zvex lofi loop junky - hows that work?

[ethrbunny]

Awesome! Thanks for posting your schematic gurutzeta. Any sample clips?

Can you translate the "Descripcion del efecto: " section? I get that it has an effects loop... the four jacks:

in
out
efx in
efx out

the fourth? what is "in MBP"?

Once you have recorded and start the 'play' cycle  - does it loop once or continuously? Looking at the datasheet for the chip it seems like it only plays once for each switch click.

[cd]

These look cool but... what about the finite life span of the EEPROM storage in these chips?  100,000 write cycles sounds like a lot but that works out to about 23 days of continuous 20-second loops.  Plenty for an answering machine but well under the expected life span of a pedal.  Maybe the write cycle specification is very conservative?  How do they behave as they die, is it a sudden event or does the sound quality degrade gradually as storage cells go bad?

Whoa there - don't think of it in terms of continuous loops, since the thing can't do sound on sound recording.  You start recording, it stops after 20 seconds or when you tell it to, whichever comes first, then it plays back.  100,000 write cycles is a LOT.  If you record 100 loops per day, every day, it will last you a bit under 3 years.

[cd]

The other thing is, you'll probably have to replace the switches you use 3-10 times (or more!) before you replace the chip!  Which is a bigger PITA, replacing a switch or popping in a new chip - I vote the former.

[gurutzeta]

Awesome! Thanks for posting your schematic gurutzeta. Any sample clips?

Not yet, I have been very lazy with this whole project.

Can you translate the "Descripcion del efecto: " section? I get that it has an effects loop... the four jacks:

in
out
efx in
efx out

-Two stompswitches, one for fx-bypass the other to change between play/record.

- Three potentiometers: Recording volume, play volume and tone control.

- Fx loop (in case you want to add and effect to the recorded sound)

- A switch to avoid overwriting the stored audio.

- It can record up to 120 seconds with bad quality or up to 60 with not so bad quality (depends on the chip used)... Still, it is Lo-Fi, it has noise, hum and hiss.

- Purely analog storage, no ADC or DACs.

- Chip available in amidata (the equivalent of the british RS components)

- The name dirtySam comes from the film Casablanca: "Play it again Sam... BUT WITH NOISE!!!"

the fourth? what is "in MBP"?

Millennium bypass... see GEOs web for more details

Once you have recorded and start the 'play' cycle  - does it loop once or continuously? Looking at the datasheet for the chip it seems like it only plays once for each switch click.

Loops continuously, the chip has different modes of operation, maybe you are looking at the wrong mode in the datasheet.

[ethrbunny]

Does the bypass jack give you a 'clean' signal regardless of whether the loop is playing or not?

Ill go back to the datasheet and try to understand the modes. Thanks for the translation!

[gurutzeta]

Does the bypass jack give you a 'clean' signal regardless of whether the loop is playing or not?

The signal is completely clean when the pedal is bypassed (by pressing the bypass switch) and it goes trough an opamp based mixer with a gain of 1 when it is not in bypass mode (when recording or playing). Is that clear? what do you mean with "bypass jack"?

Ill go back to the datasheet and try to understand the modes. Thanks for the translation!

I do not remember the mode I am using, I will need to get back to my notes (which are in some box somewhere). I moved of house and country right after I designed the pedal, reason why I kind of left this project aside slightly (and all other guitar DIY), but I am starting to get settled, so I might do some improvements on this web page soon (translating it to english is on the list)

[ethrbunny]

I guess Im still hazy on what the 'MBP' jack is for on the schematic.  Im still confused about what the fifth jack is for.

After going through the data sheet for the chip I *think* that I have some understanding of the mode(s) and how you are running it. Now Im working my way through your digital logic....

[gurutzeta]

I guess Im still hazy on what the 'MBP' jack is for on the schematic.  Im still confused about what the fifth jack is for.

OK, I get it now. MBP is not actually a jack, it is just a connection point that goes from one page to another of the schem (from the analog circuit to the digital one). The fifth jack you can see in my box is actually a power connector, it is not a jack. The box I used came from a 4 input microphone mixer and, when I took the picture, I had not bother to put any labels to the connectors or potentiometer or to remove the existing ones (INPUT, OUTPUT and so on...). I did reuse the hole of the output jack of the mixer to put my power connector.

Hope that is clear now

[ethrbunny]

Much clearer. Thank you v much.

[hair force one]

lo fi loop junkye's best sounding effect since... univibe!
Hearing the samples it turns any stringpluck into shimmering pop tunes!

Z-vex this your masterpiece!

(And what about the unconstent tremolo that pulses in its heart?)

