Calling all Thermionic Valve Experts!!

[dynamic turtle]

Hey folks,

I'm thinking about changing some of the tubes around on my amps and would appreciate any advice you have. Alexs2 & PaulWilliams particularly

With regards to pre-amp tubes, I'm happy to follow the herd and pay a premium for Mullards. The Romulus uses 3x ECC83 and 2x ECC82. The TubeBox uses 2x ECC83. Currently, the Rom pre tubes are Chelmer/CVC 83's and NOS Philips 82's. The TubeBox uses stock Pro-ject tubes (I assume they're JJ/Tesla, as Pro-ject is manufactured in the Czech Republic)

A few quick questions on the pre tubes:

1) I assume they do not need to be "matched" in terms of emissions & gas content etc. ?
2) There are quite a few different types of Mullards around! What is considered to be the best, and next best?
3) Is it really worth changing the 83's in the TubeBox, seeing as the OP stage is a cheapo, non-discrete, resistor-laden PCB? (Amazing it sounds so good, considering how bad it is!)

The power tubes are Sovtek 6L6GC's (although according to the Romulus spec, I should be using WGC's - is there an important difference? They certainly sound alright). I have it on good authority that these are a good all-round 6L6 and might not need changing. Any views on this?

If not, what is considered to be the best all-round 6L6GC/WGC? My preference would be for something lean sounding & agile in the bass department, as the Romulus is a bit overpowering in the mid & upper bass region. Or ,is this best adjusted/tuned via the bias settings (which, according to the previous owner, was set dead at 35ma, the "bassiest" setting, apparently?)

Cheers,
DT

[Paul Williams]

Hi DT

I assume you are including me in as I also use a Romulus, as I’d not consider myself an expert in any way! I always defer to Nic Rhodes, for expert advice.

As standard my Romulus came with tubes

“…Manufactured by the Reflector Corporation, (Saratov). Same as the Sovtek 6L6WGC tube, which is the same tube as the 6L6WXT, but with the thin wafer base. This is a very durable and reliable tube. Russian Military 'OTK' marking, indicates premium military grade tubes…”

and over printed by CVC. I’ve kept these and bought a few spare sets – these exact tubes are always appearing on eBay in matched Quads, I won a set for £10 and another for £18. If you don’t want to go through the Bidding process, I can give you a link to a supplier of these for £28 delivered. I did have a discussion with the designer of the Romulus and he stated that EL34 and KT66’s could be used but their life expectancy would be compromised.

As for the other tubes, I would say the single preamp tube (in the centre) is the most important one to get right. For Current manufactured tubes, the JJ’s, try one from your Phono section if you think they’re JJ’s, Sovtek 12AX7LPS, & Groove Tubes so called mallard copy, the 12AX7-M/GT have all got good followings. I hated the one I tried from E.I. For NOS tubes well the list is endless, with Telefunken commanding the highest prices, Mullard still rated as the best for top to bottom detail & smoothness (I found them a bit dark), the one I’ve not gotten round to trying was the General Electric (GE) 5751, which is often used by Conrad Johnson – this is a lower ‘MU’ tube than the standard 12AX7/ECC83, about 70% of the output so will require a bit more use of the volume control. You could pick any NOS tube and these would have a different sonic signature (as would all the modern produced ones) and I’ve got to say I quite like some of the US ones like Sylvania, over the European tubes. Either way, by focusing in on the one pre tube, this give you the most cost effective tube rolling option and if you buy in pairs, they can be tried in the Phase splitter slots (the ones either side of the pre and in you phono stage.

Off course you will need a tube tester if you're going to get S/H ones to try, hmm, now where would be a good place to get a nice simple one from The other thing I've also found is that some older used tubes or 'pulls' (sort of OS as opposed to NOS) actually sound much better than those pristine new in box (NIB) ones.

Paul

[dynamic turtle]

Yes, I'm often hassling Nic about DVD players. Didn't know tubes were his thang though....

My Romulus tubes are indeed Saratov/Sovtek branded. In fact, come to think of it, they might actually be WGC's. Didn't know the Rom could take KT66 & EL34? When you say "compromised", how long do you mean exactly, and is it actually safe to use these tubes without changing any other settings in the amp first?!

