ACL & Waldorf modules

Hello All,

I am new to this forum and I consider (nah rubish... I am pretty sure about it, no consideration needed here ;-) ) to buy a modular synthesizer system, since weeks I am at night for hours checking out on modules, the technic behind it, the websites of the manufacters, etcetera. A lot of fun while planning & checking :-) Can't wait for the moment to buy it however till then I have to be patience...

Currently I am particular interested in ACL modules and Waldorf modules. I couldn't find too many threads yet about modules of these two brands. Is there anyone who likes to share his/her experience with some of those modules? How is the (hifi) audio quality of these modules? The fun/price rate? Any particular cons/pros? Any feedback and/or information on any of ACL and Waldorf modules is very welcome.

Thank you very much in advance and kind regards,

Peter alias GarfieldModular.

You'll have specify exactly WHICH modules you're thinking about acquiring. You'll also have to build-out an entire system from scratch around them if you choose to start your first case with them. Why are they a good decision for you specifically? That's a rhetorical question only you can answer. What are you looking to accomplish and what external gear will your Eurorack case be interfacing with?

Those ACL and Waldorf might be better purchased later on... depending on the modules. Maybe not. It's all going to come down to your needs and what the SPECIFIC modules you want can do for you. A lot of what you get out of a module is determined to what other module(s) it's connected to... so take Youtube videos with a grain of salt. Here are some results you CAN achieve with all the modules that are patched. Take away one of those modules and you might have a completely different sound.

Thank you Ronin for your feedback. Since I am new to modular synths I was under the impression that at least ACL focusses on a good audio quality level. Before I got interested recently in synthesizers, I kept myself pretty busy with HiFi stuff and to be honest, it is difficult to judge which module might be an interesting one for a good HiFi circuit and which aren't. I just heard that ACL seems to be pretty good if it comes to hifi audio. So that rumour I heard is that correct?

I tested at a local shop the Waldorf Quantum, I was pretty impressed by it and before you shoot me here straight away, please allow me to explain ;-) At that time it wasn't clear yet to me what I wanted, now it's clear to me I want a modular synthesizer system (containing, at a certain stage at least, several synths within that system). Since I discovered that Waldorf has modules for the modular system as well, I was kind of interested and wonder if Waldorf modules can be mixed up with ACL modules to form one or another way one kind of synthesizer within my to be future modular system. Mind that I mean with if Waldorf & ACL can be mixed I mean that from a hifi point of view, are they about equal level if we talk about quality (hifi) audio level. I heard again a rumour that Waldorf might not be up to the level of ACL. Naturally you are welcome to mention other brands that have & concern about high quality audio; naturally the con of that is the usual high prices of the modules. So yet another planned synthesizer within my future modular system would be less focussing on high quality audio more though on functionality and possibilities of the modules themselves.

So to decide for myself (you are right of course, one needs to made up his/her mind: what do you really want with your modular system) which modules from Waldorf & ACL I am interested in, well that's difficult to decide if there is barely nothing to look for and other than the manufacturer's information about it, there isn't much additional information on these both brands' modules. For Waldorf I couldn't find really much on the Internet (youtube for example), for ACL modules a bit more but still not too much to give me a good impression and enough details to decide into which modules I would be interested or not.

I therefore was hoping people could share here their experiences with any of the Waldorf modules except the CMP1 that one doesn't interest me much (there are only 5 if I am not mistaken, so minus the CMP1, the other 4 I am interested in) and though ACL has a few more, not that huge number either. Also just general impressions, pros/cons of both brands modules would interest me, just to give me an impression. Anything at the moment is more than I know now about both brands ;-)

For many other brands, I had already a chance to test several modules (per brand I am interested in) at a local shop nearby I live however Waldorf was not available for testing and for ACL only a few modules that didn't interest me much so far. Okay from ACL currently the two modules that interest me most would be QLFO and the VC Dual Delay, however if there are users who have great (or less great) experiences with other ACL modules such information would be still much appreciated.

Thank you very much in advance for sharing your experiences.

