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SP12 Filter control mod!!
Old 24th June 2016
  #1
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m4thlab's Avatar
 

SP12 Filter control mod!!

Apologies if this has already been posted...

But I just saw this and it is f**cking awesome!



Should be a relatively straightforward mod (after a bit of research) - I'm def gonna be doing this on my SP12. I'm guessing just some pots placed in front of the target pins on the SSM2044 chips to control how much voltage goes in. I'm already doing a case mod to attach a screen contrast pot to the rear chassis, so I'll leave room now for a few more. This is pretty exciting :-)
Old 26th June 2016
  #2
Gear Maniac
 

Quote:
Originally Posted by m4thlab View Post
Apologies if this has already been posted...

But I just saw this and it is f**cking awesome!



Should be a relatively straightforward mod (after a bit of research) - I'm def gonna be doing this on my SP12. I'm guessing just some pots placed in front of the target pins on the SSM2044 chips to control how much voltage goes in. I'm already doing a case mod to attach a screen contrast pot to the rear chassis, so I'll leave room now for a few more. This is pretty exciting :-)
*Yawns* Meh.
Old 26th June 2016
  #3
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m4thlab's Avatar
 

Quote:
Originally Posted by Tha Knob View Post
*Yawns* Meh.
Thanks Champ
Old 27th June 2016
  #4
Lives for gear
Looks great. Just sp12 or 1200 too? Estimated diy cost and difficulty level? Thanks
Old 27th June 2016
  #5
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m4thlab's Avatar
 

Quote:
Originally Posted by earwolf View Post
Looks great. Just sp12 or 1200 too? Estimated diy cost and difficulty level? Thanks
Well, I'm not qualified to say - its not my video... just something I stumbled across. You could message the guy on youtube. I would expect that it's a pretty cheap mod though, and pretty straightforward to do.

I found this page, which talks a little about how this filter chip is used in other synths, and if you applied something similar here you'd be looking at the cost of a few resisters and pots, which are very cheap, obviously.

SSM2044 LP Filter designs

http://www.maxmidi.com/diy/ssm/ssm2044.pdf
Old 27th June 2016
  #6
Gear Maniac
 

Quote:
Originally Posted by Methhead View Post
Thanks Champ
You're welcome chump....
Old 27th June 2016
  #7
Gear Maniac
 

Quote:
Originally Posted by in_effekt View Post
Longest butthurt in GS history?
No hurt butts over here. I just don't take kindly to being sucker punched. Especially for no good reason, so I shot back. 'Smack me and I'll smack you back' - EPMD on 'You're A Customer'
Old 15th December 2016
  #8
Gear Nut
 
KlangGenerator's Avatar
Quote:
Originally Posted by m4thlab View Post
I'm def gonna be doing this on my SP12. I'm guessing just some pots placed in front of the target pins on the SSM2044 chips to control how much voltage goes in. I'm already doing a case mod to attach a screen contrast pot to the rear chassis, so I'll leave room now for a few more. This is pretty exciting :-)
So have you done this mod in the meantime? Would you mind sharing some details?
Old 21st December 2016
  #9
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m4thlab's Avatar
 

Quote:
Originally Posted by KlangGenerator View Post
So have you done this mod in the meantime? Would you mind sharing some details?
I've done the mod with the contrast pot on the rear, but not the filter. Too many others things happening right now, but I might look at it in the future.
Old 29th November 2017
  #10
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Anyone done this?
Old 29th November 2017
  #11
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m4thlab's Avatar
 

Never got around to this mod - sold my SP12 to fuel a eurocrack addiction. Sad days.
Old 29th November 2017
  #12
Gear Head
 

