Looking for a way out !! ...Mixers...Passive Attenuators...DI Boxes etc

From circuitbending to homebrew stompboxes & synths, keep the DIY spirit alive!

Moderators: Joe., lisa, luketeaford, Kent

Post Reply
ashley27
Common Wiggler
Posts: 119
Joined: Thu Mar 22, 2012 10:54 am

Looking for a way out !! ...Mixers...Passive Attenuators...DI Boxes etc

Post by ashley27 » Mon May 11, 2020 8:07 am

So my DIY modular is coming together and it's apparent I'll want say...... 8 outs into my DAW. What's the best way of doing this?

So far I have considered.......

- Radial Pro D8 straight into mic amps
- DIYing a bank of passive attenuators/balancing box into console line inputs
- I have panel/PCB/components to build a ST Modular SUM

The idea of Eurorack mixers scare me, one reason being how they don't seem to get much attention online. I've got Living VCOs in my rack, Serge filters etc and the idea of running it all through a DIY mixer in my head can sonically only be a limitation. I'll build the Sum regardless in hope of this being nothing more than me ridiculously overthinking things. The Sum doesn't really solve my problem of wanting multiple outputs anyway, but it will be handy when I'm not in my studio and want to play around on headphones.

I'm a mix engineer by trade so am lucky enough to have a SSL console and a big pair of ATC monitors, I can listen in a very controlled environment here... my point being that if there is even the subtlest of sonic differences I'll be able to notice. I'm happy to post results of a few patches going straight out of the modular into DI boxes/mic amps and the same signals running through the Sum, but I'm interested in whether or not anybody has already gone to these lengths to find the cleanest/preferred signal path from modular to DAW.

Thanks

User avatar
wuff_miggler
Wiggling with Experience
Posts: 468
Joined: Wed Feb 19, 2020 11:11 pm
Location: Disney, Australia

Re: Looking for a way out !! ...Mixers...Passive Attenuators...DI Boxes etc

Post by wuff_miggler » Mon May 11, 2020 8:19 am

plug the last module into any +4dBU input (thats the eurorack standard) your console line ins should work perfectly? especially SSL. This mgt sound dumb - but have you plugged stuff in and listened?

my raw osc. output doesnt clip into my rosetta 800 (when the jumper is set correctly to take +4dBu input).
you MAY need attenuator module if you're going nuts on feedback or resonance.

User avatar
EATyourGUITAR
has no life
Posts: 4566
Joined: Tue Aug 31, 2010 12:24 am
Location: Providence, RI, USA

Re: Looking for a way out !! ...Mixers...Passive Attenuators...DI Boxes etc

Post by EATyourGUITAR » Tue May 12, 2020 10:28 am

depends on the gain staging of your audio interface. depends if you want to go balanced or unbalanced. depends if you want a snake with DB25. absolutely do not run through microphone inputs. modular levels are 10v peak to peak sometimes more. if your audio interface has an input that can tolerate that voltage range without attenuation then great. if you need attenuation, that should happen closer to the audio interface. perhaps a custom solution with low noise resistor dividers on every channel would work best.

what audio interface do you have to do basic analog to digital conversion without mic preamps?
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

User avatar
Graham Hinton
Super Deluxe Wiggler
Posts: 3149
Joined: Fri Jul 02, 2010 6:28 pm
Location: England
Contact:

Re: Looking for a way out !! ...Mixers...Passive Attenuators...DI Boxes etc

Post by Graham Hinton » Tue May 12, 2020 10:51 am

ashley27 wrote:
Mon May 11, 2020 8:07 am
8 outs into my DAW. What's the best way of doing this?

So far I have considered.......

- Radial Pro D8 straight into mic amps
- DIYing a bank of passive attenuators/balancing box into console line inputs
- I have panel/PCB/components to build a ST Modular SUM
None of the above. All you need is the correct cables and what constitutes correct depends on what audio interface you have on your DAW and whether your Eurorack is correctly grounded (it probably isn't).
I'm a mix engineer by trade so am lucky enough to have a SSL console
What type? I'm an ex-SSL designer by trade.

ashley27
Common Wiggler
Posts: 119
Joined: Thu Mar 22, 2012 10:54 am

Re: Looking for a way out !! ...Mixers...Passive Attenuators...DI Boxes etc

Post by ashley27 » Thu May 14, 2020 6:25 am

Ah cool, hey Graham. I've got a 48ch G series. It came from Keith Skerett who you must know.

Are you Hinton Instruments? I'd be interested to chat further with you on all things above. For Eurorack power I use a clicksandclocks.de DIY power supply and rails, audio interfaces are Avid HD I/O, pro tools for software.

