¡Hi Geeks!

Finally, after four years of research and development (read it learning), four prototypes, many nights without sleeping, and countless soldering hours, I have finished the design of a prototype of an analog balanced line level, active summing mixer. The “MIKROSUM”

Features:

16+2 balanced inputs. 2 expansion inputs in jack format, 16 inputs in Tascam DB25.
2+2 balanced outputs. XLR main and copy for monitoring.
Balanced half normalled master insert send/return, in jack format.
Blend switch and pot, for parallel processing/ compression.
Balanced Summing amplifier with 153khz bandwidth.
Master volume control.
Power draw. 40ma aprox.

Noise level: at max volume: -74db aprox
at min volume: -78-80db aprox

As a first “shot” into PCB design, I’m happy, despite corrections and mods I had to do. The definitive PCB version will be better.

Sound Quality: ¡¡Awesome of course!!, transparent, good low end, smooth highs.

I recorded an old Roland JX3P hence my nickname JAY X, that has unbalanced outs, thru the summing inputs, and sounded more coherent: more defined stereo image, more tight bass frequencies, compared with unbalanced recording.

Also I have played stereo CD tracks from computer, thru the summing and differential return inputs, and re-recorded the result into Soundforge, and despite it is not a perfect test, the sound quality of the CD is maintained. I will attach examples ASAP.

Good stereo image: You can notice the depth and placing of instruments, and panning.

I still have to make more tests, so I will make them at a professional studio by February 21, to test the mixer in real studio conditions. It is a recording and mixing studio for rock and pop bands. Among its equipment, they have two NEVE 8816 with fader packs, millennia preamps, and protools interfaces.

Acknowledgements:

I want to thank Jules for the Gearslutz forum, over I stumbled in summer 2008, and became member by December. Tim Farrant for the original thread about summing mixer, Matt Syson for his invaluable help through these years, by messages, emails and comments on the forums. John Roberts, Harpo, and many others that with their comments also helped me to make this project a reality.

This is really a great forum to dream and make dreams come true…despite the time it takes to make it true!!

Thank you very much,
Karim Azeli Jarosch./ J.A.K.AUDIO. ”Analog plugin”

Wow looks nice! What are the building cost of this?

Neat, more info plz.

Awesome stuff, congrats!

Hi everybody!

Thank you for your comments and interest.

As recently i moved to a new flat, i could not place sound examples yet. But i will do soon.

My idea is to release this mixer commercially this year. If i was to put a price i expect it would be around 595/695 euros, depending if i include DB25 cables or not.

Still i have to ask quotations for laser metal work, metal punching, that may cut cost down quite a lot. To arrive to what you see at the pictures i spent around 3000 euros in the last five years...

JAY X

Hi Everybody!

!Today is the day! This afternoon i will be testing the summing mixer at a professional studio: Protools hd2, two NEVE8816 + two fader packs... millenia preamps, nice valve compressors, etc...

We will test the summing mixer with already recorded tracks, and hear how it works...

Meanwhile i'm working on the User manual, with drawings and pictures, and the different setup possibilities.

JAY X

Hi Everybody!

After the tests performed wednesday 13, i can say that the mixer performed very well, despite some connectivity problems, due to some cables i brought to the studio.

The stereo image was very good, and the noise level of the unit at working levels in the studio are better than expected:

Noise level: at 3: -85db aprox
at min volume: -92db aprox

When i designed this summing mixer, i placed a fader amplifier with a gain of 10db. 10db is too much, not needed at this stage of mixing, it is enough to have around 5 or 6 db of gain, thus reducing noise of the unit. If you look at other summing units that have a master gain adjust knob, you will see that the gain range is about 5 or 6 db. This is enough gain to transfer the mix without loosing volume.

We also tested the direct summing output, and the levels where ok to work with.

Next week i will upload the final audio tests, comparing tone qualities, between Protools bounce, Neve8816 bounce and Mikrosum bounce.

The studio where we performed the tests is called juglansmusic:
http:// JUGLANS MUSIC -estudi de gravació- a nice studio for recording bands.

Hi,

Sorry for the lack of communication, i have been busy the past months and still have some problems to solve...the audio files are still pending to upload.. i'll try to upload these before the end of may.

Sincerely yours,

Karim Azeli Jarosch.

what is the noise floor at unity? A summing mixer should rarely ever need more then 2 to 4 db above unity as everything is driven with a daw.

J.A.K. AUDIO MIKROSUM AUDIO TESTS by AZEL909 on SoundCloud - Hear the world’s sounds


Hi,

Above is the link to hear the mikrosum in action!

This Mixer is still a project to be improved, this is why i recently finished designing a new pcb layout, and hope to get all the bits together by end of June!

