Serendipity

I think it it really wonderful when several disparate threads come together and provide inspiration as happened to me recently. The first thread was a request for four channels of tube mic pre-amplification. We initially discussed four tube mic pres in a rack mountable enclosure but it soon became apparent that what was required was a true mixer, with EQ, pan pots, rotary faders with big knobs and a monitor section. I sent the prospective customer pictures of various tube mixers from which he selected this one as being closest to what he had in mind.

It uses the old EZTubeMixer modules and rotary faders with big round knobs. And this was the start of the second thread. I had built this mixer several years previously and used a ready made steel enclosure made by a company called Rackz. So I searched the web for Rackz hoping to buy another enclosure. Unfortunately I discovered Rackz had gone bust a few days previously and their web site was no more which was a bit of a blow because they made some really nice fully screened enclosures. An extensive web search revealed absolutely nobody making anything similar so it was back to square one.

This got me thinking about another recent enquiry, this time for a rack mounted mixer, but in this instance, the prospective customer already had a custom built 19 inch rack mounting enclosure made of wood. All he needed was a rack mounting tube mixer to go in it. So I thought, why not get someone to build a wooden version of the Rackz enclosure? Fortunately there are quite a few people who make custom wood enclosures for 19 inch racks. I chose to try out Sound Desks if for no other reason than they are are in the UK and they already make something not too far away from what I need (sounddesks.co.uk).

So I drew up a very rough sketch of what I needed and sent it to them:

There is a 10U sloping spacing split into a 4U space that will contain the faders at the bottom and a 6U space above that for the channel amplifiers. At a steeper angle above that is a 3U space for the meters. At the back there is a 6U space which should be plenty for all the connectors. All in all very similar to the Rackz box. Sound Desks responded quickly with a quote which I passed on to the prospective customer who was quite happy with it.

My only concern was that the wood provides absolutely zero screening so you have to make sure the the sub-rack is fully screened, Fortunately this is not really a problem because most sub-rack manufacturers supply them for use in harsh EMC environments (like electric trains) and provide kits that allow the entire sub rack to be screened.

And this is where the third thread came in. Back in the mid 70s when I was at Neve, I once had a meeting with the man himself, Rupert Neve. When I joined Neve, Rupert had already left. The company had run into financial difficulties and to save it Rupert had sold it. The new owners kept Rupert on as a consultant but the result was he was rarely at Neve itself. When I met Rupert he had come to see my boss Tony Cornwell and after they had talked for a few minutes Tony invited me into the meeting. Rupert had brought in his his latest design for a compact radio console (known as the CRC). It was a radical departure from normal Neve build practice. The complex metal channel module enclosures were gone; modules were little more than a plug in PCB with an attached front panel. Screening between modules was to be done by steel sheets that slid in on card guides between modules. The aim was to make a Neve that was affordable by local radio stations.

I have no idea what became of the CRC as I left Neve shortly after but I never forgot the idea of a compact console which is when the three threads coalesced and I realised I had the basis of a low cost compact tube recording console. It would use:

• Standard sub-racks with full screening which, being made in quantity are reasonably priced.

• A wooden enclosure similar to the Rackz proving a sloping space containing slider faders and channel modules and a meter bridge that could also house 3U modules like the Twin Line Amp (for use as bus amps etc) as well as meters

• Be populated by modified versions of the MarkIII 35mm wide modules which meant here would be space for 12 modules instead of just the six of the EZTubeMixer

For the channel module I started with the REDDPLUS channel amp. I needed to find space for a couple of Aux send controls with pre/post fader selection, a pan control and a mute, solo and pfl switches all of which are normally in the routing module in the standard Mark III layout.. The only space I could make available involved deleting the HPF (we can use the EQ instead) and the insert switch which is a bit of a luxury anyway ( there is still a per channel insert but it is unbalanced, again to simplify the mixer and keep costs down). But this space was not enough so I decided to have one Aux permanently post fade (for FX) and just the second one switchable pre/post fader (for foldback or FX). But there was still no room for this switch so the pre/post switch becomes global and Aux 2 of all channels is relay switched by a switch on the Aux master module. Even then there was not enough space so I ditched solo but kept PFL (so you can gain stage and check quality) and combined it with Mute on a single switch because you never need both at the same time. Putting the two Aux send pots side by side completed the transformation and it does fit in the space availabel (see below).

For the groups you have to have a compressor available but it would be nice to have it available when tracking. So there is a compressor for each of the Left and Right buses. They can be linked for stereo, they can be switched in and out. But they can also be disconnected from the bus and routed to TRS sockets at the rear so they can be patched into any channel using the Patch switch.

There are 8 channels and two buses which leaves two channels for Aux and monitoring. The Aux master module has master level pots for Aux 1 and Aux2 as well as the Aux 2 global pre/post switch. There is plenty of room left on this panel so I added a couple of Aux returns with individual level and Pan controls.

The final module is the monitor one. No serious mixer is complete without talkback so I included that in this module. There is a simple talkback level control and a switch to route it to the master L/R buses (slate) or to Aux 2 (foldback). When talkback is operated, the monitors are dimmed to prevent feedback and the Dim indicator lights.

Below the talkback section is the monitor section. This has a simple three position selector switch. In the centre it connects the monitor to the master L/R buses. To the right it monitors a 2 track playback input and to the left it monitors the two Aux sends outputs. The level send to the monitor amps/speakers is set by the monitor level control. PFL overrides any monitor setting and feeds the PFL bus output to both L and R monitor outputs (pre the level control). The meters are connected direct to the monitor outs pre the monitor level control so they show actual levels.

The basic layout of the mixer is shown below:

Below the channel amps  are the full throw faders and above them is the meter bridge. As shown, two meters are fitted which leaves space on either side for a pair of Twin Line Amp modules which act mainy as bus amps.

As shown, the mixer is 8 into 2 but if the Aux master, talkback and monitor functions were moved to the meter bridge it would be possible to add two more channels making it a 10 into 2. Including the two Aux returns there would be 12 inputs at mixdown.