1BIT Multitap Delay by FEEDBACK [UPDATE]

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1BIT Multitap Delay by FEEDBACK [UPDATE]

Post by strat-1 » Mon Aug 21, 2017 4:00 pm

www.feedbackmodules.com

[UPDATE] I updated the boards to REV2.0, with following changes :
- I added a transistor buffer for the gate led (from the switch). Now the led have the same intensity on both 5v or 10v gate signals.
The led is not powered from the gate voltage anymore, so there is no load on the gate voltage.
- I added 74HC541N octal buffer between the SRAMs and TAP Switches.
- Grounded some gates of CD4049s, for a better stability.

These changes does not affect the 1BIT Delay sound. Nothing was wrong with the previous version.
I just checked again if I can do some improvements of the circuit.

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1BIT Multitap Delay is an adaptation of classic 1bit delays from the 80s to eurorack with many interesting add-ons.
As the name states this module is a digital delay with 1BIT AD/DA and no CPU inside, similar in design with old delays like : Ursa Major, ADA and Effectron.
Even if it's digital, the module have a warm sound with analog BBD feel, but without the high loss on long delay times.
With two independent taps and outputs you can play with those classic running arps.
For example you can have a long delay on the TAP1 output, using x8 setup, and synced short delay on the TAP2 output, using x4 setup.
You can listen both taps on the mix output, or you can put them in stereo with independent outputs. You have a nice stereo effect even if you use x8 taps on both outputs.
The maximum time is 750ms-800ms. I calibrated the module in a way you can obtain dirty long delay sounds, so you can also use the module in the noise area.
With the LOOP functions you can freeze the sound, obtaining nice crazy effects. Also you can do that in sync with a gate in input.

The module uses 64K old school srams to delay the sound.
The DIY project will need 8 x 4164 64K memories, widely available on ebay. They were used a lot in old computers like commodore, spectrum, also in all the delays of the era, so a big stock of them still exists.

ATTENTION! AFTER BUYING LARGE QUANTITIES OF MEMORY CHIPS, I DISCOVERED 20-25% OF THEM ARE NOISY, DAMAGED OR NONFUNCTIONING.
I RECOMMEND YOU TO ORDER 15-20PCS. OF THEM AND CHOOSE THE WORKING ONES AS EXPLAINED IN THE MANUAL.
(this is common for all the different lots I purchased, it's depending on how they were stored, handled, electrostatic discharges etc.)

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There are 3 types of kit available on my website :

KIT1 : 3 x PCBs + Front Panel
KIT2 : 3 x PCBs + Front Panel, 8 x 4164 SRAM Chips (tested)
KIT3 : 3 x PCBs + Front Panel, 8 x 4164 SRAM Chips (tested)
8 x Minijack sockets, 2 x 8 pos switches, 1 x Momentary push switch
7 x 10KB 9mm pots, 3 x 50KA 9mm pots, 1 x 100KB 9mm pot, 1 x 500KB 9mm pots, 11 X Cream Knobs 1900h type, 3 x Big Cream Knob 1510 type
3 x 3 way header MALE, 3 x 3 way header FEMALE, 2 x 6 way header MALE, 2 x 6 way header FEMALE, 3 x 14 way header MALE, 3 x 14 way header FEMALE

Thank you Future Music Magazine and DivKid for this really well explained video :



Also ColorMySound



https://soundcloud.com/strat1/1bitdelay-synth
https://soundcloud.com/strat1/1bitdelay-drums
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Last edited by strat-1 on Tue May 12, 2020 2:47 am, edited 39 times in total.

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Post by sduck » Mon Aug 21, 2017 8:19 pm

Sign me up! That's a lot of chips.
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Post by strat-1 » Mon Aug 21, 2017 11:31 pm

sduck wrote:Sign me up! That's a lot of chips.
The project is not so expensive as it appears, except the memory ics, all the chips are classic logic ics (cds), very cheap. Also there is 1xLM13700.

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Post by latigid on » Tue Aug 22, 2017 12:49 am

Looks like a very nice creation!

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Post by BugBrand » Tue Aug 22, 2017 1:50 am

Interesting! Early digi-delays are very interesting - the schematics always made my head spin a bit.
I think a design like this could benefit from being a bit more spacious, layout-wise. The usual Euro issue!
And perhaps one can add an insert point on the feedback paths? Being able to EQ there is very useful for delays.

Great work!

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Post by strat-1 » Tue Aug 22, 2017 2:01 am

BugBrand wrote:Interesting! Early digi-delays are very interesting - the schematics always made my head spin a bit.
I think a design like this could benefit from being a bit more spacious, layout-wise. The usual Euro issue!
And perhaps one can add an insert point on the feedback paths? Being able to EQ there is very useful for delays.