A quick chime about the ACL Discrete Core Ladder and Stefan's support in general:

The module is a lovely sounding filter - my favourite in fact! It's very well thought out with a 3 channel mixer, 2 frequency cv inputs, resonance cv, outputs for 6, 12, 18 and 24 db/oct slopes, bass boost and a two feedback circuits to get either the classic ladder taper as the frequency drops or another that allows you to get the resonance pretty low. The filter takes to overdriving and fm very well. Slamming the inputs at high resonance settings sounds absolutely killer. I picked up the AJH at the same time and ended up sending it back as the ACL ladder could do everything the AJH could and then some.

Speaking with Stefan has been a pleasure too; he's a super cool guy to talk with.

Attention to detail and sonic quality is the name of the game for them and it really shines through playing with the filter. On the whole my experience with ACL has been very positive and I can't recommend trying their modules out enough.

Thank you cosmic94, I will keep an eye on that Discrete Core Ladder module.

It's a pleasure. I think the key thing to take away from it all is that ACL know what they're doing and the quality is top notch.

How do you define hi-fi? You refer to it often. Do you mean hi-fi consumer audio? Record players, amps, speakers, a collection of vinyl, etc... or hi-fidelity musical instruments? What experience do you have with creating music... especially synthesizers? Depending on where you are starting from, you'll have different challenges. My concern is that you're coming from the position of enjoying the playback of great music and now you'd like to create music. Modular is an expensive format to be your entry point into making music. While not impossible, you're stacking the odds against you if you're learning to make music at the component level. It's not a terrific analogy... but it's like buying Formula-1 race car as the vehicle you're learning to drive with.

The worst thing would you be spending a small fortune, getting frustrated and burned out, then walking away from your endeavor. Modular synths are awesome... but then again I have some bias. :) I just want you to have an enjoyable experience. Have a think about where you're at and if you're entering modular a little soon... if you're coming from hifi audio.

There are no wrong decisions and I've assumed a bit in my response. But if you've never programmed a synthesizer before, you're taking on a huge challenge.

Also, you may not want "hi-fi". For example, if you had an original ARP 2600 displaying all of its sonic capabilities, you'd wind up with damaged speakers and possibly the amp as well...because the ARP 2600 had DC coupled VCAs going right to the output. And passing DC to your speakers WILL wreck them...but you'll be getting everything the 2600 has to offer sonically!

For that matter, once you've dived headlong into electronic music, you'll wind up wondering what "fidelity" is anyway. A lot of inventive work in the various aspects of the field has come out of mistakes, errors, and general screwing around...and NOT trying to achieve some pristine-fidelity result from the instruments and/or processing. The only place you should be concerned with "hi-fi" is when dealing with your DAW's A-D and D-A conversion so that whatever results you got (be that "hi-fi", "lo-fi", "no-fi", or just plain screwed up) are being recorded and reproduced properly. Beyond that, "fidelity" means zilch in a form of music where there's not exactly anything that you're trying to be faithful in reproducing, and in many cases a result that was a pristine "fidelity" result would be utterly useless.

Oh this is ridiculous, I was writing a rather large (okay huge) reply here then when I submitted it I had to login again, and everything is gone... (going backwards didn't solve the problem). I lost several hours since I put quite a bit of efforts in my reply to Ronin1973 and Lugia... hours of "work" gone :-(

I will try to get back to you another time, meanwhile, thank you very much for your kind replies!

Hello Ronin1973, Lugia and all,

Thank you very much for your responses, yesterday I wrote a huge reply (larger than this one!) to you guys but due to a time-out on this website, I lost the entire reply and have to start all over again...

Because of the above reason and to avoid yet another loss of efforts, I will split my reply in three parts, first this common part and then I will reply to your specific questions in a different reply.

To your both questions about hi-fi and what I expect from a modular system there is no easy and/or short answer, though I was hoping you would ask and put me into this direction since I have to explain to you a bit more about my background, so perhaps you understand my questions better.

