Mark 3 Vacuum Tube Mixer

[Tubetec]

I have old i/p transformers from late 40-50's , the quality of the mu-metal sheilding goes far and away beyond what you see on even the best nowadays , nearly 2mm thick material .
I had at one point a Demeter bass tube preamp in for repair , Lt winding o/c .
I actually managed to contact the man himself for advice on a replacement tx , he was right in saying anything other than a direct replacement would erode the S/N and hum would get induced. I ended up adding a new transformer for the heaters along with the original in which the HT winding was still ok , no amount of manuvering or even extra steel shieilding around the new TX got induced hum down to inaudible . Even using very well sheilded signal transformers on the same chassis as power transformers still leaves some residual hum you cant get rid of without a remoted PSU .

 

[rjuly]

Ian,

are you making your new 12 module (35mm channel width) motherboards available for purchase? I am looking at building an eight channel tracking console based on your Mark 3 design concepts.

Also, while I am asking - two other questions:

- Is anyone interested in a group buy for the Electro Mag (Volker designed) transformers? I need three for my prototyping activities (one for the prototype channel module, and 2 for the prototype monitor module.) I believe 10 is minimum.
- Ian, do you have a source for the right angle tube pcbs?

- Richard

 

[ruffrecords]

Ian,

are you making your new 12 module (35mm channel width) motherboards available for purchase? I am looking at building an eight channel tracking console based on your Mark 3 design concepts.

To be honest I have not given it a lot of thought. The very latest version of the PCB arrived only a few days ago and I am in the process of building and testing it. This version has relay switched mic/line/phase/pad, OEP mic input transformer, provision for either OEP or Volker output transformers, a transformer balanced tape return input and mixdown switching and a four band version of the REDDEQ. This is intended for the build of the "8 tracker" prototype. There are probably many more features in this than most people will need so I may well make the earlier 3 band EQ versions available.

Also, while I am asking - two other questions:

- Is anyone interested in a group buy for the Electro Mag (Volker designed) transformers? I need three for my prototyping activities (one for the prototype channel module, and 2 for the prototype monitor module.) I believe 10 is minimum.

You are right the normal Electro Mag minimum is 10. However, this transformer uses uncommon UI laminations and their associated bobbins which are not stock items for Electromag. So when Volker made the first two prototypes I had to buy the MOQ of laminations and bobbins which, if memeory serves, was enough to make about 14 transformers. I expect therefore that the same quantity will again be the MOQ for this transformer.

- Ian, do you have a source for the right angle tube pcbs?

- Richard

The right angle tube PCBs are my own design. I am happy to supply them to anyone who wants them.

Cheers

Ian

 

[rjuly]

To be honest I have not given it a lot of thought. The very latest version of the PCB arrived only a few days ago and I am in the process of building and testing it…

My apologies - I wasn’t clear. I was referring to the 12 connector backplane pcb. I am also very interested in the latest innovations for the channel design, but since my form factor will be much shallower, I will need to roll my own versions of the pcbs for the channels and output section.

You are right the normal Electro Mag minimum is 10. However, this transformer uses uncommon UI laminations and their associated bobbins which are not stock items for Electromag.

If needs be I will go ahead and order the minimum - either I will end up using them, or over time I can sell some off at cost to tube-minded comrades on this forum.

The right angle tube PCBs are my own design. I am happy to supply them to anyone who wants them.

I want them! May I buy 30? That should suffice for my prototyping efforts and for eight channels and the mix bus output section. That of course assuming you can spare them - otherwise six would suffice in the short term.

and of course, thank you.

regards,

Richard

 

[ruffrecords]

My apologies - I wasn’t clear. I was referring to the 12 connector backplane pcb. I am also very interested in the latest innovations for the channel design, but since my form factor will be much shallower, I will need to roll my own versions of the pcbs for the channels and output section.

My bad, you did say motherboard in your original post. These are large boards so I don't have them made in large quantities. \i had five made of which four are in the Mark 3 so I have just the one left. How many do you need?

If needs be I will go ahead and order the minimum - either I will end up using them, or over time I can sell some off at cost to tube-minded comrades on this forum.

I just rolled trough y old emails and after building the first batch, Electro-Mag gave me a quote for 10-off and 20- off so it looks like you should be able to order just 10. Tje Elecrtro-Mag part number is E1257 (UI39 transformer) My contact at |electro-Mag is Luke Alexander

I want them! May I buy 30? That should suffice for my prototyping efforts and for eight channels and the mix bus output section. That of course assuming you can spare them - otherwise six would suffice in the short term.

I bought 30 some time ago and have used them all. There is no highly valuable IPR in the PCB design so I will post the Gerbers in the open source PCBs folder on my web site so you can get a bunch made yourself

Cheers

Ian.

regards,

Richard

 

[rjuly]

My bad, you did say motherboard in your original post. These are large boards so I don't have them made in large quantities. \i had five made of which four are in the Mark 3 so I have just the one left. How many do you need?