If you read the comments in the YouTube vid, the cat who uploaded it claims he's working towards putting into production an external filter box for the SP12/SP1200 that will provide the functionality in the video without having to modify the back of the SP. He's also claimed it will be a minimal install, if i remember correctly. I've subscribed to his YouTube channel & check back in on occasion, because once these are in production, I'm absolutely copping one!
Old 29th November 2017
  #13
Lives for gear
Quote:
Originally Posted by space1uno View Post
If you read the comments in the YouTube vid, the cat who uploaded it claims he's working towards putting into production an external filter box for the SP12/SP1200 that will provide the functionality in the video without having to modify the back of the SP. He's also claimed it will be a minimal install, if i remember correctly. I've subscribed to his YouTube channel & check back in on occasion, because once these are in production, I'm absolutely copping one!
He needs to drop that then an eprom switcher box and I'll buy him a caravan
Old 3rd January 2018
  #14
Gear Maniac
 
stylesforfree's Avatar
 

Quote:
Originally Posted by m4thlab View Post
Never got around to this mod - sold my SP12 to fuel a eurocrack addiction. Sad days.
Oh no! I am in the same boat except I never had an SP to sell :(

That mod looks awesome though.
Old 4th January 2018
  #15
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Sam an huel's Avatar
Quote:
Originally Posted by m4thlab View Post
Never got around to this mod - sold my SP12 to fuel a eurocrack addiction. Sad days.
You are not allowed to says that. You made a choice, you junkie.
It was sad when i had to sold my TLC restored, modified rebirthed from death cheapo SP12 Turbo (i will never get a deal like that again in my life ) and my 20 years old mint 500 records collections to eat and pay the rent. That's start to be a bit sad!

( I don't deny I bought 3 System X PCBs and frontpanels also, though )
Old 7th January 2018
  #16
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akai612's Avatar
 

To add any kind of modd to something like a SP12/1200 should be prosecuted by law. Who in the right mind would modd a 1962 Ferrari 250 GTO?

There is no way to make a SP sound bad and no way to make it sound better by the means of any possible or impossible modding.

You'll only going to lower the value in case you ever need to sell this piece of art.
Old 14th February 2018
  #17
Gear Head
 

For everybody keeping an eye on this, NoizeGearlch (the cat on Youtube who did this mod) posted the following in the comments to the video a few weeks back:

"It´s 2018 and the mod is nearly finished! Right now I´m just adjusting details, so it will be published in the following months! The following filter ICs are already working with the mod ( including high pass filtering!): SSM 2044 (from SP 12 and 1200), SSM 2045 (from Emulator II, 2 pole and 4 pole mode) CEM 3328 (from Ensoniq Mirage), MF6CN50 (from S900 and S 950) and Korg NJM 2069 (from DSS-1 and DW 8000, 2 pole and 4 pole mode)! Stay tuned, I will do demo videos about the installation and its possibilities!!"

I am really excited to hear the final version and will def be one of the first in line to cop one!
Old 17th February 2018
  #18
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atma's Avatar
wow, that's a super sweet sounding resonant filter!
Old 13th January 2019
  #19
Gear Head
 
B.Minor's Avatar
 

When I looked up this thread last X-mas, I was a little bit disappointed about the fact that there was still no progress on the finalization of the announced SP-12 filter mod solution. At least there was no information available what’s the status. When I first saw the video NoizeGearIch already provided back in 2016, I was immediately excited about the possibilities customizing the filter controls for the SP-12’s dynamic SSM2044 filter chips. I even started investigating in the meantime, but very soon I had to drop that project because of other things that had more priority.

Now, during the New Year holidays 2019 I took some time to continue working on my own approach. And what should I say, I succeeded within a few days! By introducing several potentiometers, switches and a few resistors I was able to reproduce all functionalities shown in the famous YouTube video featured at the beginning of this thread. Of course, my personal solution is non-destructive and mounted SP-12-internally (meaning that no external box or extension chassis etc. is necessary). In fact, it’s a fully integrated and very compact add-on which easily allows you to switch between the “original” SP-12’s dynamic filter behavior and a new “customizable” filter control. After adjusting a set of three different knobs (frequency envelope, frequency cutoff and frequency resonance) for each of the two available SSM2044 filters inside the SP-12, it is possible to retain those favorite settings even if switching back and forth to/from the original filter design. This new goodie adds perfectly to the other mod I already published here at Gearslutz some time ago, the so-called filter switch mod, where you can basically bypass the two dynamic filters for outputs #1 and #2 at all (setting them to fully unfiltered). Of course that also applied to the other static filters, assigned to outputs #3 to #6 (while #7 and #8 were always unfiltered as per E-mu design).

