Behringer System 55

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Re: Behringer System 55

Post by SkyWriter » Sun Oct 04, 2020 5:38 pm

SynthBaron wrote:
Sun Oct 04, 2020 5:31 pm
I'm guessing the pot problem plagues the Model D too, since I bought and sold one pretty quickly because it was such a pain in the ass to dial in sounds.
Any dial specifically? Tbh, if you look at the where-used list I made for B55, everywhere the 05A105 is needs help. Only 823 has EOT issues (fixed with ALHPA), and the 902 and 960 pots have an observable weirdness.
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Re: Behringer System 55

Post by SynthBaron » Sun Oct 04, 2020 7:34 pm

SkyWriter wrote:
Sun Oct 04, 2020 5:38 pm
SynthBaron wrote:
Sun Oct 04, 2020 5:31 pm
I'm guessing the pot problem plagues the Model D too, since I bought and sold one pretty quickly because it was such a pain in the ass to dial in sounds.
Any dial specifically? Tbh, if you look at the where-used list I made for B55, everywhere the 05A105 is needs help. Only 823 has EOT issues (fixed with ALHPA), and the 902 and 960 pots have an observable weirdness.
Especially the envelopes, IIRC. But it's been 9 months.

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Re: Behringer System 55

Post by SkyWriter » Sun Oct 04, 2020 8:30 pm

SynthBaron wrote:
Sun Oct 04, 2020 7:34 pm
SkyWriter wrote:
Sun Oct 04, 2020 5:38 pm
SynthBaron wrote:
Sun Oct 04, 2020 5:31 pm
I'm guessing the pot problem plagues the Model D too, since I bought and sold one pretty quickly because it was such a pain in the ass to dial in sounds.
Any dial specifically? Tbh, if you look at the where-used list I made for B55, everywhere the 05A105 is needs help. Only 823 has EOT issues (fixed with ALHPA), and the 902 and 960 pots have an observable weirdness.
Especially the envelopes, IIRC. But it's been 9 months.
Yeah, that would be the thing. The minimoog uses the same* circuit elements and components. Behringer cost reduction methods would dictate this part being used in any instance of 1 megOhm Audio taper. I was surprised how many different pot types were used used just in B55. There has to be saving across all these products they're doing. The 05A105 has trouble selecting at the full CCW and CC ends and at a point between 3 and 4 on the dial - you can't hit anything in those ranges reliably. Also, over all small range selectivity is awful. Timing is especially subject to displaying any short comings, where it doesn't matter a whole lot elsewhere. It does explain some of the issues with getting the things in tune - pitch being another place small displacement issues are easily found - nothing else is so visible in the system.

The ALPHA though is a huge improvement for the timing application. I have some Bourns on order - after that it doesn't look like there's much else on tap.

The only other synth I bought from them was the K-2. I sold it right away. It didn't interest me like the Korg MS-20mini didn't interest me. I tried reeeeeeeally hard to like them. My X32 and stage extender work terrific. I don't have a problem with any other part though.


*-sorry, not to go way out on a limb I know only through other folks expertise. The statement is more conditional based on "the evidence that I have seen and heard to date", rather than some authoritative claim. As some have first learned here, many if not all those parts do not exist with the same parasitic circuit elements as when the circuits enjoyed their fame. And thus, may exhibit significant divergence from that very same fame. More work for the weary :-)
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Re: Behringer System 55

Post by SkyWriter » Mon Oct 05, 2020 11:54 am

I finally stopped and compared a 911-stock, and 911-ALPHA. FWIW, while the ALPHA doesn't match all of the dial, it matches a lot of it - ignore the table data for a minute. There are inaccuracies around the 20-500ms range, the rest is fairly good. And while they don't necessarily wind up on the dot - as we've discussed, trying to get 300** degrees of solid resolution out of a 12 9 mm **diameter element is marginal - these are readily available with a demonstrable improvement over stock.

Consider:
-with the ALPHA you *can* navigate down to 3ms and up to 8 sec without any real issue. The timing is all there, it's pretty easy to hit a number within the resolution of the device.

- with stock part, it's nearly hopeless try to hit a specific number without the nudging stuff you have to do with the tuning controls to hit a +/- cent. On the 911, it's the same it's settling time, monotonacity, selectivity, etc.. are all poor.

