new project: small home recording console

[Dimitree]

I started this new project: a small and simple console for my bedroom studio.
I'm seeking advices and corrections about the concept, since I'm not a beginner when talking about recording studio workflow.

I have several synthesizers (most of them DIY by me) and other electrical instruments (guitar, bass, e-drums), so my main needs are:
- not to be forced to use the computer + soundcard every time that I want to play (monitor) all those instruments
- share my outboard effects between multiple instruments without having to plug/unplug all the connections every time
bonus:
- using the console as a summing mixer, to get the benefits of faders/knobs in terms of ergonomicity, and why not, even in terms of sound (if I decide to use a particular summing stage)

Also, I'd like to point out that I only use my "studio" for myself, I don't intend to record other people, and the console will be placed in the same room as my instruments, that's why many facilities of the bigger consoles won't be on this (foldback, talkback, etc).

so this is my idea of how a single channel could be (I think it will have 16 mono channels and 6 stereo channels).
Since I don't need preamps, EQs and Dynamic processors (I will use them as outboard when needed), the entry points would be two simple line inputs (with +/-20dB trim on each input).
One input would be used by the instrument to be monitored/recorded, the other will be used as return from the DAW. A "monitor" switch will select the input, so for I should be able to monitor, record, overdub and mix, just flipping those switches on each channel.
A direct output is provided so that I can record the channel (either after the line input or after the insert, if I want to record the outboard processing too..).
There will be both PFL and Solo-in-place. The former will have its own bus, so when active, the console output will switch from the main bus to the PFL bus. The latter will be used to hear the channel in the mix with pan and effects, so when active, every other channel will be muted, and the soloed channel (or channels) will still be routed through the main mix bus.
I think there will be four stereo Groups, and four mono AUX sends.
Every AUX will be connected to a pair of bus (using a stereo potentiometer) so that in the master section, globally for each AUX, I can choose it to be PRE or POST fader.
I still haven't decided if there will be Stereo returns, or if I will just use Stereo channels for the returns (little difference I guess, it comes down to deciding whether to put a fader or a potentiometer for the return level).
Same for the Groups, I still haven't decided if I will put a dedicated channel strip for each of the 4 groups, or if I will manually patch the output of the group into a stereo channel input whenever I need to use a group.
Lastly, a pair of momentary push buttons will be connected to a microcontroller and be used to control some DAW functions (channel select and REC arm). In the master section there will be other "digital" buttons for other DAW functions (Play, Stop, etc). I mainly use Ableton Live as DAW.

I haven't thought about the master section yet, but as I said, I think it will be really simple, because I will just use the console for myself. So I think a pair of stereo outputs (for the monitors and for the soundcard ADC) and an headphones amp for when I need to play late at night and/or record with microphones

 

[cyrano]

Shouldn't the PFL bus attach to a point before the mute switch?

 

[Dimitree]

Shouldn't the PFL bus attach to a point before the mute switch?

good observation, thanks. So PFL will work even when the channel is muted. What about the pre fader AUX? Is it convenient for it to get signal even with the mute is on? Or I should keep it after the mute?

 

[arthurdb]

Consoles have been made either way although, especially with a SIP function, I'd rather have the AUX send after the mute. You could also have a jumper on the board that allows you to select either way. That way you don't have to worry about changing your mind.

 

[cyrano]

good observation, thanks. So PFL will work even when the channel is muted. What about the pre fader AUX? Is it convenient for it to get signal even with the mute is on? Or I should keep it after the mute?

That's a question of taste. It depends on how you're going to use the aux send.

 

[OneRoomStudio]

That's a question of taste. It depends on how you're going to use the aux send.

This is the answer. Generally speaking, pre-fader aux is nice for things like headphone sends (so the mix on the board doesn't change the headphone mix), whereas post-fader is nice for sending to effects during mix-down (so the wet/dry ratio stays the same as you change the channel volume). For a line-input mixing board (as opposed to a tracking console), I'd pick post-fader.

