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Sourcing The Bottle

Valves

the detailed where and how of replacement


Despite cruise missiles and microchips, the valve still lives. Ben Duncan identifies the survivors and explains how you get hold of them.


Most of the valves used in musical equipment were designed in the 1940s. Some, like the ECC81/2/3 came later in the mid 1950s. This might sound like bad news, but oddly, it's rather fortunate, because these dates coincide with the zenith of valve development. Also, in their heyday, there were several thousand different species of valves.

Many were electrically very similar, but had different connections or bases, or simply different numbers – all designed to confuse everyone. In particular, the chaos stemmed from petty wars between competing manufacturers.

But the good news is that the mainstay valves for rock'n'roll amplification were by and large industry standard types, meaning everyone used them, all over the world. The chances are that your gear uses one of the valves listed in Table 1. Note the division: "front-end" tubes are physically small, and handle your amp's inputs, EQ, reverb and so on. You'll also find them in tubed-FX (vintage Copicats, Echoplexes and the like). Meanwhile at the back-end, the valves get bigger and hotter (ouch!), because these are the objects responsible for turning a few milliwatts into 50 watts – or more. Let's begin at the front end, though.

Front-end sourcing



All EEC... er pardon, ECC valves are European, but have direct US equivalents (see the numbers in brackets in Table 1). This is handy, because all the west European makers have ceased manufacture. Of the last, the UK's own Mullard finished over two years ago. Of course, so too have most of the US manufacturers. But the point is that the ECC series is used worldwide (albeit with the different, US numbering), so remaining stocks will be higher than for a solely European valve (like the KT88).

To confuse matters, ECC types are still made by east European makers. They're generally marked "foreign" (this category can also be taken to include oriental tubes) and here you have to be careful. It might seem churlish to say that east European valves are naff, but this is certainly a widely held opinion. They are, attractively, far cheaper – conclusion: there can be no smoke without fire.

Specifically, their lifespan is short, and they're apt to be microphonic – which means they act like a microphone. Well, not necessarily exactly like your SM58. But if they ping when you tap the amp, imagine what they're doing to the sound when the amp's external speakers or the bassist-cum-drum-machine/PA/drummer begin to vibrate the floor or stage. Microphonic tubes needn't absolutely make the sound worse – indeed the effect might be used creatively – but microphony will almost certainly alter the beloved tone, punch and attack of your amp.

If you're at all uncertain about whether a valve offered to you is kosher, best stick to one marked by one of the leading makers given in Table 3. They won't necessarily have made the tube themselves, but better a famous maker's logo appears on the valve than not.

In some fine-tuned amps, even standard valves marked with famous names may fail to bring the sound up to the original level. Here, the equipment manufacturer was probably relying on specially selected valves, often with improved resistance to mechanical shock. Generally, specially selected electronic components are a pain for everyone, except the makers. When they die/go bust/get into the offshore manufacture of videos or CD players, equipment is suddenly bereft of spare parts. Having said that, "special" tubes are almost invariably selected versions of standard types, rather than a one-off, unrepeatable design. And almost certainly, the manufacturer would be taking ruggedised "MIL-SPEC" (military specification) product destined for NATO's macho-might. These versions have doubled-up suspension and insulation for physical robustness and, more important, will be the top performers, selected from a batch of a thousand or so, and would have been thoroughly tested for "zero-defects" before being released from the factory.

Anyhow, talking to one of the leading valve stockists, Langrex, it transpired that tens of thousands of MIL-SPEC tubes are still at hand. But there's an obscurantist catch – you have to know the correct number. Asking for an "ECC83" is just no good.

Table 2, then, displays for the first time information calculated to be... drone... Official Secrets Act, Section 3... drone. Yes, we are the Special Branch, sir, and we have reason to... accompany me with your Twin Reverb to the station, sir...

Satire aside, you'll note that consistent with the MOD's obsession with secrecy, the UK "MIL-SPEC" tubes come with a completely different "M" number, whereas the US versions are just suffixed "WA" ("Weapons Atomic", one presumes). Have no fear. It's perfectly legal and decent to use these valves. Just don't tell anyone!

Output valves



Here, MIL-SPEC types will be harder to get hold of, even if they exist, but the KT series (eg KT66) is available as Gold Lions. These amount to the same thing: namely scrupulous quality control and very sturdy construction. The KT66/77/88 are also amongst the last tubes still in production in the UK, and though a couple of US makers still produce them (under the same numbers), these aren't selected, top-spec versions. Nor are there any direct equivalents with US codes (bar the 6550, which is reputedly a replacement for the KT88, but a dodgy one at that). Also, with demand in the UK falling, the Gold Lion KTs keep shooting up in price. So keeping a spare set or two on the shelf is a worthwhile investment – valves don't deteriorate on the shelf.

The KT77 originally arrived as the M-O Valve Company's answer to the rival (Mullard) EL34 (or vice-versa), but again they're not exact equivalents. In some amplifiers either valve will cheerfully amplify, but in many rock'n'roll amps the designer was pushed to squeeze as much power and performance as possible from the circuit. This is apt to make ad-lib substitution a more dicey business. But is substitution needed?

