Mark 3 Vacuum Tube Mixer

[ruffrecords]

Building on all I have learnt from the development of the EZTube Mixer, I have begun developing the next generation tube mixer. I am recording its development in a blog here:

http://mark3vtm.blogspot.co.uk/

Cheers

Ian

 

[baadc0de]

Excellent first post on your new blog Ian!

 

[ramshackles]

Looks great. Do you buy direct from fischer or can you find them on farnell?

After building various prototypes I came to a similar conclusion with regards to having a single card that can be linked up to do a lot of things. I'm settling on a 6U card for the bulk of a mixer, which can only be configured for 2 possibilities; a mic/line amp with routing or a summing amplifier.

Using 6U opens up the possibility for 2 backplanes (or a 6U backplane) with more buses. The top could host power, logic, 0V/Screens and xlr I/O. The bottom backplane could host auxillary and mix buses.

Or you could duplicate the same backplane design, but use the buses on the top plane purely for auxiliary and solo buses and the bottom buses could be purely for groups and the master mix bus. That way the less ambitious/rich builders could just make a small mixer using only the top backplane. More ambitious builders could go for a larger system with 2 backplanes.

Anyway, looks good!

 

[ruffrecords]

As far as I know you cannot buy direct from Fischer unless you are in Germany. In the UK you need to go through there distributor DAU:

http://www.dau-components.co.uk/catalogue/directory/fischer_elektronik.html

However, for the small quantities that you and I are likely to need, this is not always the cheapest option. For example, Burklin, which is a German electronics supplier a bit like Rapid in the UK, does the 3U, 14HP modules I use. Even after adding German VAT and carriage to the UK, they are cheaper than buying them from DAU.

https://www.buerklin.com/default.asp?event=ShowArtikel(71H432)&context=SE:Fischer%20Elektronik;PHNode:SE,hsvt,5711;ALArtikelProSeite:25&l=e&jump=ArtNr_71H432&ch=40601

There are further twists to this story that I will reveal in subsequent blog posts.

I am still not decided on how flexible the 6U module should be or indeed needs to be. It would be nice to have aversion that retains just the single connector and have the second as an option for more complex applications

CHeers

Ian

 

[emrr]

Very descriptive update, thanks!

 

[anjing]

Wonderfull work Ian! The new pcb's look great! Make's me wanna start all over again! ahahah

Anything to make the wiring easier! especially the pultec! How hard would it be to make stereo eq's a possibility as well?

To have the output transformer on board also would be a blessing! Maybe to have a switch to change the choice of winding of the transformer...-12 or -18 db.

To have just one connector has not been a problem for me mechanically,
i have removed the modules probably hundreds of times already...but i see the interest in it to add more routing options.
How about a backplane and a dedicated module just for the routing ?
This backplane could be feeding all the power for the logic functions...maybe a meter buffer and peak led circuit in that module? My guess is it could be used in a variety of projects as well.
I thinks it similar to what Ramshackles has in mind, but to make it a seperate module might be a good idea?

There is one thing i'd like to add to the reflection, maybe it's not really an issue.
I feel the distance between the amp and the fader could be shorter and in my case because i chose to have the pan near the fader instead of on the faceplate, that's a lot of cumulative distance.
I'd like to shorten the distance between the amp module and the fader(pan). I was thinking of reversing the amp and eq modules. Have the eq on top and amp on the bottom.
I'm not sure how far down i can have the backplane to have enough space for the eq....
I was also thinking of doing the same for the master module as i find the master fader wiring to be very sensitive to noise.
My guess is the cassette's provide enough shielding that longer internal wire runs don't matter as much?


Regards!

Pierre

 

[ramshackles]

My guess is it could be used in a variety of projects as well.
I thinks it similar to what Ramshackles has in mind, but to make it a seperate module might be a good idea?

Another possibility would be the creation of a hybrid backplane which is compatible for both tube and solid-state based designs.
The upper plane could be dedicated to power (HT, H+, H-, +16V, -16V, 5V, etc..) and external connections (fader, direct out, input) and the lower plane could be for buses.

You could then just make a mixed-type 'lunchbox' with just the upper plane, or include the bottom plane for a mixer system...

Of course, these extra possibilities comes at the expense of more/larger PCB's and parts.

 

[ruffrecords]

@Pierre,

Stereo EQ is not something I plan to do in a channel module at the moment although a dedicated 6U stereo EQ might worth looking at. Switches are the big issue because you need twice as many decks. It is hard enough getting all the tracks out from a two deck Grayhill - I dread to think about doing it for a 4 deck. An alternative is to do an all stepped version of one of the current EQs where the pots as well as the frequencies are stepped. You could put two of these side by side in a box and use then as two mon or one stereo EQ. The stepped controls would ensure they were well matched. Someone has already done this with the Helios EQ to make a stereo mastering version. That is definitely something that could be done in a 6U box.