As a kid, I played organ for years, can’t remember exactly how long, I think about 6 years or so till the moment my dad pushed me a bit too much on that matter that I give up on playing organ. A few years before that I start discovering “synthesizer” music as I called it that in the beginning, starting with J.M. Jarre and Kitaro, later followed by many other well-known artists using synthesizers and well known for that.

Though I stopped with playing music, I started to develop a serious interest in electronic music, however only from a listening point of view, after stop playing the organ I guess I had just enough of making/playing music that it didn’t came up to me to start doing something with synthesizers.

I owned all the way some seriously terrible non-quality loudspeakers but had nothing else and listened at music either with that or with headphones (much better than my lousy loudspeakers), till I bought in 2015 my B&W 683 S2 loudspeakers and about two years later a NAD C 368 amplifier. Audio heaven opened up to me with that installation and I still enjoy that almost every day. Last year I upgraded my installation with bi-amping cabling, I didn’t expect such an improvement with a rather simple effort, it’s fantastic, and if you haven’t tried it then I strongly recommend to use bi-amping (if your amplifier and loudspeakers can support that), it’s seriously worth it, but I guess that’s not a discussion for this forum :-)

So yes Ronin1973, I am a hi-fi fan since about 4 years now and I can enjoy good music on a good quality (avoiding “hi-fi” here ;-) ) audio installation. I don’t think this forum should be misused to start a huge discussion on what’s hi-fi or what isn’t, just a short description on how I understand it (which doesn’t mean that that’s correct but that’s just how I personally see it) is: a good quality audio installation, it’s that simple for me whereby everyone can decide for themselves how to define “good quality”; it usually is related to one’s available budget and one’s taste too. The entire marketing meaning of hi-fi I also don’t like, who does? ;-)

That as an introduction to my background, so you roughly have an idea “where I come from”. Several years back my son played piano and I looked at the notes he was playing and I couldn’t read even a single note of that! I was pretty much in a heavy shock because when I was young I could read fluently without any problem music notes from paper but not any longer any more, I know where the common/middle C tone is but that’s about it. I forgot all about making & playing music since I stopped playing the organ, now far more than 30 years ago... till recently...

A good friend of mine visited me for a weekend back in February this year. He had very limited luggage with him however the small but nice device in his so little luggage that he took out from his bag was a Teenage Engineering OP-1, what a fantastic device! I played less than about one hour with it I think but wow, that was the spark and the catalyst that catapulted me (back) into the world of synthesizers and making/creating music, the push I needed to get awake and started with this fantastic synthesizer hobby! After more than 30 years, I finally got awake again :-)

That was this year back in February, by early March I bought a Roland FA-06 workstation, I know, nothing compared to a modular system, I hope you don’t kill me for the fact I bought a workstation ;-) I just wanted to get started and using a device that was able of a few tasks.

Before March had a chance to finish off and handing the “time” over to April I realised, I needed something, I wanted less working in the menus and more working with direct knobs, handling direct parameters, etcetera. So, before it was end of March I bought myself a Behringer Neutron. A kind of dream came through, no menus (yes!), for everything I needed was a button to turn at and I could patch the sound the way I wanted it to flow, fantastic!

That was by end of March, before it was April, I felt after using the Neutron so intensively that I wanted “more”! Since end of March/early April it became crystal clear to me that I wanted a modular synthesizer system.

Ever since I am checking the Internet on different brands, on the several modules each brand has, the possibilities of such modules, etcetera. I was, no sorry, I still am overly enthusiastic and can’t stop checking anything about synthesizers, the different brands, their modules etcetera. So I created a spreadsheet list with, for me at least, the most common, known and interesting brands and their modules and I am close to about a little one thousand modules I got listed and partly checked in that spreadsheet till I discovered this website!

So fantastic! Almost all the modules from I guess almost all the modular brands are represented here, in an easy overview with good search functions, wow! The rack planner, that’s just beautiful and fantastic! I love it, and I therefore have a deep respect for the person(s) who created this and keep (!) maintained this, that’s really good and thank you very much for that!