I'll take your advice re the pre tube and change that first. Telefunken sounds like a good bet, failing that Mullard. Boy they're not cheap - just saw a pair of NOS Mullard '82s go for £56!

The GE suggestion is excellent, because the Rom's pot never goes above 10, which can't be ideal for channel balance and overall sound quality (actually, when I next get it serviced, I'll almost certainly get this upgraded to something better).

Hell, I might change the PS for something else outright. I think it is the weak-link in my analogue chain. Something with slightly more gain, XLR outputs and valve rectified PSU would be nice....

DT

[alexs2]

DT....do give Chelmer Valve a call....their prices on NOS tubes are usually pretty good,as well as having a lot of military stock equivalents.

The CVC tubes you currently have will be their stock lines of chinese and russian tubes,which they sell most of,but in no way compare with the old ones they have in abundance.

I'd beware of ebay unless you really know exactly what you're after,and what to look for,as many folk seem to use it as a place to unload their rather tired tubes with good names(witness the loads of EF86's there in very used condition).

Paul's comments re Telefunkens and Mullards very much mirror mine in that the Mullards tend to have a darker overall tonal balance,with the Telefunkens having a very good,open sound,but do be sure to buy OLD ones,and preferably not from the worst of the communist era,when some of the QC was poor.

For some extra background,and equivalents,the following may be useful....

www.tubecollector.org
www.r-type.org

[Paul Williams]

Originally Posted by dynamic turtle

Yes, I'm often hassling Nic about DVD players. Didn't know tubes were his thang though....

My Romulus tubes are indeed Saratov/Sovtek branded. In fact, come to think of it, they might actually be WGC's. Didn't know the Rom could take KT66 & EL34? When you say "compromised", how long do you mean exactly, and is it actually safe to use these tubes without changing any other settings in the amp first?!

I'll take your advice re the pre tube and change that first. Telefunken sounds like a good bet, failing that Mullard. Boy they're not cheap - just saw a pair of NOS Mullard '82s go for £56!

The GE suggestion is excellent, because the Rom's pot never goes above 10, which can't be ideal for channel balance and overall sound quality (actually, when I next get it serviced, I'll almost certainly get this upgraded to something better).

Hell, I might change the PS for something else outright. I think it is the weak-link in my analogue chain. Something with slightly more gain, XLR outputs and valve rectified PSU would be nice....

DT

Telefunkens seem to fetch ridiculous prices - well beyond those of Mullards - I wouldn't know if this is justified on sound quality terms. I now have an imposed £5 limit for NOS tubes. In reality, other than generalities about basic sonic signatures of differing brands, anode colours, getter wire shapes and age of manufacture - you wont really know how any given tube will sound until you plug it in and try. If you don't like Mullards, pass on Brimar and try for some American ones - I've found these to be more bold in their presentation without the forward sound of many modern tubes. I must admit that I've not really got a great deal of experience with ECC83's as quite early on, as you know, I bypassed the pre section of the Romulus in favour of the MiniMax Pre. The Minimax being ECC82/12AU7 based, most of my tube rolling has been around this tube. ECC83's I've tried are Mullard, JJ's, E.I's - think on balance I actually preferred the JJ's in the Pre slot, but went too far and put them in the phase splitter slots and this was too much of a good thing. Mullard/Brimar & JJ combination might work though. If you do go for the 5751, let me know how you get on - should be available for £15 (ish delivered). I bias my 6L6's as close to the mid-point as possible, although I have heard that biasing to the high side (is this what they call 'hot') sweetens the sounds, but reduces longevity. I can't offer any advise on the likely issues around using KT66 or EL34's, but if i ever come across a set really cheap i'll be sure to give it a go.

Paul

[RobsterD]

Must admit I bought a pair of Telefunken ECC83 17mm smooth plates from Germany for stupid money hoping it would improve my AI 500,I used it for the driver and must admit I couldn't hear a massive diff with the Mullard I was using at the time.IMO not really worth the money

[alexs2]

Originally Posted by Rob Dear

Must admit I bought a pair of Telefunken ECC83 17mm smooth plates from Germany for stupid money hoping it would improve my AI 500,I used it for the driver and must admit I couldn't hear a massive diff with the Mullard I was using at the time.IMO not really worth the money

I think a lot depends on the circuit and application....Telefunkens work very well in my Earmax,and sound a lot more evenly balanced than Mullards,and I've found very noticeable brand differences with 5687s in my 300B amps.