Just trying to line one up with the other on the scope, or by ear; the ALPHA can dial it right in, you have to play with the Behringer one to get close.

Also, consider the three dead regions on the Behringer that don't exist is any fashion with the ALPHA. Hands down, I would replace everyone. Whether there is a better one or not, at a minimum I recommend this change for anyone skilled in the arts.

Sorry, I'm not a video producer, or I would have said all this in a song. :-)

I'm going to replace the 921 tuning pots as well. They can use an improvement.
----------------
**-Not expecting to get the same resolution to hit these timing numbers anyway with a knob that's a fraction of the size of the original that is beyond the accuracy of the physical system. ALPHA approaches this far better than the stock parts does.
========================================
I feel like I have to follow up every post with "...not that there's anything wrong with that!". Some folks don't mind this kind of behavior. That's fine! My use case is different than Behringer's normal customer - or any musical instrument customer - I'm building a technical instrument to help debug another instruments (Korg Prologue Digital Oscillator) debugger-less environment. So my use case is more stringent. If you don't need my kind of accuracy, have fun! It really does sound great!

Yay, a new batch of 911's came in. I got one to fill my last slot, and a spare for experiements :-) should start replacing the 961 and 911A.
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Re: Behringer System 55

Post by SkyWriter » Mon Oct 05, 2020 5:06 pm

After more experience updating I've backed down the soldering/desoldering temps and dwell times. Haven't had a problem since with pads and barrels. The barrel seems robust. I haven't pulled one out :-) 400F for desolder, and 700 for solder - I'm quick..

These are the modified modules
(2) 911-Fast: ALPHA T1, T2, T3, 1UF cap. You can really dig into the accurate fast attacks. Also short decays. :-)
(1) 911-ALPHA: ALPHA T1, T2, T3 10UF cap. Much more usable controls.
(1) 911A-ALPHA: ALPHA Delay Time(s). Finally I can hit some attack with this that don't sound flabby. I might do a faster version of this one.
(1) 961-ALPHA: ALPHA Switch-on Time(s). Same timing circuit as a 911 and 911A, so improvement here's as well.
(1) 823-ALPHA: ALPHA HP and LP Freq. if anyone missed this one, there are dead spots at the EOT - gaps in the filter CF, it would jump from 5K to 10K at the EOT. The elements response knee splice isn't a problem here as the 'zone of confusion' is at to low a frequency to determine any issues.

In all cases there are demonstrable improvements in areas of dead spots, selectivity and repeatability. I don't have the parts to replace any other candidates yet. But I have a Bourns replacement for the 05A105 arriving Wednesday. I'll order other candidate pots. The 921 Freq controls for tuning are the next priority. Once they're stable, I'll work on some of the tuning stability once the pot is replaced.

So, that's about it until Wednesday. Cya!
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Re: Behringer System 55

Post by emuarc » Tue Oct 06, 2020 8:37 am

I have fitted the Alpha C50K to the 923 and they are an improvement, I also found some nice 14mm diameter knobs on Mouser.
I have Bourns 1MA and 5KB on order and will test at the weekend on 911, 911A and 921B.
The original Moog 921B schematic (not the 921) shows an unknown resistor R8 in parallel to the 1K Tempco, does anyone know what value it is?
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Re: Behringer System 55

Post by SkyWriter » Tue Oct 06, 2020 9:29 am

emuarc wrote:
Tue Oct 06, 2020 8:37 am
The original Moog 921B schematic (not the 921) shows an unknown resistor R8 in parallel to the 1K Tempco, does anyone know what value it is?
What would you put in parallel with a 1K 1% resistor that wouldn't swamp the 1%? Couple hundred ohms?
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Re: Behringer System 55

Post by lorez22 » Tue Oct 06, 2020 12:03 pm

The whole system 55 came this afternoon, just waiting for my custom case to be finished and then I can play
120755505_3575466235838497_6301905492356543899_o.jpg
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Re: Behringer System 55

Post by SkyWriter » Tue Oct 06, 2020 12:17 pm

That's a lot of S-trig delays!

