zvex lofi loop junky - hows that work?

ethrbunny · November 17, 2004, 10:30:19 AM

32% scaling of the jpg was too small. Is there anyway to figure out what the proper scaling would be before I order a new board?

gurutzeta · November 17, 2004, 12:46:59 PM

Quote from: ethrbunny32% scaling of the jpg was too small. Is there anyway to figure out what the proper scaling would be before I order a new board?

Print it and check that the distance between holes of pins of the opamps is correct, for example. That is how I did it at least.

Torchy · November 17, 2004, 12:48:47 PM

crp

gurutzeta · November 17, 2004, 01:25:40 PM

Quote from: Torchy
Quote from: gurutzetaIt is a JFET. I use BS170.

Thats a mosfet ...

Thanks for the correction, I was testing to see if you all were paying attentiont :wink: .

ethrbunny · November 18, 2004, 11:43:06 AM

Im trying to decide whether or not to 'frankenstein' the board with jumpers to a board with just the ICs. .. hmm.. what is my time worth.. hmmm...

ethrbunny · December 01, 2004, 07:49:36 PM

ok. got a new board. sockets fit now. am slogging ahead!

Michael Allen · December 01, 2004, 08:15:58 PM

this is gonna be righteous

ethrbunny · December 01, 2004, 08:38:46 PM

Quote from: Michael Allenthis is gonna be righteous

.. lets hope ..

Im still questing about for enclosures for this and for a 'fender blender'. Suggestions?

Hmm... I wonder if my daughter would miss her elmo doll..

"daddy - why are you stepping on elmo? and why are his eyes blinking?"

ethrbunny · December 01, 2004, 11:32:22 PM

Gurutzeta - 2 questions

1) what is d4? another 1N4148?
2) R8 - 3.2M ? Really?

Hopefully I can post a pic of the built board soon.

Michael Allen · December 02, 2004, 12:52:18 AM

how bout a picture of the board itself?

zachary vex · December 02, 2004, 01:21:58 AM

Quote from: gurutzeta
Quote from: ethrbunnyHow 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....

it's easier to just vary the supply voltage to the chip. 8^) but don't go too high! it'll make the chip freeze up. the trick is to set up an oscillator that varies the chip's power supply in equal amounts up and down from the record voltage (and turn off the vibrato during record, of course) so that the average pitch is about equal to the original guitar pitch and the overall time for playback is identical to the time it takes with the vibrato off... if your oscillation biases the average dc voltage lower than the non-vibrato voltage, the loop will play longer with the vibrato on, the sample will play back generally flat, and it will screw up the timing during performance.

Dragonfly · December 02, 2004, 10:44:01 AM

Quote from: RDVLooky here!
http://www.twinhunter.com/catalog_detail.php?id=243

RDV

hmmmmmm......ready made looper.....

gurutzeta · December 02, 2004, 03:06:11 PM

Quote from: ethrbunnyGurutzeta - 2 questions

1) what is d4? another 1N4148?
2) R8 - 3.2M ? Really?

Hopefully I can post a pic of the built board soon.

1) Yes, all diodes are 1N4148.
2) Yes, I used 3.2 M. It is making an inverter amplifier together with OA2 and P2. The relationship is ANAin = - ( P2/R8 ) * InFx
You might replace it with a different value if you also change P2 (as long as you keep the same value for P2/R8 )

gurutzeta · December 02, 2004, 03:08:11 PM

Quote from: zachary vex
it's easier to just vary the supply voltage to the chip. 8^) but don't go too high! it'll make the chip freeze up. the trick is to set up an oscillator that varies the chip's power supply in equal amounts up and down from the record voltage (and turn off the vibrato during record, of course) so that the average pitch is about equal to the original guitar pitch and the overall time for playback is identical to the time it takes with the vibrato off... if your oscillation biases the average dc voltage lower than the non-vibrato voltage, the loop will play longer with the vibrato on, the sample will play back generally flat, and it will screw up the timing during performance.

Shit!!! did not think about that!!! Thanks ZVEX...

mathflan · December 15, 2004, 05:43:12 PM

hi! guys
so thanks gurutzeta!

it's HUGE

I want to mad this effetc but can I put ISD25120P with 120s into that circuit???. so i can I have 120s , maybe it's not useful to have a lot seconde loop??

Where I can thes IC??
http://www.jameco.com

is good??thanks

gurutzeta · December 15, 2004, 06:02:00 PM

Quote from: mathflanI want to mad this effetc but can I put ISD25120P with 120s into that circuit???. so i can I have 120s , maybe it's not useful to have a lot seconde loop??

You could do it, but it would reduce the quality of the looped sound dramatically. Up to you.

Quote from: mathflanWhere I can thes IC??
http://www.jameco.com is good??thanks

I got them from http://rswww.com

ethrbunny · December 15, 2004, 07:05:21 PM

Why would the longer-storing winbond chips have a lower quality of playback?

zachary vex · December 15, 2004, 11:39:41 PM

you can look at the frequency response of each type of winbond chip at their website. they vary from somewhere in the 2k range to above 3k... i have listened to the 3k versions and i've found that not only do they sound somewhat more noisy because of the filter response, but they have a very annoying tone to them with that hard knee near 3k. it's actually a smoother sound to have them rolled off in the mid 2k region because it's easier on the ear. people over 30 especially have a sensitivity to sounds in the 3k "spike" area of the spectrum. sometimes, more is NOT better. 8^)

i don't think that the longer winbond chips have a response that's much lower than the short ones. the biggest problem with winbond is that they changed their control circuitry so many times that it makes your head spin when you try to come up with circuits to make them into effective loopers. the one i use, the 1420, can be replaced with another in the 1400 series that is slightly shorter but has higher frequency response, and i've never liked a thing about it.

ethrbunny · December 16, 2004, 12:36:08 AM

Eeeek. :shock: Well, I ordered a 2560 for my Gurutzeta box.. I hope it will work ok.

gurutzeta · December 16, 2004, 02:52:20 AM

Quote from: ethrbunnyEeeek. :shock: Well, I ordered a 2560 for my Gurutzeta box.. I hope it will work ok.

60 should be OK is from there onwards that starts getting bad. Basically the 120 is the same chip as the 60 but with a sample frequency of half of the one in the 60.

Bellow 60 the chips are the same as the 60 (sample frequency wise) but with less capacity, less "analog memory"

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zvex lofi loop junky - hows that work?