I wonder if I am the most enthusiastic member here in this forum? :-) Since that friend came to show me the OP-1, I am not lying here with the exception of 2 perhaps maximum 4 nights that I didn’t work with it, I have worked non-stop, every late evening after work and after diner when the family goes to sleep, till deep in the nights, it never was before 3 am before I went to bed and 4 am or 5 am are no exceptions and still have to work the next day at 09:30 :-( So since end of February, non-stop, literally every night I am checking out on synthesizers, the basics behind it, the different brands, the reviews, the demos listening at it, almost everything, testing for a while, on an almost weekly basis at a local shop here, the several modular synthesizers brands and many (not all though, pity :-) ) modules. It’s just fantastic. The very first time I was in that shop that I started to test on those modular thingy’s, they almost had to carry me out of that shop, I just couldn’t stop testing and trying to understand the modular system!

Does this somehow convince you that I am seriously deep into this? :-) I am now for more than one month planning and checking many modules, trying to understand them, reading the technical specifications, watching demos & reviews about it and I just can’t stop doing that, still every night I am checking and I have literally drag myself to bed to at least catch some sleep to carry me through the day times and I can’t wait till it get night and dive into the synthesizer world again :-)

In my next replies I will come to your more specific points, I have to hurry now to avoid yet another time-out and losing everything that I just wrote down now.

Oh yes just to make clear, at the moment I don’t own a modular system yet, I am currently in the planning and checking phase and just can’t wait to get one but I have to be patience first before I can go ahead with that... I just can’t wait for that (I am repeating myself out of sheer enthusiasm) and I am oh so jealous about those here who got already one ;-) Well done!

Rest me to thank you Ronin1973 and you Lugia and it goes without saying, actually all of the forum members, for your kind help, information, feedback and sharing your experiences with me and here throughout the forum discussions.

I particularly like the thread “New to modular? Maybe this can be a beacon?”, fantastic, very helpful and thus a very big thank you for that.

Hello Ronin1973,

For a common introduction please refer to my just previous message. I would like to reply to a few matters you mentioned in specific your reply.

For the hi-fi matter please refer to my common reply. Regarding hi-fi “consumer” audio... bbrrrr, the word consumer gives me cold thrills and I guess you meant it in a sarcastic or rather negative way and I only can agree with you, so no, I didn’t mean it in that way ;-)

As you can see from my previous common reply, I have not much experience other than my just now “3 months experience”, I almost not daring to mention it since it’s just close to zero experience indeed. But haven’t we all started with zero experience and starting either when we were a baby, a toddler or a youngster or like me a rather medium-aged person?

Indeed, very well noticed, I come from that “world” leaning back lazily in a comfortable chair and listening at good music from a good quality (I will avoid hi-fi ;-) ) audio installation, but that didn’t stop me, finally since February this year, to start with synthesizers, I am glad I did, the only little regret is it should have been 10, 20 or 30 years ago but hey, we all made mistakes, and this was my mistake ;-)

When I am (overly) enthusiastic, I usually am a bit “too soon” with that kind of things, either good or not I want a modular system ;-) Look at the amount of time I have spent into studying synthesizer stuff since end of February which is, in my opinion, totally abnormal, out of this world, but I did it. So, synthesizers must do something good with me, otherwise I wouldn’t have put so much efforts in it this far and this long... I guess...

Thank you for your kind warning that this is going to be expensive, I kind of “think that I know that” but one wouldn’t really know untill it’s too late, isn’t it? ;-) Anyway, I am okay with that, synthesizers became such an extreme hobby for me that I don’t mind as long as it kind of fits within the budget. The only scary feeling I have is that that budget might get extended, and extended, and extended, etcetera... yeah... sigh... isn’t that the case with almost all nice hobbies? :-)

You mention there are no wrong decisions, well isn’t that the fantastic beauty of modular synthesizers? What every you do with it, whatever you have patched or didn’t patch, whatever setting you have done or haven’t done, it might not be perfect but it isn’t a mistake either, that is modular to me! And I love it! :-)

I hope you don’t mind that I am saying this: You mention “programmed a synthesizer”, I know a bit or two about computers and programming a computer means you are going to “programme” the computer with a programming language like for example C, Pascal, Java or even assembler however I haven’t come across this with synthesizers?