Do you have 100m modules in the bottom there?
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Re: Behringer System 55

Post by SkyWriter » Tue Oct 06, 2020 12:33 pm

Sorry I must be a dummy. I completely missed finding this earlier. Taper plots for ALPHA products, which seems to be manufacturer with the most available types. The Bourns have plastic shafts (ok), but no bushings (at least on my order). Behringer's packaging matches the ALPHA parts.

I believe this is the one:
http://www.alphapotentiometers.net/html/9mm_pot_9.html but they only go up to 500K?
http://www.alphapotentiometers.net/html ... urves.html

Different alpha? Sheesh, they give you much more info than Tiawan Alpha.
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Re: Behringer System 55

Post by lorez22 » Tue Oct 06, 2020 2:11 pm

SkyWriter wrote:
Tue Oct 06, 2020 12:17 pm
That's a lot of S-trig delays!
Do you have 100m modules in the bottom there?
yeah I wanted to test the doepfer trigs as well as the Behringer
yes i have the bottom 2 rows for the 100m
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Re: Behringer System 55

Post by KSS » Tue Oct 06, 2020 7:30 pm

SkyWriter wrote:
Tue Oct 06, 2020 9:29 am
emuarc wrote:
Tue Oct 06, 2020 8:37 am
The original Moog 921B schematic (not the 921) shows an unknown resistor R8 in parallel to the 1K Tempco, does anyone know what value it is?
What would you put in parallel with a 1K 1% resistor that wouldn't swamp the 1%? Couple hundred ohms?
It's a 3% or 5% part. Marked 3% on the schematic, but these Q81 tempcos were seen in both tolerances. It sits under the 3046 and the PCB has no underside traces attached to it. Topside traces are obscured by components and a few are easily dismissed. There are a couple contenders, but the CS and SS pics I have -on this conputer- are lousy enough not to be worth the effort. I'll see if I can find it on another drive.

It's more likely a trim on the tempco than the resistance. See Ian Fritz and Rene Schmitz papers on Tempcos.
MW member guest's paper on tempco should show the resistance math based on its location in the OPA feedback.

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Re: Behringer System 55

Post by SkyWriter » Tue Oct 06, 2020 9:20 pm

@kss you are a veritable wealth of nifty info!

Ordered some toggles I hope will fit, to implement the three range switch:
L: 2ms to 1sec
M: 20ms to 10 sec "normal" <- it actually goes down to 13ms with some reduction in selectivity.
H: 200ms to 100sec
Just switch a 10uf (or two 470's if there's room) or 100uf in parallel with a constant 1uf.

Also a ton of alpha types to test circuit performance with replacements from thonk and mouser, and knobs. Unfortunately, they're in different shaft styles.
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Re: Behringer System 55

Post by mmckenzie » Wed Oct 07, 2020 7:04 am

After a little session last night, I became frustrated with the sheer number of cables just doing standard stuff. No room to get your hands in to twiddle the knobs.

So, whether to make a nice loom that uses the sockets as supplied but nicely tidies the default connections out of the way OR to delve into the back and create the CV1 CV2 CV3 and ST1 ST2 ST3 busses using the nice switches on the 992 and CP3-A-O for their intended purpose with a little breakout panel to connect keyboard ribbon controller etc.

The only problem being the input normalling to ground that exists on some modules as Rob has outlined, as one would want to normal to the buss connections allowing them to be interrupted if one plugs into the front panel. Of course in the original these things went into the mix node so were a secret extra input, but that would mean messing with the pcb and circuitry at both ends.

I'll see how the desoldering practice goes with the new 1M ALPHA pots...

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Re: Behringer System 55

Post by mmckenzie » Wed Oct 07, 2020 10:37 am

SkyWriter wrote:
Sun Oct 04, 2020 8:30 pm
The ALPHA though is a huge improvement for the timing application.
Do the pots from Thonk fit the knobs? RD901F-40-15F-A1M According to the datasheet they are 300 deg.

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Re: Behringer System 55

Post by mmckenzie » Wed Oct 07, 2020 11:00 am

SkyWriter wrote:
Sun Sep 27, 2020 10:02 am
You can fix the sine and triangle sub-audio glitch on the 921. There are two trimmers I've mentioned in the thread to address this.
My 2nd 921 arrived today and there is no glitch. So out with the #0 screwdriver for 921 No 1.
SkyWriter wrote:
Sun Sep 27, 2020 10:02 am
The Moog 991 filter function is provided by the B923 module, if you just want to filter it out to some extent. Of course, 923 also has addressible issues :-)
Ha ha. I've just discovered an unpleasant step in the 923 sweep. OK if you don't want to move it whilst the recording light is ON.

