Poor Man's Tube Mixer

[ruffrecords]

Im sure many would be be very happy with just line level in/pan  and a proper valve driven output stage , Keyboard guys especially and Daw users than want a little more old style hands on . Having the extra two mic sources though does open up your mixer to a lot of extra potential clients ,  2 mics w/direct outs  and a  couple of pairs  of  line  inputs  allows you to do a lot , for one it allows you to set up a proper direct monitoring of mic input to the cans of the performer and not have to rely on  the DAW  monitoring where a delay exists .

How would this work. What would the line inputs be used for?

Could you save gain by having less inputs on the passive side , keep the mic in's and make  the economy on having a more compact enclosure instead . 

A couple of line ins could be entirely passive - they are more or less the direct in of the originall schematic I posted.

Will you eventually create a dedicated board for this unit ?  I guess having the mic in component positions makes sense ,the customer could then decide to have it populated  only if required .

Yes the plan is there would be a single main board for the pres, input transformer and relay switching of phantom, pad, phase etc. The there would be a front panel board containing all the control switches, pots and probably the HPF components.

Cheers

Ian

 

[Tubetec]

Ok sorry ,I'll try and explain better .
Lets say your using a computer based DAW to record ,
Of course to listen back to the already recorded tracks you need to monitor the outputs of the DAW , what Im suggesting is that while you record a track ,you actually mute it from the monitor mix out of the daw , now  your 'direct out'  mic signal is sent is sent both to DAW channel input and  via the mixer main bus to the monitors/headphones of the performer , now you or the performer dont  have to deal with any latency delay in the monitor path , after tracks are recorded you either add the sound to the DAW stereo mix output ,or in the case of having a16 way passive stem ,adding the corresponding track to the monitor mix .

I find the typical(small) delay of DAW 'through' monitoring unacceptable ,as Ive found different musicians/instruments cope better or worse with it while performing ,it adds in a little 'slop in the gears' that doesnt need to be there .

Of course now Im probably going to get  a raft of people swearing blue in the face that a handfull of milliseconds delay is imperceptable , it may well not be percieved by the artist but that doesnt mean its not having an effect on their playing.
Hopefully Ive explained things more clearly , of course some soundcards do offer latency free monitoring with a mix control built in but for me the simplicity of having that function in the mixer is much better .

 

[ruffrecords]

@Tubetec.  OK I think I get it. DAW creates a stereo monitor mix and this feeds the line input. This mix is minus the track(s) being recorded. Recorded tracks come from direct outs and are mixed on the bus along with the DAW monitor mix  from the line ins so everyone can hear both in perfect sync.

Cheers

Ian

 

[Tubetec]

Hi Ian,
Yeah thats  what I meant .

at its most basic it could function as a simple 2(mic)+2(line) input - into 2 mic direct outs and two mix outputs .

Take a simple one man show as an example ,
vocals                      ch 1
guitar mic or DI  ch2
stereo line input from DAW  ch3 ch4

if you had four DAW input channels
ch1 vocals dir output
ch2  guitar dir output
ch3  mix L
ch4  mix R

As you have direct feeds of vocals, instrument and mix to the pc its easy to generate VST reverbs and delays(100%wet) which can simply be routed to daw monitor out and thus back to the mix buss of the console  . You would also have the option of routing both direct outs and mix signal to DAW tape channels for recording ,but your mix  signal will also of course feed a PA system via a level control in the live situation .

Suppose a classical sound engineer wanted a four mic recording  setup , hes unlikely to need  the monitor return from his recorder/DAW like in the live setup so he gets a couple of extra mic pre boards and patches them to the stereo line instead,
I could almost imagine the 2+2(input) : 2+2(output) like a console 'master' section with one pair of mic and one pair of line ins,
If you wanted more inputs its easy enough to reconfigure the mix buss resistances to make the best match for how ever many inputs you need ,add the extra panel real estate and connectors and extra off board pre's  or whatever you want.

If I were to 'ice the cake' or add my own personal requirement to the above it would certainly be a pair of HPF's on the mic inputs and a pair of EQ sections operable either stereo or dual mono  and patchable into either Mic ,Line or Mix paths .

I know a few people who do  one man shows ,some have spent crazy money trying to get something as simple as whats described above ,  only to end up with over complicated  digital light show that sounds bloody awfull ,even using  Neumann mics ,APi preamps , digital based  vox and instrument processing and a pc running the backing tracks .

I can do a a bit of product research on the 'one box wonder' idea  next time I talk to my gigging musician friends ,
but I know the idea of real tube circuitry input to output ,with the PC in the side chain for backing tracks,  effects and recording capabillity will appeal to both sound engineer and artist but also to the people who need to do both jobs at the same time .

 

[ruffrecords]

@Tubetec. Very interesting stuff and thank you for offering to discuss with real end users.

