#1. Here is a little experiment you can try on your early (and maybe current) Neve Channel Amplifiers (1066/1073/1084 etc.) to improve the high frequency response when EQ is selected. Although with EQ “out” the modules are flat within 0.5dB from 20Hz to 20KHz, if the EQ is selected the high frequency response will drop around -4dB at 20KHz!
The reason for this is that the two inverting sections on the B184/284 printed circuit board have roll-off capacitors scattered liberally around the first transistor (presumably around the time the modules were destined to work in close proximity to broadcast transmitters). The result is that the roll off is far too steep! The 100pF (on some PCB’s 47pF) capacitor for C2 and C11 should be reduced to around 10pF… or even removed altogether. The result is, the EQ selected, the response is flat well beyond 20KHz.
The capacitors C2 and C11 are polystyrene type that can be affected by high temperatures inside the module. Also, there are roll-off polystyrene capacitors external to the circuit board, linking pin C to E and K to M on the back connector. These should be 470pF and 180pF but I have found modules with larger values. These capacitors are across the feedback and also roll-off high frequencies and should not be larger than the values stated.
On the topic of polystyrene capacitors there is also one on the secondaries of the input transformers that has a habit, after decades, of going short circuit so that no signal can pass through the module. It’s a good first place to look if you can’t get signal through your vintage module! Polystyrenes can’t handle high temperatures but never feel tempted to change them for ceramic type. Ceramic capacitors do not belong in audio circuits and sound horrid if substituted. They should live in computer circuits, decoupling IC’s…. not in audio anywhere!
#2. The next important tip concerns cleaning and lubricating switch contacts and potentiometer tracks…
I always recommend Electrolube EML 200F and it can be a miracle worker at times, if used sparingly, but, if a contact is worn down to bare metal, a replacement is obviously necessary.
I have no doubt that folk get good results with other products but I whole-heartedly recommend this one and, once you try it, I am sure you will agree!
You can find a local supplier via this link…. http://www.electrolube.com/distributors.htmlhttp://www.electrolube.com/distributors.html
The Electrolube should be used sparingly and sprayed into the rear of push button switches, into the gap where the contacts are fitted on rotary potentiometers, and, on the Elma 03/04 sensitivity switch at the top of the channel amplifiers, gently prise the clear cover up with a small watchmaker style flat blade screwdriver. Lift it just enough to get the nozzle of the Electrolube spray against the gap and spray a measure of the cleaner into the switch contact bank. Then rotate the switch from one end of rotation to the other to spread the solution across all the fixed contacts. Then repeat this process on all three contact banks. Do not raise the clear skirt too high or it will crack!
#3. A phone call has just prompted me to add a vital tech tip concerning Neve modules…. especially expensive channel amps like 1066/1073/1081…
A few years back a very distressed guy phoned about a pair of vintage 1073′s he bought and, following the act in haste, repent in leisure principle, he plugged both modules in backwards into the two channel horizontal 19″ rack case he bought with them. A phone call this morning described a similar case with a loose 1066 module and a power supply/connector set that he connected backwards to the rear of the 1066.
On most Neve channel amps, pins A and B are the microphone input while, at the other end, pin U is +24v and pin V is ground. So, plugging it in the wrong way around connects 24v dc across the 1200 (or 300) ohm windings of the vintage Marinair or St Ives input transformer.
If unplugged in microseconds, the transformer core may be magnetised and could be de-magnetised. More likely, the transformer primary windings have vapourised and the transformer is ruined.
So, before you plug that expensive Neve channel Amplifier into the rear connector… be sure you are aligning/connecting it correctly.
The microphone input cable end goes next to the red bar knob. The power connections end goes next to the “PHASE” and “EQ” buttons.
You can buy replacement Carnhill transformer from audiomaintenance.com but can that replace the 40 year old Marinair original?
#4. A further tech tip could discuss causes of intermittent connections in vintage Neve equipment… One problem the 8058/68 consoles had was that the 12 channel wide buckets would cause the lower ISEP rails to bend with the weight of the modules such that the centre part sags and spoils the connection to the routing units in this location. The only proper fix is to measure the gap between the upper and lower ISEP rails at the junction with the cheeks and fabricate brackets (like a vertical “H”) that will screw into tapped insert into the bottom of the upper rail and top of the lower rail. This will stiffen up the frame considerably and is an essential modification for the 8058/68 consoles.
With a huge caveat of using extra care and caution, and turning off the power first, you can restore worn and closed up Amphenol connectors in a console by gently inserting either a small pocket knife or watchmaker/electrician’s small flat blade screwdriver, into the top of each contact and very gently spread the two blades around 1/64″ (0.5mm). If you spread them too much the connector won’t fit the mating socket on the module but, carefully done, this trick can revive an old console and eliminate the poor connections.
#5. I was reminded of a trick I used to do at Neve and later to clean the gold plated edge connectors on Neve plug in circuit cards and also modules like the 34128, 34149 and 33135 that used pcb edge connectors as rear connectors. I used a firm pencil/ink eraser to rub the connector face which did a brilliant job of cleaning the crud off the contacts and restoring the shine to the gold plate. The rubber particles that are created can be blown away and there’s no mess… like you would get with an aerosol solvent that might not even do such a thorough job of cleaning the contacts.
#6. As a guide to anyone wishing to rack mount a vintage Neve module, the typical current draws are as follows :-
Any of the typical 1064, 1066, 1073, 1084 modules = 122mA
1081 = 130mA amplifier supply, 80mA lamp supply
1272 and 1290 = 100mA
1276, 77 and 78 = 300mA
3104 = 95mA amplifier supply, 80mA lamp supply
Now, before rushing out and purchasing a cheap and diminutive power supply, you must remember three things…
1. The power supply needs to cope with the surge current created as the large value electrolytic capacitors in the modules initially charge… I would always allow at least 0.75 amp per module… the bigger the better!
2. The power supply is part of the audio path and the module’s noise figure is related to the noise and ripple of the supply. So cheap unregulated supplies are definitely a No-No! I would aim for a power supply noise figure of around 1mV ideally but 5mV would be passable
3. Neve modules are designed to be grounded… usually pin V on an 18 way connector. So you must use a 3 pin power plug and cord and ground the metalwork of the power supply. Also, for stability, connect ground to the 0v of the power supply at the power supply.
Then take three cores of wire to the module… typically (red) +24v to pin U, (blue) 0v to pin E, and (green) ground to pin V.
#6. Original Neve Power Connectors
Neve used four basic power connectors on the rear of their consoles, all are fixed male plugs :-
2 pin = 24 volts a.c. for meter illumination on very early consoles
3 pin = 48 volt phantom power
4 pin = 120/240v a.c. (this may have been OK in the 1970′s but is ill advised, safety spec wise, today!)
5 pin = 24v dc input (1 = +24v power, 2 = +24v sense, 3 = ground, 4 = 0v sense, 5 = 0v power)
Connectors are available from http://www.canford.co.uk/Index/C/Cannon-connectors/AMPHENOL-EP-AND-AP-SERIES-CONNECTORS