Thanks! Ash

User avatar
Graham Hinton
Super Deluxe Wiggler
Posts: 3149
Joined: Fri Jul 02, 2010 6:28 pm
Location: England
Contact:

Re: Looking for a way out !! ...Mixers...Passive Attenuators...DI Boxes etc

Post by Graham Hinton » Thu May 14, 2020 2:12 pm

ashley27 wrote:
Thu May 14, 2020 6:25 am
I've got a 48ch G series.
There's some of my DNA in that.
Are you Hinton Instruments? I'd be interested to chat further with you on all things above.
Yes. PM me or use the enquiry form on my website.

User avatar
synkrotron
Ultra Wiggler
Posts: 763
Joined: Wed Nov 09, 2016 12:48 pm
Location: Warrington UK
Contact:

Re: Looking for a way out !! ...Mixers...Passive Attenuators...DI Boxes etc

Post by synkrotron » Fri May 22, 2020 3:08 am

Apologies for butting in here, but I would like to ask Graham a question about his reply:-

Graham Hinton wrote:
Tue May 12, 2020 10:51 am
None of the above.
I'm thinking specifically of the DIY bank of passive attenuators.
All you need is the correct cables and what constitutes correct depends on what audio interface you have on your DAW and whether your Eurorack is correctly grounded (it probably isn't).
I'm not understanding what "correct cables" means.


I use the DIY passive attentuator approach to send six signals into REAPER via my OCTA-CAPTURE audio device.

The bank of passive attenuators are a simple 1/8" jack socket that is wired accordingly up to a 47k log potentiometer, all mounted in a small plastic case. I then have an "umbilical" running from that case made up of six normal size audio cables that terminate in 1/4" mono jacks which are then plugged into my OCTA-CAPTURE.

I then set up a patch using my patch cables to connect signals to my little attenuator box. I tweak the level so that I am peaking at around -18dB and I am recording at 24 bit so I believe (in my limited understanding of all things to do with recording digital) that there is plenty of "headroom" and no need to go in "hotter."

I find that the quality of the audio going into my DAW is of reasonable quality and there is only a very small amount of noise at the top end, typically over 14kHz.

So I am genuinely curious what I should be doing to make my setup more professional, if you know what I mean. Well, my finished product is far from professional, but not because of any audio recording reasons.


cheers, and thanks in advance :)

andy

User avatar
Graham Hinton
Super Deluxe Wiggler
Posts: 3149
Joined: Fri Jul 02, 2010 6:28 pm
Location: England
Contact:

Re: Looking for a way out !! ...Mixers...Passive Attenuators...DI Boxes etc

Post by Graham Hinton » Fri May 22, 2020 7:40 am

synkrotron wrote:
Fri May 22, 2020 3:08 am
I'm not understanding what "correct cables" means.

I use the DIY passive attentuator approach to send six signals into REAPER via my OCTA-CAPTURE audio device.
Correct means whatever your audio interface requires. That probably means balanced cable and whether the screen is connected to the synthesizer 0V depends on the grounding of both.

Read the spec of the interface, I know it's in Rolandese and requires some translating and reading between the lines.
TRS line inputs (balanced) have an arbitrary +4dBu maximum signal level with 16dB headroom. That means that the clipping point at 0dBFS is +20dBu which you won't get from a +/-12V synthesizer and only just with +/-15V. You don't need attenuation.
I then have an "umbilical" running from that case made up of six normal size audio cables that terminate in 1/4" mono jacks which are then plugged into my OCTA-CAPTURE.
If your interface has TRS jacks then use a TRS balanced cable. The old trick of being balanced/unbalanced compatible at the input jack predates 1995 EMC regulations and is not good practise. It forces the input to use it's local chassis as the 0V reference, rather than the remote 0V that the signal is referred to and there will be a difference between the two in terms of hum and noise.
I tweak the level so that I am peaking at around -18dB and I am recording at 24 bit so I believe (in my limited understanding of all things to do with recording digital) that there is plenty of "headroom" and no need to go in "hotter."
The use of -18dBFS is often misunderstood. If you have that as a maximum input level you are throwing three bits away. You are not recording from a microphone going through a valve preamp or trying to cope with the dynamic range of a symphony orchestra so there will be no unexpected peaks. You have an electronic source with a known maximum output and noise floor (probably not a very good one) so get the best level you can and turn it down in the digital domain taking the analogue noise floor down too. If you record above -6dBFS you are using all the bits.
So I am genuinely curious what I should be doing to make my setup more professional, if you know what I mean.
Avoid interfaces with combo jacks. That often means that they are attenuating the line input and putting it through a mic amp which is a poor gain structure and the mix amp quality is probably not the best. Get a straight line input device with a maximum input of 22dBu or more and use a separate high quality mic pre if you need one.