Right now I want to make it as flexible yet affordable as possible. So I am going to work on the basis of a maximum of 7 tubes.

A.  2 x mic amps with proper gain control (continuous pot or switched option), HPF, unbalanced insert/direct out with transformer balanced direct out as an option. Usual mic/line/phase/20dB/P48 switches. Fader and pan controls. 3 tubes

B. Optional left and right line inputs, with optional 10K:10K input transformers (or unbalanced if preferred), pair of single or one dual pot. No tubes required.

C. Optional 2 x DB25 passive stereo summer (8 Left and 8 Right inputs no pan or level controls), gain make up  and stereo fader. 2tubes.

D. Stereo bus gain make up amps with master level control. (required for option B or C). Optional transformer balanced outs. 2 tubes

E. Optional VU meters directly across stereo bus outs (no buffer).  (I might include an optional TL072 VU buffer powered from the 12V heater supply).

I will create a single PCB for this and people can fit what they like.

Controls and HPF for the two mic pres will be on a separate PCB that fits to your front panel.

Line ins need one or two faders (pots) which builders can fit direct to front panel so no PCB needed for these. Similarly the Stems fader and master fader do not need PCBs

The only other thing I thought of was a 10dB pad at the output so people can drive the tubes a bit harder for some extra tubiness if they want it.

Cheers

Ian
c

 

[kambo]

i didnt skip ur question btw, left it to "Tubetec" and on same page with him!

is 3 tubes for two preamps? so, sharing one triode/half i guess...
cross talk is pretty poor for todays standards, when shared a tube on stereo applications tho,
if you can  A/B same design with 4th tube, and 3 tubes, high frequency stereo detail is totally audible !

 

[kambo]

i never complained about my first half working car either!

‐120dB maximum @ 1kHz, ‐1dBFS signal

 

[kambo]

For preserving what's there already sure.  But I doubt there's an analogue mixer that can achieve that in a mixing situation once you introduce panning circuits.  I could be wrong and I'd like to know how they're doing it

introducing panning doesnt change a thing! if u have the stereo width u have the stereo width!
hard pan L and R information doesnt change, they stay exactly where they are! ( edit: depending on ur crossover crosstalk  figure)

 

[kambo]

I'm not talking about mixing stems that are stereo pairs with all L/R info done in the box bud.  I'm talking about an analogue mixer that you are using to mix.  Introducing pan most certainly will mean a crosstalk figure considerably less than your -120dB figure.  Also, the best faders are only about 70dB down at full off,  which is why there are switches on the end of P&G's to kill the last bit of track resistance.

OMG, hard pan L and R nothing  changes,
mix couple of tunes, then we talk again!

 

[kambo]

this is enough hijack!

 

[Winston OBoogie]

LOL. There not an analogue mixer in existence can meet that spec.

Cheers

Ian

Ian, I went through this with him already.  Apparently I don't know what I'm talking about.

 

[JohnRoberts]

Come on guys, nothing here to argue about or get upset over.

JR

 

[Tubetec]

Hi Ian
I had a chance to briefly run the 2+2:2:2 concept by a buddy tonight , he does one man shows most nights a week and carts way more gear around than he needs to , 
I think its fair to say he was very interested in the idea ,but did, without my mentioning of,  say EQ's on voice and instrument would be nice .

Its like having 'the Master module'  with a couple of mic pre's to get you up and running ,from there you can take it into a fully fledged console if you wish  or keep it compact and rackmounted ,  the end user is free to incorporate any of your pre existing modules or any of their own stuff in the design .  Even a slightly long in the tooth Mackie or Behringer used as a sub mix into the
tube mix buss would be amazing for when the one man show has a band alongside.

One other thing that came to mind was , I know there are many people working on nice  simple A/D and D/A to USB convertor boards here , line level ins and outs ,of course you can do it all externally with any number of audio interfaces , but a simple solution designed by another member probably already exists , 4 ins 2 outs over usb for the basic ,but being able to plug in a computer  and instantly without even patching  a lead , have maybe 8 or 16 Daw output channels appear on your passive mix buss would be a very nice option to have .

You can join the club for the cost of the basic board , the 'iron work' is at your own discretion ,
its a great gesture to the community Ian and hopefully it will encourage lots more to get involved  .

 

[Winston OBoogie]

Come on guys, nothing here to argue about or get upset over.
JR

It was beginning to look a lot like Gearslutz for a minute there   I've already tried to declutter the thread by removing my above posts but, my apologies to Ian and the forum for my part.
I suspect there is a cultural aspect to what Kambo and I constitute as rudeness and I'm certainly not upset. 
Regarding the specifications relating to analogue mixers, I didn't make the rules and you yourself know more than most about that subject.
Cheers John.