 

[Dimitree]

Yes, each chanell will have both pre and post aux sends. The doubt was whether the mute should affect the pre aux send or not

 

[OneRoomStudio]

Yes, each chanell will have both pre and post aux sends. The doubt was whether the mute should affect the pre aux send or not

In that case, post-mute is nice in case you need to suddenly mute the send to headphones (due to feedback, overload, etc).

 

[RoadrunnerOZ]

In that case, post-mute is nice in case you need to suddenly mute the send to headphones (due to feedback, overload, etc).

Or you can have an on/off switch in addition to the pre/post switch for each aux send on each channel like on the earlier Neve consoles - you may need this if using desk channels as fx returns as a safety.

 

[RoadrunnerOZ]

Are you planing on aux sends from the stereo channels? - as you will need to sum them to mono to go to the aux bus.
I know you want to do pre/post only in the master but it may be useful to also have pre/post on the channel for things like reverb sends which will need to follow the fader for most but you may want to have a reverb tail hanging as the sound is faded by using a prefade send while the others just drop the send with the fader. Depends on if you are going to use the console for dynamic mixing or just summing.

 

[thor.zmt]

I started this new project: a small and simple console for my bedroom studio.
I'm seeking advices and corrections about the concept, since I'm not a beginner when talking about recording studio workflow.

Ok, can I suggest a totally leftfield take?

When I had a similar problem I got a 2nd hand Yamaha 01v96 V2 VCM instead. Like this:

Yamaha 01V96 V2 | Reverb

At the 2nd hand price these are hard to beat.

You get a 16 In / 8 Out (or more if extra I/O cards are fitted) at 24/96 with a fairly high audio quality, which is not too hard to improve when you do a service.

For a few 100 Bux US you get a full solution, with a really nice MIDI interface to your DAW from the flying faders and a lot of transport controls etc...



If you want and can do SMD soldering both ADC & DAC IC's have pin compatible upgrades, many Op-Amp's can be replaced by modern types.

Personally, I converted all eight output's into "impedance balanced" using a very much simplified analogue circuit and line driver. I also included a 8/2 passive summing mixer I can route to a analogue in, to mix "OOB". I did similar cleanup on input channels including lower noise transistors for Mic-In.

Realistically a 16 In to 8 Out 96/24 high end sound card plus all the rest is way more than I ever was/am able to use in practice. I found the VCM effects pretty decent, better than many DAW plugins you can get.

Right now the whole studio and other stuff is stuck in China in a Wherehouse (pun intended) and I'm not sure when I will ship it out to where I am now.

Thor

 

[Dimitree]

Are you planing on aux sends from the stereo channels? - as you will need to sum them to mono to go to the aux bus.

yes stereo channels will be summed to mono before hitting any AUX bus

Or you can have an on/off switch in addition to the pre/post switch for each aux send on each channel like on the earlier Neve consoles - you may need this if using desk channels as fx returns as a safety.

you are right, thank you, I decided to follow your suggestion and put a PRE/POST switch on each channel AUX.. so this is the new channel diagram.




I also rearranged a little bit the front-end, I don't think I need a trim control for the "tape return" input (the signal from the audio interface) since those levels should always be predictable and "standard", so the trim control is now only on the "instrument" line input.
I also think that I will remove the MAIN MIX switch, and I will make sure that when pressing one of the GROUP switches, the signal won't be routed through the main mix bus, so it's either routed through the main mix bus or through one (or many) bus.

Ok, can I suggest a totally leftfield take?

When I had a similar problem I got a 2nd hand Yamaha 01v96 V2 VCM instead. Like this:

thanks, but that won't be as fun as building it
I've built guitars, tube amps, synthesizers and stompboxes..most of them would have been worth buying instead of building, but building is my hobby

 

[RoadrunnerOZ]

yes stereo channels will be summed to mono before hitting any AUX bus


you are right, thank you, I decided to follow your suggestion and put a PRE/POST switch on each channel AUX.. so this is the new channel diagram.