Given the right situation,they CAN be worth it,but the problem is not always being able to guarantee that,and having to lay out the money in any case to try.

[dynamic turtle]

Thanks again guys, I know tube rolling can be a pretty dry topic of conversation, so I do appreciate your input.

There seem to be plenty of branded 6L6GC's about: The TAD's look the most interesting of the current production. Seem to be designed for guitar amps though: http://www.tubeampdoctor.com/product...roducts_id=814 .

NOS 6L6GC's from Raytheon, GE, RCA etc. are a little bit pricier (£20-£30 each). I'll certainly consider them though. Most of them seem to be in the US, which is a bit of a pain.

TAD also do premium ECC83's, but I am quite keen on trying out the low-gain NOS GE 5751's you suggested (£19 at tubeshop). Would these be OK to use in the phase splitter role too?

Mullards & Tele's are maybe a little too pricey on reflection, especially as I need 3 of them! Rob's comments have also made me think twice!

BTW Alexs2, that Earmax amp is a nice looking bit of kit. I don't need one, but would certainly like one!

DT

[Paul Williams]

Originally Posted by dynamic turtle

Thanks again guys, I know tube rolling can be a pretty dry topic of conversation, so I do appreciate your input.

There seem to be plenty of branded 6L6GC's about: The TAD's look the most interesting of the current production. Seem to be designed for guitar amps though: http://www.tubeampdoctor.com/product...roducts_id=814 .

NOS 6L6GC's from Raytheon, GE, RCA etc. are a little bit pricier (£20-£30 each). I'll certainly consider them though. Most of them seem to be in the US, which is a bit of a pain.

TAD also do premium ECC83's, but I am quite keen on trying out the low-gain NOS GE 5751's you suggested (£19 at tubeshop). Would these be OK to use in the phase splitter role too?

Mullards & Tele's are maybe a little too pricey on reflection, especially as I need 3 of them! Rob's comments have also made me think twice!

BTW Alexs2, that Earmax amp is a nice looking bit of kit. I don't need one, but would certainly like one!

DT

DT

With a Push/Pull amp like the Romulus, I'm not at all sure you'll get any real benefit from rolling the 6L6's. If you put a thread on any of the dedicated Tube Forums for advice, the overwhelming response will be to try small signal & rectification tubes first. This is on both cost & sound changes. (£20-£30 x 4 ) Be a bit of a pain to revalve the the 6L6's only to find a £10 ECC83 made more difference!

do email Chelmer for a quote as Alexs2 suggests

http://www.chelmervalve.com/

They are really helpful, but you do need to try and source your tubes as economically as possible to start with.

I would have a look on eBay - If you pick the vendor sensibly you can get some great bargains - but it is frustrating at times (I've PM'd you a link to an auction that looks right) just be sensible with your limits.

Paul

[dynamic turtle]

Understood, but if that's the case, why do so many people roll their power tubes?

I've had a look at CVC, but they don't list their NOS. I'll fire them an e-mail.

Cheers,
DT

[Paul Williams]

Originally Posted by dynamic turtle

Understood, but if that's the case, why do so many people roll their power tubes?

Cheers,
DT

I'm not saying it won't make a difference, just that there's probably a more dramatic result to be had from rolling the smaller tubes 1st with this type of amp.

Paul

[alexs2]

Originally Posted by dynamic turtle

Understood, but if that's the case, why do so many people roll their power tubes?

I've had a look at CVC, but they don't list their NOS. I'll fire them an e-mail.

Cheers,
DT

They have a lot of NOS stock,but don't list it,preferring to keep it for those who ask,I think.

Power tubes....a lot depends on the amp and the tubes....if you look at the 300B related discussions,there have been a lot of poor copies until fairly recently,when things like the KR and TJ 300B's came along,whereas a lot of the 6L6/EL34/KT88 replicas are actually pretty decent.

[Nic Rhodes]

DT are you sorted?

[dynamic turtle]

Originally Posted by Nic Rhodes

DT are you sorted?

Nope, not just yet. I was outbid on some GE 5751's ("dropping the kids off at the pool" at the time ) and am on the lookout for some more. I'm quite set on replacing the 83's with 5751's, as their low gain should suit the Romulus well.