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Re: Behringer System 55

Post by kwaidan » Wed Oct 07, 2020 11:22 am

mmckenzie wrote:
Wed Oct 07, 2020 7:04 am
After a little session last night, I became frustrated with the sheer number of cables just doing standard stuff. No room to get your hands in to twiddle the knobs.
Try using right angle cables like Tendrils.

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Re: Behringer System 55

Post by SkyWriter » Wed Oct 07, 2020 1:12 pm

mmckenzie wrote:
Wed Oct 07, 2020 10:37 am
SkyWriter wrote:
Sun Oct 04, 2020 8:30 pm
The ALPHA though is a huge improvement for the timing application.
Do the pots from Thonk fit the knobs? RD901F-40-15F-A1M According to the datasheet they are 300 deg.
The D-shaft thonk knobs are a 1:1 replacement - only way better. It appears you could swap shafts and stuff between them if you had to. Ask @kss he's knowledgable on that subject. But, yeah it's proper fit.

Hmm.. I thought they were 280? Not sure why thought that though. Welp, this thread is my engineering workbook on this subject, if it ain't here idk what to tell you :-) is the spec a mechanical only, or is it electrical too?

---------------

Looking back on the photos I forgot that there's 2 sine trimmers, you have to muck with them both. I finally did my 2nd 921, waiting on my 3rd to take factory measurements first. The 921 has finer screw hardware, unlike any of the others.

Yeah, the 923, is like nice... nice.... nice... ugh, wtf happened to the top end?! The C50K we found has a round shaft though, and candidate knobs will never size out to the push on. Not enough plastic to hold screw. I haven't found a better one though. You can satisfy every pot from Thonk, except this one. And it's bad on the 923. On the 904A, I haven't been able to detect it's problems, but I'm going to swap one out to see the difference anyway. The 911 wasn't obviously deficient until you put a scope on it, then you understna twhere all the slop and ambiguity comes from. It's ain't from what they copied. It's a shame though, this one part is glaringly poor. The rest are a toss up without a deep look into each one (like I have... and will be swapping all the pots, .... well, just because that's what I do. :0)

I have 5 or more of each type ordered from thonk, the knobs too. I would appreciate ANY help organizing these parts and progress with howto's, docs, wiki's, whatever internet-bob thing that helps people mod stuff on their own.

My Bourns came in the shorties 20mm are 500K, the long ones 25mm at the A1M's. Plastic shafts. The 500K's are too short, although they will hold a knob, are for an experiment.
A0DA7657-2A77-485A-BCDD-AFDB6222B828.jpeg
I have a pair of 911's coming to mod with these parts today...
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Re: Behringer System 55

Post by mmckenzie » Wed Oct 07, 2020 1:47 pm

Yes. I attacked the first 921 with my magnifying glass and tiny screwdriver this eve twiddling those two pots with the help of the scope. Bouncing from no glitch in the LF to a square wave at audio frequencies and back again. Knowing that the other 921 was OK led me to persevere until the best compromise was reached.

OK. Thonk order tomorrow... New desoldering rig arriving on Monday.

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Re: Behringer System 55

Post by SkyWriter » Wed Oct 07, 2020 2:02 pm

mmckenzie wrote:
Wed Oct 07, 2020 1:47 pm
Yes. I attacked the first 921 with my magnifying glass and tiny screwdriver this eve twiddling those two pots with the help of the scope. Bouncing from no glitch in the LF to a square wave at audio frequencies and back again. Knowing that the other 921 was OK led me to persevere until the best compromise was reached.

