EMI Tape Recorder L4A

[monaro0162]

Found this at the Enfield Pageant today amongst the autojumble. It came with some nice accessories and seems to be in very good condition. It's going to need a new belt, but I can't find much information on it. I've had a look inside and the quality of construction is amazing! I'm guessing its from the late '60s early '70s, as its transistor based and runs on a 13v battery pack. Where would have this machine be used when it was new?

[ms660]

The EMI L4 was circa 1965, there's a bit about it here, magazine page 55:

http://www.americanradiohistory.com/...nd-1967-02.pdf

And a bit more here, magazine page 381:

http://www.americanradiohistory.com/...nd-1967-09.pdf

Lawrence.

[Ted Kendall]

A product which misfired to some extent, this - the L2 and its transistorised variants were getting long in the tooth and this was EMI's intended replacement as standard BBC wear. Trouble is, the Uher 4000 series worked better for routine tasks and the Nagra 3 worked better for the more specialised stuff - both had transistor-regulated motors which made the L4's governor look (and sound) clumsy by comparison. The BBC didn't buy in any quantity, and they ended up being sold off for £59, if memory serves, about 1969. Alec Tutchings' review in Tape Recorder was distinctly lukewarm...

[beamcurrent]

None the less a very good find and in such nice condition too, I have been on the lookout for one of these for a while to add to my collection.

I would be interested to see a picture of the battery pack if it is still with the machine?

Regards Brian

[monaro0162]

Pictures of the inside attached.

I can't find much information online for this unit. Can anybody help with operating instructions, or even a service manual, if one ever existed?

The main flywheel drive belt has turned to goo. There is another, smaller, flatter belt type in there which seems to run an idler wheel. Ideally this needs replacing too.

I would like to try powering it up later, and have a listen to the amps and try the mic. Also I need another small reel 11cm / 4.25 inches in diameter, I can only seem to find 5 inch ones on e-bay. Anybody?

[stevehertz]

Lovely find and such immaculate condition too. I hope you get it going again, best of luck.

[monaro0162]

Turns out the belt that had turned to melted chocolate only drives the take up reel ... the flywheel and capstan are driven by an idler and the smaller belt ... so it's almost working! The capstan and pinch wheel are running at both 3.75 and 7.5 but no take up until I find a belt. Tried plugging in the mic and listening to what was coming out of the line and headphone sockets, using a 3 pole jack to twin phono cable into an amp. There is an audio path there although the level is low and sounds distorted at anything but minimum gain.

Until i get some technical information on it, I'm not sure what it is expecting in terms of input levels and what it puts out on the line and headphone socket. Both are 3 pole jacks despite the unit being mono. Balanced outputs?

[Ted Kendall]

Inputs and outputs are balanced. You could be reading the output one-legged. For XLRs, the usual standard is 1-ground, 2-hot, 3-cold.

[paulsherwin]

High impedence phones were standard as well, so modern phones with 32 ohm drivers won't produce much output.

[stevehertz]

Can't you find a suitable strong elastic band that would replace that missing belt on a very temporary basis to enable you to play further with the machine for now? What is the rough spec of the belt? length, cross section, diameter/width? Just a thought.

[Hartley118]

Originally Posted by monaro0162

Tried plugging in the mic and listening to what was coming out of the line and headphone sockets, using a 3 pole jack to twin phono cable into an amp. There is an audio path there although the level is low and sounds distorted at anything but minimum gain.

Until i get some technical information on it, I'm not sure what it is expecting in terms of input levels and what it puts out on the line and headphone socket. Both are 3 pole jacks despite the unit being mono. Balanced outputs?

You'll have noticed that those 3-pole jacks are professional Post Office tip ring sleeve type as used on studio jackfields. Ordinary consumer stereo jacks don't usually make proper contact in the sockets.

As already suggested, input and output are most likely to be transformer balanced and floating (on ring and tip), so you'll need to ground one side (either ring or tip).

Martin

[monaro0162]

Line out socket - DC resistance across ring and tip - 20 ohms stable
Phones socket - DC resistance across ring and tip - ~15kohm drifting/variable

So assuming the line out is via a transformer I put a 20ohm resistor across ring and tip and took a parallel feed as ground and signal to phono in on my amp.

With the mic plugged in I couldn't hear anything on the line out, via my amp, but plugging into the phone socket revealed a clear signal path from the microphone at last. It sounds really good, very clear sound with no distortion so far. I pointed the mic out of the window to listen to the birds and the trees, impressed!

I can't seem to get anything out of the line out at the moment, but thinking about it, it may be that the machine actually needs to be recording/playback mode before it will do so.

As well as the mic input via XLR(?)that I've used so far, it has two other inputs, another mic in via a 3 pole jack, and a line in via 3 pole jack. Need to try these next, what should I expect in impedance/resistance values for the inputs?