May I assume that you meant to say “configuring a synthesizer”? Since being honest, I don’t believe that any one of us here really has “programmed” a synthesizer with perhaps a few rare exceptions if you had worked for example for a synthesizer manufacturer and you had there indeed hardcoded programmed some of their modules or something like that. We rather are doing complicated configurations, making patches, etcetera, yes, that one indeed you are right, I only start doing that since I got the Roland FA-06 in early March, before that, I never had configured indeed a synthesizer...

By the way, I had the opportunity of playing for about an hour with the Nord Lead G2 synthesizer, if of all synthesizers one comes close to “programming it” then it’s the G2, it’s still configuring it but on a very high and respectable level. For this moment, indeed, I consider that synthesizer as a few levels too complicated for me since my lack of experience. On the other hand, modular synthesizers are, at least that’s how I feel it, inviting me, almost screaming at me, to discover them, to test them, to figure them out, to get them “under control” ;-) and last but not least get some fantastic sounds out of it! That’s how I feel and I just can’t stop talking about modular stuff... sorry...

Oh yes, one last thing, you mentioned, modular is an expensive format to be your entry point into making music. Yes indeed, I do realise that and I wish it was about one tenth of the actual price, then it would be all more affordable ;-) But “making music” with it, you might be surprised with my reply on that matter however to be honest with you I don’t think I will make music with that, I don’t consider myself a musician and for the moment a modular system for me is the fun combination of testing it, trying it, getting weird and fun (and sometimes perhaps beautiful) sounds out of it and trying to understand it. So rather towards testing and sound design than really making music with it; well at least for the moment.

I love huge challenges, I always did and I always welcome new huge challenges, that’s one of the reasons why modular systems intrigue me so much that I want to get one, hopefully as soon as possible :-)

Thank you again for your kind help and I hope you will continue supporting me with my future questions/matters regarding modular synthesizers, very much appreciated!

Hello Lugia,

I think I have explained enough about hi-fi ;-) See my common reply and my reply to Ronin1973. Talking about the ARP 2600 though... I never had the chance to test or listen at it live but what I have heard of it, people talking about it, it must be fantastic. I had the chance, in a local shop here not far away from where I live, to test the nowadays available ARP Odyssey and to be honest with you I was a bit disappointed about the touch and feel of it. The sound was about okay but I wasn’t overly impressed. I heard on the Internet a demo of the to be released Behringer Odyssey and I must say I was pretty impressed about that sound, at least more impressed than about the ARP Odyssey. So let’s hope that the Behringer Odyssey gets closer to that sound of the ARP 2600.

You make me a bit worried about your warning about passing DC to my speakers that they will get wrecked, how bad is that? I was so far under the assumption that as long as I would put my amplifier not too loud (I stay usually away of volumes that go beyond -20 dB, with my mixer level at mid or zero and within the green LEDs level with perhaps sometimes hitting one orange LED), would that still be able to damage my speakers? :-(

If the answer is yes, what should I do then? Get monitors instead? Are they able to withhold DC signals? Wouldn’t there be the same problem?

Since I am a bit technical guy, I actually don’t understand the concern of DC signals? DC signal is, at least theoretically, nothing more than just the positive half of an AC signal :-) For which part of the loudspeakers would it be the killer? The subwoofers or the tweeters? But if one plays at a moderate level (which I usually do), I actually can’t see an issue here? Please enlighten me here, thank you!

Okay let’s avoid the word “hi-fi” for the sake of a good atmosphere within this forum, ha, ha ;-)

So please allow me to call it then... good quality audio? :-) And as in my previous common reply, “good quality” everyone can for themselves define what that is, it’s partly a personal taste rather than a pure technical specification only.

So back to “good quality audio”, with that new modular system I am planning, to start with I think I want to get started with two “synthesizers” (two synth voices?) within that new system. One for the... indeed more focussed on the “good quality audio” and the other one more for the fun tests, for squeezing out the sounds, for getting weird stuff out of it, in the search of an interesting sound, and then yes, I agree with you, the quality of the audio becomes then less important.

