DC jack hum/ battery no hum

[Kipper4]

my TS808 hums when the dc jack is in use but when i use a battery in the box it doesnt.
Whats going on here.
I've been wracking my tiny mind and cant think for the life of me where the problem lies.
I tried differant grounding points for the input jack switching.
The thing is i also made a rat and it does not do this. so i cant see why it would be the wallwart when it doesnt do it on the rar but does on the TS.
Stumped of Lincolnshire!!!!!!!!!!!
Help me out guys.

[GGBB]

Could still be the wallwart - RAT uses a 47ohm series resistor on the power input which will reduce hum.  Jumper it on your RAT and see if it hums.

[ashcat_lt]

Could still be the wallwart - RAT uses a 47ohm series resistor on the power input which will reduce hum.  Jumper it on your RAT and see if it hums.

That resistor does nothing of the sort!  It does help set the cutoff frequency of the LPF with the big cap across the rails.  It also helps limit in-rush current, but that's beside the point.  The cap will still filter some of the hum with that resistor shorted, because the voltage source is not "ideal".  If the TS doesn't have a big cap across the rail, adding a resistor won't help.  If it does, the resistor might help tune the filter, but so will changing the cap.

Of course, since we have no idea what scheme the OP followed...

[Kipper4]

Schematic is the GGG its 8
i tried a series 100r across the power supply and it doesnt do anything for the hum is still there.
I thought it might be the resistor i put on the power suppyl for the led (that i didnt bother to put in so i tied it to ground and it didnt help either.
i just compared it to an older ts808 i built which with the same dc wallwart doesnt hum.
so i guess there could be a fault on the board.
time to remove the series 100r and tie to ground from the 4k7 led resistor seeing as it didnt work
thanks for the time guys.
I'd really like to stop this hum now.

[induction]

Have you tried a regulated PSU?

[Govmnt_Lacky]

Double check the electro cap across the power rails. Is it the proper value and voltage rating?

I once accidentally put a 10V electro on a power rail for a 12V pedal. Hummed something terrible 

[GGBB]

That resistor does nothing of the sort!

Really?  http://www.muzique.com/lab/hum.htm 4th paragraph.

[Kipper4]

I dont know if the supply is regulated (probably not) but i have it on the 7v setting the reason being it measures 8.85 volts on the DMM. i figured its as near as i'm going to get to 9v from its setting. I'm sure i checked them all before and it was the closest.

I double checked the cap voltage rating one is 25v the other is 50 v across the supply.

The thing i dont get i guess is how come when both supplies are similar voltage (DC jack and Battery) why does it only hum when powered by the dc jack?

And why when i checked to old unboxed build did it not hum?

if it was something on the circuit wouldnt i get the hum no matter what the supply. Although i am aware that battery supplies are inherantly less noisy.

btw my enclosure is powder coated and i scraped that away at the input jack to ensure a good ground connection. but again wouldnt the resulting hum be present what ever the 9v supply?

I'm sorry if this is annoying. I'm sure its been asked a million times already.

[Mark Hammer]

That resistor does nothing of the sort!

Really?  http://www.muzique.com/lab/hum.htm 4th paragraph.

The resistor works in tandem with an electro cap to for a lowpass filter to reduce ripple.  On its own, it doesn't.

[induction]

The reason I asked about the regulated supply is that I find regulators reduce hum quite well, especially on circuits with a path from V+ to the input of a gain stage via a biasing voltage divider. Some of my builds have required regulated power (or a battery) no matter how much I filtered V+ and Vref. I don't know if that's the case here, but it might be worth knocking up a simple 78L05 regulator circuit on a breadboard (with filtering), powering it with an unregulated 12V adapter, and testing your pedal with that.

[Kipper4]

I have this

http://beavisaudio.com/bboard/projects/bbp_FilteredPSU.pdf

Permanently on the breadboard.
I'll try it out when I get up in the morning. Would this do as a test?
Don't think I don't appreciate the help . I do.
Everyday I learn more and think more about .
I have used some of the techniques before especially for bjt and fuzzes to quiet the power supply's with good results.
I really should get round to building the huminator too.

[GGBB]

That resistor does nothing of the sort!

Really?  http://www.muzique.com/lab/hum.htm 4th paragraph.

The resistor works in tandem with an electro cap to for a lowpass filter to reduce ripple.  On its own, it doesn't.

Just to be clear - I am aware of that - my comment was in reference to the difference between the TS and the RAT.

[induction]

I have this

http://beavisaudio.com/bboard/projects/bbp_FilteredPSU.pdf

Permanently on the breadboard.
I'll try it out when I get up in the morning. Would this do as a test?

There's no regulator in that.

[pappasmurfsharem]

I dont know if the supply is regulated (probably not) but i have it on the 7v setting the reason being it measures 8.85 volts on the DMM. i figured its as near as i'm going to get to 9v from its setting. I'm sure i checked them all before and it was the closest.

I double checked the cap voltage rating one is 25v the other is 50 v across the supply.

The thing i dont get i guess is how come when both supplies are similar voltage (DC jack and Battery) why does it only hum when powered by the dc jack?

And why when i checked to old unboxed build did it not hum?

if it was something on the circuit wouldnt i get the hum no matter what the supply. Although i am aware that battery supplies are inherantly less noisy.

btw my enclosure is powder coated and i scraped that away at the input jack to ensure a good ground connection. but again wouldnt the resulting hum be present what ever the 9v supply?

I'm sorry if this is annoying. I'm sure its been asked a million times already.

Does it measure that with the circuit connected or without? If not then it probably drops closer to 7 with a load on it

[Kipper4]

that was measured with the circuit on mate.

[petey twofinger]

the boss ps120 and the one spot are the quietest i have tried , whats in those compared to the beavis circuit ... prolly the same thing i am guessing .

[induction]

the boss ps120 and the one spot are the quietest i have tried , whats in those compared to the beavis circuit ... prolly the same thing i am guessing .

I'm not surprised those are quiet. They are both regulated. It makes a huge difference.

The beavis he posted just adds filtering to an existing adapter, which might or might not be regulated.

[J0K3RX]

I am on the same page with induction... you can tell if it's regulated if it reads the same with no load or a load. So if it's 9.5v then it will read 9.5v unplugged from the pedal or plugged into the pedal. Unregulated 9v adapter will read something anywhere from 11v to 14v unplugged and will drop down when you plug it into a pedal but should be somewhere around 9v... If not then I wouldn't use it.

I would not use unregulated power for anything audio related especially guitar pedals etc... but that's just me.

Look here..
http://www.beavisaudio.com/projects/Huminator/  

Good page! A Dummies' Guide to Working with Wall Warts
http://www.dxing.info/equipment/wall_warts_bryant.dx

[Kipper4]

your are all right.
I found a regulated 9v power supply a buddy lent me and tried it the hum is gone.
thanks guys.
Geez i feel stupid.
i really ought to get a regulated power brick supply for future testing.
Thanks guys
How do i know its regulated it says so right on the top.

[stallik]

Rich, I would not normally recommend a kit on a diy forum but many years ago I bought a 1.5 amp  power supply board kit from Maplin. It's a Velleman project and has never, ever given me any hum or other artefacts no matter what the mains supply. Its well regulated and incorporates a trim pot for voltage regulation. just add a transformer...Worth a look.