Reticon SAD1024 Delay Chip

Question

Reaching out to the people on this web site.......

I'm after a SAD1024 delay chip, they were manufactured by Reticon and are now discontinued, and have been for around 30 years. I'm hoping someone here may have one lying around....... if so can you get back to me and I'll make you an offer to buy it off you.

As a heads up this is required for a planned pedal build, for the near future, but it all rests on being able to obtain this IC chip.

The data sheet is available to read here

http://www.pmerecords.com/Docs/Archer_SAD-1024_Tech_Data.pdf

Andy Betts · Accepted Answer

I had a surprise in the last few weeks. I received an email from a gentleman named Niels who said he had 2 SAD1024 chips at work that they didn't need. Without any further ado he mailed them to me free of charge!!! I emailed him back and said i wanted to pay-pal him some money as a token gesture which I did to cover postage and give a small bit on top as a thank you. people I've met through this forum have been really helpful, and selfless and will always try to help where they can..... This has got to be one of the best support forums for electronics out there. many thanks Niels, you have saved me a lot of heart ache, and expense.... i'll be sure to post the end result of the build on here once it's been completed. HAVE A GREAT 2018 ALL, MAY THE COMING YEAR BE GOOD TO ALL

jw0752 · Answer

Hi Andy,

I checked and I do not have this chip. Apparently it was sold for a while by Radio Shack under stock number 276-1761. There was some talk on the following link about using a MN3007 as a possible substitute.

http://music-electronics-forum.com/t23353/

I see that there are two or three listed on ebay but the sellers know they have little pieces of gold judging by the price tags.

John

w5txrlabs · Answer

I have 5 original SAD-1024A Analog Delay IC's Line New still in the package w/the spec sheet (Sealed - Never opened) Im an American ham radio operator W5TXR. e-mail me at w5txr B(at) w5txr (dot)ty West Of course ignore the West An(net)te The address is intentionally messed up to fool bots. interested I can send you some pics

michaelkellett · Answer

I thought about making a replica using modern bits, ADC , digital processing, DAC. Because of the way the chip works an exact replica is tricky:

For an approximation:

AD SSM2604, 24 bit 96kHz sample rate dual ADC/DAC for about £5 from Farnell, controlled by a little FPGA or possibly a DSP - the parts shouldn't cost more than £20 in total but you will need a PCB and the software won't be easy.

To make an exact duplicate is harder because the original chip samples at up to 2MHz and you would need to use SAR ADCs and a fast DAC - parts up to maybe £60 or even more.

So, for the time being , it's probably better to just bite the bullet and cough up for the old bits.

MK

Andy Betts · Answer

I've done some digging, and a while ago a company called Hartman brought out a clone of this pedal... I don't believe they sell it any more, but i could try looking for a schematic for that. From all the write ups I've read, it's exactly the same as the old Electric Mistress however I believe they substituted a different IC in that position. Unfortunately I've yet to find a schematic for that pedal as it's a boutique pedal, and these manufacturers are fiercely secretive about releasing schematics for their pedals. Here's a You Tube video that AB tests the Hartman against a genuine Electric Mistress..... I need to find out what components they used. He does say in this video that the Hartman uses the same delay chips as the original... Which may be true, and also might answer why they don't make them any more

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michaelkellett · Answer

I can - but I'd need to to see enthusiasm (huge amount) or business (less huge) It won't be exactly the same but should be very close. You need a dual channel simultaneous 16 bit ADC and drivers, a small FPGA and a dual DAC and filter. It won't be the same size as the original chip and won't have the same distortion and noise profile - the Reticon chip distortion increases with signal level but an ADC based system will have low distortion at high levels but quantising distortion at low levels. The parts will cost about £30 (100 sets built) and more if a smaller number. If I sold such a thing at £60 a pop - I'd need to sell more than 500 to make it commercially viable. I'd consider it as a community project if there were enough support. MK

madboy · Answer

I have 4 that I am looking to part with... a gift from my now ex father-in-law. They have never been used... Let me know if this is something I can help you with! Martin

michaelkellett · Answer

Andy,

You may know these people:

Small Bear Electronics

They have clones of the MN3207 chip.

Why must you have the SAD1024, can you post the circuit of the thing you want to build. It is possible to make a replacement for the SAD1024 using an ADC, tiny FPGA and DAC - it won't be the same size (on a hobby budget) but would work fine, and offer all sorts of other possibilities.

MK

Andy Betts · Answer

Hi Michael

Yeah, I know small bear... US supplier, and expensive to get shipped over to the UK.

The circuit is attached

From what I understand, the SAD1024 is pretty peculiar to this circuit, however if there's a good substitute I'm willing to look into that.

