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#1 · (Edited by Moderator)
Pre-amp valve selection! The valves/tubes you choose to use effects your tone in a big way (almost as much as a new pickup!) luckily it doesn't cost as much (unless you have more than 4 preamp valves). It is also 'lucky' that you HAVE to change them. Otherwise you could end up with a tone you hate for the rest of your life! Most people who aren't up on valves think "an 12AX7 is a 12AX7" This is totally wrong! There are many types of ALL valves (EL34s, 6L6s I mean ALL valves). They are normally have a designator, which follows them (e.g. 12AX7-C) This represents different types of tube, It also Represents their origin.

Key:
C- Represents China made Valves
R-Russian
R2-Different Russian factory
S-Formally the Telsa factory now owned by JJ. In the Czech republic
Y-Yugoslavian
GE-USA only Groove tubes use this key (I think)

These are the stock 'codes' for Groove tubes. Although some Dealers advertise all valves this way. I am not going to go into the argument of makes because I am sure I will offend somebody who swears by a certain company.

Also in my personal opinion we shouldn't get too wrapped up in the NOS game (unless you have a vintage amp and lets face it if you can afford a vintage amp you would be able to afford those ridiculous tube prices!) . I know many say that they love Mullards and I agree but it is really risky to buy them! Firstly they cost a bomb more than a set of new valves! Also as they are 'old' it means they weren't used when they were new, This leads me to believe that they were 'duds' in their prime in some cases. So always ask a supplier to test valves before you part with your cash EVEN NEW VALVES! Also you don't know whether NOS tubes have been used or not!! so you could end up with some really old valves that are dead!! Also the original box is a must (all though I believe lots of people make fakes and charge top $$$).

Also despite common belief there is only a small number of tube manufacturers in the world. So a China valve from one company will sound similar to another (although their will be some differences due to different active components used and glass thickness)

Right onto selecting valves. Like choosing pickups you need to know a few things:
1) What type of amp you are using? This is similar to what pickups go with what body woods. But as with pickups some people like weird combos! A 'good' way to determine good combos is to know what tube the amp was designed around (stock tube) because most companies are looking to save money the use the cheapest valves they can get their hands on. So to make up for it they optimise the amp around them to sound better. So a valve from the same origin is considered to be 'right'. Also vintage amps were designed around NOS tubes so those should sound 'right'.
2) What style of music do you play? If you need a lot of headroom a valve with a lower gain rating would be desired (for output tubes a slower break up)
3) This is most important and is the same as choosing a pickup. What is your sound lacking or have too much of?
4) An obvious one. What type/brand of tubes does your amp have in the first place? If you have a REALLY bright set of tubes in there and think it is too bright go down to a medium brightness unless a huge loss is required. Also if it is sounding weird even after the tube change TAKE IT TO A TECH. It will most probably be drifting values of some kind.

Right now that is said lets move on. So the main type of valve (and the most used audio valve of all time!) is the ECC83/12AX7/7025 despite a minorities belief these are the same. The 7025 never used to be though, it started out as a higher grade ECC83 but now most people regard it as the same valve.

Lets start off with the China made these normally have a fair bit of gain. And have a fat warm tone. There are rumours of low quality valves coming from China but I hear the new ones are quite good (hopefully). It also meets the original ECC83 spec very well (almost perfect) so they work well in vintage amps! Although in modern amps (usually designed around Russian valves) it may have too much gain and hum a bit. Although I know a few people who love these in modern amps. Although there is a bad sign over at www.watfordvalves.com which policy states:
"Chinese valves
For the performing Musician and professional audio industry we have found that these items to be lacking in both terms of reliability and performance. Watford Valves therefore cannot recommend fitting such items and as company policy do not stock or offer items of Chinese Manufacture." They also slate their tone and regards it as 'wasp in a jam jar' and fizzy. So they are good for reliability but not for tone!!

Secondly lets look at the good Old Russian valves. (AKA SovtekWA) These are probably the most used in modern amps. Reliability is pretty good with these although not many people like the tone. It is generally lower gain and darker than most other valves on the market. (So maybe good for bright Fenders?) It is also very mid orientated. The balance between the 2 sides of the valves is normally very poor so I wouldn't use them in a phase reverser or driver stage!

