EZ Tube Mixer

[ruffrecords]

dude Helios 69 type EQ's lined up after vintage style tube pres channel after chanel.. AWESOME!!

I would love to hear a mix that was entirely done through this console with a small variety of industry standard mics.. But thats probably asking a lot.. 

I think the coolest thing about the EZ Tube Mixer is it is modular both at a mechanical and an electrical level. The EQ boards are separate so you can use them any where - channels, groups, on their own for mastering, with tubes or with solid state.

The tube mic channel PCB also doubles up as a a pair of mix bus amps. The tube mic pre can be made into a stand alone module with EQ with transformer balanced in and out or it can be used as a channel in a mixer with a separate routing module and channel fader. You can build a mic amp in a 3U high module or with EQ in a 6U high module.

That was the idea anyway!

Cheers

Ian

 

[MrZpliff]

This is a great, great project.
Thank's Ian for making it available here !

I'm seriously considering a 16Ch mixer  but I need to dig a little deeper in the construction of such a beast.
Probably with 4 mic preamps and the rest with just line amps.

Best regards
Magnus

 

[ruffrecords]

This is a great, great project.
Thank's Ian for making it available here !

I'm seriously considering a 16Ch mixer  but I need to dig a little deeper in the construction of such a beast.
Probably with 4 mic preamps and the rest with just line amps.

Best regards
Magnus

Excellent!! What are you thinking of in terms of EQ? Per channel or on the buses or something else?

Line channels range from a doddle to fairly easy to do depending on what per channel facilities you want - PAN, AUX sends, EQ etc.

If you can add a bit of detail to what you are thinking I can explain the options. And that naturally leads onto the mechanics

Cheers

Ian

 

[MrZpliff]

Well, some kind of a "dream setup" would be:
Each CH with EQ, switchable L/R/Mono, 1or 2 fx sends, insert.
4 subgroups with inserts....

 

[ruffrecords]

Well, some kind of a "dream setup" would be:
Each CH with EQ, switchable L/R/Mono, 1or 2 fx sends, insert.
4 subgroups with inserts....

OK, I have given this some thought. Let's start with something fairly straightforward and we can work up from there. The standard V3 card has two identical amplifiers on the card.  The first will do a mic/line pre and the second amp can be used as a gain make up for EQ. That's the standard way to use it and that's OK for the four mic channels but its a bit of an overkill for the line amps. For a line only input you don't really need both amps - just one will do. You come in through a 10K:10K transformer and straight to your 10K fader which feeds the EQ. Only one amp is needed for the gain make up of the EQ so we can get two of these in one module's width. The only question is can you squeeze two EQs into this width.

The standard module width is 14HP = 2.8 inches wide by 6U high and exactly 6 of these will fit across a standard sub-rack so if we can get two EQs into one of these then one sub-rack will hold 12 line amps which is exactly what you want. I tried one EQ card above the other in a 6U module but that does not work because the top one fouls the tubes. However, you can just get two Helios EQ cards side by side in a 14HP width. So if we use Helios EQ it can be done. I am not sure about the Pultec EQ because this has quite a few more knobs than the Helios - this would need further thought. So we can do 12 channels of line input in one 6U high sub-rack width and there is probably enough room above the EQ to fit the routing controls - L/R/Mono, sub group select and FX sends. We don't need the mic gain switch or the standard mic input push buttons, so all that front panel real estate is available to us.

In another sub-rack we could fit the four mic channels with whatever EQ you fancy which leaves two standard module widths. We can use a divider kit to make this space into two pairs of 3U high modules and we could fit a V3 card into each one giving us 8 more amps to play with. We could assign four of these to the four sub-group bus amps, two for the FX sends and use a pair for a stereo FX return. So at a push we can just about get everything we need into this second sub-rack.

If we bolt these two sub-racks together we end up with a 16 channel tube mixer that is just under 3 ft wide that uses just 14 V3 cards.

What we haven't addressed is the inserts and how you might do that depends on whether you want them balanced or not.

What do you think?

Cheers

Ian

 

[wave]

Ian,
I'm finding this very interesting. Could using concentric controls work?

Dave

 

[ruffrecords]

Ian,
I'm finding this very interesting. Could using concentric controls work?

Dave

That's a very good idea Dave. All the Pultec EQ pots are external to the PCB so you could use just one set of concentric ones instead of two separate sets and save a lot a panel space. That way there's a good chance you could get two Pultec Eqs into one channel module.

Cheers

Ian

 

[anjing]

I still haven't decided on a final plan yet but this 16 channel configuration is really apealing to me.

I have been thinking about the inserts as well. I saw that a forum member designed a self etch balancing card. Going from unbalanced to balanced and balanced to unbalanced using 5532 opamps. I just bought a self etch kit and was going to test the card. the thread is here http://www.groupdiy.com/index.php?topic=29333.0
I don't know if it's a sin to use opamps in a tube mixer, i guess if it's transparent enough it would not matter.

 

[ruffrecords]

I still haven't decided on a final plan yet but this 16 channel configuration is really apealing to me.

I have been thinking about the inserts as well. I saw that a forum member designed a self etch balancing card. Going from unbalanced to balanced and balanced to unbalanced using 5532 opamps. I just bought a self etch kit and was going to test the card. the thread is here http://www.groupdiy.com/index.php?topic=29333.0
I don't know if it's a sin to use opamps in a tube mixer, i guess if it's transparent enough it would not matter.

That's a very handy card. I see no reason not to include it in a tube circuit and it's a lot cheaper than two transformers If I were going to choose an op amp I would choose the 5532. It has a very interesting circuit that even the great Douglas Self has not been able to fully unravel. The bottom line is it is well known to perform particularly well.