As for output tubes, depending on the forthcoming salary/bonus "review" (in brackets, because its more of a management apology session ), I might splash out on some RCA or GE 6L6GC's. Not cheap though.

Just busy reading-up & researching alternatives in the meantime...

DT

(Also looking a bit too closely at new phono stages )

[Nic Rhodes]

Okay lets see if we can confuse you some more

5751 for ECC83 is a good try. 5751s are a nice tube, I like the RCA black plate 'Command' from the 50s but there are many good US makes (avoid the fat Russian bottle as it is not a true 5751). The PhilipsECG is still widely available. [It was not so long ago that no one ould sell these tubes!!]

6L6
Right this is one of my favourite tubes and is a great choice for Hifi amps (WAD / Romulus / Quad etc) but you need to know a little about all the different types as all are not interchangeable. Here is why:

Tube Max power anode voltage screen voltage
6L6 / G / GA / GB 19W 360V 270V
KT66 (1940s+) 25W 500V 400V
EL37 25W 800V 800V
5932 21W 400V 300V
5881 23W 360V 270V
6L6 GB/ WGB 23W 360V 270V
6L6GC 30W 500V 450V
7581 30W 500V 450V
7581A 35W 500V 450V

There are others like WE350s, 6L6 metals etc that we probably don't need to go into details about.

You will see these are quite different and relate to UK / USA production ONLY.

Many Russian production tubes are actually 6P3S and are 'not really' a 6L6GC, not as we understand the USA designation [though are often labels as such]. There also now true 6L6GCs but ask how long they will stand 35w at high voltage and see what people say . Do not use the 6P3S beyond 400v, probably 350v tbh. There are MANY mislabled tubes out there from Russia / China in particular but also other sources. Buyer beware. Just because it says 6L6GC does NOT mean it can handle say 35w!! I have never met a chinese one yet that can for a decent amount of time!

The Russian 5881 / 6l6WGB / 6L6WXT is quite a nice tube and is accurately rated. It one of my favoutite Russian / Chinese tubes along with the Russian ECC88 / 6DJ8 / 6922. It is a tough tube.

You will see from this you will need to know a 'little' about the voltages used (and the current). If you can get this info it will help loads. 35mA is 'not very much' so you shouldn't be stressing the tube too much unlike the guitar guys who often work these babies to the limits and beyond.

I can recommend unreservedly WE350s, KT66 (originals only GEC / Marconi) and EL37s (Mullards), though several of these tube pull more current for their heaters. These are ALL great sounding tubes but if you think 6L6GC RCA are expensive, you have seen nothing yet!! All serious money unless you bought a while ago If you find some at good price also buy a lottery ticket that week

US 6L6GC in general will tend to give a fatter heavier bass, the RCAs in particular. They are good however but probably are prefered by guitar folks more than 'audio' boys. The bass is full however and if you want lean....I like them though. The GE and sylvania GCs are good as well. The miltary number is 7581a and is a meaty tube that is worth looking out for, though prices seem to have trippled in a few years. It is however way over specced for the Romulus I think but I like them.

5932 are a great tube but as rare as rocking horse... Forget finding 4 unless you win the lottery this week and are on a role of luck.

Now we get to the 5881 / 6L6GB /6L6 WGB.

The Russian tube is great and comes in several forms. Waffer base, big base WXT etc. To be honest I am a fan of them all. I would take the WXT give the choice between the 2. It is actually up there with the best NOS but don't tell anyone Guitar folk love this as well.

Then we have NOS 5881 that are still available and affordable. These are a great tube and a tough thing that sounds good. They last for ages, particualrly at 35ma!! The 'classic' is the Tung Sol. Smashing baby There are also some lovely GE from Canada. I can't tell the difference. These are both a little rarer but the 5881 / 6L6GB from PhilipsECG (1980s production) is still around. These are still available and is a smart choice. It is actually not that expensive as you might think either, see

http://www.angela.com/

see tube section for hifi, $70 for matched Quad. Steve is a great guy to deal with as well. All pre tested at load.

So where does that leave us. Try and find out voltages the amp use and then:

I would look at 6L6GB PhilipsECG and Sovtek 5881 WXT as great replacements unless you have more money to spend.....

Confused yet?

Let me know if you need more help on ECC83s