If there is enough feedback or interest, I can publish the new filter control mod here at this place as well, summarizing all necessary steps in order to achieve the desired functionality, of course also by providing the electrical circuit schemes along with some other useful tables, hints and technical information. I could even add some back-panel layout ideas if appreciated. Converting all my notes into a readable format may take some time and efforts, so just let me know. However, in case I get started with it, please also be gentle, as English is not my mother tongue. Tell me what you think.
Old 13th January 2019
  #20
Gear Maniac
 

this is a dumb mod imo. just buy a moogerfooger lowpass pedal or use an 8 channel mixer. the filter in the sp is not so mind blowing sounding that its worth doing this to it. if you could program filter movements in the sequencer itd be one thing, but honestly, i dont see the benefit.
plus things like the sp12-1200 work well because they have limited parameters, and you make a beat that sounds kind of raw without fussing over all those micro elements of the process. if you like to fuss over that stuff, buy an octatrack or use a computer.
Old 13th January 2019
  #21
Gear Head
 
B.Minor's Avatar
 

Abusing my SP-12, e.g. by fussing it over with additional stuff is and was never my intention. If you look at that (non-destructive/revertive) approach again, it's just a set of frequency controls added to the two SSM-related filters which are already built-in; however, their full capabilities were never used so far. Yes, E-mu limited the characteristics by introducing a "default" setting to these two dynamic filters which can work out great for most purposes.

In the meantime I worked now more than 30 years with my SP-12. Believe me, in some cases it would have been very useful to tweak the loaded samples "right in the box" in order to make them snap into the rhythm just with the "right feel" so that you'd get what you've finally expected. With filter controls you have lots of variations available - from very small frquency corrections up to freaky effects. I just made such a tweaking work now - it's nothing more or less than that. No need for massive sequencer effects etc.; that's not what my SP was ever foreseen. Btw., you can do the mod for less than 20 bucks, so no need for any external boxes that would cost up to 20 times more...
Old 5th February 2019
  #22
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Sam an huel's Avatar
Hi B.minor very interested indeed. Good job!
Old 30th June 2019
  #23
Gear Head
 
B.Minor's Avatar
 

Due to the relative lack of feedback, let me just post some photos of my final SP-12 filter control solution in order to prove that such a mod can really pay off in case you do it right: by adding value, not by abusing the device.

Contrary to the opinion of those who may find this mod useless, I already figured out many use cases for altering tuned or untuned percussion samples in a very effective way. Any personal adjustment can be entirely made undone by just switching between the "customized" mode and the "original" sound design.

Filter switches are anyway obligatory.
Attached Thumbnails
SP12 Filter control mod!!-panel1.jpg   SP12 Filter control mod!!-panel2.jpg   SP12 Filter control mod!!-panel3.jpg  
Old 1st July 2019
  #24
Gear Head
 

B. Minor, man you killed this! The control layout, integrating the filter controls with your display controls, the SP12 font. This is a very clean mod. Props!
Old 8th July 2019
  #25
Lives for gear
Fantastic work B. Minor.

Is this likely to stay a DIY project, or will you look to sell kits that look like this and have minimal installation?

Have you done any PSU rebuild work on your 12? Mine is hot and noisy, as so many are.
Old 8th July 2019
  #26
Gear Head
 
B.Minor's Avatar
 

Quote:
Originally Posted by Sam an huel View Post
Hi B.minor very interested indeed. Good job!
Thanks for your great feedback.

Quote:
Originally Posted by space1uno View Post
B. Minor, man you killed this! The control layout, integrating the filter controls with your display controls, the SP12 font. This is a very clean mod. Props!
Thanks a lot for your kind words.