Hi geeks!

i'm still waiting for tghe new boards to come!! so the new version will not be ready until mid july... that's life!!...meanwhile.. !enjoy life!

JAY X

Hi Geeks!

A long time since my last post... i was studying... electronics,
Have passed ok all the first year exams... ufff now for the second year in september...heh

Meanwhile i ordered laser cut front and rear panels. these are the pictures:







With the new boards the output noise level @ unity gain is about -80.8db with one input routed.

I have a quite old soundcard, a wt 192m with unbalanced inputs and outputs, (+4dbu) and i suspect this audio interface has some noise impact in my measurements.

Today there are far better soundcards available, with better noise specs.. i suppose, so these may help to reduce even more the overall noise in the system...

JAY X

Hi Geeks!

I'm here back again!

The last two years i was back at the institute...studying a professional formation course about electronic maintenance...

Now i'm going to give this project a new kick forward, and add output transformers...and re build the pcb layout...

I would like to know if summing inputs in protools format : 1L & 2R in the same db25 connector... would be more interesting than to have all the lefties in one connector and the rights in another one!!

thanks for your opinions!

JAY X

How about one stereo pair XLR out that is transformer to electronically balanced switchable.
Maybe even switchable summing amp...
I was contemplating a box with these that had selectable API ACA, Neumann 475 or tube summing amp...

Love to see this box you are working on!

Hi Stitch!, everybody!

¡¡Happy new year!!

¡I Got Good news!... last 6 months i was working on the final version of the summing mixer...with some new features...32 inputs...(16 stereo pairs)... and more...

Stay Tuned!

Jay X

Hi All!

Right now i'm waiting for the boards to arrive maybe in a week or so...

Then i will start testing and stuffing the boards by sections. Besides i finished designing the 1u rack metal box...and hoping that all the connectors will fit the holes... all must fit exactly in their place...

Still some work to do, but getting near the goal.

Jay X

How does the summing mixer actually create better stereo image ? I would assume the processing creating minor distortion gives the information a sonic quality making it more detailed ? or is it something else ?

interesting

Hi Maxx!

The main benefits of summing are a few but important: Better perception of the stereo field. This translates into a better perception of the left - right positioning when panning, and front - rear perception when adding reverb or other spatial effects. Mixing is basically this: placing the instruments into the stereo field.

But, ¿why is this? ¿what happens when you take your stems/groups, out of just a stereo pair?

Well, i'm not an expert in psycho acoustics, but i think that routing your groups into different stereo pairs and summing externally would give some more headroom for your audio...the summing amps in my mixer, have nearly 100khz bandwidth for each 4 audio signals... this means nearly 25 khz bandwidth for each audio signal. It is as you have a wide pipe for a few water running into it. Better than jumping into a crowded subway..

Other reasons, are more related to a TONE, a particular imprint to the sound that can give transformers and preamps, as they do in large mixing desks. That is why big brands are still so much appreciated. I hope to reach that quality too!


JAY X.

Oh. My. Goodness.

Thank you Jay , i appreciate the info , ive used various summing mixers and found differing results , even the basic ones however showed a slightly audible difference , looking at the signals befroe and after say with a Flux Stereo Tool , you can see a slightly wider spread ( which i needed to qualify if my hearing wasnt in placebo mode )

I sat in on a mix last week , them using a custom made summing mixer , it looked very plain but the difference was really noticeable , they could bypass it with their matrix selector and i was really impressed with the difference.

I would assume the " quality " of the difference would be down to the components , ie transformers , caps etc internally , where do you find the good ones ? what brands are known for their great audiosonic qualities ? ( in relation to components )

And yes i understand running the signal into a pre amp is probably where a lot of the quality comes from as well.

Have you got any sound bytes of before and afetr using your prototype ? im really interested in getting something for my home studio.

Cheers

M

Hi Maxx!

Well, about transformers, i try first sowter line output 8403X, good iron!. and for this last prototype i try lundahls as they come in pcb version and fit in a 1u rack case.
Capacitors don't have a"sound" on theirs. But they are used to build lowpass filters and block dc in opamp circuitry. The cutoff frequency is key in the design. As for opamps i usually try bipolars from TI, onsemi, national, NE5532 is a good start, it is a classic opamp widely used. For fet input opamps i would try OPA2134 range, rather than the classic TLO range, which are toooooo noisy for today standards.

But, the main clue in audio design, is to get all the pieces together, properly designing each audio stage.

The prototype i'm currently building is not tested yet. I will do as soon as i finish soldering parts and fitting in a custom case i designed...

But two years ago i tested another version which was build only with opamps and line drivers, in a professional studio, where they have two NEVE8816 to compare to, and the owner liked the sound of my unit, as it got a special tone...it was interesting.