OK. Thonk order tomorrow... New desoldering rig arriving on Monday.
Yeah, I'm hoping to get enough data to steer anyone in the right direction out of the box. I was saving the previous 921, but I got antzy and calibrated it straight ahead know I had one more in the wings (near term) I can take measurements on one and document the post-factory calibration. From my sample of two (qualitative pictures previously posted), they may be sacrificing audio range perfection for low frequency corruption - idk why, but suppose there is a rational - I prefer low frequency accuracy as I use 921 primarily as an LFO, if I want spectral purity, I'll use a 921B. I haven't really even noticed any audio rate waveform distortion, so to me it's a complete miss in factory calibration. Nobody posts to the contrary, but nobody seem to confirm much either.
-----------
Ugh, the Bourns have a package solder tail of 2 mm. Yeah, the spec was right. They don't fit the plated hole Behringer provided. Welp, I'm sold ALPHA is what I'm building to I guess. This package/value pair is "not well represented in the market". @emuarc, your Bourns selection any better than my blind ordering? :-) Thonk has all the ALPHA parts, if there's a US distributer I cannot find. Please elucidate :-)
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Re: Behringer System 55

Post by mmckenzie » Wed Oct 07, 2020 3:27 pm

SkyWriter wrote:
Wed Oct 07, 2020 2:02 pm
I prefer low frequency accuracy as I use 921 primarily as an LFO, if I want spectral purity, I'll use a 921B. I haven't really even noticed any audio rate waveform distortion.
Yes. That's exactly what I wanted it for and in my little sessions so far, I kept needing a second LFO - hence the latest acquisition. I suppose there'll be another set of 921AB next. Sigh. And I've just thought of a reason that one might want another couple of 911s. At least they're cheap.

In my twiddling, I seemed to get a kind of rounded square wave at audio frequencies, but I settled on the moment when I couldn't hear the harmonics and there was only a tiny blip at LF.

What I didn't do was compare the audio frequencies with the other 921 on the scope which seems to have been adjusted properly at the factory. There was no noticeable glitch at LF on that unit - either by ear or on the scope.

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Re: Behringer System 55

Post by SkyWriter » Wed Oct 07, 2020 3:34 pm

Interesting!SW just got my final 921 in stock, and all my pre-ordained slots will have been filled. With a spare!

My 921's were from early domestic stock together. This later model may prove better. It always possible they will address field issues through tightening up the test process. Processes are living breathing, screwed up, wonderful things! It will deal you bad power supply after power supply, only to come in with a prototype wafer in record time. I would trade the former run of the mill experience for the latter gift from beyond any day!

Looks like I'm all in on ALPHA parts for my ... 6? 911's. Well five (6) anyway. The spare can await further developments. The range toogle, as @KSS points out, somewhat obviate the majority of timing issues. I can pull pots all day, not everyone can*.
========
Looked at trimming down the Bourns solder-tail, or cutting it off, but nah... it's 1mm or nothing; must have feature.
========
*-Once I got the range, they're easy to replace. I do mine a little light, I'm not a knob yanker, and I might have to replace them again someday :-)
FC6B4B6C-426D-42D8-8E54-3417A64A0680.jpeg
The one on the left is factory.

==========
Received my (last) 911's today. I clipped the Bourns solder tails just to try anyway. It was so disorienting I didn't even look at it after the first couple of tries. Went back to spec to check I got the right taper. Omg. It's EOT and low end are worse at first glance. I didn't take a second. @emuarc, if you

I used the two standard 911/902 groupings: FAST and STANDARD. Wow! I put the Dual FAST on 904A and 902, the Std Triad goes to the three inputs of my Plaits module. Wow I am in transient heaven. Shaving ms here, adding it there. Thinking about modding the 911A for FAST operation to be able to offset those fast attack/decay with sub-ms precision.I LOVE THE CONTROL NOW. I feel like my whole system went from limp loser to razor sharp killer w/precision slicing mode! Thanks @KSS, and everyone else for the support.
A89DB2F2-0526-4FC8-AAF8-3C4200AF8A14.jpeg
See ya!
047ADA61-28A1-4100-8D90-F82230A629E1.jpeg
That leaves one spare 911 to proto the toggle work on.
========
Also, replaced the other C50K pot (C50K and 05C502 columns were supposed to be the same). It's the Resolution control on 904A.
@emuarc, you replaced one cap on the 904B? Rob, what else can we do to improve the performance of this module? The Freq is another C50K, that will help in dial accuracy. The C50K evens out the Q response. I expect a similar set of dead zones on this elements as on the 05A105, however only the one in the middle - A/B comparison with an unmodified 904A. I really like the low Q sound of these filters. High Q is just not my bag, but it's fun to play with. I'll work more on the 904A tomorrow - still awaiting the toggles probably saturday I can show a prototype.