Original SAD chips are expensive, for that very reason....... They are gold

Andy Betts · Answer

EBay, they go for anything from £70 to well over £100 each https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=sad1024&_sacat=0

shabaz · Answer

I don't entirely know what the effect pedal does, but if the requirement is to capture audio and delay it and perhaps re-feed the output to the input, then there's another (quite exotic) chip, which too is obsolete but is still available occasionally on ebay due to not being so popular in the audio sphere.

It is the FX802LS, by CML micro.

It's main advantage is that the codec is integrated, no need for separate codec+DSP/FPGA. However its main technical disadvantage (apart from the obsoleteness : ) is that it is intended for speech, so has a 3kHz bandwidth. I don't know how badly that would impact a guitar sound.

Anyway, it is quite an unusual chip because it allows simultaneous record/playback, which is what is needed to implement a delay, but could also do extra effects with little effort, because the instructions to tell it what to do can come over a reasonably slow serial bus, enabling even an Arduino to control it. The simultaneous thing was a specific use-case for this chip compared to other basic speech recorder chips of that era.

I have 2 of these chips, unused, plus equally vintage 1Mbit DRAM chips that should work with it. I do remember constructing up a speech recorder with this chip, it was feasible with point-to-point wiring on a perforated board, since the FX chip is quite large PLCC sized, and the DRAM chip is 486 PC era : ) I can't recall what microcontroller I used to control it, probably a 6805, nothing speedy.

It would be a fun project for someone familiar with Arduino perhaps, but as you say spending the £60 is easier and cheaper than the time to prototype this and write the code. Besides, it may sound totally different to the original pedal.

jc2048 · Answer

I don't know much about musical stuff, but from that circuit I'd say that the flange effect comes from sweeping the clock up and down in frequency.

The 470p being charged by the transistor (set up as a current source) and then being reset by the comparators is evidently the actual clock. The period of that clock is determined by the slower triangle waveform generated by IC4a (the 22u integrates up and down depending on the state of the flip-flop IC3a, which flips backwards and forwards in the way that flip-flops like to do).

Unless you could simulate that I don't think you would have flanging, though you'd be able to do other interesting stuff with it.

michaelkellett · Answer

The really hard part about exact replication is that the BBD (Bucket Brigade Delay) device varies its sampling rate as the clock changes and the clock in the flangers is swept. This means that data is sampled at one clock speed but then passes into the delay chain and may be sampled at the output at a different rate from that at which it was captured.

Typical ADC - DSP- DAC chains sample at a constant rate and will have serious issues if swept sampling is attempted (and only ultra pricey parts can go fast enough). It is possible to achieve the entire effect with constant rate sampling but the DSP will be required to interpolate and resample at both input and output and I would guess that an audio sample rate of 192kHz will be needed to come close to the behavior of the SAD1024. This kind of DSP stuff is possible with DSP chips or FPGA (@ DAB - way out of PSOC league). The development effort in software is significant (if I were quoting a customer I would allow 8 weeks for the FPGA HDL work).

The other way to do it is to use a non-conventional chain with SAR ADC and ladder type DAC where the sampling is on demand with negligible latency. 16 bit 2MHz parts will be needed to match the SAD1024 dynamic range and speed. The FPGA needs to do very little other than buffer the data (needs 2k bytes of internal RAM so a Lattice ICE40 series part would do - and would keep the power low.

The problem is that the 16 bit 2MHz ADC and DAC are quite expensive.

MK

jc2048 · Answer

John Wiltrout wrote: Hi Andy, There was some talk on the following link about using a MN3007 as a possible substitute. The MN3001 looks a better match. It's got two, independent 512-stage delays like the SAD1024. There are some for sale here https://www.cricklewoodelectronics.com/MN3001.html Not pin-for-pin. Might be that it could be made to work in the same circuit (I haven't looked at the datasheets in detail, so don't quote me on that). One obvious difference is that it has an additional Vbb supply which you'd have to generate (a substrate bias to stop it latching up and toasting itself when the clocks overshoot). Perhaps consider a small adapter board that would plug in and replace a SAD1204.

mmcphail · Answer

just be aware that those reticon SAD chips are really prone to just dying on you, they are sensitive to static and even if you buy one now theres a real good chance it will on some random day just stop working. the MN300x series are generally used and recommend are modernish replacements for the old BBD chips of the past. be aware that these are reissue MN3007s on smaller and the like. now if memory serves correct you can replace the SAD4096 with the MN3205 but rigging up an adaptor board (geofx or somewhere like that might have the exact details details). the MN3207 is used all over as replacements for old pedals so google some adaptor schematics ect and lets us all know how you go.

Reticon SAD1024 Delay Chip

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