As for the belt I would love to be able to slip on a rubber band, but I can't see a path to route the belt, without some dismantling. I will attempt this over the next couple of days, also going to try winding some tape onto some sort of circular base as mini tape pancake to use as the missing reel.

[paulsherwin]

You should be able to use standard 3” reels, though obviously they won't give you much recording time, especially at 7.5ips.

I wonder if the inability to use standard 5" reels was a factor in this model's lack of success. The BBC edited interview recordings on big studio decks, so couldn't use thin tape on the portables. In fact they routinely used reels with large centres to reduce the stress on the tape during editing, reducing an already low reel capacity still further.

Wasn't the balanced line standard impedence 600 ohms?

[Hartley118]

The mic input probably goes into a balanced step-up transformer, in which case the primary winding may measure a few hundred ohms resistance. On the other hand, being intended only for short local mic leads, it may connect unbalanced straight to a transistor input amp via a capacitor.

Martin

[Hartley118]

Originally Posted by paulsherwin

Wasn't the balanced line standard impedance 600 ohms?

Most studio line inputs are designed with a 'bridging' 10k impedance, but DC-wise you could be looking into a transformer primary of anything between a few hundred ohms to a few kohms. If it's a transformerless input, you may be looking into a coupling capacitor.

Martin

[paulsherwin]

They are 10k now, but back in the valve era I'm pretty sure they were mostly 600 ohms both in and out using transformers. At a guess, this recorder will follow that standard.

[Ted Kendall]

Originally Posted by paulsherwin

I wonder if the inability to use standard 5" reels was a factor in this model's lack of success. The BBC edited interview recordings on big studio decks, so couldn't use thin tape on the portables. In fact they routinely used reels with large centres to reduce the stress on the tape during editing, reducing an already low reel capacity still further.

Large hub 5" reels were used more for playing inserts, for example single musical numbers in Radio 2 programming, where the point was to avoid wow, something to which the Studer A62 was particularly prone with small hubs on the feed side. Local Radio, at least, nearly always used standard hubs, to reduce the number of reels the reporter had to carry.

Undoubtedly the spool capacity was a factor in the L4's failure - its predecessors had used 5" - but the major factor was the availability of the Uher 4000L, which was lighter, cheaper, arguably easier for reporters rather than engineers to use, and did not suffer from motor hash. Look at the screening arrangements around the L4's motor, needed to keep the noise of the governor contacts out of the audio circuitry. The Uher's control system, being contactless, was inherently free from this problem.

[monaro0162]

Got the line in socket path tested - fed ring and tip direct to earth and signal on a phono socket, then to the tape out on the amp. With some music coming from tape out into the recorder, I am able to monitor this via the phone out. Gain adjustments seem to make no difference to the level out, so seems to be a fixed input level. Would only work with tip and ring one way around. It sounds ok although I suspect that there is still an impedance mis-match, tried adding a 500 ohm resistor across tip and ring but it just seemed to reduce the audio level, and may have introduced a little more distortion, not sure.

Switching back to the mic, with the wind now dropping I've turned off the bass cut and the birds sound crystal clear.

Although commercially a failure, because of its design limitations, and being behind the times, its a fascinating little machine from the era.

Reading elsewhere that EMi made these to BBC specs, and were aimed for broadcast and journo use, and not intended for domestic as well, like the Uhers, which were domestic hifi compatible? (may be talking complete rubbish here!) So certainly not a hifi product, but capable of making high quality recordings for playback on a better machine. Possibly one (of several) reasons for their 'commercial' failure.

[paulsherwin]

Ted, you know a lot more about this stuff than I do, but when I used to hang around BBC Radio Stoke in the early 70s they definitely used 5” spools with large centres on the Uher Reports then in use. The Reports had been modified to record whole track mono and the tapes were edited on big console Studers with (I think) a NAB reel on the right hand side, though it may have been a standard 7" spool.

I thought the Studers were the most wonderful machines I'd ever seen, though I was only about 17 at the time They must have been scrapped when BBC local stations re-equipped for stereo a few years later.

[Ted Kendall]

Fair dos - my experience comes a little later, when B67s had replaced the A62s. The B67, like the A700, didn't mind what size the feed hub was, but the A62 definitely did, so I suppose it would have been a sensible bit of idiot-proofing at the time to standardise on wide hubs.

It is fair to say that the L4 was "butcher", more professional in intention, but the Uher actually produced better recordings and was adequately robust. If tapes were to be replayed at base and most use was with a stick mike with a short lead, the presence of professional interfaces was irrelevant. Not that the Uher was perfect - the gated speed change was frequently manhandled or left "in gear" - field modifications were not unusual.