@KSS, what does your experience tell you to look at first? AFAIK there's The historical transistor and cap matching stuff... what else can we look at? 904B too, naturally!

Really loving this rig! It's getting to be more like my Moog Modular wet dream... :-) the ALPHA's are a huge improvement in tonalities. It's like night and day having access to reliable fast attack/decays on this gear. YUM!

I forgot to say thank you Uli for providing a monstrously good basis for a killer sound!! just up the quality of the pots in a few instances, and it's pure gold. As it is, I don't want to see the S-trig ecosystem downed by a single critical fault. Upgrade to ALPHA and make everyone happy, add a three way trigger mode (bump it up to the next tier module pricing). It's a killer 911 then - and 911 performance is the backbone of the system. I love the look and feel - it's in my bedroom. We even show it off! But without this the 911 wasn't flying for me. Now, glory! Lol!

I love system 55! Moog was a genius :-) it's banana's!
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Re: Behringer System 55

Post by emuarc » Thu Oct 08, 2020 8:58 am

Hi,
I have modified my 904B with matched 680nF polypropylene capacitors in the low range, and a pair of 180nF + 220nF polypropylene capacitors in parallel for the high range. Its a tight fit to get all the caps in, and the 180nF are mounted on the rear of the PCB. I like the sound. 

My 904A has new matched polyester caps, with a second 904A getting "1967" value polypropylene caps using a daughter board. Just about to fit Alpha 50KC pot for Resonance and Alpha 1MA pots into 911/911A, along with daughter boards for 993 module connectivity.

I have put Bourns trimmers into 6x921B's along with plasticine (!) over tempco and 3046. Full VCO setup instructions are on my website, still looking to get a scale drift improvement.

New modules being added: PPG VCF, Moog S&H, Moog Dual Ring Mod, 904C with analog switches rather than massive rotary.
And agree, big thanks to Uli and the UK team who developed the B55. Its a lot of fun!
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Re: Behringer System 55

Post by SkyWriter » Thu Oct 08, 2020 11:25 am

Beauty!

Summarized all in one place: I've replaced all the 05C502's with C50K's, and 05A105's with ALPHA A1M's here:
- 911's T1-3.
- 911A's, Delay 1 & 2
- 961, B-column delay 1 & 2
- 923, HPF & LPF cutoff discontinuity at EOT
- 904B, Resonance effects undetermined as yet.
To do (selectivity issues specifically with B25K)
- freq controls on 921, 921A, 921B. Timing is too touchy. ALPHA's are solid and repeatable.
- 914, dialing resonance is hard. Final touch ups on feedback resonance like wack-a-mole.
- 911, Esus CV to pitch difficult to dial in offset
- 902, 960, strange "foldback" from 0-2 on all controls with B5K on these modules.

This will take a while to get the parts shipped here to demo replacements of each potentiometer in the where used list. But given the known deficiencies in the pots, I can provide a one of two rationals to replace every pot. It depends on your end goal. Turnover is a big thing in the eurorack field, change is important too; these two things work against my use cases. So I'm more inclined to fix or modify what I have already then dump it for something else. These modules hold a lot of value for me, now that they're upgraded - more so, and more so, and so on! The mods are simple and increase it's value geometrically!

Product of the year for me, for sure! 2019 was Prologue :-)

Also, big thanks to @KSS and everyone else on the thread for taking the time to lend expertise to the project to help skip dead ends! now, back to work! It's not going to do itself.
Prologue 16 - an adventure worth having!

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SynthBaron
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Re: Behringer System 55

Post by SynthBaron » Thu Oct 08, 2020 11:33 am

emuarc wrote:
Thu Oct 08, 2020 8:58 am
I have put Bourns trimmers into 6x921B's along with plasticine (!) over tempco and 3046. Full VCO setup instructions are on my website, still looking to get a scale drift improvement.
Didn't 921's/Rev. 2 Minimoog oscillator exponential converters use one of the transistors in the 3046 array as a heater to make the temperature stable enough to stop things from drifting? Maybe the bootleg SMT Coolaudio/Behringer 3046's are on too modern/small of a process to heat up much, thus causing Bob's clever hack not to work?

Perhaps try substituting a resistor as a heating device?

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