New proud owner of Aleph 5 freaking out 'cause of hum

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About a week ago I reported I have finished my Aleph 5, and I also told I don't have any hum. That's a big lie. Actually at first I did have some, then I messed around and it almost dissapeared. But I thought it dissapeared because it was less hum than the first try.
I tried moving away AC runs under the grounded aluminum plate, but it didn't help. I tried all the possible connections suggested in this forum, but no luck. I measured AC ripple on the PS caps and the meter showed around 80V. Is that possible? What is the next thing to try?
Please help, this hum issue can really make person feel frustrated and helpless.
For my grounding schemes please see this thread (page 1 & 2)
 
Measure the ripple with an oscilloscope if you have access to one. I think 80 volts ripple is impossible unless your diodes are shorted, but that makes no sense. Your meter may not have a capacitor in it on the AC range? Is it possible you have a bad or miswired filter capacitor? I still think grounding is the problem. Does the hum go away when disconnecting your preamp? Did you use the 10 ohm thermistor to isolate ground and chassis (earth gnd), if you did, make sure you measure 10 ohms between chassis and your power supply ground. I am no expert, I am just trying to give you some ideas.
 
Nobody wants to help poor guy

OK I see nobody i interested in my problem, I guess thats because there were a lot of questions concerning the ground loop problem and lot of possible solutions. BUT I'WE TRIED IT ALL!!!!!!!!! Newest thing I did was disconecting AC plug earth completely from the chasis, but the hum is still there (when preamp is connected). What to do? I tried using rectifier bridge, resistors, thermistors and no luck.
Please advise something, I'm loosing my mind.

kilowattski thanks but I allready tried the thermistor and resistors and no luck.
 
Firstly, some hum will remain because the power supply rejection is not infinite. It's a problem only if you hear it from the listening position. It's "normal" if you can hear it at say, 2 inches from the speakers only.

Grounding: from your scheme I see 2 things I would have done differently:

- chassis should go directly to the IEC ground wire with no resistances or diodes. This is for safety and also the point of earthing the chassis. The diode-resistor connection *then* connects from the chassis to the star ground for all other grounds, that you already have.

- the pin 1 (ground) of your XLR should not go anywhere. It should be connected to the chassis at the entry point of the XLR. Thinking of which, I hope your RCA input ground is isolated from the chassis...
 
Could it be that the additional length of cables to the mosfets is picking up noise from the surrounding equipments. Did you tried moving those additional wires & see if it makes any difference? Or even moving the amps away, say away from the TV?
 
roddyama,
I tried to completely disconnect AC inlet earth pin from the chasis (if that's what you mean) and hum is still there.

MBK,
" chassis should go directly to the IEC ground wire with no resistances or diodes. This is for safety and also the point of earthing the chassis. The diode-resistor connection *then* connects from the chassis to the star ground for all other grounds, that you already have. "

Isn't that the same thing as I connected. I saw this type of connection in A75 article.
I completely disconnected XLR from the board and from the ground. Now I just have a jumper beetween XLR - and ground on the PCB.

fcel,
I did try moving all the internal wires but nothing changed. The thing is if Mosfet wires are making problems there would be some noise when premp is not connected. Am I right or not?

Nelson,
Do you mean shorting input RCA grounds with a wire while preamp is disconnected. If yes, I did try that and no noise with or without the shorting wire while preamp is disconnected. I tried using rectifier bridge as you used in one design, but no luck there. I tried to use 5.1R/1W resistor together with two diodes in antiparallel conection and it's not working. Do you have any other suggestions?
:bawling: :dead: :confused: :apathic:
 
If you have tried all of the suggestions so far the only thing I can think is that your rca jacks are touching your chassis or somehow your circuit ground and chassis are directly connected somewhere. A quick measurement with an ohm meter should verify that. If you read zero ohms that is your problem. You have verified you have a ground loop problem because the hum went away when you disconnected your preamp. Could the ground problem actually be in the preamp? What happens when you connect your source directly to the amp without the preamp?
 
Hi to all..
I am also involved to this problem - boris and I know each other.
Attached is the latest grounding for his amplifier.
Kilowatski - do You suggest to disconnect signal grounds of the central point of the star ground that is on the chasis?

Another thing- could it be that he has some problems with his neutral, fase and grounding in main power supply that is coming to the amplifier. His preamplifier also has the same connector (live, neutral and ground) - it could be that there is the loup.
Unfortunatelly we did try to disconnect the grounding wire (only live and neutral remained connected) and the hum was still there. So it could be also that in his house the ground is not properly installed?????
We would try that tomorow- by connecting the amp in the house of my parents since I am sure that they have good power instalation in the house.

