power supply section and the right way to wiring the GND-Earth (lm3886)

[madapj]

wow... amazing!!!
again, i have only to thank you!!!

tomorrow i'm going to do the pcb...
let's see

[madapj]

i don't know, the preamp project still not working...
i made everything good (i guess), check and check the things over and over again...
Maybe is a connection pots problem, i do the same that is show in the ESP pages... but still not working. I think that i'm going to let it go.
Have you got some other suggestion for a clean preamp?

[J M Fahey]

Hi Madapj.
Did you protoboard it or went straight to the PCB design?
I'm sure you have some small error.
Proto is better because of the ease to correct or modify anyhing.
Post some pictures and measure the voltage at every IC pin, and the transistor too.
If you give up on your first problems, what will you do on your next project(s)?
Your LM3886 did work, if I'm not mistaken.

[madapj]

I did pcp design direct 'cause i'm pretty good in that. ( i think )
I have done a lot of pcps, in school and also for work, and i'm pretty sure to have done correctly.
this is not the first pcp that i have done, i have controlled it a lot of times.
The problem is that i worked a lot with digital stuff, like PIC and uProcessor, so my knowledge about analogic signal is not enough to understand where the problem is.
(I really have to start study analog circuit!!!!). (any good volume suggestions?)
I really didn't want to give up, and i'm happy that i find someone, like you, to figure out where is the problem. I say you thank again.

So, first of all, i use, instead of the BC549 another transistor, the BC550, higher voltage and same noise (on the cover is write CC550...)
Second, i left the low input disconnected, ( R2 input not connected, i have to connect it to GND? ).
Here the voltage from every PIN from the IC: ( no signal in input ).
1: -13.17
2: -13.13
3: -12.01
4: -14.62
5:   0
6:   0
7:  0
8:  12.79
The supply is a little bit different cause i add a green power LED with a 600 Ohm resistor in parallel with the 15 Volt positive rail)

It seems that no signal is coming from the tone section, so i guess is a pots problem?
i follow the figure is the esp pages, there's a draw with the pot connections, and is write that the view is from front... i don't know
how can i understand if is only a pots problem?
can i make a bridge from the out of the 1 pin to R9 and check if is working?

the amp is workin good, i tried and is perfect.
I post some photos...

[J M Fahey]

Hi Madapj.
The voltage measurements were important.
V(oltage)(at pins)5/6/7= 0V are ok.
V1/2/3 close to -V supply are not.
You might have a bad IC1, although that's not very common.
Pull it from the socket, and measure V1/2/3 , you *should* have 0V there.
If not, specially on Pin1, follow the traces, you can either have a layout/design error or some solder bridge or small metal burr or flake (or an improperly etched area) .
Turn your PCB file (silk screen side, copper side, check plot) into a gif or jpg, and post it to follow the wiring.
If voltages are good, pop in another IC and check.

[madapj]

i check all the pcb, and now is working.
Like you said was some kind of flake, 'cause i wash the pcb with some CRC and now is working good.
The voltage now, in the 1-2-3 pin are quite close to GND, and the project is working.
But i have some other problem:
Is so importante that the power is right +15 and -15?
i have -14.55 and +14.37. they have to be equal?
Second thing, everything is a little bit noising... at home i have a NE5532, that's a lot of people sayd that is a good IC for audio. can i put it instead of the TL072, that maybe is a little bit compromise for the bad that append before?

[J M Fahey]

Hi mdapj, don't worry.
The TL072 can work from +22 to +4V and from -22 to -4V and any combination between those two; from pin 8 to pin 4 you should have no more than 36V and no less than 8V.
Do you have noise with the input shorted to ground? What kind of noise?

[phatt]

Hi madapj,
              The Hum maybe due to not having the *Circuit Common Grounded to the Case*?   I can't seem to see that in all those pictures.

Nice neat work by the way :tu:
Phil.

[joecool85]

Nice neat work by the way :tu:
Phil.

I'm impressed as well.  Excellent job!

[madapj]

Nice neat work by the way Thumbs Up
Phil.

I'm impressed as well.  Excellent job!

thank you. i apreciate that.

Now... noise problem.
I change the TL072 with a new one... just to be sure
I connected the central GND star between the to big caps direct to the gnd chassis, where is also connected the Earth from the home power.
The noise now is a little bit less.
But the problem still exist.
If i leave the signal connector free there is a lot of noise, i have to power down 'cause is really annoying and if i connected it to the gnd the noise is less, but still.

In the second jpg that i post you can see al the connection that i have do.
I a few worg i have one power board that supply to different board, one for the amply and one for the pre.
Every board have his own gnd connection.

1: How can i solve the problem noise?
2: is a problem that the plus and the minus voltage are a little bit different? (like +14.50 and -13.80)
3: if i turn all off the master volume the noise really go up.

i wanna try to do another pcb for all the caps with a singol connection, to avoid the problem with all the cablage cause i see that if i get the hand close the system start to noising... is that stupid?

Thank.... Marco

[joecool85]

I'm still thinking grounding issues are the cause of the noises you are hearing.  Are they loud noises or just kind of in the background?

[phatt]

Hello again madapj,

Go back to ESP schematic and note the *One* ground node is at the input socket. His design, so start there first. If no luck then we will look at other issues.
Phil.