Remix/ReMangle" Challenge is Closed. Now to work on the file management, uploading, playlist, voting thread, etc. Thanks to all that participated. Get ready to vote!

Prizes generously donated by:
ADDAC System (Eurorack 3U)
Endorphin.es (Eurorack 3U)
Fred's Lab (DIY Paraphonic Synth)
Northern Light Modular (Buchla-format h-series OR Eurorack3U)
Rattly and Raw (Wiggler Approved Kontakt Instrument)
Studio.h (Buchla-format 4U)

Challenge rules and format thread is here.

ARP 1601 clone Build Thread

From circuitbending to homebrew stompboxes & synths, keep the DIY spirit alive!

Moderators: Kent, luketeaford, Joe.

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MrRoper
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Post by MrRoper » Sat May 30, 2015 4:10 am

nickster wrote: I may be able to help you out. I have a bunch on order. Provided I get the correct items I should have some spare. Once these have arrived I'll get back in touch.
That would be amazing Nickster, thanks a lot :tu:

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xpmtl
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Post by xpmtl » Sat May 30, 2015 6:59 am

nickster wrote: I may be able to help you out. I have a bunch on order. Provided I get the correct items I should have some spare. Once these have arrived I'll get back in touch.
Interested in 3 as well ;)

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Altitude909
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Post by Altitude909 » Sun May 31, 2015 4:15 pm

Just a tip for anyone getting ready to do the 3.5 jacks:

Use the faceplate as a template to line everything up, the foot print is pretty loose and the holes are "tight like man's anus" as Borat would say. Going blind will probably result in much cursing later when you're pounding the faceplate on or desoldering the jacks

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magman
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Post by magman » Mon Jun 01, 2015 11:50 am

Ok, time for some more thoughts on the spacer issue I raised earlier. I had the pleasure to meet Kipling at the Brighton Synth meet and saw his build, which made things a little clearer for me.

It now turns out that I didn't exactly follow Kipling's build instructions about mounting the switches, I actually mounted the switches directly to the PCB, flush with the step on the switch solder lugs. This makes the switches around 11mm from the PCB surface, within a few 10th's of a millimetre.

If the jacks are also mounted flush with the PCB, these actually come in at a height of around 10.8mm, so I think on balance I'm quite happy with choices I have made, but the mounting method that Kipling has described will also work. So the choice is over to you folks.

Oh, and by the way, the sequencer was very well received at the Brighton meet, with at least 5 more people interested in taking one on, and a lot of Kudos for Kipling. :hihi: :hihi: :party:

Regards

Magman

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ultravox
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Post by ultravox » Mon Jun 01, 2015 3:17 pm

Finished and calibrated..with the following findings..

During the A/B MOD adjustment I got +4.34 volts instead of "near +5 volts". In normal operation the A/B Quantized outputs reach +10 volts when the pitch sliders are only 7/8 of their full position. Also the clock stops running when the Clock Freq slider is lower than 1/4 travel. Finally, when turning on the unit it automatically steps to pitch slider 2 instead of staying on pitch slider 1.

I don't know if these are issues or normal operation, but it works fine with my TTSH and Odyssey, and it looks great! :hihi:

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Image
Image

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Kipling
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Post by Kipling » Mon Jun 01, 2015 4:48 pm

ultravox wrote:Finished and calibrated..with the following findings..

During the A/B MOD adjustment I got +4.34 volts instead of "near +5 volts". In normal operation the A/B Quantized outputs reach +10 volts when the pitch sliders are only 7/8 of their full position. Also the clock stops running when the Clock Freq slider is lower than 1/4 travel. Finally, when turning on the unit it automatically steps to pitch slider 2 instead of staying on pitch slider 1.

I don't know if these are issues or normal operation, but it works fine with my TTSH and Odyssey, and it looks great! :hihi:
Certainly does look good with those end-cheeks, and nice neat internal layout.

The pitch sliders are B2 taper so reach max or min a few mm before hitting the end stop. A shame they are not available in B1 taper where the carbon track goes all the way to each end, unlike the 45mm version where B1 is available.