 

[JohnRoberts]

It was beginning to look a lot like Gearslutz for a minute there   I've already tried to declutter the thread by removing my above posts but, my apologies to Ian and the forum for my part.
I suspect there is a cultural aspect to what Kambo and I constitute as rudeness and I'm certainly not upset. 
Regarding the specifications relating to analogue mixers, I didn't make the rules and you yourself know more than most about that subject.
Cheers John.

so stop already

JR

===

I have gone back and removed a few more posts (including mine) but strictly speaking these are not strictly breaking the rules just subtracting from the discussion at hand.

I'm glad you guys aren't discussion politics.

 

[ruffrecords]

Hi Ian
I had a chance to briefly run the 2+2:2:2 concept by a buddy tonight , he does one man shows most nights a week and carts way more gear around than he needs to , 
I think its fair to say he was very interested in the idea ,but did, without my mentioning of,  say EQ's on voice and instrument would be nice .

That is probably a different product. The 'old' tube 3U 19 inch lunchbox project could come very close to what you need. It used 70mm wide 3U high modules. One could be a mic pre and the one beside it could be a 3 band EQ for it. Two of these therefore uses four modules. One module for the passive mixer and one more for the bus amps fills the 6 available slots. No room for meters though.

The 'new' Mk 3 design has modules half the width. So you could have a 'classic' mic pre with a REDD EQ beside it in 3U x 70mm. Two of these takes four modules with 8 left. Use two modules for the master bus so you can have proper virtual earth mixing. Two more modules should be wide enough to hold a couple of small VU meters one above the other. Still four module spaces left for passive mix bus and line ins etc or an extra mic pre or two.

Of course this would be a lot more expensive than the poor man's  tube mixer but it would be capable of much greater configuration and facilities and it all fits in s 3U rack mount box.

Its like having 'the Master module'  with a couple of mic pre's to get you up and running ,from there you can take it into a fully fledged console if you wish  or keep it compact and rackmounted ,  the end user is free to incorporate any of your pre existing modules or any of their own stuff in the design .  Even a slightly long in the tooth Mackie or Behringer used as a sub mix into the
tube mix buss would be amazing for when the one man show has a band alongside.

Yes that is definitely a Mk 3 lunchbox project

One other thing that came to mind was , I know there are many people working on nice  simple A/D and D/A to USB convertor boards here , line level ins and outs ,of course you can do it all externally with any number of audio interfaces , but a simple solution designed by another member probably already exists , 4 ins 2 outs over usb for the basic ,but being able to plug in a computer  and instantly without even patching  a lead , have maybe 8 or 16 Daw output channels appear on your passive mix buss would be a very nice option to have .

I expect that would not be too hard to build into a 3U module - a tube lunchbox plus digital IO could be very attractive.

You can join the club for the cost of the basic board , the 'iron work' is at your own discretion ,
its a great gesture to the community Ian and hopefully it will encourage lots more to get involved  .

I think there are two projects/products here; the poor mans and the lunchbox. I started work on the poor man's PCB layout last night. Looks like the seven tubes and ten (mostly optional) transformers will fit onto a 12 inch by 8 inch PCB. It basically consists of my twin line amp pre-configured as a pair of mic pres with optional output transformers plus four uncommitted mu followers (just like the ones in the classic solo project), positions for passive mixer input transformers and optional line in transformers and optional bus out transformers. I will post a pic once it has progressed a bit more.

Cheers

Ian

 

[kambo]

Ian, I went through this with him already.  Apparently I don't know what I'm talking about.

thats exactly right! mix couple of tunes, then we talk 

Ian, i am not gonna argue over 5-10db on crosstalk, but last time i measured my tube line mixer was better than 115db crosstalk!
its stereo image much wider than shared triode! not everybody needs the widest stereo image!

edit : btw, i do not see any reason why wouldnt anyone could mix a grammy winning track with this new mixer, next summer! this side of things are not arguable at all  8)

edit2: what i posted on "edit"sounded little off to me re reading after couple of drinks  8)
i meant : i am looking forward to see a grammy winning song mixed on this mixer
hopefully it would be me this year, with its modified version  ;D

 

[ruffrecords]

@Tubetec,

Further to my last post on one or two products, while messing with the PCB layout last night it suddenly struck me that with four uncommitted mu followers you could use a couple as passive EQ gain make up for two mic pres if you wish. You would lose the 16 stem input passive mixer but you would still have the two line ins and the master bus so monitoring would still be possible. So you could have EQ on the two mic pres if you wanted.

Cheers

Ian

 

[Tubetec]

Thats all shaping up into a very versatile box Ian,

 

[ruffrecords]

Thats all shaping up into a very versatile box Ian,

I agree. Now its time to stop talking and get designing.

Cheers

Ian