Eela S340 Mixing Desk

Eela S340 Mixer - user manualI recently purchased an Eela S340 “split” Mixer so this page will detail my progress on getting it broadcast ready.  To be fair, it’s actually in good shape despite its interesting history – the usual issues of sticky faders and dirty buttons but nothing a bit of TLC (and some cleaning solution) can’t sort out.

This particular mixer started its life at Century 105 at Salford Quays in Manchester.  The station’s launch (and the mixer itself where the late John Myers spent many frustrating hours attempting to teach Deggsy how to drive it) were featured in BBC’s Trouble at the Top which you can watch on Youtube here.

I am fortunate that, with the mixer, came a very detailed manual with operating information, configuration plus circuit diagrams and wiring layouts.  This makes it very easy to service, modify and operate!  With any decent mixer running on a splt-rail supply, audio headroom is very generous and despite being over 20yrs old, sounds very clean.  The Dutch not only make great radio – they also make excellent mixers.

That quality does come at a price – using the pricing spreadsheet, the spec of this one comes in at just over £15k (£18k EUR).  The S340 model was used at several places here in the UK, including the Chiltern Network Centre (Dunstable), Gem 106, Real Radio along with a full-frame S340 starting life at Egton House for BBC Radio 1 (here’s a clip from Youtube) before being “split” and spending some years in Y3 at Yalding House alongside 2x S440 models.

My S340 seems to have found its way into a GWR/GCAP studio later in life as a couple of extra modules have been added and the channel EPROMS are marked as such.  There’s also some fax (whooooo?) correspondence with Eela about some mods/fixes between 2001-2007.  I should point out that Eela themselves have been very helpful in filling in the blanks with regards some missing bits from the service manual – So I’m grateful for their assistance.

The desk is in great working condition – aside from the initial wiring hurdle of 25-way sub-D connectors, the sound goes in and comes out when and where it should – There’s plenty of record, aux, clean-feed outputs and a 12-way source selector which, in this instance, has been wired to the “External Monitor” for off-air listen.  It could easily be switched into an Outside Source channel and used as a multi-input selector.  An LED PPM meter module is included and I’ve also got a spare “timer” module which replaces some “in-house” routing buttons that must have been fitted during its GWR/GCAP days.

Below is the right-hand console after a button re-fit: New labels and new 15mm P&G fader knobs:

Eela S340 Mixing Desk - button start

I’ve kept the original button inserts but replaced most with my own – and added a splash of colour, too.  Probably everybody’s favourite button on a mixer is DUMP, right?!

Eela S340 Mixer - buttons

Wiring at the back of the console is extensive, yet quite straightforward – Everything is available on a socket/pin which allows you to tap into it, or get a signal out.  Along with the standard wiring, a few pages are dedicated to “factory mods” performed by Eela for the Century Radio installation.

Eela S340 Mixer - distribution board

Although working on this desk is quite easy, learning how it works from an operator’s point-of-view – when it’s sitting on your table with just 3 cables coming out of it is quite an education… The DTX feature took a few goes before I worked out how the routing is handled: Internal dip-switches allow for a channel/s to be assigned to “Direct to TX” with the others being de-routed.  Mine is set so that the 4 playout faders remain on-air with all others assigned to the Record Bus allowing off-air voicetrack/tel-rec to take place.

Eela S340 Mixer - toprack wiring

There’s a lot of sub-D connectors on this thing – and some of the wiring pinouts are shown below:

Eela S340 Mixer - output connections

There are 2 ribbon-cables connecting the 2 mixer frames together, and I will probably make my own shorter ones in due course.  The main PSU is a 19″ 3U rack enclosure and may need a minor service at some point.  Like any well-designed audio mixer, the op-amps (NE5532, TL072 etc) are all seated in IC-holders making replacement a doddle.

The S341 Mic/Line modules can be specified as either Mic/Mic, Mic/Line or Line/Line on the A/B inputs – and mine are Mic/Mic which means that there’s +48v and a fair amount of gain in residence.  Shown below is the circuit for the rear connector plate which details how easy it is to alter the Mic input to become “Line”.  Hint: You remove some resistors from the +48v feed and swap some 0k links for 4k99 resistors.  You could, for flexibility, perform the mod on just the “B” input, keeping “A” a powered microphone input and “B” a line-level one for mono channels or if you wanted an external mic pre-amp.  I had thought about a non-invasive mod by running my dBx286s directly into the “Insert” point however the Insert is located post-Gain and post-EQ.

Eela S340 Mixer - S341 microphone circuit

I found the Mic Gain quite generous, as a generic condensor mic only required the Gain pot to be set at the 10 o’clock position to hit PPM5 on the meters.

So far, I’ve completed the following tasks:

  • Connect, power-up and test desk for audio in+out
  • Removed all channels and re-lubed the faders
  • Fitted replacement P&G fader knobs
  • Replaced buttons/switch labels with new ones

What don’t I like about the mixer?  Well, for a start it’s ‘king heavy!

More to follow..