MISTAKE ON DIRTYSAM loop pedal!! (ISD chip) do this modifications!!

[ethrbunny]

mathflan - I audio-probed the ANA-IN and wasn't getting any extraneous noise. Im sure its not as clean as what you propose but its ok. The noise Im getting is entirely within the 2560. I tried disconnecting  ANA-IN entirely and still got the noise.

[mathflan]

Jaicen, Yes that's true that Effect loop is very important on this pedal, very cool sound..
But I have still a problem with this effect loop :

- when I plug a jack in SEND or RETURN, I have a big POP noise, like ground disconnected...
- It's the same noise when I activate the effect plugged in the effect loop...
- When  the effect which pluged to effect loop is OFF, I have distortion when I pump up the PLAY volume.

So if you have an idea, that's would be cool...


ethrbunny,:

Check that you have Put the ground to the metal box ( if you have build this in a metal boxe).
before the modifications, I had the same problem noise as you maybe a liitle less than you..
The Circuit before AN in is the problem,.
TRY to  reversed pin 14 and 15 of the ISD as I said on my site, i don't know if it's important, But try...

[Jaicen_solo]

I'm not sure what could be causing distortion with your effects loop, does it do it when you use tue bypassed pedals??
I've re-done my layout using Bill's Mobius Loooper's analogue circuit. Check out the layout below. Only just finished, so let me know if you spot any errors! I added some extra low pass filtering on the ana-in, to cut some of the highs which won't be recorded. I figure this might improve the signal/noise ratio.
Let me know what you think! (Layout is 2.3x2.3 Inches by the way).

[ethrbunny]

ethrbunny,:

Check that you have Put the ground to the metal box ( if you have build this in a metal boxe).
before the modifications, I had the same problem noise as you maybe a liitle less than you..
The Circuit before AN in is the problem,.
TRY to  reversed pin 14 and 15 of the ISD as I said on my site, i don't know if it's important, But try...

I tried disconnecting the ANAin altogether (at the 2560) and still got the background noise. Did it both 'free' and grounded. No change. I guess Im confused as to how the circuit before the ANAin could be the problem if the problem doesn't change / go away when the circuit is removed.

[mathflan]

Hi,

I don't really understand...
you removed the ANA In circuit but How can You verify if it works better or not if you don't have anything in input and record new sample?
In fact You removed the ANA in circuit  and PLAY the last sample that you recorded, Am I right??
If it's that it's normal that you have noise again.
do modifications on ANA In circuit to have more signal which goes to ANA In of the ISD.
The Ana in circuit give a very bad signal to noise ratio.

I gonna think about your problem...

[ethrbunny]

I don't really understand...
you removed the ANA In circuit but How can You verify if it works better or not if you don't have anything in input and record new sample?

I disconnected ANAin and put the circuit into 'record' mode. When I put it in 'playback' mode I get the noise and nothing else. Whatever sound (+noise) was there before is gone. Only the noise remains. The 'noise' is as loud or louder than the input signal.

FWIW: my circuit is boxed and grounded to the box.

[mathflan]

OK,
I gonna see on my looper if I had lot of noise when I disconnect the ANA In circuit.

Do 2 things:

- Put a speaker directly to the ISD  at the SP +and SP- pin, to see if you have again the same noise.

- Take a Jack cable, with a side with JACK and the other side with just two wires stripped. You put the JAck to a mixer, or amp anything to hear, and you solder the ground of the Wires stripped to the Ground of the dirtysam, with that you can test with the other wire stripped on the whole circuit to see where is the problem.

Sorry for bad english, I don't know If you will understand..

[ethrbunny]

You're talking about an 'audio probe' yes? Ive done this. I get the noise immediately at SP+ and SP- and nowhere before.

[mathflan]

YEs, a audio probe, this helped me a lot to debug some pedals I built.
I Guess that you check many times your PCB of the dirtysam...
I don't know really what to say to help you... sorry

[ethrbunny]

Pulls out gun. Aims at head. Shoots pedal instead. 

Its some mistake I made on the board. I just dont have a clue how else to find it. I checked and rechecked the value of each component. I looked as carefully as I could for solder bridges. I've tried extra decoupling on the power, extra grounds, blah blah. The circuit works.. mine doesn't.

Bang bang bang. The sound of me pounding my head on the wall.

[mathflan]

try to check the traces of the PCB with a ohmeter with a low scale to see if there non bad connection ...

Are your components are new??

[ethrbunny]

Yep. Everything was NIB from Mouser. I even replaced the 2560 thinking I had a dud. I used an o-scope to check the power for 'irregularities' and it looks ok too.

I realize it would be a big pain but would you be willing to compare pin voltages on the 2560 with me?

[mathflan]

Ok.

No problem if you want to compare  the Voltage with me.
I don't think it's a problem of voltage...

Do You use Fx loop, if no, you have to connect FX LO and FX LI.
If you have noise on SP+ and SP-, There maybe a pin which not connect to ground or something like that.

Check that you did a Star grounding, only one Ground.

this link could help you..
http://www.tonepad.com/getFile.asp?id=76,

[ethrbunny]

all taken during the 'record' cycle.

pin / voltage
1 / 0
2 / 0
3 / 0
4 / 0
5 / 0
6 / 0
7 / 0
8 / 0
9 / 5
10/ 5
11/.3
12/0
13/0
14/0
15/0
16/5
17/1.5
18/1.6
19/0
20/0
21/.25
22/4.5
23/0
24/.14
25/5
26/0
27/0
28/5

[Bunyaman]

Hey men! I found a project of this lo fi looper . I`ve done pcb. But now the url on layout parts list and schem is not work!I have not nominals....Have anyone this? Give me layout and schematics, please!