If that doesn't help than we must do the amplifier all over again checking every wire and every connection since everyone here really don't know what to do more.... (I mean here at his place- not on the forum)

The humming is from the grounding that is only for sure and it is gone when the amplifier is not connected with preamplifier. Also it is not humming but more like buzzing and it is not that loud. It can be heard from the point one is listening the music.
Oh, well we would be masters of the groundingness when we finish with that one.....:D :D :hot:
regards
daniel
 

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kilowattski said:
If you have tried all of the suggestions so far the only thing I can think is that your rca jacks are touching your chassis or somehow your circuit ground and chassis are directly connected somewhere. A quick measurement with an ohm meter should verify that. If you read zero ohms that is your problem. You have verified you have a ground loop problem because the hum went away when you disconnected your preamp. Could the ground problem actually be in the preamp? What happens when you connect your source directly to the amp without the preamp?


What do you mean? Where do I have to read zero ohms. Preamp is integrated, but it also works as a preamp or amplifier. I didn't have any problems with it before. When I connected the other preamp it was the same situation. When I connect the cd player same thing.
Interesting thing is when my preamp is disconnected from the AC outlet, and interconnects are connected from Aleph to preamp hum is still there. It goes away completely just after I disconnect interconnects either from preamp or an Aleph.
 
Nelson,
OK now I understood what did you mean by connecting shorting plugs on the input RCA jacks. I took one old interconnect connector and made a shorting plug with it. When I connect it to an RCA jack on the amplifier humm stays the same.
What does that mean? Does that mean I have a ground loop inside the amplifier. WHY? :bawling: Somebody please explain me!
I'm becoming aware that this is a one God damn big problem with grounding.
 
From your schematic, your IEC earth is NOT connected to chassis directly, it connects to your star ground via diodes/resistors, and it is your star ground that IS connected to chassis... It should be the other way round. Besides, your RCA is also connected to chassis this way, and possibly your RCA connects at the entry point to chassis as well.

SO:

- your star ground should NOT connect to chassis
- your IEC earth line SHOULD connect to chassis
- star ground to IEC earth connects via diode/resistor network

Your XLR: there are 3 pins, "ground"=shield=pin1, then pins2 and 3 for +in and -in. The -in should not connect to chassis or earth at all. The pin1 is the shield and should connect to chassis directly, NOT to the star ground.

Basically, pin1 of the XLR, earth line and chassis all are used only as shields and not as part of your electronics. They should all connect directly, and so you have a "chassis earth" for shielding and for safety. All other "grounds" are part of the circuit, and are called "signal ground", and unlucky word, you could better call it "signal returns" (all rca grounds, speaker grounds, and PCB grounds). "Ground" and "earth" are not the same thing, it's a confusing terminology that keeps being used by force of habit.

Chassis earth and the star ground of all signal returns/grounds make up two independent circuits. These two circuits should be connected at one point only, and the connection is not direct, but via the diodes/resistors.
 
HI MBK!
That we will try. I have awake this morning and realize that the suggestion of kilowatski and trigon to remove temporarily rca ground is not tried yet. We will try to do that and to make two completely separated ground- one for earthing the chasis and one for grounding the signals (signal returns).
thanks guys
daniel
 

rif

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Joined 2003
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(This is meant to be lighthearted, no offense intended.)

You lied about hum and now have trouble getting rid of it. I'm no religion/philosophy expert, but there's gotta be many fables since the beginning of time all around the world about that ;)

I also don't know if Mr. Pass called them Aleph because it's the first letter in the Hebrew alphabet, but the Zen series is definitely a reference to Zen Buddhism. Either way, I don't think any of his work is meant to make hmmm's not hums. (ha ha -- I made a bad joke).

So what's my pont? None really, just saw some slightly correlated connection between it all. I'd offer some constructive help, but I'm no where near experienced enough to do so (give me a few years though...). So I guess my true point is that I know little, but write much. Ah.

But here's my layman snake oil advice: appologize to the php mystic powers, and meditate over the infinity of recursive acronyms.

(again, no offense to anyone/thing intended -- I'm just trying to be a little humorous where I saw an opportunity).
 
O.k. !
Sparkle and I have tried the last schematic and some more things like disconnecting gnd from rca plugs and the buzzing is still there only that we have more of it (very much more of it) when we diconnected the rca ground.

Killowatski - schematic tried- buzzing still there.

Everything You have suggested we have tried and still nothing. We will work tomorrow again. Suggestions welcomed
regards
boris
 
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