautiful amp you have there!
Granted that my M2X is in a 5U chassis, I do not have (knock on wood) issues with hum even if the Edcor on both channels has no shield. I believe you have enough space that it will not require a shield also.
In your case, may I suggest to try the following:
- Try connecting the speaker output Negative directly to the GND of the PSU Out rather than going back to the board. Example is the pic below of my AlephJ. Yes, the LED indicating + is Green unlike conventional Red.
- If you can rotate the PSU board 180 degrees so that the DC out wires runs to the floor of the case rather than above, close to the PSU filter caps (very noisy).
- Move the AC line connector block further down towards the back plate of the case, thus, creating distance away from the input transformer. Relocate the IEC GND connection to the chassis as close to the entry point as possible (now, behind the AC power block) then connect the ICL from here. I would rather have long GND wire from PSU to star ground than long IEC power wires (Neutral and Hot) running along the chassis.
- After doing #3, re-route the speaker wire of the R channel (closest to the AC block) to the edge closer to the back plate, then straight going towards the front, then up to the + (Red) speaker terminal. Remember, the Black (-) is now connected directly to DC PSU Ground.
- Also, try to get some distance between the two rectifiers if possible. Move the L channel (facing the amp) further back about 2-3 inches, then the R channel, aligned to the L, to the opposite side of the transformer making the AC out lines pair (from trafo, Blue and Green) separated from each other tuck neatly at the side of the transformer.
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@amandarae I think your reply to Plott was more to me. Plott's chasing down a turn on/off DC out spike, and I'm chasing hum.
That said, this is very helpful advice and I will incorporate many of the ideas over the coming days.
I am also going back to school with HiFiSonix's treatise on preventing hum and noise, here. Even a little more understanding on my part will help guide my quest.
I just remembered that I have, buried somewhere in a closet, a +/- 24v power supply. If it can supply enough current (and if I can find it), it might be a great A/B test, bypassing the transformer-based PSU in the amp right now, probably revealing that it is the Antek's EMF leakage being picked up by the amp boards (and most likely the Edcors).
That said, this is very helpful advice and I will incorporate many of the ideas over the coming days.
I am also going back to school with HiFiSonix's treatise on preventing hum and noise, here. Even a little more understanding on my part will help guide my quest.
I just remembered that I have, buried somewhere in a closet, a +/- 24v power supply. If it can supply enough current (and if I can find it), it might be a great A/B test, bypassing the transformer-based PSU in the amp right now, probably revealing that it is the Antek's EMF leakage being picked up by the amp boards (and most likely the Edcors).
Hi @amandarae many thanks, my problem is not the hum have some DC offset issues, maybe.
have some DC offset issues, maybe.
I stand corrected! Yes, I am referring to Toadroller's post regarding hum.
Toadroller, yes, I know about that article (read it many times) and that's why I suggested moving connections, minimizing and separating wires to decrease the loop area. For example, in your case, the IEC power lines supplying the power transformer and the AC line to the main transformer. Moving the the AC block will eliminate the loop created by those wires.
good luck and hope you will resolve your hum issues soon!
Also, I noticed that your trafo has a cover (hopefully touching the chassis and if so, acts like a shield). You can try flipping the amp board so that the input side is close to the input RCA's making the input wire to the board as short as conveniently possible.
Toadroller, yes, I know about that article (read it many times) and that's why I suggested moving connections, minimizing and separating wires to decrease the loop area. For example, in your case, the IEC power lines supplying the power transformer and the AC line to the main transformer. Moving the the AC block will eliminate the loop created by those wires.
good luck and hope you will resolve your hum issues soon!
Also, I noticed that your trafo has a cover (hopefully touching the chassis and if so, acts like a shield). You can try flipping the amp board so that the input side is close to the input RCA's making the input wire to the board as short as conveniently possible.
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Yep, it's the official Antek shield: base, cover, slots on the bottom of the cover for the wires, plastic cap-nut. The base is bolted to chassis (therefore chassis ground)
The amp boards were swapped side to side (which puts the input on the "wrong" side) as part of testing, i.e. did it make a difference. No. They'll go back.
