Poor Man's Tube Mixer

[ruffrecords]

Wow, the wish lists are getting longer and more unrealistic by the moment 

So Far I am resisting attempts to add new things. The 'unrealistic' ones are probably already catered fro in my Mark 3 design which is a different beast entirely

For me usually the first treatment I reach for is to trim the bass end ,per channel  , very often a good balance can be found with careful  mic selection and a touch of low cut filter.  I also found with some of my experiments that relatively simple circuits with switched values of coupling capacitor and relatively shallow curves worked adequately for most HPF jobs .

That is basically how my HPFs work. Two series caps and two Rs to ground for 12dB/octave. Second R is usually the channel 10K fader. Simple 3 position selects one of two frequencies and third position shorts out caps for flat response.

Cheers

Ian

 

[Tubetec]

Ive done  a similar thing to the Baxandall HPF below ,just single section
I used a 12 postion single pole lorlin switch ,
Of course its gradual  and it starts rolling off  well up into the midrange ,but having 12 postions 
you generally find a sweet spot where your source is pulled into sharp focus with out sounding either bloated or thin .

Ive always found the  'Thru-80-120'  steepish  HPF adequate  where you have the luxury of Hi/lo eq as well ,
but maybe an  extended range switchable HPF over one or two stages of coupling cap might be an idea
I  chose my coupling cap values by ear for a relatively even step in the bass response

http://douglas-self.com/ampins/wwarchive/Baxandall%20preamp%20Jan55%20p1.jpg

Its foundations of wireless technology , but its easy on the ear .

 

[kambo]

6db with pot to ground works actually a lot better than fixed frequency 12db filters!
a lot of people use what they offered to use!

 

[ruffrecords]

6db with pot to ground works actually a lot better than fixed frequency 12db filters!
a lot of people use what they offered to use!

So basically you are saying a single  fixed value cap with a variable series R to ground.? So the load impedance seen by the driving stage varies over the range of the pot.
Cheers

Ian

 

[deuc224]

If taking a poll, I would say why not make a full fledged channel strip, that way you make it once and be able to omit things people dont want to populate.  Then a back plane PCB to connect a number of channels to the master buss.  Then get a frame worked out so people can just order from the manufacturer you selected without being the middle man on that part so its less hassle for you.  I say channel strip because maybe some people dont need dynamics or eq or pre, you can have a jumper to bypass that section.  Hell I would put up money to star that project if you need some starting donations.

 

[JohnRoberts]

So basically you are saying a single  fixed value cap with a variable series R to ground.? So the load impedance seen by the driving stage varies over the range of the pot.
Cheers

Ian

A variable HPF is a (nice) premium feature, especially in a tube mixer that has limited gain stages to throw at such features. A modern solid state mixer that may be more limited by front panel real estate than innards, a one pot HPF could take up about the same panel space a one switch with more utility.

Band passing individual stems makes a lot of sense to clean up LF mud, and help clarity of individual instruments in large multi-track projects, but for a simple 4 mic mixer I would KISS. 

Of course I would never make a tube mixer, so feel free to disregard my opinions.

JR

 

[kambo]

So basically you are saying a single  fixed value cap with a variable series R to ground.? So the load impedance seen by the driving stage varies over the range of the pot.
Cheers

Ian

i did that when i was building tube line level mixer from ur EQ calculation tones!
this was coming after the mic trx... limiting the pot, so u dont short the pot to ground! i didnt hear any load
affect at all... i finished a big job with it, everybody is happy...

 

[ruffrecords]

i did that when i was building tube line level mixer from ur EQ calculation tones!
this was coming after the mic trx... limiting the pot, so u dont short the pot to ground! i didnt hear any load
affect at all... i finished a big job with it, everybody is happy...

Finding a position for it that does not require another tube to buffer the signal is the problem. One place to put it is, as you say, right after the mic transformer. Unfortunately this is a high impedance low level circuit and I try to keep connections to and from it as short as possible to avoid pick up. Popping up tot a front panel control and back again is not good practice in my book. I would be interested to see your schematic.

