Feeler: EZ Tube Lunch Box

It has been suggested to me that there might be some interest in a lunch box based on the EZ Tube Mixer design as this would provide a much easier project than building a full blown tube mixer so the purpose of this thread is to determine the level of interest in such a project.

Nothing is set in stone yet but I would suggest an external PSU would be the way to go. As for the size of the lunch box it could be quite small, just two modules wide and 3U high. This would allow you to build two mic pres or one mic pre plus EQ in a lunch box. Thinking about it, you could probably get two mic channels in one module using the Twin Line Amp card so you could have as many as four tube mic pres in a box little more than 6 inches wide. It might even be possible to do a kit.

As always, comments and suggestions are welcome.

Cheers

Ian

Sounds exciting, do you think it would be possible to make it extendable? Say start with two modules and then later able to add two more modules etc?

mylesgm said:

Sounds exciting, do you think it would be possible to make it extendable? Say start with two modules and then later able to add two more modules etc?

Click to expand...

Interesting idea. It raises a couple of thought in my mind. First the power supply - how big do we make it? Big enough to power two modules, four, six or more?? HT and phantom power is probably not going to much different but the heater supply could become expensive. Needs some more thought.

Secondly, how do we do this physically? Do we have independent two module wide lunch boxes or should we have a scheme that allows building a four module one or bolting two together?

I am all for flexibility but if we are to have a chance at a kit, especially if it includes the mechanical bits, it has to be fully determined at the outset.

More food for thought.

Cheers

Ian

Absolutely. This is the kind of thing I need for the odd few EZ tube modules im putting together.
Extendable would be good, but most important is the PSU.

I'd be in favour of 2 modules, which would be desktop friendly, but making the PSU to power 4 or 6 so building another couple of lunchboxes is cheap and doesnt take up more power sockets

For inspiration, two Electrodyne tube amps in a lunchbox.
With internal PSU, makes the channel closest to the PSU a little noisier.
I wouldn't use that channel on a quiet source with a ribbon mic, otherwise it's ok

//M

And back....
Sorry for the crappy iPad pics.

//M

Dr Gris said:

For inspiration, two Electrodyne tube amps in a lunchbox.
With internal PSU, makes the channel closest to the PSU a little noisier.
I wouldn't use that channel on a quiet source with a ribbon mic, otherwise it's ok

//M

Click to expand...

The noisier one; is it just more hum on that channel? What type of mains transformer did you use?

Cheers

Ian

If we had an eq on the second channel, how about a switch on the back panel to insert the eq in the first channel?

Pierre

ruffrecords said:

Dr Gris said:

For inspiration, two Electrodyne tube amps in a lunchbox.
With internal PSU, makes the channel closest to the PSU a little noisier.
I wouldn't use that channel on a quiet source with a ribbon mic, otherwise it's ok

//M

Click to expand...

The noisier one; is it just more hum on that channel? What type of mains transformer did you use?

Cheers

Ian

Click to expand...

Mains hum from a vertical mounted toroid. Can't remember the solution for phantom power.
Haven't been inside it for a while and I didn't do the lunchbox racking.
At one time I moved the PSU just outside the box and the hum disappered, and my guess
Was that the proximity between the toroid and input transformer caused the channel closest
To the PSU to hum. The other channel is fine (to me). It doesn't bother me so much so I haven't
Tried to dig any deeper into getting the hum as low as possible.
It was done for Larry DeVivo who posted here some time ago about selling his beloved Electrodyne
Tube console, poor guy.
If you'd like I can take an inside pic.

//M

Ian,

This sounds like a great idea! 

Are you thinking a modular system like 51x (51x-t lol?) and be card based? If so I'd guess that the psu would need to be quite beefy to future proof it.  e.g. I immediately thought "LA2As!?" when I read it.

Would you want it to be only tube based - e.g. no PRR 176?

In any case this sounds like a really good platform for DIY gear - as I've found your 350HT board to be - so I'm all ears!


Regards,
Ian

irfrench said:

Ian,

This sounds like a great idea! 

