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Old 19th October 2009, 06:55 PM   #51
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Hello Kenji

Did you done the modifications I've suggest in the post #43 ?

Bye

Gaetan
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Old 19th October 2009, 09:55 PM   #52
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I am not getting any hum or hiss at this point so I am keeping things as they are. But if in future I get any problems with hum again, with another cd player connected to it, then I will try the modification.

Thanks
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Old 20th October 2009, 03:53 AM   #53
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Quote:
Originally Posted by Professor smith View Post
can you just explain what you mean more clearly? I am confused by what we are plotting, the ouput voltage as a function of distance or resistance or what?

If we take a discrete example say with 3 inputs xohms= x_1, x_1+x_2 and x_1+x_2+x_3. The output is F(x).
When we swap the wires we automatically swap the inputs which become x_3, x_2+x_3 and x_1+x_2+x_3.
I cant see how we can calculate G(x) such that G(F(x)) gives us back the original x's.

This is the diagram I refer to:

A---B---C---D
x_1 x_2 x_3

Voltage V is applied between A and D and the x's are the resistors.

Thanks.
Just in case this has been missed, can someone settle my query once and for all please?

Thankyou.
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Old 20th October 2009, 08:11 AM   #54
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Kenji, 53 posts have gone by and you have decided to stay put, just because your troubles have ceased temporarily. I had briefly followed your other thread posts on your AKSA experience.

With whatever setup you have at the moment, minus the hum and the buzz, may I ask as to what should be your logical conclusion? While you figure that out, I would endear you to ask an experienced tech or diyer to completely replace/redo the wiring in your AKSA amp. Having learned such things the hard way over the last two decades and more, I can tell you assuredly that you are getting poorer performance than with a well executed amp. You had asked what difference, a piece of ground wire could cause to the performace - well, it does make a world of difference to subjective performance as well as measured performance most often, if not always.

I cannot recall whether it was T.Giffard or T.Giesberts who reported in Elektor that moving the RETURN wire from Star Ground to Ground on Amp PCB resulted in much lowered measured THD.

See what Douglas Self has to say on the NFB take-off point on a PCB and you will realise that there are points in a circuit which are more critical than others.

Now it is up to you to choose to either be proactive and seek help or wait for the next low tide.
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Old 20th October 2009, 04:52 PM   #55
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Quote:
Originally Posted by Greg Erskine View Post
The standard way of connecting, as per instructions, work fine with my AKSAs. A single star earth with lift resistors on each PCB, but on your system could be different to normal.

When I have my AKSA connected directly to my source (no preamp) it is very quite. Conecting a tube preamp introduces a very small amount of hum that is not usually noticeable. I have tried a couple of cheap DVDs (double insulated) as sources and these caused servere hum when not playing music. Luckily my CD player and Transporter are very quite.

When looking for ground loops you need to look at your entire system not only each piece of equipment. Remember the safety earths are usually connecting all your eqipment's earths together back at the GPO. Look for any equipment that is connected to a different earth potential.
What you say is the same thing I've experienced, where some sources are dead quiet and others hum badly. Does this suggest it is something to do with the design?

Why do the instructions tell me to connect both channel pcbs to the rca ground yet Gaetan advises me to disconnect one and link the rcas together? I am confused.
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Old 20th October 2009, 05:20 PM   #56
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Professor smith View Post
Can I ask if a groud loop existed and I were to connect just one input on the amp, would the hum disappear?
Quote:
Originally Posted by Professor smith View Post
I am trying a passive pot as a preamp. .............in what sense is the performance affected?
Stop!!

Have you found the grounding error? and solved it?

Do that first.
Then we may look at your new topic.
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Old 20th October 2009, 06:52 PM   #57
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Quote:
Originally Posted by AndrewT View Post
Stop!!

Have you found the grounding error? and solved it?

Do that first.
Then we may look at your new topic.
Hello Andrew

Looking at a video of the case interior and connections of his Aksa amp done by Professor smith, I have found a ground loop wen connected to a preamp and some cd players.

Look at my post;
preamp for aksa 55

I agree with Samuel Jayaraj, Professor smith should not wait at the next hum and moise problems and should do the modifications I've suggest in this other post;
preamp for aksa 55


Bye

Gaetan

Last edited by gaetan8888; 20th October 2009 at 06:55 PM.
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Old 20th October 2009, 09:25 PM   #58
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Why do the instructions tell me to connect both channel pcbs to the rca ground yet Gaetan advises me to disconnect one and link the rcas together? I am confused.

If 'there is a ground loop' why does it hum with some cd players but not with others?

I need the answers to these questions before I start fiddling about with it. Does Hugh know the answer?
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Old 20th October 2009, 10:59 PM   #59
AKSA is offline AKSA  Australia
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Kenji,

The big question is whether you will actually commit and consummate the ground loop error discovered by Gaetan (merci beaucoup, M. Gaetan!).

Beyond that, I do not, indeed cannot, understand........

Hugh
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Old 21st October 2009, 12:28 AM   #60
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Quote:
Originally Posted by Professor smith View Post
Why do the instructions tell me to connect both channel pcbs to the rca ground yet Gaetan advises me to disconnect one and link the rcas together? I am confused.

If 'there is a ground loop' why does it hum with some cd players but not with others?

I need the answers to these questions before I start fiddling about with it. Does Hugh know the answer?
Hello again Kenji

Not all preamps and cd players do have the same types of grounds connections, so some will do a ground loop with your Aksa amp.

You need to disconnect one input wire ground on the pcboard because it will break the ground loop, and you need link the rcas plugs together because somes preamps and cd players will not have the ground connection link the way it need to have both channel playing.

Look at my post #43

PLEASE Kenji, will you have some confidence in us, since me, Hugh, Bigun, Nico, and AndrewT, we have lot of experience in diy projects, why would we want to confuse you, we just want to help you !!

If you still turn arround like that, allmost nobody will want to help you again !!!

Bye

Gaetan

Last edited by gaetan8888; 21st October 2009 at 12:32 AM.
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