On the other hand, tens of thousands of EL34s were bought out from Mullard (when production ceased) by makers like Marshall, and stockists like Langrex. However, stocks at warehouses are mostly standard (ie unselected) versions. This is fine for amps which don't depend on premium grade valves, but if there's any element of fine-tuning involved, it's tempting to look at the KT77 in the 'Gold Lion' format. In this instance, you'll just have to suck it and see, keeping an eye out for overheating, oscillation or any other misbehaviour.

If the KT77s seem to work OK, but don't last long, they're almost certainly being pushed. A long term solution in this instance is to have the amp "tweaked" to match the KT77. This should be worthwhile, because Gold Lions are likely to be around for a lot longer than selected EL34s, already in scarce supply. Alternatively, if fussed, you could try purchasing official Marshall EL34 spares (say) from a dealer. These will be premium grade types, of course, but with a price to match.


How?



The chances of obtaining most of the valves we've been discussing from high street shops are... well, forget it. But relax: all are available from a handful of big mail-order warehouses, namely:

1. Langrex Supplies Ltd, (Contact Details).
2. PM Components Ltd, (Contact Details).
3. AEL, (Contact Details).

You can either contact these companies directly for prices or (easier) pick up a copy of Wireless World magazine. Langrex and PM advertise in there and list hundreds of valves and their prices. In general, these prices will be below the norm because you're dealing direct with the supplier and equally because there's competition between the companies listed. As a result, you may end up purchasing the (inevitably more costly) MIL-SPEC varieties for less than the usual retail price of the bog-standard types.

One Two readers living in southeast London can check with the suppliers listed to see if direct collection is OK (it's no good struggling across south London's crowded roads if the valves you're seeking are out of stock). But failing this, you can do it by mail-order from the luxury of your own garrett. If you're not familiar with ordering electronic parts by mail, here's how to go about it.

1. Phone up to confirm the price. Or send a list marked "Quotation please" with an SAE. Or send a cheque marked "Amount not to exceed £...", allowing 10% to 20% extra on the calculated amount.

2. VAT is usually excluded; if so, add 15% by multiplying the total by 1.15. You'll also need to add 50p or so for postage – the brochure or ad's small print will give details.

3. Print your name and address clearly on a sheet of paper, list the valves, and show the amounts for each, the total including VAT, then attach a cheque to your order. Failing this, send crossed postal orders.

4. Never send cash because, while companies are generally very honest with customers' money, it's tempting providence to do so. Electronics mail order companies are in general very safe to deal with, but if you do come a cropper, most magazines operate a reimbursement scheme, provided you purchased as a direct response to an advert in their pages.

5. Postal Orders are quickest (they don't bounce), and if your valves are in stock you can expect to see them by return of post. Most companies will want to clear your cheque before parting with the goods (writing your cheque guarantee number on the back isn't strictly legal) so you may be kept waiting seven to ten days. If you desperately need spares for Friday's gig, the best course is to state this clearly on the order: "Useless if delayed – Express cheque clearance requested – dispatch per Express post".

Banks will charge around £3 for fast clearance, so be sure to add this to the amount, and in addition, sufficient to cover the express-post – about £1.25. To be doubly sure, you should phone to check whether the supplier (a) has the goods and (b) whether they can make all the arrangements needed to guarantee delivery on Friday morning.

Another speedy method is to phone through your credit card number. This is cool if you have one, and if the company accepts credit cards. Often not...

Two other tips: shop around, taking into account the carriage charges. And second, as valves don't deteriorate with age, any spare cash (hah!) you have can be usefully invested. Even if you end up selling your amp, the fact that you can advertise it with a brand-new, boxed set of spare Gold Lions and M8136s will make quite a difference to the money you'll make on the sale.

TABLE 1

STANDARD VALVES

(US equivalents in brackets)

Front-end
ECC81 (12AT7)
ECC82 (12AU7)
ECC83 (12AX7)
EF86 (6267)
- (6BR8)
Output
EL84 (First four
EL34 no direct
KT66 US equivalent)
KT77
KT88 (6550)
- (6L6GT/G/GC)


G, GC and GT types are physically different but should be electrically identical. If it fits, use it.


TABLE 2

MIL-SPEC VALVES

Creme-de-la-creme versions of standard valves (left column).

ECC81 = M8162 (UK) or 12AU7WA (US)
ECC82 = M8137 (UK) or 12AT7WA (US)
EEC83 = M8136 (UK) or 12AX7WA (US)
KT66/77/88 = Ask for Gold Lion version made by GEC/M-O in UK.


Table 3

REPUTABLE BRANDS

Europe
Mullard, Philips, Telefunken, Siemens, M-O Valve Co, GEC.
US
RCA, GE (nothing to do with GEC), Raytheon, Sylvania


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E-Mu Systems E-Drums

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Bass Amps


One Two Testing - Copyright: IPC Magazines Ltd, Northern & Shell Ltd.

 

One Two Testing - Sep 1984

Feature by Ben Duncan

Previous article in this issue:

> E-Mu Systems E-Drums

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> Bass Amps


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