View attachment 118098


I also rearranged a little bit the front-end, I don't think I need a trim control for the "tape return" input (the signal from the audio interface) since those levels should always be predictable and "standard", so the trim control is now only on the "instrument" line input.
I also think that I will remove the MAIN MIX switch, and I will make sure that when pressing one of the GROUP switches, the signal won't be routed through the main mix bus, so it's either routed through the main mix bus or through one (or many) bus.

You may want to have a Direct Out level control - perhaps taking the unprocessed after the trim instead of in front, as in your original diag.

How is your DAW channel select going to work?

Group select switching can be fun if you use the push switch type that unlatch whatever switch is currently engaged - these allow latching of more than one switch at a time like in the 1176. Then you’ll have the ability (if you include a main mix sw as well) to assign to more than one group or main and group. The switch outputs would need to be buffered so as to not back feed other channels that go to a dedicated group to the main mix or other group bus as well. Just a thought - you may not need it.

 

[Dimitree]

You may want to have a Direct Out level control - perhaps taking the unprocessed after the trim instead of in front, as in your original diag.

How is your DAW channel select going to work?

thanks, moved DIR out after the trim control.

the two DAW buttons are digital buttons (connected to a microcontroller) used to control DAW functions via MIDI. There will be other DAW buttons on the master section too, for example, tap tempo, play/stop..etc

I drew the rest of the console.. groups, aux and master.. Mainly copied by various modern console, and tweaked to my taste.
I decided to only use mono channels and no stereo channels.
I still need to decide many things:

1) aux returns with faders or rotary potentiometers
2) channel mute stops the signal before the pre-fader point or not
3) aux sends on aux return channels (i.e. AUX #1 will have sends for AUX #2, #3, #4.. don't know if it is useful)
4) group outputs pre or post faders. Still don't know if I will ever need group output..since I mainly use groups only to control multiple channels at the same time during mixing
5) replace MONO switch with a pair of switch, MONO L and MONO R, more versatile maybe
6) using a "not transparent" summing mixer for the main mix bus (I'm thinking about Neve 1272)

View attachment diagram.png

 

[RoadrunnerOZ]

1: ok
2: should be shutting off everything
3: not really useful - if you need to series up effects, that can be achieved with a single Aux send
4: maybe a pre/post switch - you may want a controlled send to a group or in some circumstances uncontrolled. Normally groups work exactly the same as the channel send to the main mix bus with fader in place. Groups can be handy for assigning a compressor to a whole drum kit as a parallel or inline - could be handy to have a main mix assign button on the groups
5: doesn’t make sense if you have dual mono master out channels - which I’d suggest is a good idea - in that instance you just mute (I’d include a single mute for each of L & R plus a stereo monitor mute and a dim switch) or pull down the fader of the unwanted side and hit your mono switch to feed the active Chanel to both sides
6: nice idea

 

[Dimitree]

about those two points, some additional thoughts

1) aux returns with faders or rotary potentiometers

why they usually put rotary potentiometers on the AUX return levels? to spare money on the faders? or is it because AUX return is more comfortably controlled with a rotary control?

6) using a "not transparent" summing mixer for the main mix bus (I'm thinking about Neve 1272)

trying to understand how Neve summing works, I guess I need to balance the signal after the "MAIN MIX" switch, then passive summing of the balanced signals --> transformer --> amp --> insert --> fader --> output transformer. Then from the output transformer, the signals goes both to the main mix output and also to the monitor path (as shown on my diagram).
Or maybe I don't need to balance the channel outputs and I can directly mix the unbalanced signal?
I don't want to implement the Neve summing on the group summing, aux or pfl bus, only on the main mix bus.
I'm wondering if that's a good idea or maybe a recipe for disaster.