Great work!
The hard/soft/off switches, are EQ switches. I tried various pot combinations, and in the end I kept the switch version. Hard cuts the highs giving a bbd feel
to the effect. Middle pass a some highs and off let a lot off digital garbage to come thru.

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Post by DisappearHere » Tue Aug 22, 2017 6:29 am

What's the depth of the module (at the present revision)?

Looks great, I would definitely be keen.

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Post by strat-1 » Tue Aug 22, 2017 6:37 am

DisappearHere wrote:What's the depth of the module (at the present revision)?

Looks great, I would definitely be keen.
Just like TWO59 Shaper - 48mm with power connector inserted

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Post by tobb » Tue Aug 22, 2017 6:38 am

damn,awesome! :hail:

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Post by dubtoms » Tue Aug 22, 2017 7:30 am

:hail: Would you mind sharing the list of CD40XX ics used in this project ? I'd like to check what I already got :)

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Post by SoundPool » Tue Aug 22, 2017 7:43 am

oof, first eurorack project to actually tempt me in a long while. love this kind of sound.

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Post by strat-1 » Tue Aug 22, 2017 7:48 am

dubtoms wrote::hail: Would you mind sharing the list of CD40XX ics used in this project ? I'd like to check what I already got :)
1pcs RC4558
3pcs TL071
4pcs TL072
4pcs TL074
1pcs LM311
1pcs LM13700
3pcs CD4013
3pcs CD4015
3pcs CD4016
2pcs CD4019
1pcs CD4046
3pcs CD4049
1pcs CD4051
2pcs CD4520
8pcs MN4164P or KM4164B or other 64K sram with the same pinout

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Post by strat-1 » Tue Aug 22, 2017 7:51 am

SoundPool wrote:oof, first eurorack project to actually tempt me in a long while. love this kind of sound.
I have several 80s rack unit delays, I made this project because I always wanted something like this in my eurorack.
I'm not satisfied by other euro delays I have, the PT delays are a bit too dirty, the pro delays with dacs and arms sound a bit too metallic and the long time bbd ones losses a lot of highs on long delays.

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Post by BugBrand » Tue Aug 22, 2017 8:01 am

Glad you've not peppered the design with tantalum caps across the power lines like the old classics!

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Post by strat-1 » Tue Aug 22, 2017 8:06 am

BugBrand wrote:Glad you've not peppered the design with tantalum caps across the power lines like the old classics!
Tantalum caps are dying in time. I prefer Panasonic FC and Nichicon UTT

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Post by BugBrand » Tue Aug 22, 2017 8:19 am

Yes, my point (not clearly made).
I've resurrected a couple of nice machines due to such failures.

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Post by dubtoms » Tue Aug 22, 2017 8:39 am

Thanks for the list Andrei, I just found 11 NEC 4164 ics (which seem to be pin compatible with yours) in one of my drawers so I'm definitely building this ! :party:

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Post by strat-1 » Tue Aug 22, 2017 8:41 am

dubtoms wrote:Thanks for the list Andrei, I just found 11 NEC 4164 ics (which seem to be pin compatible with yours) in one of my drawers so I'm definitely building this ! :party:
take good care how you handle the pins, you can burn them with electrical discharges from the hands :)

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Post by dubtoms » Tue Aug 22, 2017 8:47 am

Thanks for the warning, I've been spinning some records today so I may have built some static and killed a few without knowing it :hmm:

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Post by spneca » Tue Aug 22, 2017 8:58 am

This is great. I'm in for one.

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Post by windspirit » Tue Aug 22, 2017 9:59 am

Dude yes,love the sound and love to have some variety in DIY from the pt based delays (nothing wrong with those but nice to have options). Any chance you will be selling the memory chips so that we know we are getting chips that have been tested and work?

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Post by strat-1 » Tue Aug 22, 2017 10:01 am

windspirit wrote:Dude yes,love the sound and love to have some variety in DIY from the pt based delays (nothing wrong with those but nice to have options). Any chance you will be selling the memory chips so that we know we are getting chips that have been tested and work?
I'm trying to secure memories for kits. The PCBs are almost ready and still working on the manual, BOM etc.

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Post by Dimitree » Tue Aug 22, 2017 10:13 am

I'm curious to understand how this work. I'm aware of 80's digital delays with no cpu and only dram+adc+dac and all the logic needed for addressing, but they usually employ 12 bit converters. How can you do it with 1 bit converters? And what's the sample rate?

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Post by sduck » Tue Aug 22, 2017 10:46 am

Cool! I just bought a lot of MN4164P on ebay. Looking forward to this!
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Post by Swyndger » Tue Aug 22, 2017 12:21 pm

Wow! Great! Looking forward to build it :)

EDIT: Oh, I see 16 MB8264A-12 laying arround here. Pin layout seems to be the same ... maybe they are OK?
Last edited by Swyndger on Tue Aug 22, 2017 12:48 pm, edited 1 time in total.

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