I'll have a think about the clock freq slider - mine seems to be fine and I haven't calibrated that bit yet - just left the R19 freq cal trimmer mid-position. Haven't touched the PW cal trimmer yet either - mid position again and it seems fine to me as is.

Mine also powers up and jumps to position 2 more often than not so I guess it's a 'feature'. Jusy hit reset to start at position 1.

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ultravox
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Post by ultravox » Mon Jun 01, 2015 5:07 pm

My iPhone didn't do it any justice. Maybe I'll ask the wife to use her DSLR since she's a better photographer than me.

The sequencer works great and there's no real need to fix those snags. I'll only need to open it up later this week when I install the rubber feet. After that it'll stay closed up till time for it's next checkup.

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Post by fuzzbass » Tue Jun 02, 2015 8:45 am

ultravox wrote:Finished and calibrated
Looks great, can't wait to get past my current paid jobs so I can build one of these!

You have both a linear supply and DC/DC converter. How come you didn't just put in a +/- 15V linear supply and leave it at that?

[edit] Oh yeah, its a switching power supply. I think I get it now.
Wired for weird

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ultravox
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Post by ultravox » Tue Jun 02, 2015 9:04 am

Hey fuzzbass, I had a stash of those switchers and that was my last one. All my future builds will be linear. :hihi:

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Post by Altitude909 » Wed Jun 03, 2015 6:33 pm

do the buttons seem skippy for anyone? Start stop is somewhat intermittent on mine and skip will skip more than one step often

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ultravox
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Post by ultravox » Wed Jun 03, 2015 10:44 pm

Altitude909 wrote:do the buttons seem skippy for anyone? Start stop is somewhat intermittent on mine and skip will skip more than one step often
Start/Stop is a little intermittent here, but Skip seems to work ok. I found that giving Start/Stop a quick press works better than a longer press.

Been watching youtube for some ideas on what this thing can do. Looks like once you get the hang of using the gate bus outs you can get into the Depeche Mode realm of things. :tu:

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duff
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Post by duff » Thu Jun 04, 2015 12:04 am

Altitude909 wrote:do the buttons seem skippy for anyone? Start stop is somewhat intermittent on mine and skip will skip more than one step often
I find start stop often appears to start then stop, like it double triggers. Not really noticed it on any of the other buttons, but that may be because I have mostly been using the CV ins rather than the buttons.

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Nordcore
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Post by Nordcore » Thu Jun 04, 2015 12:22 am

Is a schematic for the clone out there?

Looking at the original: try to increase C5 from 10nF to 22nF.

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Kipling
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Post by Kipling » Thu Jun 04, 2015 1:45 am

Nordcore wrote:Is a schematic for the clone out there?

Looking at the original: try to increase C5 from 10nF to 22nF.
It's in the service manual on post #1. I suspect it's a contact bounce issue with the Cherry MX switches and needs de-bouncing for a permanent fix. If anyone has a solution I can try to squeeze it onto a future Rev 3 PCB.

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Post by Nordcore » Thu Jun 04, 2015 1:51 am

C5 is the cap intended for debouncing.

It limits the toggle speed of the start stop flip flop Z2B.

The trick is that it does not introduce delay. The first pulse on clock input throws the flip flop. But further pulses do nothing, until C5 has charged/discharged, which takes a couple of milliseconds.

That explains why *one* direction might work better than the other: if the trip level of the data input is not exactly half supply than the behavior gets asymmetrical.

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magman
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Post by magman » Thu Jun 04, 2015 2:04 am

I've seen loads of circuits for this type of function, here's one I found after a quick Google search:

http://www.ikalogic.com/de-bouncing-circuits/

Looks like it would be useful to add a Scmidt trigger in the circuit if possible. I might have a go at a dead bug mod to see if it helps.

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Post by Nordcore » Thu Jun 04, 2015 3:20 am

You don't want to add the debouncing time - about 20ms - as lag to the start input.

There is a 4011, which might be replaced with a 4093, same logic but schmitt trigger inputs.
Than you could add the debouncing RC to *one* of the NAND inputs and dedicate that to the button. The other one, w/o RC, stays for the jack circuitry.
Needs:
- one trace cut (switch to 4011)
- one pin of 4093 not in the socket.
- two resistors, one cap in "point to point" wiring.