I need just one, if you can spare it. Fair warning though - I am planning to butcher it - I will cut it into two pieces of nine connectors and three connectors; the smaller for the prototype, and the larger for the nine slot final version. I assume that cutting it in half should not be problematic - what do you think? my plan is to fit the mix/monitor section into one 35mm slot, along with the eight channels to make a 9 x 35mm slot chassis.

I just rolled trough y old emails and after building the first batch, Electro-Mag gave me a quote for 10-off and 20- off so it looks like you should be able to order just 10. Tje Elecrtro-Mag part number is E1257 (UI39 transformer) My contact at |electro-Mag is Luke Alexander

Just emailed today for a quote. Thanks for that information.

I bought 30 some time ago and have used them all. There is no highly valuable IPR in the PCB design so I will post the Gerbers in the open source PCBs folder on my web site so you can get a bunch made yourself

That sounds great - thank you.

- Richard

 

[ruffrecords]

I have uploaded the tube socket PCB zip file to the open source PCBs folder of my web site Custom Tube Consoles - DIY. Just click on the OpenSource PCBs folder and in their you will find a zip file named tubesktV2.zip which contains all the Gewrber files needed to manufacture the board. Please read the "readme" file in this folder before downloading any filesas it includes important licensing information.

Cheers

Ian

 

[rjuly]

I have uploaded the tube socket PCB zip file to the open source PCBs folder of my web site Custom Tube Consoles - DIY. Just click on the OpenSource PCBs folder and in their you will find a zip file named tubesktV2.zip which contains all the Gewrber files needed to manufacture the board. Please read the "readme" file in this folder before downloading any filesas it includes important licensing information.

Cheers

Ian

Many thanks for that Ian. I'll be sure to read the licensing document.

- Richard

 

[rjuly]

I have started a thread about my mixer build here: A tube tracking console using ITB’s MkIII concepts - so as not to clog up this fine thread ;-)
- Richard

 

[ruffrecords]

I just updated the Mark 3 blog with the latest gear porn.

Mark 3 Vacuum Tube Mixer

Cheers

ian

 

[Tubetec]

That really packs in a lot of features you often find missing from smaller solid state mixers , its astounding that you've managed it all with three double triodes per channel.
Makes good sense to have the tubes up at the top of the module , now the natural convection currents draw cool air up over the components .
Could the channel output and the tape return be simultaneously fed to the mix bus to double the number of inputs on mixdown ?

 

[rjuly]

Hi Ian,

The new channel is looking sweet.

- What are you using for the mic input switch? - looks very compact.
- Is the Carnhill trafo a separate line tranformer? I didn't realize that would be neccesary.
- Does this channel have inserts? I would have expected to see a pair of tranformers for that, or are they just very small?

Nice to see the next iteration!

- Richard

 

[ruffrecords]

Hi Ian,

The new channel is looking sweet.

- What are you using for the mic input switch? - looks very compact.

It is a subminiature toggle switch. Quite a few people make them with minor differences. TYpically I use either 2MD1T1B5M2RE Farnell part number 9473068 or MC2MD1T1B5M2RE CPC part number SW02449

- Is the Carnhill trafo a separate line transformer? I didn't realize that would be necessary.

That transformer is for the third input, the tape return. The regular line input is via a pad into the mic transformer

- Does this channel have inserts? I would have expected to see a pair of transformers for that, or are they just very small?

It does not have a built in insert. In the Mark 3 mixer there is a separate routing module. The transformer out of the channel amp goes to the insert and the return goes to the input of the routing module which contains a 10K:10K transformer. This is exactly the way is was done at Neve back in the 70s.

Nice to see the next iteration!

- Richard

Yes, it is really starting to come together.

Cheers

ian

 

[rjuly]

I just updated the Mark 3 blog with the latest gear porn.

Mark 3 Vacuum Tube Mixer

Cheers

ian

That photo is of the module without it's metal side panel, correct? I take it you are still using the same method as shown in your 'Coming Together' blog post - attaching the pcb and metal panel to the front panel with the brass standoffs? Also, wher do you source the steel plates? Are they pre-cut and drilled to size?

- Richard

 

[ruffrecords]

That photo is of the module without it's metal side panel, correct? I take it you are still using the same method as shown in your 'Coming Together' blog post - attaching the pcb and metal panel to the front panel with the brass standoffs? Also, wher do you source the steel plates? Are they pre-cut and drilled to size?

- Richard

Yes, that module is being commissioned so it does not have its side panel attached. I am still using the exact same panel as before only now I use galvanised steel rather than regular steel which I have found rusts surprisingly quickly. I think the last steel plates I got here: Buy Metal Online · Sheet Metal & Plate · Steel Suppliers & Stockholders I get them to cut them to 233mm by 160mm then I use a scrap channel PCB as a template to drill the holes.