User avatar
synkrotron
Ultra Wiggler
Posts: 763
Joined: Wed Nov 09, 2016 12:48 pm
Location: Warrington UK
Contact:

Re: Looking for a way out !! ...Mixers...Passive Attenuators...DI Boxes etc

Post by synkrotron » Fri May 22, 2020 8:30 am

Graham Hinton wrote:
Fri May 22, 2020 7:40 am
snip...
Hi Graham,

I've snipped your post only so that it doesn't clutter the rest of this topic.

Thank you very much for taking time to go through all that.

Unfortunately, a lot of that went over my head. But I hope you do not take that as meaning that you have wasted your time. I need to read and digest and make sense of what I can.

Regarding the use of balanced cables.

I only have to pieces of equipment that support balanced cables. My active nearfield monitors and a Lexicon MPX 500 effects unit. I use balanced cables for those.

Everything else, my the hardware synths and my modular system does not have balanced outputs.

I always thought that there was no point in using a balanced cable to a device that does not have balanced connections. Am I wrong in that assumption? I can understand that the shielding may possible help to keep out radio frequency interference but not any inherent circuitry noise.

My Eurorack modular system, as far as I understand things, does not have balanced outputs at any point along the audio signal path. So, again, I thought that there would be no way of making them balanced.


As you can probably tell I am quite a numpty when it comes to the heavy technical stuff like this and did consider not even asking the question. Only because, as is the case, I wouldn't understand the answer.


cheers, and big thanks,

andy

User avatar
Graham Hinton
Super Deluxe Wiggler
Posts: 3149
Joined: Fri Jul 02, 2010 6:28 pm
Location: England
Contact:

Re: Looking for a way out !! ...Mixers...Passive Attenuators...DI Boxes etc

Post by Graham Hinton » Fri May 22, 2020 10:40 am

synkrotron wrote:
Fri May 22, 2020 8:30 am
I only have to pieces of equipment that support balanced cables. My active nearfield monitors and a Lexicon MPX 500 effects unit. I use balanced cables for those.
You must have more than that, what are you connecting to them?
Everything else, my the hardware synths and my modular system does not have balanced outputs.
Your Octa-Capture has balanced inputs.
I always thought that there was no point in using a balanced cable to a device that does not have balanced connections.
A balanced cable can cancel interference picked up by the cable, but that feature is overrated. Real world interference does not conveniently come from an infinite distance away to conform to theory. It is more likely to come from an adjacent cable, in which case the geometry is totally different and the best you can hope for is some reduction rather than perfect cancellation.

The important advantage is being about to have differential signals and to avoid grounding problems.
I can understand that the shielding may possible help to keep out radio frequency interference but not any inherent circuitry noise.
To meet modern best EMC practise and legal requirements a screened cable should be connected to a grounded chassis each end. That isn't possible with something as badly designed and subsequently corrupted as Eurorack. The original Doepfer Eurorack was incorrectly grounded, the Americanised versions are usually not grounded at all.
My Eurorack modular system, as far as I understand things, does not have balanced outputs at any point along the audio signal path. So, again, I thought that there would be no way of making them balanced.
You can easily use any unbalanced output and wire it to balanced, just not the other way around. Not easily anyway. Ironically any balanced outputs modules with XLRs usually incorrectly connect the cable screen to 0V (because there is nowhere else).

The simplest way is to have a 3.5mm TS to XLR or 1/4" TRS cable or the equivalent in an adapter box.
ts_trs.png
The cable screen may or may not need to be connected at the TS end. What you are trying to do is give the balanced input the true signal, rather than the difference between the signal and some other part of the system including other hum and noise. Try connected first, if that has problems disconnect the screen and if that still doesn't work then you need a line isolation transformer (unity gain, not a DI box).
You do not have the required permissions to view the files attached to this post.

User avatar
synkrotron
Ultra Wiggler
Posts: 763
Joined: Wed Nov 09, 2016 12:48 pm
Location: Warrington UK
Contact:

Re: Looking for a way out !! ...Mixers...Passive Attenuators...DI Boxes etc

Post by synkrotron » Sat May 23, 2020 7:28 am

Graham Hinton wrote:
Fri May 22, 2020 10:40 am
You must have more than that
My setup is quite simple. That is all I have.

Besides, I do not have any problems with noise. Nothing that cannot be fixed "in the box."

Thanks,

andy

Post Reply

Return to “Music Tech DIY”