The R2 Russian valves seem to be really bright. But can be prone to microphonics. The quality control is meant to be an issue with the Groove tubes though. It has a higher gain than the other sovteks WB.

Sovtek LPS are pretty good too. They are pretty similar to the EH brand tubes but a few people regard them as better because of a flatter freq response. Although I have never had both side by side to compare.

There are also Electro Harmonix Sovteks these are really great valves. Low microphonics and good gain. Also it has a spiralled filament so AC wiring noise is kept to a minimum. It is definitely based around the higher frequencies! Real trebly!!

Next comes the Telsa factory (Czech Republic) . The newer JJs are regarded as some of the best tubes of today. They are also very similar to the Electro Harmonix tubes in sound. It has a huge output much bigger than any other new valve. They are fairly high treble response and is favoured for hard rock and metal. (Especially in high gain amplifiers) These have a very thick glass (on JJs) Also really low microphonics on the new JJ/Telsa's. And a long life. It is clear to see why they are so popular!

Next we have the Yugoslavian tubes. They are immensely bright and biting and may become brittle in Marshall's! But they complement Fenders very well (and early Marshall JTMs which are basically fenders!)

American Brand tubes are always quality! Groove tubes have their GE series, which are great from what I hear but are expensive. Sylvanias are also regarded as great tubes. Very rich and warm sounding. It's a standard rock valve with average gain but cleans up nicely.

Another brand is Svetlana.They are replicas of the Mullards which is a good sign! But are not regarded as top quality by 'audiophiles' I have never had any experience with these so I can't comment.

I am unsure of their origin but the Harma valves have been a favourite of mine. In the USA I think you call them European STRs? Anyway I love these valves! They have a sound reminiscent of the sort after Mullards but are cheaper and easier to get hold of. They are also Brian May's favourite of the new valves. He now uses them in all his AC30s! I am probably going to use these in my amp when it is built.

Also Mesa Boogie now have their own brand tubes. They are said to be the only valves that work in their amps. But they aren't being strictly true ;) Any tubes can work in Mesas fixed Bias amps. It is not that hard to do with either a slight knowledge for amps or a good tech ;) Firstly you need to locate the Bias resistor. And take it out. You then need to replace a trimmer in there. Bias like normal. Get the trust VOM/Multi meter and measure the resistance. Replace the trimmer with a resistor of the same value and you are done! This will only work with valves with good quality control though. Other wise it would all go wrong! There are also numerous mods to install a bias trimmer to mesas you can find them on any good schematic site.

Another thing to add to choosing pre-amp tubes is they are pretty much universal! You can (almost) use any 12xx7 in place of a 12AX7! Why would you do this? For a different sound. It doesn't need any modification to the amp to do this (unlike output tubes.) I am inclined to get a set of 12AY7s for my Marshall DSL. It reduces the preamp gain by over ½! It also makes modern Marshall's to (almost) like the old Plexis! I am just looking for a model that will make it a little darker sounding as well. Then adding fast 'break up' EL84s will make things really scream ;)

The 12AT7: This is usually used in the driver stage section of modern amps, but in Fenders early days was also used in the preamp as well. It has less gain than an ECC83. Another name for the AT is an ECC81. In modern high gain amps it can be used to reduce the gain (and most probably noise).

The 12AY7: It has a tiny amount of gain, which leaves the big distortion up to the power stages ;) It is less than ½ of the gain of the AX. Leading to a lot less noise and a 'cleaner' feel. But it has over double the output! This will really pound your output/power tubes to the compressed saturated distortion! So if you think your amp is too high gain try these!

The 12AU7: It has a tiny gain compared to an AX. Only just over a 1/10!! But the output is almost 10 times as much!! It has huge clean headroom though. Favoured by fingerpickers and adds a softer touch to the tone. Another name for this is the ECC82.

I have hunted around the internet for all these 'reviews' but mostly it is from Watford valves. Also regarding Some of the output and gain info is from the amazingly good book by: Aspen Pitman and is called "The tube amp book".

Class dissmissed :lol:
 
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#14 ·
For biasing there's this thing called Bias Master by Ruby that should make biasing jobs easy. www.rubytubes.de and see the menu on the left for "TAD Bias Master".

When it comes to those Mesa preamp tubes, I hear what they're basically doing is getting russian tubes (ie. Sovteks) and just putting their own name on them. So you might be just as happy putting in some 12AX7EHXs...

