[NEW] Serge Resonant EQ for Euro by R*S

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medbot
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Post by medbot » Tue Dec 06, 2016 5:51 pm

muffdiver wrote:Can anybody give an explanation of the how the outputs should route the various bands?

I'm still not convinced my build is working properly in this respect. :despair:
Here's the schematic, in case you haven't already taken a look at it. A quick glance might clear things up for you, or at least give you an idea of where to start looking.

http://www.cgs.synth.net/modules/cgs202_reseq.html

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Post by Sleipnir » Wed Dec 07, 2016 11:47 am

muffdiver wrote:BTW...managed to fix the 115hz band by swapping out the poly caps.

Still mystified by the output behavior. Just out of curiousity how are the outputs supposed to work or how are they working for everyone regarding L EQ bank / R EQ bank.
Hey - sorry you don't seem to be getting much love for this.
COMB 1 out should contain the left bands (5.2k, 1.5k, 411, 115, 29)
COMB 2 out should contain the right bands (11k, 2.8k, 777, 218, 61)
Both outs should contain both bands - they're just summed together.

It sounds like you have an issue between the COMB 1 signal and the summing for the combined outs.

IMO if would have been cool if the 2 outs were phase inverted (you have the signal available at the feedback switch), but I guess it was meant as a sort of active splitter.

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Post by muffdiver » Wed Dec 07, 2016 6:57 pm

Thanks for the reply!

Yeah, after looking at the schematic and the PCB I think I've narrowed it down to one of those 47k resistors or potential one of the OPA ICs. Was a little confused about the dual outs as the schematic only has 1 out. I kind of assumed (it sounds like correctly) that they were pretty much parallel but identical configurations.

Will need to dig the module out the case in the next day or so and see what I find.

Totally agree about the inverted output - that would be an ideal enhancement. Going to experiment with one of my inverted mults with the feedback now.

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Post by muffdiver » Wed Dec 07, 2016 7:33 pm

Curious now if inverting one of the outs would be an easy mod?
Last edited by muffdiver on Thu Jan 05, 2017 7:05 pm, edited 1 time in total.
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muffdiver
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Post by muffdiver » Thu Dec 08, 2016 12:52 am

Fixed it!

Embarrassingly enough a 47k was missing. It was from the RS kit so I may have just dropped on the floor or something. Getting the definitive answer on the functionality of the outs definitely helped. :banana:

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Post by ddoyen » Sun Dec 18, 2016 10:18 am

Made an order and ended up forgetting the 100k resistors for the main board. I have a few 5% carbon films laying around. Anyone have any idea if I can get away with those there instead?

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Post by ronski » Sun Jan 15, 2017 10:01 am

Having the same issue on the two EQ's I've build the 115hz band doesn't work.
Are the polystyrene caps very sensitive to heat? Can't believe breaking all four off them though.

With both modules the the left and right combo's are outputting practically the same signal....

any ideas?
muffdiver wrote:BTW...managed to fix the 115hz band by swapping out the poly caps.

Still mystified by the output behavior. Just out of curiousity how are the outputs supposed to work or how are they working for everyone regarding L EQ bank / R EQ bank.

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Post by ronski » Sun Jan 15, 2017 4:34 pm

Turns out I forgot one resistor, it's right below the two poly caps. Because there relatively bug you can't see the empty spot for the 820 k resistor below.

I'll check if this solves my combo issue as well.

[quote="ronski"]Having the same issue on the two EQ's I've build the 115hz band doesn't work.
Are the polystyrene caps very sensitive to heat? Can't believe breaking all four off them though.

With both modules the the left and right combo's are outputting practically the same signal....

any ideas?

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Post by Biom » Thu Mar 09, 2017 5:30 am

So, for those who built it already, does it really sound authentic?
Especially interested in feedback, like here:

Noticed some differences on youtube demos between the STS Serge and RS Euro version. Maybe because of the added mixer levels?
Last edited by Biom on Fri Apr 14, 2017 9:20 am, edited 1 time in total.

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Post by didahdrieghe » Thu Mar 09, 2017 6:45 am

Biom wrote:So, for those who built it already, does it really sound authentic?
Especially interested in feedback, like here:

Noticed some differences on youtube demos between the actual Serge and Euro version. Maybe because of the added mixer levels?
Mine sounds the same as this.

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Biom
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Post by Biom » Thu Mar 09, 2017 1:02 pm

Have you compared it to the original?

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Post by Sleipnir » Sun Mar 19, 2017 11:13 am

Biom wrote:So, for those who built it already, does it really sound authentic?
Sorry, I've been holding off, but that is a silly question.
Did the various YouTubers mention what signals they were feeding back? I didn't see any patch notes.
You think that might have an effect on the feedback? :hmm:
It screams, it growls, it sings, and it's even a really handy EQ.
In this case -- possibly more than any other module type -- what you feed in determines what you get out.
As for "authentic", this isn't a Bheringer clone. Serge himself worked with R*S and approved the design.