I plan to allow the transformer to be wired so you can change the ratio with links or jumpers but also to allow it to be connected to OUT1 or to OUT2. Set to OUT1 you can do a pre EQ insert and use the extra input transformer to unbalance the signal on the way back in.

A dedicated module just for routing is definitely the way I am thinking. More about that in the nest blog post. The 6U module is now much more like a traditional Neve channel amp - balanced in and balanced out. No fader, just mic pre and EQ. In Neve consoles, routing was always done is a separate module. I tried to avoid that in the EXTube Mixer because it is more expensive than including routing inside the channel module. However, routing inside the channel module is rather limited so for anything more ambitious than two buses and two AUXes you would need an external routing module.

Of course, with a separate routing module, mounted below the channel module, the wiring to the fader is much shorter so it solves that problem too. A dedicated routing modules could have a completely different backplane.

Cheers

Ian

 

[ruffrecords]

Second instalment on line:

http://mark3vtm.blogspot.co.uk/

Cheers

Ian

 

[audiomixer]

Nice writeup, Ian.

when designing the cheek as you call it I would suggest to use a proper CAD like autocad. not saying FPD is not suitable... In bigger CAD programs you can adjust the origin and rotate the axis to an angle so positioning holes for the slanted section can be done precisely. sometimes its even easier to duplicate the manufacturers specs in a proper X/Y orientation and to adjust the grouped set of features. I also learned (by own mistakes....) that it is usually helpful to add the original side panels into the design so that you can check fit in the digital domain. layers and grouping as well as colors helps not to loose orientation.

countersunk holes can be made into thin panels as well, no problem. when working with wood you might add metal inserts so that you can mount the sides with smaller diameter screws..

an other thought might be to design a dual cheek into a 1m plate, one rotated by 180 degrees. or use a laser cutout service. I found this to be a rather cost effective solution when delivering digital data to the manufacturer.

and prototyping - I used a cardboard model cut by a CNC cutter (ok, with friends help) just to with out that I did shift some buttons by 0.5mm - bummer. but rather now then later.

my to cents....

- Michael

 

[ruffrecords]

@audiomixer

Many thanks for the tips.

The thing I like about FPD is that it is pretty intuitive but of course its feature set is a considerably cut down version of those you would find in a proper CAD program. LibreCAD is a proper CAD but it definitely is not intuitive. I am sure it has the features you mention. I just need to decide whether to make the effort to learn them.

The 500 cheeks Frank made for me do not have countersunk holes because the two cheeks need to be mirror images of each other. It was easier just to countersink them myself. The cheeks were 3mm thick and I was happy with the strength of the fixings after countersinking. I am not so sure if they would be as good in the 2.5mm material used by sub-rack manufacturers for their end plates.

I forgot to mention metal inserts into the wooden cheeks in the blog. I have some Insert nuts type E to use for that. The nice thing about this type is that they fit flush with the surface of the wood.

Interesting idea about mirrored cheeks. There is certainly a lot of wastage when cutting a cheek out of a square sheet and a mirrored pair would require a lot less than double the area.

Prototyping is definitely a key issue. Right first time is OK for gods, but for us mere mortals mistakes do happen no matter how many times you check.

Cheers

Ian

 

[zayance]

Makes me even more want to build one......
Nice work.

 

[ruffrecords]

Third instalment now on line:

http://mark3vtm.blogspot.co.uk/

Cheers

Ian

 

[braeden]

Congratulations on the new project,
Would you ever plan on releasing the full schematics or project files in the event that a DIYer wanted to fabricate their own PCBs to fit a custom chassis?

Braeden

 

[ruffrecords]

Congratulations on the new project,
Would you ever plan on releasing the full schematics or project files in the event that a DIYer wanted to fabricate their own PCBs to fit a custom chassis?

Braeden

I certainly plan to publish the schematics and I think I have said elsewhere on this forum that all my designs are free for anyone to build for their own personal use. I know several people have built point to point versions of my designs and at least one has done his own PCB layout. Both are fine by me.

Cheers

Ian

 

[iprovlek]

Great project Ian...

 

[Travis1000]

I caught up on the blog posts this morning and I was very inspired!

 

[ruairioflaherty]

Enjoying the blog Ian, thanks.

Cheers,
Ruairi

 

[soapfoot]

Also want to say I'm enjoying this, and learning from it.

 

[ruffrecords]

I just posted part 4:

http://mark3vtm.blogspot.co.uk/

Cheers

Ian