Quote:
Originally Posted by earwolf View Post
Fantastic work B. Minor. Is this likely to stay a DIY project, or will you look to sell kits that look like this and have minimal installation?
Thank you, glad you like my mod as well. No, I don't intend to sell any DIY kits; I wouldn't have the time anyway and I'm not someone who'd like to make money with such stuff which really isn't that complicated. To be honest, I was also hoping first that NoizeGearIch would be releasing his solution here in this forum, but soon after this didn't happen for a while, I figured out that it's not that hard to achieve that goal if you know about electronics, if you can read circuit diagrams and if you know how to handle a soldering iron.

Quote:
Originally Posted by earwolf View Post
Have you done any PSU rebuild work on your 12? Mine is hot and noisy, as so many are.
Yes indeed, the original SP-12 gets so hot that you could fry an egg on it - mine as well. If you are wondering why I had the space on the backpanel to introduce a "2 x 8 control matrix", it's just because of the fact that I moved one rear-mounted rectifier to another spot in order to gain the necessary space. I thought it might look cool if the controls are exactly placed on top of outputs 1 to 8 and are not scattered around the backpanel just because of internal limitations. However, the small power intervention (of course using a new thermal paste) neither improved the current heat situation, nor introduced any additional harm to the unit. But who knows, if there's a good proposal on how to replace the existing power supply someday with a proper and modern model, maybe I'll pick up that idea again...

As mentioned already, in general I'd be willing to share my filter control approach with the community, even if that would take some efforts; at least I'm counting three interested guys already .
Old 8th July 2019
  #27
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Sam an huel's Avatar
Hell yeah, please share the mod. Yours looks fantastic.

Quote:
Mine is hot and noisy, as so many are.
It's hot because its a HOT machine. Seriously, it's hot because the heat dissipator is still well fitted and works as well as he can. Cold SP12 are in fact having a problem.
Old 9th July 2019
  #28
Gear Head
 
B.Minor's Avatar
 

SP-12 FILTER CONTROL MOD - PART I:

GENERAL INFORMATION AND FIRST APPROACH CONSIDERATIONS

Okay, I've decided to publish my personal SP-12 filter control mod here officially – so watch out my next few post if you’re interested. I'm not going to throw bits and pieces of information over the fence just like that; I also decided to mention and to explain all of my personal thoughts, any expectations of the mod, my self-imposed rules, technical evaluations and final decisions related to the mod design in order to make clear for anyone else what was the trigger for me to do it exactly that way – and not differently. I'm very sure there are guys out there who might criticize my approach and might know better; however, as mentioned, the presented solution I figured out during a couple of days (after studying again the SP-12 layout, skipping through related internet sources, exploring datasheets and performing several empirical experimentation) was finally tailored to my own personal needs. These don't necessarily reflect requirements others might have; on the other hand my approach doesn't need to be justified in any way, as it is perfectly working for me as intended. The solution is solely using any SP-12's dynamic filter capabilities which were already built-in by E-mu but never have been activated so far, so no new filter chips originally not part of the device or whatsoever are to be introduced. While NoizeGearIch still may come up with any related mod supporting several other filter chip types, I decided to stay focused on the native capabilities of the SP-12.

You may like my mod and even improve it by providing some feedback, or you may just ignore it in case you don't agree with my approach. I only hope that there are not people out there who are immediately starting to create DIY kits etc., e.g. by duplicating parts of that approach just to make money out of it. That was not the reason for my decision to post my approach here. You don’t need many parts to perform the described changes; in best case you need to spend a few bucks only. In my opinion everyone who owns such a great piece of gear should be able to get the maximum out of it, for free – of course without abusing the device. Of course it took me some days to figure everything out, to put things together and to sketch down the solution. However, I'd also expect the same information transfer from any other owner as well who is willing to share own findings with other interested forum members whenever creating improvements, gimmicks or whatsoever. After all, that's how forums like this one work. Okay, now enough of the philosophy, let's get started by providing some basic information on the central part of the filter control mod, the SSM2044 filter chip.