Cheers

Iian

 

[kambo]

cant find the schematic, but inspired EQ from Ivory' s input, i was using
http://www.xaudia.com/xmanuals/PreliminaryDocs140614.pdf

 

[kambo]

Wow, the wish lists are getting longer and more unrealistic by the moment 

i think i missed the the unrealistic wishes! where are they  :

 

[Rocinante]

Ian helped me build my 'Neve-er Ending Summing mixer' and it has been a somewhat  success since.  I originally built it with the intention of having a second more 'Neve' sounding summing mixer to work along side my console but his input proved invaluable and took it to another level. He made it so everyone  of my engineer colleagues wanted one.
It has pan, fader, mute, and solo and

 

[ruffrecords]

i think i missed the the unrealistic wishes! where are they  :

I am very grateful for the input from everybody in the group. I spend a lot of time talking to people who would love to have a tube console but very often, what they want they cannot afford. Tube designs with their transformers, tubes and power supplies just are not cheap. Many is the time the last thing they say to me is there must be some way I can afford get your tube sound into my signal chain.

So what I have decided to do is begin with the simplest/cheapest way of achieving this both while tracking and mixing. So the very first version will have just two mic pres with gain and HPF and 16 stems of passive mixing, both feeding a tube bus and a couple of (optional) VU meters. This will need a total of 6 tubes and a fairly modest power supply.

Cheers

Ian

 

[cyrano]

Sounds like a good plan, Ian. I was already wondering what exactly I was, if even the poor man's mixer was out of budget...  ;D

 

[kambo]

is it possible to use one of ur passive EQ in between two Mu followers (mic/line input)
Trx + Mu1 - passive EQ - Mu2 + Trx -  out
with the gain loss
full gain with EQ bypass! and with current 10K gain pot!

 

[ruffrecords]

is it possible to use one of ur passive EQ in between two Mu followers (mic/line input)
Trx + Mu1 - passive EQ - Mu2 + Trx -  out
with the gain loss
full gain with EQ bypass! and with current 10K gain pot!

Yes. This is very similar the the Classic Solo design which was two mu followers in series. Max gain 70dB and 14dB to 20dB less if you insert a passive EQ between them depending on which EQ you use.

Cheers

Ian

 

[ruffrecords]

Just been talking with a guy in a UK studio about the cut down version with just two mic pres and a 16 input stems passive mixer. He pointed out you don't normally need the mic pres when using the passive mixer so why not make switch the mic pres inputs for this purpose; track or mix. We then don't even need to bus. This would allow us to drop from 6 tubes to two tubes, or have a bit more mic gain and make it switchable with three tubes.

What do you think? Do you need mic pres when passive mixing?

Cheers

Ian

 

[Tubetec]

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 alot , 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 .

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 . 

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 .

 

[kambo]

Just been talking with a guy in a UK studio about the cut down version with just two mic pres and a 16 input stems passive mixer. He pointed out you don't normally need the mic pres when using the passive mixer so why not make switch the mic pres inputs for this purpose; track or mix. We then don't even need to bus. This would allow us to drop from 6 tubes to two tubes, or have a bit more mic gain and make it switchable with three tubes.

What do you think? Do you need mic pres when passive mixing?

Cheers

Ian

how exactly would you be monitoring DAW without the summing mix when recording a mic!
u would need another something to control volume etc!
this idea is way too poor 

 

[kambo]

Like the joke if you don't know who the sucker is in the poker game you may be the sucker. If you don't know who is making unrealistic wishes, it may be you.  :

JR

better luck next time! i have SSL SIX, all my analog synths and DAW out patched in to, with M7 and Eleven on sends, and i have another small yamaha mixer next to my eurorack for doing mix sounds n the other side!
its pretty damn good setup! i have 8ch tubeline mixer but dont really use it on daily work, plans to extend to 24CH for dedicated mix work...

 

[ruffrecords]

how exactly would you be monitoring DAW without the summing mix when recording a mic!

I don't understand the question. How would you monitor the DAW if you did not have the summing mixer? - presumably the DAW can do this all by itself. The summing mixer is for mix down not tracking. You could not mix DAW outputs and mic outputs in the tube mixer because of the DAW latency. It would work with tape where you have the zero latency sel sync head for monitoring. Or do people just put up with DAW  latency and hope for the best?

Cheers

Ian