JAY X

Yeah i tried one at my home studio this week and the difference is noticeable , it takes away that clinical box sound and opens the mix up.

I really like working in a DAW but combining it with analog gives it a sound digital just cant replicate.

Im looking forward to seeing what your new design looks like ! please keep us posted

I recently ordered a Vintage maker summer. I'm still waiting for it to show up. He will make them to your specs. I elected for 3xDB25 in and 3xXLR pairs out and a passive/active switch with a good transformer. It should show up in about two weeks. I also went for half of the input channels (on each DB25 input) switchable from mono to stereo. Each pair of inputs has an on off switch. In this way I can use it like a 24 input preamp matrix to the daw and another gain choice and mic choice by turning unused inputs off. Past those kinds of options things can get complex and cost much more.

Question for Jay X

Should you take your line level down to mic level before external FX or after ?

ie

Box > Summing ? External EQ and FX Chain > Box

or

Box > External EQ and FX chain > Summing > Box

obviously both via yor IO

Cheers

M

Hi Maxx!

I don't understand well your question... i think you have a little confusion...

Let's see. Summing mixers work at line levels, and any external fx/or eq or compressor also work at line levels. They all should match their input and output levels to maximize headroom.

The summing mixer i'm building has a master insert send/return, wher you can hook up your comp/eq..etc... just set up properly their input and output levels.

Microphones need a preamp to amplify their weak output signals, and bring them to unity gain and then record them in your DAW.


Another question is settting up the gain levels for final summing. This is a good thread to understand how to setup levels of a mixer depending an the number of channels going to the mix.:

Noise & Headroom in Mixers.


I don't know if i answered well your question, but i expect i put some more light.

JAY X

Sorry i should have explained my slef better, i meant if you wanted to use a pre amp back into the box. Should you bring it back down to Mic level from Line level as the final stage before pre amplification ?

IE Box > > IO > outboard fx > summing mixer with -40 db pad > into mic pre on io > back into box

i read this post , https://gearspace.com/board/11742873-post50.html


Seems like good info

Hi Maxx!


hmmm, now i see what you mean, You are talking about a passive summing mixer followed by a preamp for gain recovery....

In this case, as more signals are summed, the more gain you need to bring the signal to unity gain. The output of every mic preamp is line level. so you don't have to worry about bringing it back to mic level, because you will record the mix output thru a LINE INPUT, not a MIC input. That's the question!

If you are using the preamps that come within your audio interface... ok..you have to set the mic preamp gain as much as to have a proper level to record.... say -12db or so... it is a question of headroom, because you may want to apply after some dynamic processing, eq ,fx... and finally mastering...

In any case the major drawback of passive mixing is NOISE, because you are using a high gain preamp to recover the level lost in the summing node. And besides you don't need a 40db pad!!.. in the passive mix the signals are yet attenuatted!!

In an active summing mixer, you just need an inverting summing amplifier with a gain of 1 or a bit less to get your mix right. This way the summing amp does not put sooo much noise out as with the preamp. This is why ACTIVE SUMMING, has become today so popular! Of course... if you want to add some colour to your mix...yes! transformers help a lot! thats why i put trafos in my mixer!!

JAY X

Thank you Jay

Im going to experiemnt with different scenarios and see what sounds cool and what i can get away with , i want to see if various tube pre's i have add anything to the sum i put through them in particular after a comp or expander , transistor compression sounds great with valve pre as a final stage ( talking outboard gear ) so i want to experiment with the various combinations and see if the noise floor matters on consistant instruments like drums or bass.

The charachter is what im after , trying to break away from the clinical in the box sound.

Just as a side note ive been playing with a Vitalizer as part of my outbord mastering stage and i put it up against the plug in and the difference is quite noticeable , plus the ability to tweak an attenuator just has a different feel , you can take your eyes off the monitor and use the ears which is totally im used to addmittedly , that tactile interaction is whats missing with in box mixing and hybrid analog and in box mixing is totally where its at for me .. im really loving the marriage between the two.

you got any pics of your prototype yet ? do you need a guinea pig to test on ? ( oink oink )

Hi!

Yeah!, hybrid mixing is the way!. No plugin can emulate that warmth!.Although there are good emulations out there. In that sense, i like the idea of combining the power of plugins, with a summing mixer as an analog front-end.

No pics of the mixer by now! ¡sorry!. I'm testing voltages, and finishing stuffing parts. After that i will take the board to mechanical designer to take some measures to fit the boards in a custom enclosure. Not an easy task!.

Guinea Pig?...¡say no to animal testing! ¡only humans! hahaha!

JAY X

Ok ive been experiemnting with mixes and drums this week and i found on " some " vintage outboard gear you can run them into a mic pre and get even more charachter out of it !

analog summing is so much fun to work with !

waiting on a photo !