The SSM2044 filter chip and its history:

As you may know, the SSM2044 chip is the heart of the SP-12/1200's dynamic filter design, even though it looks like E-mu used that chip on both models just to create simple low pass filters with fixed pre-set values for channel outputs #1 and #2. Unfortunately many of the SSM2044 features were never considered to be part of the general SP design, even though it wouldn't have been much effort to add some additional potentiometers and switches to the front or to the rear panel. However, the E-mu engineers used the same chip type for their Emulator designs as well, and many other companies did the same by developing SSM2044 filter circuits on their gear in order to provide those typical synth effects everybody liked to hear in the late eighties. The SSM2044 chips were very popular, still cheap and easy to get at that time, so there was no need to think about keeping masses of them on stock. Nobody thought about the possibility that manufacturing would be discontinued very soon – but exactly that happened in the late nineties. And what more, even the original design sources for the SSM2044 got lost completely, so nowadays it would be only possible to re-build this chip functionality from scratch by performing some kind of reverse-engineering. Even E-mu had to face the situation that the SSM2044 was no longer available on the market when they already had started to release their latest version of their SP-1200. In 1998 – and only for the last 125 units of that SP-1200 "Final Edition" – they had to “emulate” the original SSM2044 low pass filter functionality by designing a separate PCB which contained discrete op-amp components on it (see attached pictures showing both the original SSM2044 layout as well as the alternate replacement board). The PCB was just hooked up to the original mainboard sockets where the original SSM2044 chips used to sit in earlier models. I have never seen or tested any of these late models personally which were equipped with those new filter boards, so I let owners of such late SP-1200 models comment how the filter behavior really differs in general from the original filters, or if that original “feel” could ever be re-created in the proper way.

To be clear, of course we’re focusing here exclusively on those SP machines providing the original filter chips; after all these are the ones we’d like to tweak. However, just one recommendation from my personal experience: If you own such an E-mu machine and you can still obtain SSM2044 filter chips from trustworthy sellers/sources, just go for them *NOW*, as it's always a good idea to have some spares available. During the last 32 years of my SP-12 operation, it already happened to me twice that one of the SSM2044 chips started to produce audible hiss, eventually caused by permanent overheating inside the chassis; so finally I had to replace it when it was slowly starting to die. As you know, the SP-12 is something you could fry an egg on, so overheating could always be a general problem, in worst case making some components fail. Hmmm, what about a power and fan mod? No, not at this point…

Some personal conventions and rules for the introduction of the planned filter control mod:

Thinking about the main goal I wanted to achieve, I soon figured out that any filter control mod to be introduced to my precious SP-12 would only make sense if I’d also be able to revert back to the original filter behavior at any time, e.g. in case I don't need to use any newly introduced filter features. That would give me the chance to mess around with any customized filter settings and finally leaving the related knobs at my favorite positions while being able to toggle between the E-mu "original" filter design and the "customized" mode without any further action. As my mod includes a set of three customizable filter controls ("ENVELOPE", "CUTOFF" and "RESONANCE") for each of the two available SSM2044 filter circuits (IC125 and IC123), also two additional "triple on/on toggle switches" are necessary to bring in/out those new filter controls at once. That said, these new "filter control" switches are working fully independent from any other existing "filter bypass" switches (which in my case were already implemented more than 3 decades ago). For those who are also interested, I described my implementation in another thread (refer to the "filter switch mod" here). Just to recap, while any of the existing switches might turn any SP-12 filters on/off for output channels #1 to #6 in general (not necessary for SP-1200 owners, as there you can achieve the same effect by just “half-unplugging“ cables attached to any individual outputs), the switches to be newly introduced now are just there to switch between the "original" and the "customized" dynamic filter design and are exclusively related to the first two SSM-filtered output channels #1 and #2.

Another personal convention I was following up to now (and which I didn't want to break in the future) is that my SP-12 mainboard should be kept as clean and unmodified as possible, meaning that any new design changes aside from those already applied by E-mu Systems (they called such a fix "KLUGE" in their service manual) should be realized off the mainboard as much as possible. That should finally avoid any electronic mess on the mainboard and would let me introduce all add-ons in a structured way (which could also be comprehended later on in an easy way). That means that any additional electronic components necessary to complete the new circuitry should not be soldered directly to the mainboard. Instead, wires from SP-12's mainboard should lead towards the back-panel where all the new magic should happen. Of course, some modifications always need to be done directly on the mainboard in order to make a new design fly; there's no other way if you want to get full filter control. But don't worry, as in all of my other mods, you don't need to cut any traces. The worst thing that may happen is that you have to de-solder specific resistor ends in order to apply wires or plugs to those (or that you have to solder wires to the mainboard directly).