Are you thinking a modular system like 51x (51x-t lol?) and be card based? If so I'd guess that the psu would need to be quite beefy to future proof it.  e.g. I immediately thought "LA2As!?" when I read it.

Would you want it to be only tube based - e.g. no PRR 176?

In any case this sounds like a really good platform for DIY gear - as I've found your 350HT board to be - so I'm all ears!


Regards,
Ian

Click to expand...

The basic idea is that it would use any of the PCBs currently available as part of the EZ Tube Mixer project. These all have a common 32 way connector that plugs into a backplane. There are defined pins for HT and heaters as well as mic and line in, phantom power and a couple of unbalanced outputs. Most of the other pins are bused so can be used for anything you like. I already have a two slot backplane PCB that I use on my own projects so it's mostly a packaging exercise.

There's already an all tube mic pre PCB that is configured for either Sowter, Jensen or Cinemag input iron. Output iron is off board so this would need to be attached to the lunch-box metalwork somehow. The REDDEQ and the 3U Helios 69 EQ boards are compatible so in a two slot lunch-box you could make a complete all tube channel strip.

Power requirements are not too tough. Heaters are 12V at under 0.5amp per board so a 2 amp supply could power a pair of lunch-boxes. HT could be via the HT350 board that you are already familiar with although I am toying with the idea of a combined PSU PCB for this project that does HT, heaters and phantom power in one.

The Twin Line Amp PCB is also compatible so if you wanted to make an opto compressor that board would make a good basis. And of course there is nothing to stop yu designing your own PCbs to plug into it.

Cheers

Ian

A combined PSU PCB would make things a lot easier for the average DIYer, plus component values for 2 modules...

Where/how would you get the metal work?

Lunchbox/modular approach is enticing.

ramshackles said:

A combined PSU PCB would make things a lot easier for the average DIYer, plus component values for 2 modules...

Where/how would you get the metal work?

Click to expand...

Good point about the combined PSU - I'll do that.

The metal work is always the tricky but. The EZ Tube Mixer boards are designed to work with standard 19 inch sub-racks that are made by several manufacturers. This means no matter where you are in the world, you can get one. It comes in standard sizes and is made in large quantities so it is likely to be cheaper than anything we could get made bespoke.

But the lunch box won't be 19 inches wide - unless you want it to be. The thing is you can get a basic 3U sub-rack frame from Farnell for less than £50 and that is one deep enough to fit a couple of big Carnhill output transformers at the back.

As these things are basically two side plates with extrusions between you could always make a lunch box just by cutting down the extrusions of a standard off the shelf sub-rack. That might actually be the cheapest option. Companies like Schroff do sell shorter lengths of extrusions and all the other bits separately. They have an MOQ of about £100 so a group buy of just the parts we need might be a possibility.

A 19 inch sub-rack is 6 EZtube modules wide. At 3U high, a channel strip with EQ needs two module widths. So, if I felt confident we could get a PSU in 2 module widths that would also not interfere with preamps in the sub-rack I would suggest using a standard 19 inch sub-rack, have 4 module widths for electronics and the PSU in the other two. Mechanics problems are solved because everyone can buy their favourite mass produced sub rack. There's one small problem with this which is that you also need an extra couple of extrusions a the back to mount the rear panel onto and they don't come as standard.

So bottom line is I am not 100% sure about the mechanics right now.

Cheers

Ian

Hi,

Sorry for the stream of thoughts below.  I don't know how many of these are going to be any use!

I personally am totally 'up for' a 19inch rack unit.  If there are off-the-shelf suitable units this really makes the mechanics side accessible for everyone without huge costs.

If the psu can be the first two slots that's great - could the psu be card based too? (I guess I'm worrying about current for the heaters and the card-slots) - that'd only be useful if you could power a second rack from the same PSU though otherwise you'd need a psu in each rack anyway... but this leads too...

If we are talking about units of 3s could the backplane pcb not be 3unit based and made chainable so that two could be used to make the back of a rackable 6unit box?  I'm probably oversimplifying this - but if the psu is card based the same backplane pcb is just repeatable?