The only question I would have is where in the signal path would you want the inserts to be?

Cheers

Ian

 

[MrZpliff]

I'd say balanced inserts since all my diy stuff is balanced. And probably pre EQ so you can tweak the sound after a compressor for an example.

 

[ruffrecords]

I'd say balanced inserts since all my diy stuff is balanced. And probably pre EQ so you can tweak the sound after a compressor for an example.

OK, pre EQ is quite normal these days. Would it be pre or post fader? I would recommend pre fader.

Just as an aside, when I was at Neve there was not such thing a pre EQ insert. You had a channel module which included EQ and it had balanced ins and a balanced output. The insert point was at the balanced out so it was always post EQ but pre fader.


Cheers

Ian

 

[MrZpliff]

I'd say balanced inserts since all my diy stuff is balanced. And probably pre EQ so you can tweak the sound after a compressor for an example.

OK, pre EQ is quite normal these days. Would it be pre or post fader? I would recommend pre fader.

Just as an aside, when I was at Neve there was not such thing a pre EQ insert. You had a channel module which included EQ and it had balanced ins and a balanced output. The insert point was at the balanced out so it was always post EQ but pre fader.


Cheers

Ian

Yes, pre fader. Post eq is ok too if that's easier...

 

[kante1603]

I'd say balanced inserts since all my diy stuff is balanced. And probably pre EQ so you can tweak the sound after a compressor for an example.

OK, pre EQ is quite normal these days. Would it be pre or post fader? I would recommend pre fader.

Just as an aside, when I was at Neve there was not such thing a pre EQ insert. You had a channel module which included EQ and it had balanced ins and a balanced output. The insert point was at the balanced out so it was always post EQ but pre fader.


Cheers

Ian

Hello Ian,

.....but a post eq point has one disadvantage when using compressors:you must always correct the threshold point on it after changes in the eq.
That's why I would prefer it pre eq too.
On the other hand one might say that you can eq the signal first to drive the compressor better,e.g. getting rid of some subsonic stuff first to not make the compressor start pumping.
But if the compressor has a hpf in the sidechain then everything is different again,hahahahahaha..... ;D
Inserts everywhere is the way to go,hahahaha.......or even swappable eq/dyn. sections........

In summary all has pros and cons,one can not have everything......
So I would say it's more an individual preference.

Best regards from germany,

Udo.

 

[ruffrecords]

In summary all has pros and cons,one can not have everything......
So I would say it's more an individual preference.

Best regards from germany,

Udo.

I agree, and that's the best thing about DIY, you can build exactly what you want.

I don't think there are many mixers that offer a balanced pre EQ insert so this is one area where DIY definitely has an advantage. I have an AKAi DPS24 digital work station and that has post EQ dynamics and no way to change it - and it is all in the digital domain so it would be easy to do. The Mackie 2404 has pre EQ insert but they are unbalanced and we can do that on the EZTubeMixer anyway. I found a Cadac mixer that has  balanced inserts and EQ that can be switched pre insert so I guess that means it is normally post EQ but you are definitely talking big bucks for that.

So I reckon DIY rules!!

Cheers

Ian

 

[kante1603]

Yes Ian!

The big bucks....I have Cadacs at my work,we even had the Concert Board a few years ago.Now we have J-Type and the "small" S-Type.
Sadly they're not mine...hahaha.....but gives a diy guy some nice dreams-and ideas!

Rock on Ian

Cheers,
Udo

 

[ruffrecords]

I just had another thought about using op amps for creating a balanced insert in the EZTubeMixer. The one thing you have to remember is that these little tube amps will put +34dBu into 10K with ease and that's well before clipping. Just to put that into context, +34dBu is 40V rms or about 56V peak so you are probably going to need +/-60V rails for the op amps to be able to keep up!

OK, I know there's no such op amp but it does perhaps give a clue as to the enormous headroom of tubes when you remember that most op amps will only do about +22dBu or about 10V rms. And I guess it is not surprising that Rupert Neve is designing transistor circuits no with 70 volts rails.

Cheers

Ian

 

[MrZpliff]

Just a thought concerning the inserts  ???
Since most soundcards are balanced linelevel couldn't you just put the inserts before the
line input for each channel, i.e. soundcard output - Insert - mixer... That's How I do it now with my passive summing + PM makeup...

 

[kante1603]

Just a thought concerning the inserts  ???
Since most soundcards are balanced linelevel couldn't you just put the inserts before the
line input for each channel, i.e. soundcard output - Insert - mixer... That's How I do it now with my passive summing + PM makeup...

Hi,
Yes,in mixdown mode like you describe it sure,as it's all line level.
In recording mode the signal must be brought from mic to line level first,so you can't set up external line level gear in front of the mic input.The first possible insert point is after the mic pre then.

Cheers,

Udo.

 

[MrZpliff]

Just a thought concerning the inserts  ???
Since most soundcards are balanced linelevel couldn't you just put the inserts before the
line input for each channel, i.e. soundcard output - Insert - mixer... That's How I do it now with my passive summing + PM makeup...

Hi,
Yes,in mixdown mode like you describe it sure,as it's all line level.
In recording mode the signal must be brought from mic to line level first,so you can't set up external line level gear in front of the mic input.The first possible insert point is after the mic pre then.

Cheers,

Udo.

Then I think balanced inserts pre channel for those with just line-in and unbalanced inserts pre EQ on the
mic channels (+ balanced insert - pre channel) is what I'd go for.

 

[anjing]

I was just thinking the same last night, insert between the converters and console at mixdown and  insert between the direct out and  converters when tracking.