Marco's 'tube rolling' and valve power amp adventure

[Marco]

Ok, valves first...

Mike sent me four ECC83-type valves to try:

1) Mullard CV-4004
2) CV-493 military spec 12AX7
3) Golden Dragon ECC83
4) A 'mystery' valve

Everyone raves about the CV-4004 as being the best Mullard (or ECC83) there is, and I have to admit for that reason I wanted to buy the CV-4004 from Mike there and then, however that's not quite how it panned out...

One of the things I've learned so far with valves (and I've learnt quite a lot over the last couple of months with experimenting) is that NOS valves always sound better than modern valves - they just have a much more natural sound. Modern valves tend to exaggerate frequency extremes one way or the other and consequently have a more 'mechanical' kind of presentation. This is why I've gone the extra mile to kit-out the Croft with NOS Mullard ECC83 and 35s.

But, and this is the crucial thing, it's not just a matter of obtaining any NOS valves, the performance varies depending on the vintage. 50s and 60s NOS valves, for example, sound different from 70s or 80s ones, and what I've discovered is that there is nothing to beat the sound of the earlier valves from the 50s and 60s. They used different materials and processes in their production that are now illegal, and this is why they have such a unique sound. A while back Anthony sold me a 1950s Mullard ECC83 and this is what I use as my benchmark to compare equivalent valves against.

In that respect I tested the ones Mike sent me against the 1950s Mullard and quite simply none were better than it, not even the CV-4004. The results in order of performance were as follows:

1) 1950s Mullard ECC83
2) CV-4004
3) The 'mystery valve'
4) CV-493 military spec
5) Golden Dragon ECC83.

The CV-4004 is very good, but lacks the 'magic' of the 1950s Mullard. It sounds great until you hear the 1950s Mullard, which simply has a broader and more neutral tonal palette and a musical coherence that all the other valves lacked. The mystery valve was also good, but had a slightly 'processed' quality compared to the 1950s Mullard and CV-4004, and a touch more 'grain'. The CV-493 was pretty good but compared to the best here had a slightly dull sounding character and appeared to overemphasise bass notes somewhat. The Golden Dragon was really quite disappointing and was bright and brash sounding in comparison to the rest.

So there you have it - 1950s valve technology wins!

As for the digital cable Mike sent me, I haven't finalised my decision yet as I'm a firm believer that cables need to run-in for a period of time before you can analyse their performance effectively, so as I want to give his cable a fair chance I will come to a definitive conclusion about its performance in a few days.

As this post is mainly about valves I will move the valve-related content to my 'tube rolling' thread in the D.I.Y room later. The bit about the digital cable will remain here.

Marco.

[Mike]

Ha!... There you go!

Told ya not to get too hung up on the CV thing.

What they do on a tester does not necessarily translate to what they sound like.

By the way, a CV4004 isn't strictly speaking an ECC83, it's an M8137, like THIS (type in CV4004 - near as damn it the same thing though).

Now then, care to guess the vintage and price of the 'mystery valve'?

Cheers,
Mike.

[lurcher]

I may be teaching grandmothers to suck eggs here, but remember that CV is the UK version of VT, it was introduced during the war to rationalise and standadise the huge pre war selection of valves from many makers, so a particular CV492 could have been made by any of the companies and factories that were producing ecc83/12ax7 and the fact it was numbered CV doesn't mean they changed how they were made.

Also, have you tried 5751s as ecc83 replacements, a bit less gain, but nice sounding (IMHO)

[Marco]

Hi Nick,

Good to see you posting now - please don't be 'shy' in future

I'm sure Anthony and you will have much in common

Thanks for the info on the CV rating - noted. I'm fast becoming a total valve anorak

However, sadly, I have to admit to finding all this stuff quite fascinating. I've not tried 5751s. How would you say they compare in sound to a Mullard ECC83 of similar vintage?

Marco.

[Marco]

Ha!... There you go!

Told ya not to get too hung up on the CV thing.

What they do on a tester does not necessarily translate to what they sound like.

By the way, a CV4004 isn't strictly speaking an ECC83, it's an M8137, like THIS (type in CV4004 - near as damn it the same thing though).

Now then, care to guess the vintage and price of the 'mystery valve'?

I would say almost certainly it's a new valve, probably of Russian or American origin. Cost? No more than £8 (or the equivalent in Dollars, etc)

You're absolutely right that: "what they do on a tester does not necessarily translate to what they sound like" and I now understand why. However, it also shows that even though I was influenced by the CV thing it didn't skew the results. My ears still told me that the 1950s Mullard was best - so much for 'expectation bias', eh?