Cheers

IAn

 

[zamproject]

regular steel which I have found rusts surprisingly quickly

that's normal, if you have even little moist at finger when handling non protected steel you can see within hours rust finger print

Cheers
Zam

 

[rjuly]

Yes, that module is being commissioned so it does not have its side panel attached. I am still using the exact same panel as before only now I use galvanised steel rather than regular steel which I have found rusts surprisingly quickly. I think the last steel plates I got here: Buy Metal Online · Sheet Metal & Plate · Steel Suppliers & Stockholders I get them to cut them to 233mm by 160mm then I use a scrap channel PCB as a template to drill the holes.

Cheers

IAn

Thanks Ian - I will check them out.

 

[ruffrecords]

that's normal, if you have even little moist at finger when handling non protected steel you can see within hours rust finger print

Cheers
Zam

I have no mechanical skills so it came as a bit of a surprise to me. I first tried zinc passivated steel but that looks horrible so I ended up using good old galvanised.

Cheers

Ian

 

[rjuly]

A few questions about your current Mark 3 design:

- VU metering - Are you using the circuit you discusessed in the thread:
https://groupdiy.com/threads/alternative-to-jlm-vu-buffer-boards.78287/Have you made any changes or updates for this latest version of console?

- REDD four band EQ - Can this latest version be derived from your three band with make-up gain circuit design? I'm keen to see if I can build a pair of these into an 'outboard' console channel module that can be patched into the inserts of any of the channels or 2 bus.

- Power Suppy - Are you using the same power supply design as discussed in your blog for the EZ tube console? I have a feeling I remember reading a post of yours in which you mentioned that (I paraphrase my recollection) you don't build your own supplies anymore - that off the shelf are perfectly adequate and cost effective. Did I mistake something else for that?

In any case, many thanks for spending valuable time on questions of this sort...

- Richard

 

[ruffrecords]

A few questions about your current Mark 3 design:

- VU metering - Are you using the circuit you discusessed in the thread:
https://groupdiy.com/threads/alternative-to-jlm-vu-buffer-boards.78287/

The Mark 3 is still under development so things can change. The VU buffer board I mentioned in that thread was designed for the Compact Recording Console but, as it fits right across standard Eurorack backplane extrusions it can easily be used in any design. The Mark 3 has a 3U high area right across the top that is at present largely unallocated but would typically be used for talkback, line up oscillato, a couple of big meters and maybe even a compressor or two. I had planned to create a TLA sized PCB version of the VU buffer it so it could just plug right into a backplane but yesterday I got an email from Holger Classen who has found some rather neat bar graph VU meters:

LED VU meters

so I thought I could also use the same card to unbalance and level set signals to feed to these LED VUs as well (plus create the required 5V supply rail.

Have you made any changes or updates for this latest version of console?

Updates are happening all the time and I try to ensure these are covered in the blog as soon as they become firm. One change that will be made is to the monitoring. So far, all my builds have used the Neve style fully balanced monitoring via big set of switches. However, wring up these switches to and from their various XLRs is a royal PITA so now the plan is to monitor all individual channels via a PFL/SOLO bus which will override the main monitor output by relay (as in your design). Any balanced out that needs monitoring can have its own dedicated meter.

- REDD four band EQ - Can this latest version be derived from your three band with make-up gain circuit design? I'm keen to see if I can build a pair of these into an 'outboard' console channel module that can be patched into the inserts of any of the channels or 2 bus.

The present EQ design is in part derived from my original REDD EQ but it is significantly different. It uses a technique that allows boost and cut Q to be the same for an EQ with up to +-6dB range which is ideal for mastering purposes. The +-10dB range in the four band version used in the Mark 3 channel amps has sharper Q in cut than in boost (which is more typical of the Helios EQ. The original REDD EQ maintained eqaul boost/cut Q over a +_10dB range but required much more complex switching and twice the number of inductors to achieve it). So it is really a very different design and unfortunately not yet available for DIY.

- Power Suppy - Are you using the same power supply design as discussed in your blog for the EZ tube console? I have a feeling I remember reading a post of yours in which you mentioned that (I paraphrase my recollection) you don't build your own supplies anymore - that off the shelf are perfectly adequate and cost effective. Did I mistake something else for that?

The power supply is also under development. For heaters I no longer use home built linear supplies; I use MeanWell SMPS. They are smaller and electrically quieter than any linear supply. For small mixers using up to 100mA of HT I use the International Power IHB250-0.1 available from Mouser. The HT supply for the |Mark 3 is still under development. The basic plan is to use a Meanwell 300V/500mA SMPS which is then regulated down to 250V.

Cheers

ian

Cheers

Ian