That’s the reason why I am interested in ACL modules and I was hoping Waldorf too, since I had the impression they might be focussing a bit more than average on good audio quality, for my, let’s call it: better quality audio output :-)

Then the other output or voice, the focus is not so much on good audio quality but rather on experimenting with sound and then I am thinking of Erica Synths and Make Noise modules; checking it out sonically :-) For me, both ways of approach have fun parts.

For the sake of my lack of experience, I will put Doepfer somewhere in between these two options, borrowing a few models for the fun bit of sound creation and a few other modules perhaps for the more audio oriented output of sound.

I hope you that it’s okay for you that I have this “split approach”, in that one way I focus a bit on the audio quality, whereby you might not agree with me ;-) and the other way I focus more on experimenting with sounds, and I think looking at all the modules I have checked so far, that my main focus will be anyway on those modules that create fun and weird sounds so for those modules, I totally agree, the “so called audio quality” is or shouldn’t be an issue there, it’s sometimes even wanted that it doesn’t sound too good ;-)

Well thank you too for all your help, and though we might have a minor difference in defining good quality audio, I hope you are still willing to support me further with possible future questions and matters I might have with this crazy nice modular synthesizer hobby! :-) Thank you!

Oh this is ridiculous, I was writing a rather large (okay huge) reply here then when I submitted it I had to login again, and everything is gone...
-- GarfieldModular

My sincere apologies. One day I will find and fix that bug...

...
You make me a bit worried about your warning about passing DC to my speakers that they will get wrecked, how bad is that?

Bad as in permanently kaputt.

Since I am a bit technical guy, I actually don’t understand the concern of DC signals? DC signal is, at least theoretically, nothing more than just the positive half of an AC signal :-) For which part of the loudspeakers would it be the killer? The subwoofers or the tweeters?

You might kill your woofer first. Due experimenting may proove me wrong though ;-)
Problem with DC on any audio signal chain is that it does not alternate and thus cannot be heard. More specifically it takes away from your headroom/dynamics usable for audio and puts useless stress on your speakers. That is why P.A. power amps usually have steep hi-pass filtering to void any DC in their output. (More smoking details on speaker death by DC on demand.)

-- GarfieldModular

Thank you ModularGrid, I don't think it's a bug, to me it "looks" like more a time-out issue. I was typing (checking things in between as well and read over my huge reply a few times to get rid of my biggest typos) and that was for over 3 hours in total, so perhaps you have a look into the time-out issue of being logged in (meaning after a certain period of time one get's kicked out of the system)? If you don't want to increase the time-out timer (at what time is that set? Then I can put an alarm just before that moment ;-) ) another approach to solve the "issue" is that at least one wouldn't lost the reply one was just busy with... so one would have at least an opportunity to copy the reply, then login again, then paste it and then it can be submitted.

Thanks a lot in advance for looking into this!

By the way, for every reply I try to submit, I get every time (so far I haven't seen an exception to that) this error message in red above the reply message I am typing:

reCAPTCHA error: timeout-or-duplicate. Just try again!

Are you able to do something about that as well? Much appreciated! :-)

Hello Wiggler with a lot of fives ;-) Thanks a lot for your reply!

Bad as in permanently kaputt --> that's bad indeed! You make me even more worried...

So that seems to be pretty bad indeed... perhaps I should approach this issue from a different angle then... what can I do to make sure that there wouldn't be a pure DC signal at the output signal of my (upcoming) modular system? Any "protection" module for that, or is there an easy trick to make sure of whatever goes out towards a line signal wouldn't have any "DC issues"?

Otherwise... how would we all be able to use modular synths if nobody can listen to it because a DC signal might destroy our speakers... it's somehow a bit confusing to me to be honest...