I'll remember this particular experiment next time I'm in a debate with a belligerent cable sceptic

Marco.

[lurcher]

However, sadly, I have to admit to finding all this stuff quite fascinating. I've not tried 5751s. How would you say they compare in sound to a Mullard ECC83 of similar vintage?

Well, I have only tried them myself in simple phono stages. To my ears they have much of the qualities of the mullard, but less of the slightly overbearing forward mid. Slightly less gain, so that may be a problem for some.

Btw, I checked that the RIAA response was the same before comparing the sounds. Often in a phono much of the difference can be down to differing Ra of the valve (often increased if the valve has been used in the past) altering the RIAA equalisation.

[Marco]

Hi Nick,

Well, I have only tried them myself in simple phono stages. To my ears they have much of the qualities of the mullard, but less of the slightly overbearing forward mid.

Interesting.

I can't say I've found that at all - in fact quite the opposite!

Mullard ECC83s (and in fact all Mullards) sound the most neutral to me of any valves I've heard so far, and I've heard a few, although certainly not them all or as many as you're likely to have heard.

Which ones would you suggest then that have all the Mullard qualities but without, in your opinion, the "overbearing forward mid"?

I wouldn't want to lose any gain, though, as in my experience lower gain often makes for a softer sound. I like just the 'right' amount, not too much or not too little. Lack of gain is something that infuriates me with certain active MC phono stages. It's one of the reasons I use a step-up transformer into a valve MM stage. I like to achieve the same listening level on the volume pot as I do with CD. I don't doubt though that 5751s sound great in the right circuit.

Btw, I checked that the RIAA response was the same before comparing the sounds. Often in a phono much of the difference can be down to differing Ra of the valve (often increased if the valve has been used in the past) altering the RIAA equalisation.

Yes I don't doubt that would be the case.

Marco.

[lurcher]

I like GE 5751s, The difference to the Mullard is very slight, I may have over described the difference, but I think its there. I guess it depends on your overall system balance as well.

They can also be very cost effective as they are not so widely sought after as the equivilant NOS 12ax7

I agree entirly about the importance of the gain structure of the system. one hing I have noticed is that using a MC cart into a valve phono without a step up can at first sound rather nice, but its a false sound, almost like analog dither.

I also agree about the quality of Mullards, you should talk to Steve in a couple of weeks about the info he has on the Mullard production process (esp pre Phillips), and how they controlled every step from smelting the ore onewards. Problem is, because everyone wants Mullards you can find well used examples described as NOS, and even rebadged ones.

[Marco]

Hi Nick,

I agree that it depends on the overall system balance. I reckon mine is pretty neutral - it's certainly been tailored that way in purpose, and is one of the reasons I'm able to detect subtle difference between valves and cables quite easily.

If someone's got some GE 5751s at Owston I'll give them a go

I've asked Steve to bring some valves along already.

Getting the 'gain structure' right, as you refer to it, is crucial, particularly in phono stages. The amount of flat and lifeless phono stages I've heard because of insufficient gain is incredible, and not all of them were cheap! The worst offender, although not expensive, were the old Naim phono boards, where you used to have to adjust a NAC52 to about 12.15 on the dial to get decent volume on phono! The Prefix was no different, although their new phono stage has addressed this issue. I found the Graham Slee Reflex/Elevator EXP combination also a bit like this, and strangely that was with using an active head amp as part of the combo. There are plenty of others too I've used that have sounded limp and dynamically restrained because of insufficient gain. The only active MC stages I like are those with adjustable gain, loading and impedance. The fixed ones are generally crap unless they've been designed with a particular cartridge in mind.

Strangely this sort of thing is considered normal by many people. Significant loudness differences between CD and phono is not normal or indeed correct. If the gain structure (I like that word!) is right listening levels between phono and CD should be almost identical. With the step-up transformer I can switch between both inputs and with very little adjustment of the volume control achieve the same listening level. The gain on phono is slightly less but not much.

I will definitely talk to Steve about Mullards. It sounds like a fascinating subject to discuss over a few beers and some pork scratchings, or whatever (not that I eat pork scratchings but you get my point )

Ian Walker will be coming too, incidentally. He's looking forward to meeting you again.

Marco.

[Mike]

I would say almost certainly it's a new valve, probably of Russian or American origin. Cost? No more than £8 (or the equivalent in Dollars, etc)

Spot on!... It's a current production Chelmer, I don't remember the exact price but certainly under a tenner. I think it's pretty good. Some retailers want £60+ for a Mullard CV4004, and I don't think they're six times better than the Chelmer.

If someone's got some GE 5751s at Owston I'll give them a go

Where/when is 'Owston' ???

Cheers,
Mike.