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

[ethrbunny]

Jaicen: I checked the voltages to the 2560 and its a consistent (and clean) +5V.  I put it on an o-scope to be sure.

I audio-probed the 'out' of the 2560 and found the noise there as well. All e-caps are properly oriented. Ive tried other decoupling caps of various sizes without any result.


EDIT: Bleah. I would swear that the playback that I can hear is flat by a fair amount. Does this mean the voltage to the 2560 is wrong? It looks like a happy and healthy +5V as near as I can tell.

[Jaicen_solo]

Well, it seems to me that even a 1M resistor is pretty high for a series resistor before an op-amp. The noise probably changed as it is loading down your guitar pickups less. Try putting a bypassed Boss pedal in front of it and see what happens.

Also, I'm not too wise when it comes to biasing opamps, but i'm fairly sure that the + input should be going to Vbias, rather than +5v.
Also, I don't like the look of P1 wired between the +'ve and -'ve inputs of the 386. That just looks like a dodgy arrangement to me. A better way would be to remove that pot, and wire it between pins 1 & 8. At 0 resistance, that sets the 386 to unity gain.
There really should be a series resistor before the Analogue In pin also.
Though I hate picking holes in things, the overall output of the ISD will be inverted in comparison to the input, as the ANA IN is buffered by an inverting op-amp. It is then inverted again at the output mixer, where the clean signal is also inverted, hence the out of phase arrangement. Correct me if i'm wrong though!
For what it's worth, the layout of the ISD portion of the Dirty sam is not a million miles from my own design, except for the latching CMOS arrangement.

EDIT: I just found your second post after i'd posted!
Did you try probing up to the ANA IN pin to see if there's noise there? If so, it's starting to sound like there's something not quite right with your 2560 arrangement.

[ethrbunny]

I put a pedal in front of it that has a buffer just for kicks. No change.

Why am I getting a lowered pitch? Im assuming that there are things wrong with my box and not so much the design. Im not faulting your commentary - its over my head for certain. 

I probed back to ANA in and it sounds fine. The noise is coming from the chip as near as I can tell. The first place I can find it is at the SP+ and SP-.

[Jaicen_solo]

I think I see a problem in the schematic actually. On the dirty sam schematic, pins 4&5 are taken high when recording, and pin 7 is held low permanently. According to the apps notes, pins 7, 9 & 10 should always be high, and pin 4 should be high for loop, and low for single playback. This is all to do with the chip being in operational mode, which it needs to be to use the CMOS switching. I can't say I fully understand the switching arrangement to be honest, but it appears that a Millenium bypass 2 is being used to send a +'ve pulse to the PD pin, to reset the chip when bypassed. This same high level activates the CE (Chipe Enable) pin. OVF is simply sending a High pulse everytime playback reaches an EOM marker, which makes the RED LED flash at the start of each loop. Quite neat really.
Anyway, the important note I'm trying to make is that Pin 7 should be tied to +5v, not ground to use this CMOS switching.
Just a note, ignore all that stuff I said about the 386, according to Winbond that's how it should be implemented. I'm not going to argue with them!
I'll think this over some more, let you know if I come up with anything else tomorrow morning.
Goodnight!

[mathflan]

hi,

So I modify the whole schematics before ANA In of the dirtysam, I replace it by the schematics of the mobius trip looper:

http://www.generalguitargadgets.com/index.php?option=content&task=view&id=203&Itemid=228



The signal which goes to the ANA IN is better now ,the schematics of the dirtysam before ANA IN wasn't very good...
I put a expander and it clean a lot the signal, I'am trying to put a compressor before ANA in,but I think I have to put a attenuator before the compressor..
I'll record some sample..

I put a TL072 instead of LM386 (LM386 and TL072 don't have the same pinout) , I think LM386 is not appropriate,it has a lot of noise.
but I have a very distortion and the Play pot doesn't function very good..

How I can I change the LM386 with a TL072 or other opamp With keeping the tone pot and Effect loops?

[ethrbunny]

Dang. Im working off of a PCB and would really be bummed to lose all that work. Im still hoping there is a way to salvage what I have. It would be soooo cool.

[mathflan]

ethrbunny, you can just modify R8 TO 100K, P2 by a resistor of 100k and you put the POT REC of 100k ( see shematic ABOVE) after C6, you should cut a little trace on pcb.

I'll try record some sample today...

[mathflan]

Oh! I found an other mistake, I don't know if it's really important but PIN 15 and PIN 14 of th ISD are inversed.
On the schematics , SP15 go to C3 then R6 then PIN 3 ( input +) of LM386, Therefore on the PCB, SP 15 GO to C3 bit R7 then PIN 2 (input -) of the LM386.
I'll Correct that on my pedal,
I'am trying to Replace the lm386 by a tl071 and Try to keep the Tone and Effect loop..