[Ansil]

hmm i know i shared this with sic.  but to do fun things in that same vein.

there is a cheap kit available from circuitspecialists.com  in their kit section and all you need is to wire up a couple of foot switches and something to freak out the clock.

i ocudlnt' find the online link but its in the catalog and in stock i am not at home or i woudl go look it up.. however its quite nice and sound really good. by lifting the ground you disable the internal clock function.   and you can get 40seconds continuous play with the kit which is around 28usd

[ethrbunny]

Gurutzeta - I can't get the link to the PC board to open. Its a .doc file but MS Word won't open it.

I'd like your permission to create and populate one of these boards. It wouldn't be for sale - just for me. Let me know if this is a problem.

[gurutzeta]

Gurutzeta - I can't get the link to the PC board to open. Its a .doc file but MS Word won't open it.

Don't know what could be happening. I suggest you download the image from:

http://humano.ya.com/guruzeta/Guitarra/dirtysam/images/pcbdirtysam.JPG

and then resize it to 32% (I think)

I'd like your permission to create and populate one of these boards. It wouldn't be for sale - just for me. Let me know if this is a problem.

Sure, no problem, I will be honoured. Could you tell us how did it work out when you are done?

One thing that might be interesting would be to play a bit with the oscillator circuitry... I am sure we could create some sort of vibrato effect as the lofi junky has.

[ethrbunny]

How would you go about adding the vibrato to the circuit? Just having the effects loop is v nice. Maybe just a 'blend' control to set how much the effects loop touches the sound.

Some questions about the schematic:

1) SW12 and SW20 appear to be connected by a trace - accurate?
2) FXin and FXout - only one connection point for each - is the other a ground?
3) Same for LED2 - only one connection?
4) You have 4 pots - but Im only seeing 1 pad for P2 and 2 for P3 - where are the rest?
5) what are FXlo and FXli for?

Thanks - the answers are probably right under my nose.

[gurutzeta]

How would you go about adding the vibrato to the circuit? Just having the effects loop is v nice. Maybe just a 'blend' control to set how much the effects loop touches the sound.

I would need to check the datasheets again, but I guess it is a matter of disconnecting pin 26 of the ISD chip (XCLK) from ground and putting there some weird oscillator that changes frequency... sort of a pwm of a sinusoidal LFO, maybe... I am not sure if I left that very clear.... basically you need to have a clock with an oscillating frequency... Something like the oscillator used for flangers, a VCO which is fed an LFO, I guess.... Anyway... lets go to what I can actually answer more precisely:

Some questions about the schematic:

1) SW12 and SW20 appear to be connected by a trace - accurate?
2) FXin and FXout - only one connection point for each - is the other a ground?
3) Same for LED2 - only one connection?
4) You have 4 pots - but Im only seeing 1 pad for P2 and 2 for P3 - where are the rest?
5) what are FXlo and FXli for?

Thanks - the answers are probably right under my nose.

1) That is correct
2) Correct again
3) Wrong!!! That one goes to 9V (you can see it in the schem)
4) There are only 3 pots:
* P1 (the play volume control) is after R7 and R6 and before LM386. It is used as a variable resistor, so you only neer to connect the middle pad and one of the other two. Depending on how you connect it it will work clockwise or anticlockwise.
* P2 (Record volume control)  is connected between R8 and C6 (and 2 pins of the TL074). It is again working as a variable resistor.
* P3 (tone control) works as a variable resistor also, so again you only need to of its pads (which you have found)
5) FXlo is FX loop out. That is the send of the FX loop
   FXli is FX loop in. That is the return of the FX loop

[ethrbunny]

FXin comes from the jack and InFX comes from the switch? Its making more sense now. Pardon my ignorance.

On the digital design page - what is the symbol immediately to the right of the inMBP jack? a JFET?

[gurutzeta]

FXin comes from the jack and InFX comes from the switch? Its making more sense now. Pardon my ignorance.

inFX comes from the switch. Where did I use FXin, I do not seem to find it.

On the digital design page - what is the symbol immediately to the right of the inMBP jack? a JFET?

It is a JFET. I use BS170. Please check geofex for more info about the millenium bypass circuit: http://www.geofex.com/Article_Folders/Millenium/millen.htm

[RDV]

Looky here!
http://www.twinhunter.com/catalog_detail.php?id=243

RDV

[ethrbunny]

RE: caps in the layout -

I got the PC board in the mail today and most of the parts from Mouser. Still haven't tracked down a good place to get the ISD2560 from.

In the spec - you don't give an indication of the polarity of the caps. Is there a cue for this that Im missing?

[gurutzeta]

In the spec - you don't give an indication of the polarity of the caps. Is there a cue for this that Im missing?

I assumed those capacitors  bellow 1uF are non polariced (i.e. ceramic, polyester...). For those above or equal to 1uF, you will need to check the schem. The curved side is the negative and the straight is the positive (I hope nobody gets offended by this :wink: ).

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