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Post by Biom » Fri Apr 14, 2017 9:17 am

Well, most of the youtube patches do really have a good description (thanks for that, guys!), at least it's more than enough for me. Sometimes there's even no need in that if the patch is not too complex. The other thing is that you can't really judge the sound right, so that's why I'm asking.

I know quite a lot about what the module can do, including feedback, pinging and stuff, but thanks anyway.

And regarding the input signal you mention, I must say even more: even the newly selected chips/opamps in RS version affect the sound dramatically, against the vintage stuff (which determines that exact serge sound).
Knowing all that, I asked if someone AB'd RS version with, say, STS and are there any differences in sound.

Now do you think your answer was helpful? Thanks for letting me know it's not Behringer. That clears a lot for me now

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Post by woodster » Fri Apr 14, 2017 12:11 pm

I've built the R*S Resonant EQ and also 2 of the CGS 202 Resonant EQ's behind the Negativespace/Clark68 panel with sliders.
It's really the Cap's that make the biggest difference in the sound, not the chips as far as I remember. However, saying all that, all 3 of my builds share 'that' sound, so it's rather subjective really.

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Post by Triglav » Fri May 05, 2017 1:56 pm

Just built mine, sounds amazing!
Just a couple of questions:
– The phase inverted feedback doesn't seem to do much, it just gets a bit quieter. Am I missing something?
– The build docs mention that the OPA2604 has nice clipping. Does this mean more distortion or just more pleasing distortion compared to the 2134?

EDIT: I've tried the 2604, can't really notice any difference.

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Post by XAXAU » Thu Aug 17, 2017 6:23 am

Anyone know if the mouser cart posted early in this thread is accurate?

http://www.mouser.com/ProjectManager/Pr ... ?AccessID=

Also, are polystyrene caps from Mouser "up to par"?


Cheers!

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Post by Midiot » Mon Oct 23, 2017 4:48 pm

My beginnings, and some tips from an intermediate DIYer.

Just ordered the res/eq "Panel + PCB" from Modular Addict (USA). They also have the pots, jacks, and euro (10pin to 16pin) power cable (I already have knobs).

