What kind of noise is this?

[psychepool]

I made one channel deluxe reverb clone. (AX84 California Dreamer)
The schematic is here.
http://home.comcast.net/~daniel.souder/ ... tic_V3.pdf


It sounds good. And all funcion is alright.
The only problem is....noise.

The noise when turn the volume knob is not problem.

I want to remove the background noise.
It even occurs in Volume 0 setting.

The clip is here.
https://soundcloud.com/psychepool/noise
The incerased noise at 15~20sec is volume knob turn.(min~max) I don't mind this gain noise.
Only just want to know about the cause of the background noise.


Please give me advise.

[xtian]

Well, that's not bad. I can hear a little radio hash that could be because you have the chassis open and it's getting noise from overhead lights or whatever. Or you may have some lead dress issues that we can clean up if you show us some photos. Is your V1a grid resistor right on the tube pin?

[psychepool]

Yes, my amp chassis is not in a cabinet.
Does it go away if install the chassis on shielded cabinet?

Frankly, the noise not very loud.
But the other amp I made has no noise like this.
So I thought it can removable.

V1a grid stopper(68k) is installed at input jack.
It is connected to pin2 with coaxial cable.

Unfortunatly, I have no photo now.
The chassis is very compact and structure is unusual.
I hope it is not the reason of this noise.

I'll upload the pictures soon.
Thanks for your answer.

[Stevem]

Does it go away when you bolt the amp up to the shield ?

[psychepool]

Nothing is changed with shielding.


Here's gut shot.
http://s935.photobucket.com/user/psyche ... t=3&page=1

Chissis's length is 330mm.. The space is so tight.
I tried to take detailed as possible.

There no change when i move the wires with stick.

Can you figure out the cause of noise?

[Stevem]

After looking at your shots and not even listening to your audio I would have to say that your issue is due to your grounding schem of having that main ground buss wire!
You need to break that up into a start grounding layout which you can find tons of info about on line!
In the least all the needed grounds for each gain stage section can be bussed down and the then the output plate and screen filter along with the any PT secondary taps need to all go down to the same chassis ground.

With your current build if you plug in a guitar, turn down its volume and open up all the controls on the amp with a meter set for AC volts across the speaker what mv level do you read?

[Phil_S]

There is a diversity of opinion on ground schemes. I'm not saying what's wrong or right, just saying that a star ground may not be necessary. It would really help if you can capture a single shot that shows the whole circuit and one that shows the whole ground buss. FWIW, I'm inclined to agree with the ground scheme diagnosis, just not necessarily agreeing about the best solution. It looks to me like you may have stuff hanging on the buss wire that really should go direct to the chassis, but it is hard to see without a different view.

EDIT:
A cautionary note to forum members: I suspect it is the link to the OP's pictures that generated a pop-up session in Mozilla for PC Keeper that I surely didn't want or like. I am not certain this was it, but it is likely the only unfamiliar place I went today. I am generally careful about where I go on the net, not wanting to catch something evil.

EDIT2:
I have no way to be certain of origin. I ran Malware Bytes and it found one executable and three Trojan entries in the registry. Yuk!

[Structo]

No red flags here.