Photos as requested Zen Mod
Views are Top, Underside with marked wire points, a couple of side views to see solder
FR
Attachments
PSU is also from Tea Bag
Whole kit with Edcor ect
May get time tomorrow to take some photos for you
FR
I have read your blog
I am willing to redo all the wiring
But the reality is that No mistakes were made as it was assembled by an electronics professional
Wiring has been triple checked and on my part of the build - a simplified star earth has been implemented
What else do you suggest ?
FR
All I have is a App on the iPad called Frequency that measures in Hz
Measurements have been posted on a previous post
FR
is that a measurement taken by microphone or did you hook it up?
The firstwatt page states the M2 to have 500uV noise, which I presume to be mostly hum. IIRC your speakers are very efficient. Maybe you are there already.
I am with agreement with Zen. The problem is more than likely on the board somewhere. Everyone makes mistakes even professionals. At this point I do not believe the hum is in the wiring. I can feel for you because I know that you have been fighting this for many months now but there is a solution. My M2 is quite with my horns.
Have you tried to put those toroid outside chassis to find out if those hum still exist? separate chassis for power supply is the best way if you are willing to do extra work.
My horn speakers are a minimum of 104db same as wdecho
As I don't have proper testing equipment I have decided to take the M2 in to another technician as the original tech has retired
Normaly I wouldn't give up so easily but this issue has stumped me and lingered for several months, and it's time to seek professional help
Will update as information is at hand
Let's hope I don't have a long wait time
FR
As I don't have proper testing equipment I have decided to take the M2 in to another technician as the original tech has retired
Normaly I wouldn't give up so easily but this issue has stumped me and lingered for several months, and it's time to seek professional help
Will update as information is at hand
Let's hope I don't have a long wait time
FR
On the other hand, it is such a simple amp (although genius) that it is really odd this problem persists. I once had a TV set (old days non flat screen) that continued to have a funky reception problem in the upper right corner of screen. No amount of degaussing helped. Finally, using a small device that senses electric fields, (allegedly to "properly orient" non polarized plug components ) and I found a very strong field right where the TV was. Going in crawlspace I found a bunch of the house's electrical system directly under where the TV was. Problem solved. (by moving it) Seems like you stated before that your problem persisted even with amp at other locations? If so, disregard. This is a real stumper.
I would keep my money in my pocket, de wire it and rewire exactly as Zenmod advises.
Otherwise, priest and exorcism is only other thing I can suggest! this is odd...
Russellc
I would keep my money in my pocket, de wire it and rewire exactly as Zenmod advises.
Otherwise, priest and exorcism is only other thing I can suggest! this is odd...
Russellc
Hi FR,
Are you able to use a multimeter to measure the AC mV at the output as Elfishi
suggested?
http://www.diyaudio.com/forums/pass-labs/281520-official-m2-schematic-171.html#post4962834
At the very least, that can give you a quantitative baseline value to compare
changes against.
I hope you can get this sorted out soon.
Dennis
Are you able to use a multimeter to measure the AC mV at the output as Elfishi
suggested?
http://www.diyaudio.com/forums/pass-labs/281520-official-m2-schematic-171.html#post4962834
At the very least, that can give you a quantitative baseline value to compare
changes against.
I hope you can get this sorted out soon.
Dennis
A couple items,
If you think you are having interface issues between source component
and input of M2, or if you are losing Jfets, then increase the value of the
input resistor, the one between the rca hot and the Gates of the Jfets.
You can go to quite high values, say 10K if necessary without a performance hit.
Also, for FR's humming problem, what happens when you short the output
of the transformer to ground?
If you think you are having interface issues between source component
and input of M2, or if you are losing Jfets, then increase the value of the
input resistor, the one between the rca hot and the Gates of the Jfets.
You can go to quite high values, say 10K if necessary without a performance hit.
Also, for FR's humming problem, what happens when you short the output
of the transformer to ground?
You are a lucky man Zen Mod - They say behind a good man is a woman in the drivers seatwell , I married a Professional
go figure
Thanks mate
Yes I have tested the amp in other houses with same hum issue
Now I have installed a Thor PS10 power filter - still hasn't fixed the issue
I will have to do it if its a last resort
Yes I have an air gap
Its a pair of large circular washers made from rubberized cork that is used as gaskets in power transformers
Also the center of the donut is filled with resin and a plastic seating washer
The amp hums even if the RCA interconnects are not attached/connected from the Nakamichi CA5 Pre to the M2
I am not losing JFets its just been agreed by the forum brains trust to use a different set that have better numbers and should equate to more punch
-----------------
I have contacted the tech and he asked me to drop the M2 off on the 27th for a diagnosis
As a mechanical engineer that can read a schematic, also with great soldering skills I have come as far as my knowledge will allow
Now the M2s fate rests on other peoples knowledge that exceeds mine
PS - I make some mean but cool crossovers
FR
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I had a hum issue as well. I ended up using a different power supply transformer. Not all toroidal are created equally. Try moving it around and see if the hum changes. Even rotating the toroid will move the hum left to right. My drivers are 115db/W and it is almost silent.
I put the same noisy transformer in my F6 and it made that amp hum too. So use reputable transformers and stay away from the most economical.
I put the same noisy transformer in my F6 and it made that amp hum too. So use reputable transformers and stay away from the most economical.