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Old 9th October 2019, 10:29 PM   #31
pan53 is offline pan53  Austria
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H hh hi, Maty,
Ja, oui, yesss, sí señor, you arrr rright,

Dynavoxxx ! Hick!


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Old 11th October 2019, 11:23 AM   #32
pan53 is offline pan53  Austria
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Default hum from the speakers

I have a little hum problem from my saksa and I can't find the references to appropriate measures to get rid of it. In a distance of 1 m I can hear a distinct noise in my speakers. It is not only a clean low 50 or 100 Hz sinus hum but contains also a "scratchy" component. (Don't know how to describe it better)

Currently I run the yellow earthing cable from my saksa to a bolt I fixed to the subchassis of my enclosure. From there I run another earthing cable to the earth terminal of my IEC mains socket.

Is there a tried and tested procedure to follow to minimise this noise? Are the earthing cables still just to close to the transformer?

Should I turn around the module so that the heatsink is between PCB and transformers?

Should I position the grounding bolt to another part of the enclosure?

Is it important that the distance from the grounding bolt is the same for both modules (the second module is going to arrive soon) ?
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Last edited by pan53; 11th October 2019 at 11:28 AM.
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Old 11th October 2019, 11:34 AM   #33
AKSA is offline AKSA  Australia
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Peter,

If you disconnect your input RCAs, do you still have the hum?

Try one, then the other to see.

Hugh
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Old 11th October 2019, 11:43 AM   #34
pan53 is offline pan53  Austria
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If I disconnect the RCAs, the hum looses some of the "scratchy" (higher frequency) component and becomes a cleaner hum. The lessening of audibility is about 30 to 40%.
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Old 11th October 2019, 12:12 PM   #35
AKSA is offline AKSA  Australia
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Peter,

Try disconnecting the green earth wire from the chassis earth. (Pull off the spade on the pcb connection, easiest to do.)
Before you do this, test that there is 10R resistance from RCA ground (disconnected from source) to chassis earth.

Hugh
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Last edited by AKSA; 11th October 2019 at 12:29 PM.
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Old 11th October 2019, 12:28 PM   #36
pan53 is offline pan53  Austria
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Thanks, Hugh I will do that. Now (13:30 local time) I have to leave to pay a visit, will do it at night (in about 6 hours) and report back.
Peter
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Old 24th October 2019, 10:37 AM   #37
pan53 is offline pan53  Austria
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Hello Hugh,
today I received my second AKSA. I must admit that my joy was considerably spoiled by one fact: The heatsink does NOT have the 4 threaded holes that my first sample has! Therefore I cannot mount the module into my enclosure where I have everything prepared to mount it the same way as my first one.

A big disappointment.

For the moment I do not know what to do. I have no experience in cutting threaded holes so I have to acquire that skill and take the risk in drilling right beside the PCB.
Any suggestions?
regards,
Peter
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Old 24th October 2019, 11:30 AM   #38
AKSA is offline AKSA  Australia
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Peter,

You do not need threads, this is a rather small aspect of the product - the heatsink is identical thermally. When you drill place the piece downwind of the pcb to avoid sprinking the filings. You can avoid using threads; drill holes in the outer fins and then use a nut and bolt to attach. This works very well, Peter, you don't need threads here.
OTOH, I regret this, it's spoiled your second purchase.
BTW, did you solve your hum issue? I'm quite happy to help you further.......

Hugh
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Last edited by AKSA; 24th October 2019 at 10:42 PM.
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Old 24th October 2019, 03:03 PM   #39
pan53 is offline pan53  Austria
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Hugh,

OK, after the first "shock" abided, I had a closer look. Then went to YouTube and informed myself how to make threads in aluminum. Then got myself a toolkit for thread cutting and actually managed to make two M4 threads in the heatsink (on the kitchen desk without damaging anything...) Fortunately I have a harware store just around the corner and this problem is solved.

Due to space constraints any other way of fastening the module would have been above my possibilities. Photos will follow later.


Re my hum issue:
I did not solve it yet. After connecting everything together I will hook the amp up to input and speaker cables (with lid open) and with the system switched on move the cables around inside as possible and listen if its a matter of proximity. I remeber also having read somewhere that blue LEDs can cause noise problems.
I will report back when I have found the time to do it.
With your help I am sure will get there... :-)
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Old 1st November 2019, 04:34 PM   #40
pan53 is offline pan53  Austria
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Join Date: Sep 2018
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Default Some progress

re hum: Before mounting the second SAKSA I turned around the first module so that the heatsink was between transformers and PCB to see if the heatsink would provide some shielding and the increased distance would reduce the hum. That wasn’t the case so I turned it around again and mounted the second SAKSA (see photos). Thanks to the extra length of signal cable Hugh provided I could reroute the signal cable along the side walls of the enclosure, as far away from the transformers and the power supplying wires as possible.
I also moved the ground bolt close to the IEC power input socket at the rear of the enclosure.
I tried to run all the cables as symmetrical as possible.
Result: A little overall reduction (20%) of noise. Only when I disconnected the ground wire from the PCBs to the grounding bolt of the enclosure I achieved a reduction of noise (mainly hum) on the RIGHT channel only. On the left channel (the new module) there is still a a bit of hum audible from about 50 cms and closer.

Fortunately it is not really discernible when music is playing (and I am sitting 2,8 metres away from the speakers and not 50 cms…). Still, it is something I need to remedy in the long run.

Any hints and tips what I can try to get rid of the hum are very welcome!
Specific question: Would 2 aluminum „walls“ between the transformers and the modules be promising? As this would be difficult to organize (can’t do it myself) I’d like to be rather sure about the result before I try this measures.

But now I am just enjoying the marvelous sound. At one point of listening to a classical recording I was just overwhelmed by the beauty of the sound. It cannot get any better than that!

Next on my llst will be meticulous positioning of the speakers and subwoofers in my room.
It MIGHT still get a bit better than how it is now….
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