Back when the first synths were concocted by Bob Moog and Don Buchla, you didn't encounter a lot of DC-coupled amps. Those came along a little later, as solid state electronics for power levels typically used in amplification became more common. As a result...plus as a result of the idea that you should be able to tap a CV at any point in a patch where it might be present, including the output...the idea that the output stage of a synthesizer should be DC-coupled was rather typical, and even persists to this day with some module designers. And that's yet another reason I strongly suggest to users that they make use of a proper output module, because these tend to be (but not always!) AC-coupled only. When you have a transformer or other isolation device before that final output point, the potential for DC-caused failures drops to zero...and you also get a bit of iron in the signal path that might sound good if pushed into a bit of saturation, plus that also helps with noise and ground-loop issues. Note that this isnt the result you get by simply using typical attenuators to step the levels down for output...that, in fact, is guaranteed to pass any DC that is present on the input side of the attenuator, just scaled down but still quite capable of causing harm.

EDITED May 23rd 2019, 04:06

Otherwise... how would we all be able to use modular synths if nobody can listen to it because a DC signal might destroy our speakers... it's somehow a bit confusing to me to be honest...
-- GarfieldModular

As Lugia said, using a transformer coupled output module is a safe and professional way to avoid DC problems in studios and going into a P.A. system (if a bit costly). In real life all mixers I have used, even cheap ones, remove DC from their outputs. If things sound gnarly out of your speakers when they shouldn't you probably have DC in your signal going into the mixer (or other monitoring device). A scope will help you see that.

EDITED May 23rd 2019, 07:15

Yup...in fact, I have used (and plan to after the studio upgrading here is finished later this summer) a pair of tube bandpass filters in the analog side of my mixchain which I set up to roll off everything from 10 Hz down and from about 15 kHz up. The filtering eliminates potential low-end losses due to detrimental subsonics and/or DC, as well as countering the 'brittle' sonic issues that result from excessive high-frequency aliasing, particularly in the octave immediately prior to the Nyquist frequency. Plus, this puts 11 active 12AX7A stages per channel into the mixchain to add some extra euphonic even harmonic emphasis, thereby warming things up a tad and deepening the presence of the higher-mids and highs.

Hi Wiggler55550 and Lugia,

Thanks a lot for the information. Okay fair enough to take a "decent" or "good" output module to bring modular audio output to a line input on a mixer or to speakers, all fair enough :-) It's good to know for certain. I am still worried but at least I got an idea of how to handle this a bit better --> getting good output modules.

Now when I would consider to buy an output module, do I understand you correctly to watch following matters.

Output modules:
- should be AC-coupled based
- just a simple attenuator should be avoided (for using as an output module)
- any other matters to be aware off or to be checked?

If the manual of such output doesn't mention that's AC coupled or not, is there any way of seeing or recognising if it does or doesn't?

About mixers, Lugia, are you saying most mixers are already AC coupled? So I guess that should be mentioned somewhere in the (technical) manual of the mixer? Since I am planning to lead all outputs of the modular system to the mixer first before it's going to my audio installation, I should be fine or is there something I still should be aware of and/or take care off?

Thank you very much in advance for saving my audio installation! :-)

Some mixers are AC coupled. Some aren't. The best way to make sure you're not passing DC to your amp, though, is to make sure of this in the source itself. In this case, you're looking for output modules that have transformer isolation or offer balanced outputs (which generally implies transformer isolation). Happy Nerding offers two that are worth consideration: the Isolator is a basic, two-channel transformer-isolated output level attenuator, and their OUT not only offers this, but adds a headphone amp plus a second parallel stereo input which can be used as an effects return, plus you get stereo LED level metering. Also, Bastl's Ciao! does this w/o metering, but has input clip indicators for both stereo in pairs and a potential second stereo (3.5mm TRS) line out and a few headphone monitoring tricks that can allow you to have one stereo pair going to the outputs while the other can be monitored on headphones, allowing you to work on an entire second patch at the same time that the other is playing. Any of these would be very useful.

Thanks a lot Lugia! I will check out those modules and a few others. I need time (currently a bit busy) to figure out about the output modules. For Happy Nerding I was planning perhaps one or two modules so I certainly will consider their output modules. I haven't planned Bastl modules into my system yet, if you have any good experience with any other output module, you are welcome to let me know (regarding getting rid of the DC signals) :-)