I hope this helps rather than hinders.  This really would be an amazing project and potentially a standard for DIY tube modules - at least there are not the mechanical restrictions as the 51x to 500 compatibility required.

Ian.
8)

A 19"rack seems to be the best solution.
Personnally i prefer an external psu. But to have an internal psu would make things more sound mechanichaly. In a standard rackmount you could fit two channel strip(2x28HP) and it would leave you 28hp for the power supply.

Maybe we could find a way to mount the output trafo to the channel module instead of the rack, that way we can have the input and output connectors soldered directly to the backplane.

Regards,

Pierre

anjing said:

Maybe we could find a way to mount the output trafo to the channel module instead of the rack, that way we can have the input and output connectors soldered directly to the backplane.

Click to expand...

Thinking again i forgot the new backplane design had molex connectors so i'm not sure it's needed to have the xlr soldered to the backplane.

ruffrecords said:

irfrench said:

Ian,

This sounds like a great idea! 

Are you thinking a modular system like 51x (51x-t lol?) and be card based? If so I'd guess that the psu would need to be quite beefy to future proof it.  e.g. I immediately thought "LA2As!?" when I read it.

Would you want it to be only tube based - e.g. no PRR 176?

In any case this sounds like a really good platform for DIY gear - as I've found your 350HT board to be - so I'm all ears!


Regards,
Ian

Click to expand...

The basic idea is that it would use any of the PCBs currently available as part of the EZ Tube Mixer project. These all have a common 32 way connector that plugs into a backplane. There are defined pins for HT and heaters as well as mic and line in, phantom power and a couple of unbalanced outputs. Most of the other pins are bused so can be used for anything you like. I already have a two slot backplane PCB that I use on my own projects so it's mostly a packaging exercise.

There's already an all tube mic pre PCB that is configured for either Sowter, Jensen or Cinemag input iron. Output iron is off board so this would need to be attached to the lunch-box metalwork somehow. The REDDEQ and the 3U Helios 69 EQ boards are compatible so in a two slot lunch-box you could make a complete all tube channel strip.

Power requirements are not too tough. Heaters are 12V at under 0.5amp per board so a 2 amp supply could power a pair of lunch-boxes. HT could be via the HT350 board that you are already familiar with although I am toying with the idea of a combined PSU PCB for this project that does HT, heaters and phantom power in one.

The Twin Line Amp PCB is also compatible so if you wanted to make an opto compressor that board would make a good basis. And of course there is nothing to stop yu designing your own PCbs to plug into it.

Cheers

Ian

Click to expand...

There could be a summing module using the twin line and the db25 summing pcb . Also maybe a tube DI variant? Stereo mastering eq using the twin line...


Regards,

Pierre

I think the modular route would be amazing if it is at all possible.

I don't know if there was a basic framework idea, but in my slumberous musings I've pictured it as a 3u tube version of the 51x system developed in these glorious halls.  So far it seems like a rack system would be the simplest (from a metalwork perspective) route to go down, but if flexibility for a lunchbox could also be built in that'd be a great option.

I guess it really depends on the scale we (or more specifically Ian) are thinking about.  I have a habit of taking things to the nth degree so I've had thoughts of a separate PSU, lunchbox (3unit), rack (6unit) and card based PSU (2units wide).  I guess if the psu can be card based there is no reason why it could not be used inside an external psu - one psu to rule them all.

What sort of power requirements are we looking at for variations of modules?  I'd imagine that more so than the 51x system there is potential for a much greater variation on power draw because of tube numbers and tube types?  Again thinking of the LA2A as an example.  OR heck even a Fairchild. 

I'd love to see this get of the ground so if there is anything I can do offer - let me know!

Ian.

If we can have a PSU on 1 eurocard that will supply all needed voltages, then the builder could decide whether to put it in the rack or in a separate enclosure.

Personally, Id put it in a separate enclosure as I am making my own solid state eurocards as well so Id need another PSU

If the enclosure is just a standard subrack, Im not sure how much it differs from the mixer project - would it be the same back plane?