Dean Hazelwanters Mobius Trip Looper build questions

[optimus_prime_1985]

OK. I am about 95% done with this project http://www.generalguitargadgets.com/index.php?option=content&task=view&id=203&Itemid=228 and I have a couple questions.

1. over which pins of the ISD chip does the disc cap get soldered?
2. What is the value of this disc cap?
3. Where do the 2 footswitches "record/play and on/off" connect to the      board?
4. Where does the record safe toggle connect to the board?
5. What kind of LED does the layout call for. I see 3 connections. Is this a  multicolored LED?

I know these are a lot of questions. This is my first time doing a project with a layout like this. Pot logs being numbered and so on. I tried answering these questions by looking at the schematic but since it deals with several ICs and I am not as familiar with the symbols I am having a bit of trouble. Thanks a lot guys.

Karl

[optimus_prime_1985]

It appears  I was a bit hast about question 1 and 2. The link I provided gave the cap value and the pin numbers. So please disregard question 1 and 2. Sorry guys.

Karl

[Dean Hazelwanter]

Hi...

I used little 0.1" pin header connectors for the off-board connections.

#3: On the connector outline labelled 'Switch', O, C and R refer to 'On', 'Common', and 'Record' respectively. 'On' goes to the node connected to pin 23 of the ISD1000. 'Record' goes to the node connected to pins 4, 9, 10, 27 of the ISD1000. 'Common' goes to 0v.

#4: You'll notice on the schematic that the Play/Record and Safe/Record switches are in series. Both of these switches have to be closed (connecting pins 4, 9, 10, 27 to 0v) for the chip to record. If either switch is open, it won't record. The Safe/Record switch is optional.

#5: On the connector outline labelled 'LED', R, C and O refer to 'Record', 'Common' and 'On'. R goes to the anode of the Record LED, O goes to the On LED anode, and C goes to both cathodes, as per the schematic. You could also use a bi-colored LED with a common cathode, But I would use a separate red LED for Record, and a green LED for On.

I didn't label things as clearly as I should have, so if you have more questions, feel free to ask!

Here are some notes as to how it operates:

Here's how it works. With both switches (thus LEDs) off, close the Record/Play switch, which turns on the Record (red) LED, and *arms* it to record the sample. (The Record/Safe switch is just a safeguard to not arm the chip to record a sample, to prevent accidental erasure of the current sample.) Note that it's not actually recording yet. Open the Enable switch, and you're recording *now*, and the 'On' (green) LED comes on. When done recording the sample (less than 20 seconds), Close the Enable switch to stop recording. Disarm recording by opening the Record/Play switch, and the red LED goes off. Now open the Enable switch (which turns on the green LED), and it will continue to play the sample until you close the enable switch again, or unplug it. Note that it still keeps the sample in memory even if the circuit is unplugged.

[optimus_prime_1985]

Dean. Thanks so much. It is crystal clear now. Thanks for a great explanation.

[mathflan]

Hi,

I finished to build the mobius trip with a ISD 1020AP from smallbear but It doesn't work. I have the
I have some questions:

- I Don't understand the connections of The Switch Record /play. On the schematic , "C" goes to Pin 1 of 4001, IC 2 whereas ont the PCB, "C" goes to ground, I have the feeling that "C" and "R" are inversed.

- Is the Switch Record Play is a  ON/OFF/ON switch?

- On the PCB pin 1,2,3,5,6,26 of the ISD are not connect to 0V,
I have the feeling that there are some mistakes...


thanks if you can help me

[putrefusion]

this is a good thread, bookmarking...

[Dean Hazelwanter]

Mathflan:

- On the PCB pin 1,2,3,5,6,26 of the ISD are not connect to 0V,
I have the feeling that there are some mistakes...

WTF?? Crap, you're right!  :shock:  Mine works, and uses the same board layout. I'll add the jumper tonight on my board, just to confirm it doesn't cause any problems.

- Is the Switch Record Play is a ON/OFF/ON switch?

Nope, On/On.

