Question Mullard CV4003 / Jan Philips 5814A questions

A question.

bullinachinashop

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Evening all, new to tubes (and qiuickly realising it's an even bigger rabbit hole than solid state amps..) so would appreciate any advice. Just collected a Unison Research Unico which came with two sets of valves for the pre-stage. 20230215_230954.jpg 20230215_231004.jpg
I've done some research (with the help of Myles' reply below) and edited my original post as I think the CV4003 is a Mullard design military-spec tube, but may not have been manufactured by Mullard?

And 81-32 could be a date code; manufactured in week 32 of 1981?

They also have this etched in the other side but not sure if it's signifcant
631
R1E2

It also seems possible that the Jan Philips set were also an upgrade by a prevoius owner, though much cheaper to buy than the Mullards.

I'll certainly try the amp over the next few days and compare the sound of the two sets, but interested if anyone's got any more info on the CV4003s? Mullard branded ones seem to sell for £150+ on eBay, but I assume mine aren't as desirable?
Not looking to profit from them (in fact at £80 I think I might have overpaid...) but wondered if there's better options for the money they might fetch to get the best out of the amp?

Thanks
Ross
 
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ovlov854

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Apparently both Mullard and Brimar military valves were made in the same factory with the same tooling. So these could be Brimar unless you know for certain.
But don't worry Brimar sound as good but they are cheaper than overpriced Mullard
I use them myself in my Hovland
 

Jazid

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Ignore! I was having a brain freeze this morning and what I wrote was totally off topic. Duh :-(
 
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rabski

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The CV4003 is proper Mullard as far as I know. The milspec ones often don't have a manufacturer logo, but again AFAIK the Brimar equivalent has M8136 printed on it. Jury is out as to whether there was any rebranding, but Mullard and Brimar both had production facilities.

The manufacture and date codes are always a bit hit and miss with Mullard, but it's the ones on the back that show the dates and manufacture. According to the sheets I've got, 631 is the type and R1E2 is the manufacture. Four characters means manufactured after the mid-late 50s. R = Mullard Mitcham factory. 1 = 61 or 71. E = May. 2 = 2nd week of the month. Without the logo (which changed) it's hard to tell the decade. I can't find revision lists for the type either.

No matter. It's for all intents and purposes a Mullard CV4003, either 1961 or 1971.
 

rabski

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They were certainly still manufacturing cathode ray tubes (as a confirmed pedant, this is the only correct British use of the word tube) in the 50s. To be fair though, all UK manufacture post WWII seemed to treat record keeping as an unnecessary burden.

All the valve books and sheets I have from the early days are meticulous in identifying types and dates of manufacture, but UK stuff in the 1950s and 1960s is a total mess. I love all the stories that the 'yellow print' Mullards are either special quality or OEM rejects, depending on which conspiracy theory you believe. The only real explanation I've seen came from an ex-employee at Blackburn who reckoned that when someone ordered the paint, they got the colour code wrong and ended up with a pile of yellow instead of white. Rather than sending it back, they just used it randomly. Anyone involved in UK industry in the 60s and 70s will probably recognise that mindset...

The 1950s, 60s and 70s codes are all over the place. The type, date and factory are usually correct, but there always seem a load of extra codes for which the records are long ago lost and there are as many possible explanations as you care to guess at. While the date codes are usually accurate, the demise of the valve was widely believed to be likely, so it's unsurprising that nobody apparently thought it necessary to include the decade on the codes. Of course, at the time valves were just disposable consumer goods, produced in vast numbers and expected to be thrown away.
 

TECUMSEH VALLEY

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Just following on from the info provided above, IMHO these are late production Mullard CV4003s manufactured in 1981.

Mullard continued to produce a limited range of valves until 1985. A lot of the later valves were destined as spares for military equipment.
 

bullinachinashop

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This is fascinating, thanks for the input!!

I found some similar threads with plenty of opinions that CV4003s are about as good as 12au7s get

Is that still the case? Is there anything of equivalent value it would be worth comparing them too?

Thanks again
 

rabski

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Everything depends on the circuit and how the valves are run. As a ballpark though, I've had phono stages in the past with ECC82s in them and I'd rate the Mullard CV4003 about at the top of the pile (though I'm not the greatest fan of most Mullard small signal valves). Cleartop RCAs are also extremely good, as are older Siemens. The Telefunken gold pin ECC802S is up with the CV4003 and slightly different tonally (a touch 'brighter' top end possibly, so may suit some things more than others).

As always, these are relatively (very) minor differences. Just the icing on the cake.
 
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TECUMSEH VALLEY

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Another vote for the Mullard CV4003 from me - a first-class tube with the added bonus of long life and excellent reliability.

The M8136 / CV4003 was one of Mullard's range of 'special quality' valves designed and manufactured to a very high standard. - low noise , low distortion with 'ruggedised' heaters.
 

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