Just placed a Mouser order using this B.O.M. as a reference... https://www.mouser.com/ProjectManager/P ... dca4c4a741
....but I won't know if everything is correct until I populate the board(s).
~~~~~~~~~~~~~~~~~~~~~~~

Caps:
Mouser does not carry all the polystyrene caps, but those can be found on ebay.
I still get confused when reading cap values, so I always use a "value conversion chart" printed off the net, for reference. Here's one: http://oshgarage.com/capacitor-conversion-chart/

Tips when searching ebay for caps:
Because some cap values can be expressed 3 or more different ways (but are really the same value) ....you should preform different searches for each expression..... if you want to find all the listings on ebay.
For example: 2n2 = 2.2n = 2200pf = 0.0022uf ....all mean the same value. Ebay sellers decide which expression to use, so if you only search "2n2", you'll miss the listings titled, "2200pf", and so-on.

One trick to converting the expressions without a chart, is this:
...Move the decimal point three places.
If it's 0.22 UF, move the decimal 3 places to the right = 220 NF.
Move it again 3 places right = 220000 PF.
Works in reverse too..... 5600pf = 56nf = .056uf.

Larger voltage ratings usually mean bigger caps. Anything rated 25v and above, will work fine.
I always order extras, for matching (if desired), and for future projects.

Here's a good conversation on polystyrenes:
Polystyrene Caps for Filters
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Resistors:
I don't have the board yet so I hope my alternative choices for resistors will not be too long (length). According to the above B.O.M. recommendations, a resistor length of 6.8mm will work. (I ordered some that are 7.2mm L......we'll see)
I will be matching the caps and resistors to better than 1%, for the individual filter circuits.
I am not claiming that this will alter or improve the sound in any way, but it may make me feel better and satisfy my OCD. :)
Because these EQ filters are already variable (the pots), matched resistors might be pointless. EDIT, NOT TRUE. THESE ARE FIXED FILTERS WITH GAIN. Perhaps the more important spec for my resistor choice was temperature coefficient, where I went for a low value here (25ppm or less). This should help any small drift in the EQ filters as the board heats-up -- and I want a setting to stay where it is, over time. Again, this is minutia.....and such resistor accuracy/tempco is really for building "fixed" filters, so not here.
My knowledge of filter equations is weak, but basically it's the relationship of resistor and cap ratios, called an R-C filter.... ...that target a desired frequency. http://www.muzique.com/schem/filter.htm

Resistor matching tip for 2 or more resistors.....You generally don't need to buy .01% expensive parts ($2 ea +). You just need a half-way decent DVM, and find pairs/sets that match among a pile of cheap 1% resistors ( @50ppm tempco).... $0. 14 ea.
I believe many (most ?) popular resistors are sorted at the factory for accuracy, before labeling (called: binning). 5%, 2%, 1%, 0.1%....separated into different bins.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here's a question though...
The build docs claim the 2604 "has a nice clipping behavior".
Does "nice" mean as in 'soft-clipping', or as in 'gritty and lovely-nasty' like some people desire ?
Last edited by Midiot on Sun Dec 03, 2017 10:45 am, edited 1 time in total.

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Post by Midiot » Mon Oct 30, 2017 10:16 pm

My above post probably went over-board (read = overkill).
The board is done, except for the polystyrene caps.
I have them, but I might use polypropylene caps instead (on order, WIMA FKP type).

My reason for this is that even though styrene's are generally known to be the "best" choice......I'm concerned about the quality of using these from various "old stock" sources....and some "internet aficionados (old pros)" claim that not all styrenes are not of equal quality (see my link in the above post). Plus, they don't fit very well on the EQ board.

The 22n and 47n's are the most problematic to fit, and the styrenes will hover over the resistors and even the adjacent opamps. Maybe you've had a different experience.
Polypropylene caps are the "next-best" option it seems, from my research.....and they will fit flat to the board (the 47n's might still be a tight fit, though).

I might buy another board/panel kit (I have enough extra parts), and employ the styrenes, to see if there's a sonic difference.

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Post by Midiot » Sat Nov 04, 2017 9:51 pm

Here's what it looks like with WIMA polypropylene. (and Vishay for the 22n, 47n ).
The black resistors I ordered were too long @ 7.2mm (my oversight), so they are installed "up on one knee".

Image

Image



Next, install the SIP pins, clean the flux off......and as standard precaution, I'll apply power without the chips, and check the voltage pins for +12v on all the (empty) op-amp sockets.......then again with the chips installed. ....before going in my rack.

.

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Are styrene or styroflex a MUST?

Post by tetsutestu » Sun Dec 03, 2017 9:57 am

Hi guys!
I was unable to find the styrene or styroflex 0.0022uF (2n2) caps on mouser or on any other sites within Japan. BUT I did find these comparable parts:
https://www.mouser.jp/Search/ProductDet ... YX1H222KTP
and
https://www.mouser.jp/Search/ProductDet ... 22J50J01L4

What I'm wondering is how vital it is to have these as styrene caps? NEWB here so I'm not sure whether substituting the above parts would cause trouble or not. Shipping from aboard is prohibitively expensive and I'd like to source as much as possible in one go from mouser...
Thanks in advance everyone!

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Midiot
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Post by Midiot » Sun Dec 03, 2017 10:59 am

As far as my research about caps, in order of choice...

#1...Polystyrene (stryene, styroflex)
#2... Polypropylene (what I used)
#3...PPS

You should find them in one of those styles, just check that the dimensions of the lead spacing will work, and the actual cap dimensions will fit too.
"We'll be living in all the oceans now."
(type of music I make.... drone atmospheres, deep late-night beats.)

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Post by templar » Mon Dec 04, 2017 1:26 pm

Mouser have these: https://www.mouser.jp/Search/ProductDet ... key23PS222


13 weeks to wait till they're in stock though

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Post by diode_destroyer » Mon Dec 04, 2017 11:10 pm

I keep thinking of building this but then always get annoyed that there's not bypass switch. Do you guys use some kind of separate switching module in order to do quick A/B comparisons while dialing in (if so, please recommend me a module)?

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Post by Sleipnir » Tue Dec 05, 2017 12:17 am

diode_destroyer wrote:I keep thinking of building this but then always get annoyed that there's not bypass switch. Do you guys use some kind of separate switching module in order to do quick A/B comparisons while dialing in (if so, please recommend me a module)?
You could use any mixer or splitter+mult setup to mix in the dry signal, but, frankly, I don't think this module is for fine mastering tweaks of -/+1db type of stuff.
This module is for, as the kids say, FUCKING SHIT UP. And it does it quite well.

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Resonant Equalizer Modification ?

Post by Hansi026 » Fri Dec 08, 2017 1:43 pm

Hi Guys, first of all, i’m not a DIY expert.

It is possible to mod the Reso EQ ? e.g. with an extra panel that contains 11 cv inputs for the frequencies and the feedback ? And as an option, can the knobs at the Reso EQ then acts as attenuverters ?


thanks :-)

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