Aleph P 1.7 problems

[Buhl]

Hi all
First a happy new year to everyone!

Hope somebody has some experience to share on this one, because I am about to go sligthly crazy

I have built an P1.7, which plays really good I think, apart from quite a lot of hum! I have a stepped attenuator at the output, so it increases with the volume. The thing is that I am using KK's PCB, which has a lot of ground connections on it, and Im not sure I am connecting them correctly. I have done the wireing just as I did my BLS, which has no hum....

Basicly, I have a wire that go from the common input jack ground to the input ground which is shunted to negative input, as I am only using single ended. Then the output signal goes to the attenuator - ground for the attenuator connects at a "star point" at the input jacks, where the ground for the output jacks are also connected. Everything should be jolly!

But what about the negative output, should this also be shunted to ground?
And what about "all the other grounds on the board" - KK's P1.7 have 5(!) grounds pr. side: one power ground (unbalanced PSU design), then an ground for -out, one for +in, one for -in and one for +out. Should all these signal grounds meet at one point?

Hoping that someone has something to share on this one....?

Best regards
Hans

 

[generg]

I got only all hum free with the same boards when I left all output grounds open.

All devices seem to be connected already by the the third "Schutzkontakt". I do not know the english word....- the less connections I had inside. the less hum

 

[Zen Mod]

besides any other solution ( please upload pictures of preamp ) - why don't you ask KK for recommended grounding scheme with his pcbs ?

I know - we'll help you as much we can , but I have repetitive impression of constant lack of any guidance from KK's side ;

 

[generg]

All these five ground possibilities are connected on the board, if you ground one they are all connected to ground.

The English word for what I meant is
Protective earthing
On the amplifier, preamplifier and cd-player made enough connection between the devices

 

[Zen Mod]

safety ground

 

[generg]

thanks Zen Mod

 

[Bill Fuss]

I too had hum problems with the KK boards, but only in balanced output mode. I was using the Dantimax output attenuator which has the channel grounds tied together on its board. That forced me to use the Dantimax board as my star ground point.

I eventually rebuilt it with boards from Veteran with no problems whatsoever. I still use it every day.

 

[Buhl]

Good idea actually, to ask KK. He have been very fast and polite/helpfull in the past - but there have also been some long delays - however, I can not put a finger on his service, in the view of what kind of business he is running.
I have emailed him regarding grounding advice for his PCBs.

I tried to leave all grounds open, only connecting the ground next to the negative input with a jumper, where I route my wire to star point - together with ground from the input and output RCA, and attenuator ground.

There is a difference though, right channel has more of an aggressive buzz to it, left channel a more "relaxed" hum. When I connect a 1mm copper plate that seperates the PSU section from the rest of the preamp to star ground, the left channel gets considerably more quiet - not much to detect on the right channel. Can I have a ground loop of some sort on just one channel?? If the screening helps on one channel, then that indicates induced hum for that particular channel?

Thanks for your efforts trying to help me out!

Best regards
Hans

 

[Zen Mod]

pictures could help

 

[Buhl]

Good evening ZM!
Do you really want to see pictures of my birds nest preamp?
Or PCB - or the circuit?

BR
Hans

 

[Buhl]

Ok, here is a picture of the PCB - you can see all the ground connections - I have shorted ground and negative input, and use this point to connect to the star ground, which on the other picture (apologize for the wireing, but the input selector suddenly gave up and had to be....erhm....changed) on the copper bar that runs through all the input jacks on the right back side of the casing.

BR.
Hans

 

[Zen Mod]

try like this

all lines are simple wires , not screened cables

 

[Buhl]

Very interesting - I will try that right away when I get home today!
I have not thought of this strategy - but it seems obvious to try and consolidate the grounds where the ground "begin" - at the ground of the PSU....

Thank you very much so far!

/Hans

 

[Zen Mod]

there is no just one way to skin a cat .....

if you're wakoo enough to think about skinning a cat

 

[Buhl]

Well spoken - but sometimes one gets limited by the way that experience teaches us to approach a problem - I think it is nice to get input from talented people and view ones problems in a new way!

I have actually skinned a fox - that can not be to far from a cat...??

 

[Zen Mod]

conclusion is that you are wakoo enough

talent is matter of luck ........... and certainly matter of later work ;

unfortunately - I know enough ppl with some talent , some work but also big enough ego to prevent them of asking any questions .....

I realized that in time , so here I am - asking questions all the time , and trying to have fun ........ all that trying to compensate lack of talent and formal education in electronic

 

[Buhl]

Well, there certainly are several ways to skin a cat....
Tried the suggested wiring as per the drawing - see picture - still buzz/noise - same amount as before. Then started to look for the dog for something to skin - and thought of the toroid transformator - tried to unscrew it, and place it a little bit out of the casing - see picture (good thing that I am to lazy to cut wires when building) - and voila!! - the buzz is gone !!!!

Sound is cleaner/more detailed now - sounds like the buzz has clear effects on the audio signal, even though it is lower than the music signal....

Thanks everyone - ZM - I owe you a "Jélen Pivo"!!!!

Now on to remove the buzz in my Aleph 30....maybe the toroid should out of the casing in that also

Regards
Hans

 

[Zen Mod]

you can still have xformer in case , but with much shorter supply and signal pats

that maybe will even demand screened signal routes

anyway - your call

in your boots - I'll reorganize position of pcbs to have shorter paths , and take another small case for that grumpy Donut

 

[Itsmee]

Had a similar problem once - induced eddy currents, try removing the copper screen and refitting the transformer.

 

[Buhl]

"Grumpy donut has to go" - well, Mr. Donut and Ms. Aleph got seperated today - Mr. Donut got a new, small confinement this evening, complete with his own soft recovery bridge and a couple of 1000uF/100 volt caps - and a nice long PSU wire with a speakon plug in the end, so he can stay far away from the lovely Ms. Aleph 1.7 (I really think that circuit sounds lovely!) and hopefully not bother her again, just pay her clean, noisefree "allowences"...

(Who said anything about lead less solder NOT making you wackoo?? )

/Hans