 

[RoadrunnerOZ]

about those two points, some additional thoughts

why they usually put rotary potentiometers on the AUX return levels? to spare money on the faders? or is it because AUX return is more comfortably controlled with a rotary control?


trying to understand how Neve summing works, I guess I need to balance the signal after the "MAIN MIX" switch, then passive summing of the balanced signals --> transformer --> amp --> insert --> fader --> output transformer. Then from the output transformer, the signals goes both to the main mix output and also to the monitor path (as shown on my diagram).
Or maybe I don't need to balance the channel outputs and I can directly mix the unbalanced signal?
I don't want to implement the Neve summing on the group summing, aux or pfl bus, only on the main mix bus.
I'm wondering if that's a good idea or maybe a recipe for disaster.

I’ll have a look at some Neve schematics to give you an overall picture - the internal summing is done differently for Aux sends and main mix. Aux send per channel is resistor fed to the wiper of the Aux master pot, as well as each Aux per channel has a spear off the channel bus fed to the wiper of each Aux send pot. Aux out and Direct out are unbalanced, Tape sends and returns are balanced - if I remember correctly Inserts are also unbalanced. The internal mix summing is unbalanced - I’ll see if I can post some schematic sections for you to have a look at from a later console which would be appropriate for what you’re doing - the schematics for a whole console would cover a squash court floor when laid out.

 

[RoadrunnerOZ]

Rotary pots for Aux masters and returns are because the main level controls are usually at the device being sent to and to use slide faders would add a lot of surface real estate unnecessarily - they are more like trim controls.

 

[Dimitree]

so I tried to drawn a schematic of what I drawn before as a simple block diagram.
With some bit and pieces took from other mixers schematics and books, and the precious help of Thor regarding the balanced input configurations (I hope I understood that part well), this is what I came up with, so far.

I'm quite sure there are still some mistakes to fix

my doubts are:

1) for the Send and Direct Out, I tried to implement the "Zero impedance output" that I read on the Douglas Self book, but I'm not sure if I need a resistor from ring to ground to match the build out resistor on the tip.
2) also on those two outputs, do they need a capacitor on the opamp inputs (IC4-4 and IC4-3) so that the rest of the circuit does not see their DC input bias current?
3) the postfade amplifier could need some tweaks, since it was designed for NE5532 but then I used a spare opamp section from the quad OPA1679.
4) I may need to add some sort of RFI protection on the input connectors (and probably output connectors too?)
5) which node of the circuit to take the signal for the bargraph meter

 

[RoadrunnerOZ]

Ok.
First, from what I see your Aux sends are going to short the Aux busses when turned fully down affecting the bus by the position of the wiper relative to ground - I’d maybe feed the wiper with a resistor and take the output from pot top via another resistor rather than from the wiper, thus giving the main Aux busses a constant (almost) impedance feed, you don’t want the send pot on a channel to affect the send bus levels of other channels. Or you could use a quad IC on each Channel to drive the Auxes.
Second: Your send and return for the Insert leaves the send/return open - this means silence when you switch to insert, with normalling in place you still hear the channel with nothing inserted - consoles normally either allow a send without interrupt (for sidechain as an example) and normalling break on the return when a jack is inserted, or vice-versa to allow mixing return signal from alternate source - whichever way the normalling is configured you can mix by coming in on the unswitched or sidechain going out on the unswitched - in effect you should have switch normalling but you seem to have opted for balanced return which makes it tricky if not impossible normalling unbal out to bal return - do you really need balanced return?
I would suggest looking at channel schematic diags for some consoles and see how it’s done - remember the channel schematic may not show the normalling that occurs at the patchbay but you’ll see the architecture of the send return system. Some of the earlier Neve used VMOS output drivers on the Direct Outs and Insert sends to drive low impedance gear - (not sure how good the OPA is for that but should be OK depending on the target device(s)). All usually unbalanced, the Insert sends and returns are 1/2 normal at the patchbay - I would not use full normalling as you can’t take a side feed or mix in without interruption of the signal path.
4 The datasheet for the OPA1679 should provide examples of suppression - they include a section on filters as a link for audio design.
2 it seems the inputs should be decoupled
5 bargraph should be maybe switchable to pre everything except gain trimmer for input gain metering and then to post everything including inserts and channel fader.