- I Don't understand the connections of The Switch Record /play. On the schematic , "C" goes to Pin 1 of 4001, IC 2 whereas ont the PCB, "C" goes to ground, I have the feeling that "C" and "R" are inversed.

No, C and R (and O) are right on the PCB. They stand for Record, On and Common - as in the common connection that goes to one side of each of the switches. There is no O, C, R designations on the schematic, and I drew it in a way to make it clear what was happening when it was being switched. I could have just as easily used SPST switches, but it wouldn't have been as clear.

Does that help?

[mathflan]

Ok thanks

So Everything is ok, all works.
I'll try to add a compander to clean the noise of the ISD ans A FX sen and return

Bye

[ryanscissorhands]

I just took a look at the PCB and see the pins that are not connected to ground. What is the best way to connect them to ground, jumper pins 6-12/13?

[Dean Hazelwanter]

Ok, I just added a jumper from pins 5&6 to 12&13, and tested it with both the ISD1000AP and the ISD1020AP. Although it seems to work the same with or without the jumper, I STRONGLY recommend adding it, since it's never a good idea to leave inputs like this floating.

[optimus_prime_1985]

Dean,

 I should still have a 0.1 disc cap between pins 12&13 and pin 28 right? Mines not working either but I am still going through the debugging stage and it's almost certainly a goof on my part. All the Leds light as they should in record and play position and the dry signal level pot works when the effect is engaged but its not recording. When I switch from record to play it makes slight sound like its ramping up for about a second and then silent. I will try these jumpers and see if I have some luck.

[Dean Hazelwanter]

I should still have a 0.1 disc cap between pins 12&13 and pin 28 right?

Yes.

All the Leds light as they should in record and play position and the dry signal level pot works when the effect is engaged but its not recording.

- Make sure that the REC and PLAY pots are wired correctly and are turned up.
- Try swapping the opamps. If the dry signal stops, you found the problem.
- Check solder connections and component values around U3 (the dual opamp closest to the ISD1000).

[ryanscissorhands]

How crucial is it for the pin 12/13 to 28 capacitor to be ceramic disc?

[keninverse]

this is just a bypass cap so you can use film or ceramic.  But, ceramics are better suited here b/c this is a digital circuit  (they're also low in inductance and work well for screening RF).  That's not to say that all disc caps are good.  If you're planning on stocking up on some ceramics for bypassing, get the axial variety that look like little beads.

[mathflan]

HI,

I'am wondering Why the mobius trip looper and dirtysam use the Speaker's ouput, We cannot use the ANALOG OUT??
I

[The Tone God]

I'am wondering Why the mobius trip looper and dirtysam use the Speaker's ouput, We cannot use the ANALOG OUT??I

Read the all knowning datasheet.

Andrew

[mathflan]

sorry I'am not very good in english and I didn't see anything which talk about that.

Just an other thing, I know  that I post stupid questions :oops: .
Is that possible witch ISD chips to reverse the playback, that's would be cool!

[optimus_prime_1985]

No, unfortunately the ISD chip will not play backwards. In fact I don't know of any analog ic based delay that plays backward.  I have seen plenty digital units that do but not analog.

Hey guys are there any analog delays that play backward or is this just not possible with analog ic based delay?

[The Tone God]

sorry I'am not very good in english and I didn't see anything which talk about that.

Well either reading the pin description or looking at the block diagram will tell you that the "analog out" pin is only the output of the internal preamp section before the digital recording section.

Is that possible witch ISD chips to reverse the playback, that's would be cool!

Nope. Everything is controlled but internal clock and processor which there is no access to. Remember that these ICs are basically ment to replace answering machines, tape recorders, and pre-recorded audio to be called up on demand. They are NOT delays.

Andrew

[coma57]

Hi
I try to build this one with an ISD2560P, but the pin configuration is not the same! It have 9 adress buffers! So here is my question:
Do I have to connect A9 and A8 instead of A6 and A7, and connect all other AB to the ground? Or just ignore pins A9 and A8?
I'm a bit lost in this!
Thanks