[mathflan]

I Inversed PIN 15 and PIN 14, I also replace the LM386 by a TL071.
It's better, less noise.
I have recorded a sample ( sorry for bad guitar play )

http://sounddiy.free.fr/DIRTYSAM%20(%20with%20modifications).mp3

- I move FIRST the TONE POT, PITCH DOWN POT , PLAY POT and AFTER BYPASS SWITCH.

I have some problems to solve:

- I have to modified the effect loop section, play pot and tone play doesn't respond very good, like you have listened ..

[ethrbunny]

IS the TL071 a drop-in for the LM386 or does it need to be re-routed?

Thanks for the sample. Clearly my box is sick sick sick. 

[Jaicen_solo]

Matlflan, your looper sounds great if you ask me!
I especially like your pitch down pot idea, I'd considered using a similar idea with an expression pot myself, but I discarded the idea as it affects the playback speed as well. I figured I could always add a whammy in the FX loop , but I actualy do like the slow down effect. It really is like pulling the power on an old tape or record player. Very cool, I think I might add it in after all!
If you do a search for my design, you'll find the schematic I made up for adding an optically variable power supply using an LM317. This can give you vibrato effects, as well as the manual pitch down effect if you're interested. For the most effective vibrato, you'll need to mess with the brightness of your driver LED so that the LM317 is outputting 5V at 0 depth, which will give you the maximum swing of + 4.5v - 6v. I chose the resistors to provide exactly enough swing for this.
Keep up the good work, I think it sounds great so far! 

[mathflan]

ethrbunny, yes you need to do  little modifications, TL071 has not the same pinout for output and V+ as the LM386





Jaicen_solo, thanks! , It's tru that My new dirtysm after modifications sounds really better.
Where is your schematics for Vibrato,that's a cool idea!
I have some problems with the effect loops, Since I change the LM386 by a TL071 and put PLAY pot before tone pot (PLAY' s POT : PIN 1 go to ouput of TL071, PIN 2 goes to TONE's pot and PIN 3 goes to GROUND) the play volume and Tone pot are not very smooth....if yo have an idea.

[mathflan]

Ok I found your Vibrato Schematics, I have all components but I don't know if I could be Put the circuits in my BUSY analog looper!

[Jaicen_solo]

Haha, I guess it could be a tight squeeze

If you want to try it, just build it on a bit of perf and temporarily connect it to the power pins on the existing circuit.
I'm going to try building my looper design next week when I get paid. If it sounds as good as yours i'd be more than happy!

[mathflan]

Ok I finished my analog Lo-fi Looper!!






I Have two problems I want to resolves=d:

- I have a little noise on the sample, maybe bad schematics...

- When I Plu a effect in effect loop,I have  distortion on the sample when I begin to move the play pot at 60% , this distortion disseapear when I engage the effect in effect loop, strange...

GO To MY WEBSITE, I WROTE  A PAGE ON THIS PEDAL
http://sounddiy.free.fr/AnalogLo-fiLooper.html

[Jaicen_solo]

Mathflan, that is some excellent work! 

I'm really impressed, particularly with the high quality finish you got on that box. I've decided that adhesive labels are the way forward!
I also like the sound samples you did. Did you wire the play speed/pitch knob as a variable resistor or as a voltage divider? I'm adding that to my build for sure! I'm going to use break jack on my optical voltage circuit, so that I can plug in an expression pedal and modify the pitch on the fly.
I also really like those samples you did of the Rebote, you should let FP host them on Tonepad. Sure convinced me to build one! (I was leaning before). I think it sounds better than my DD-3 with analogue mod, though the delay time is shorter and not as clean. Be good to have both I think

[mathflan]

Thanks jaicen

I use a potentiometer for the Pitch, I can Put a variable Voltage circuit, My boxe is too busy

Yes the Rebote is very good delay, There the New rebote 2.5 on Tonepad, maybe better than My rebote 2.
I have Built PT-80 t which is cleaner than Rebote delay..

[ethrbunny]

Yarg! My board is all soldered up already. Oh man. Oh man.


Must.... not... weasel... out.....

BTW: Mathflan - outstanding site! Makes me want to build / buy a BMP now.

[mathflan]

tnanks for the compliments,

I'm sorry to disturb your work on the dirtysam.
You could first just add this:



with that, you will have a more clean sound.

[Jaicen_solo]

Well Mathflan, I've just been back to your site and played the samples at full volume (was about 2am last time!) and i'm even more impressed! I especially like the clips of your looper processed with delay. Sounds really full, and not all that lo-fi actually!
I'd be interested to see if by modulating the power supply in the same way, we could get the rebote to do that pitchshifting as well. That would make for some interesting tones!
Anyway, enough idol worshipping! I'm taking my looper back to the drawing board to add in an effects loop. I just can't do without that anymore after hearing your sample!