Thanks again for the time spent looking at my layout.
Ahhh, I see, flipping the board does not matter (which you indicated on the post #6305 with pics, I should have read it more carefully!). So it means the shield of the main trafo is effectively minimizing stray fields that can be picked up by the input trafo. Please try my suggestions (#2,3,4 and 5) if you can, it is based on what I observed from your pic in post #6305.
Good luck!
Good luck!
I'm making all 8 daughter boards.
I've completed ishikawa, tucson, mountainview, cedarburg and ips7.
Other boards are waiting their parts to come.
In changing ips boards, I do the bulb testting every time.
Unfortunately, in case of ips7, it smell some burning something at right channel.
The left channel was singing properly.
There is not a problem in the bulb testing with no input and no load.
I've took it off and watched the right channel of ips7 but there is nothing burnt part to my eyes.
I've compared both ips7 boards but could not found any difference.
Do I need a new ips7 board?
Is there any suspicious part that I try to change?
I've completed ishikawa, tucson, mountainview, cedarburg and ips7.
Other boards are waiting their parts to come.
In changing ips boards, I do the bulb testting every time.
Unfortunately, in case of ips7, it smell some burning something at right channel.
The left channel was singing properly.
There is not a problem in the bulb testing with no input and no load.
I've took it off and watched the right channel of ips7 but there is nothing burnt part to my eyes.
I've compared both ips7 boards but could not found any difference.
Do I need a new ips7 board?
Is there any suspicious part that I try to change?
Yes you'll need to discard the bad board (or carefully strip it bare) and build a new one.
Before you do, a quick experiment would be to remove the DIP-8 from its socket and see whether the problem disappears. Might just be a bad chip (?)
I notice that in the wooden display case, IPS7 boards have "L" and "R" marked on the big capacitors. But not in the other photos, no L and no R.
Before you do, a quick experiment would be to remove the DIP-8 from its socket and see whether the problem disappears. Might just be a bad chip (?)
I notice that in the wooden display case, IPS7 boards have "L" and "R" marked on the big capacitors. But not in the other photos, no L and no R.
Wanted to make sure that my thought process for what I want to do is solid and will not pose any problems.
I built an Aleph J back in 2020 and I want to pull my Aleph J boards out of my current chassis and then build and install M2x boards using the existing power supply, powered by an AntekAN-5218 - 500VA 18V transformer, and 4u chassis. I built the Aleph J with single-ended RCA inputs only. This should work without any expected problems, yes?
I then plan to use the Aleph J boards and build out a pair of monoblocks using those boards along with pair of new chassis, power supplies, etc.
Im pretty confident that the power supply I had built using the Aleph J build guide will be suitable for the M2x but figured it would not hurt to confirm with the group.
Or maybe I skip all that nonsense, keep the Aleph as is and just build M2x monoblocks. Decisions, decisions...
I built an Aleph J back in 2020 and I want to pull my Aleph J boards out of my current chassis and then build and install M2x boards using the existing power supply, powered by an AntekAN-5218 - 500VA 18V transformer, and 4u chassis. I built the Aleph J with single-ended RCA inputs only. This should work without any expected problems, yes?
I then plan to use the Aleph J boards and build out a pair of monoblocks using those boards along with pair of new chassis, power supplies, etc.
Im pretty confident that the power supply I had built using the Aleph J build guide will be suitable for the M2x but figured it would not hurt to confirm with the group.
Or maybe I skip all that nonsense, keep the Aleph as is and just build M2x monoblocks. Decisions, decisions...
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…though you may encounter hum issues in the tight confines of the 4U chassis. It has been hit and miss throughout this thread.
I reverted my M2X to my 5U 400 and have minimized hum to an acceptable level. Still there, but much reduced, to the point that I know the amp is on. But when the music starts, oh what joy!
I reverted my M2X to my 5U 400 and have minimized hum to an acceptable level. Still there, but much reduced, to the point that I know the amp is on. But when the music starts, oh what joy!