Going one step further:

After looking at the final amount of electronic components needed, considering the resulting cabling complexity and the required space on the SP-12 back-panel, I decided to put all additional components onto a dedicated "homebrew" PCB. In other words, instead of mounting switches and potentiometers just in a "loose" way to the SP-12 chassis and bothering with all the different cabling to be carefully soldered to separate resistors, pins, potentiometer terminals, soldering plugs etc., I felt that it might be a good idea to put all stuff together on a circuitry board which finally could be mounted to the chassis in one single piece. Indeed, this is more or less representing the same effort as to build a solution using an external housing etc., on the other hand all of my “controllable” mods could be located on that single PCB as well, making the solution extremely elegant and compact. In fact, aside from the filter control mod to be explained here in this thread, also all switches and potentiometers from my previous filter switch and LCD display mods should be included on the new board, thus simplifying any cabling efforts as well, as removable and labeled cable plugs should help to keep all connectivity simple and neatly arranged.

However, as there was finally the need to include eight switches and eight potentiometers in total, I decided to align any control components on the SP-12 back-panel in two different rows with eight controls each. In order to make that fly, one bolt on the inside of the SP-12’s chassis needed to be shifted to another position. More precisely, the existing bolt holding the rectifier so far needed to be removed carefully and a related hole had to be drilled (e.g. between the voltage transducer and the main inputs) where the rectifier could finally be mounted instead by using a normal countersunk screw. Compared to other mods I have seen so far (where holes were randomly drilled anywhere on the SP-12 rear just to make things fit) I think that my final alignment makes sense from an operational perspective, but most of all, it also looks great. After all, the eighth hole I drilled was exactly located there where the implied bolt was previously located, so no special problems arose when attempting that additional step to remove it.

Finally, I decided to attach a specially designed steel plate at the SP’s backside, applied with proper switch and knob labelling, previously laser-printed and then applied to the metal via transparent foil. This finally makes the modification even look professional in the end (please refer to one of my previous posts in this thread where I attached pictures showing my final panel design for all additional controls).

To be continued…
(I just realized that I should have published a book instead of writing such "instructions"...
In fact it may take a little bit longer than I thought first - so stay tuned...)
Attached Thumbnails
SP12 Filter control mod!!-01-ssm2044-filters-top.jpg   SP12 Filter control mod!!-02-sp1200-filter-pcb-side.jpg   SP12 Filter control mod!!-03-sp1200-filter-pcb-top.jpg  
Old 9th July 2019
  #29
Here for the gear
 

Re SSM2044 stopped production, there is the newer SSI2144 IC, while not a drop in solution, filter functionality seems similar. See a converter example.

Thanks for detail about last SP1200 production, I didn't know EMU has to emulate the SSM2044 in the last models, from looking at picture it seems emulation does not allow to trim cutoff frequency though
Old 9th July 2019
  #30
Gear Head
 
B.Minor's Avatar
 

Quote:
Originally Posted by keefaz View Post
Re SSM2044 stopped production, there is the newer SSI2144 IC, while not a drop in solution, filter functionality seems similar. See a converter example.

Thanks for detail about last SP1200 production, I didn't know EMU has to emulate the SSM2044 in the last models, from looking at picture it seems emulation does not allow to trim cutoff frequency though
Thank you keefaz for sharing details about that new SSI2144 chip. I've already heard about it. Some people reported already that it should sound very accurate compared to the original SSM2044 chip, others aren't that enthusiastic. At least it's good to know that there's a replacement available - even if you need those "converters" in order to provide the original pinout.
Attached Thumbnails
SP12 Filter control mod!!-ssm2044-ssi2144-e1492758275364.jpg  
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