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Post by Altitude909 » Thu Jun 04, 2015 6:57 am

Nordcore wrote:You don't want to add the debouncing time - about 20ms - as lag to the start input.

There is a 4011, which might be replaced with a 4093, same logic but schmitt trigger inputs.
Than you could add the debouncing RC to *one* of the NAND inputs and dedicate that to the button. The other one, w/o RC, stays for the jack circuitry.
Needs:
- one trace cut (switch to 4011)
- one pin of 4093 not in the socket.
- two resistors, one cap in "point to point" wiring.
22nF cap helps a little, but doesn't solve it.

Can you elaborate on the 4093 approach?

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Post by fuzzbass » Thu Jun 04, 2015 6:58 am

Nordcore wrote:You don't want to add the debouncing time - about 20ms - as lag to the start input.

There is a 4011, which might be replaced with a 4093, same logic but schmitt trigger inputs.
Than you could add the debouncing RC to *one* of the NAND inputs and dedicate that to the button. The other one, w/o RC, stays for the jack circuitry.
Needs:
- one trace cut (switch to 4011)
- one pin of 4093 not in the socket.
- two resistors, one cap in "point to point" wiring.
This is exactly why I stand back and let nordcore do the rev1 build first!
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Post by ultravox » Thu Jun 04, 2015 1:29 pm

ultravox wrote: During the A/B MOD adjustment I got +4.34 volts instead of "near +5 volts". In normal operation the A/B Quantized outputs reach +10 volts when the pitch sliders are only 7/8 of their full position. Also the clock stops running when the Clock Freq slider is lower than 1/4 travel. Finally, when turning on the unit it automatically steps to pitch slider 2 instead of staying on pitch slider 1.
I was able to get the Clock Freq slider to work full travel by increasing the resistance of R17 to approx 222.5k. I didn't have a resistor of that value so I put a 100k trimmer in series with R17 and adjusted it so that the clock will still operate when the slider is set to min. The Clock Freq slider now gives 1Hz - 100Hz from min to max travel. :tu:

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Post by Nordcore » Thu Jun 04, 2015 5:30 pm

fuzzbass wrote:This is exactly why I stand back and let nordcore do the rev1 build first!
oh .. I don't build one. I don't like vintage digital.

Idea:
untested, *NOT* recommended for a board revision, that could be done better[1]. Cap value might be a little on the large side - half should be enough!
Replace Z1, CD4011 with CD4093!

Image


[1] Use a hex schmitt trigger inverter for Z1. That would give you two free inverters. Put them in front of the data input of the flip flop (Z2-Pin9). Than the 10nF could be increased sufficient to debounce any switch.

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Post by Altitude909 » Fri Jun 05, 2015 8:36 am

so 4011 to 4093 and break the connections in your diagram?

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Post by Kipling » Fri Jun 05, 2015 9:15 am

Altitude909 wrote:so 4011 to 4093 and break the connections in your diagram?
Plus the extra resistor and capacitor.

Not at home now so don't have the PCB to hand so unable to say which side of the board the relevant tracks are.

One word of caution if cutting tracks - the board is 4-layer and the inner layers are the power planes. IIRC the component side is the +15V plane so the side facing the panel is the 0V plane. Make sure you only cut through the signal track and not too deep so it could short to the power plane.

If I can test this myself I certainly will (I won't have a CD4093 for certain) and if there's still time I could hold the PCB manufacture and revise the board accordingly for round 2 if the mod is successful.

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Post by Nordcore » Fri Jun 05, 2015 9:28 am

May be you first try out, if it does work with 47nF for C5.

Have a look with a scope what really goes wrong there...

===

Pin 5 of Z1 must not be a cut trace - just bend the pin away a little so it does not go to the socket. Solder the resistor to the pin.
(And no, you will not kill the chip with the soldering iron. At least I never succeeded in that ... and I've tried hard ... )

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Post by Altitude909 » Fri Jun 05, 2015 10:03 am

got it. I'll have some 4093s tomorrow to give it a whirl

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