And from my personal experience I can recommend JJs. They don't have as much gain as the chinese or russian tubes, but are MUCH quieter. The tone's nice, with kinda grainy midrange.
 
#16 ·
Al M said:
You dont have to get a trim pot installed though!? The guy at euro tubes told me he can just supply tubes for mesa amps as long as you tell him its for a mesa they will work fine.
Not all vendors are willing to do that :wink:

Also its not only the current boundaries of a tube that matter! Mesa's screening process allows them to see if tubes will develop a problem later in life :wink: I reccomend a bias trimmer on any amp that doesn't have one. It allows a wider range of tubes and sometimes Mesa's stock bias resistor goes off value (all components do at one stage or another) this will make the sound gradually out of bias you probably won't notice until you find a stock one. THis is the logest I have ever talked about Mesa/Boogies *shudders* :lol:

Grindfiend it is possible to adjust mesas with a quick mod. 'Better' is debateable but I would like the added reassurance that I could use any tubes. 8)

To clarify the Mesas don't self bias!! some people allthough not on this board (luckily) seem to think that mesas automatically adjust to any tube. Back to the point normally the mod is a quick replacement of a resistor (I think some use parralel resistors too) for a trimmer.

Mr Orange Mesas (or any amp for that matter) can take pretty much any preamp tube without modification. The bias for pre-amp tubes (yes they are biased!) is pretty variable. I think it is because the original specification for pre-amp tubes is still pretty close to what they are made like now where as power tubes have drifted. I haven't done any research on this but some of the modern measurings seem way off for power tubes!

judasbane I will look into that when I have more time but there area few swaps that can be made. A KT88 will be a straight swap for a KT90 it is just a 'newer' or military version of the tube. With a quick glance at a data sheet it seems like it may be a straight swap between a KT88-KT66. DON'T try it though I have done no research yet. Also the maximum voltage for the 2 valves is different a KT88 can work in higher voltages. Also if people didn't know the KT88 and 6550 names are used interchangably.

sanchez There are many ways to bias an amp. You will need to know the bias voltage to do it no matter what! (Even though its actually the current that needs to be 'biased' its harder to measure.) I think the easiest way is with a VOM meter or similar. I will post up an in depth 'guide' when I have a bit more free time.
 
#17 ·
i just looked up some info on KT88 (6550) and KT66 (6L6) tubes. They both have the same negative bias, which means they can be changed without modification (according to a few internet sources) they also use an octal base. Although some amps may need to be 'compensated' for the change in output and tone.

6550: Is a tube that Marshall started sing in Marshall Majors, and is a firm favourite with Ritchie Blackmore. But originally it was used as a high grade audio valve. KT88s have a signature bass which is heavy yet tight, and also screaming highs.They are one of the most high output valves on the market. It distorts very slowly (hard to distort) and have that 'hard' valve sound compared to an EL34s soft sound. There are also KT90 and KT99 versions which are even higher output. 6550s are normally associated with heavy metal but especially 'shredders' due to their imense clarity.

6L6: This started out in the guitar amp world in fenders designs such as the Bassman and Tweed. It has a sweet and warm tone with alot of balance. As fenders got 'hot rodded' the valve has taken on a new side. It now appears in many high gain amps. It's distortion is less scooped than an EL34 and less bright than a 6550. Its output is much lower than a 6550 and an EL34 and breaks into distortion evenly. THis is probably the most 'alround' valve because it appeals to not only rock and blues players but jazz players, heavy metal players (and the list goes on).

EL34: I just though I'd do a quick analysis of EL34s in general, I must point out though that a change of bias is required to swap these! They are scooped in tonality and are favoured in Marshalls. THe output is in-between the 6550 and 6L6. They have a character 'soft' sound with a squishy treble. They break up pretty quickly and alot easier than 6550s and possibly quicker than 6L6s (although there is alot of argument). The 'Mullard' sound pretty much characterises the EL34 sound :wink:

Thats just a quick analysis, I will look at models and brands at the weekend or some other time.

This thread has just become stickied!!! :D Lets try and keep it full of information, tips and reviews. Anyone feel free to review a tube you have just bought and liked/dis-liked/broke
:p
 
#18 ·
power freak said:
Mr Orange Mesas (or any amp for that matter) can take pretty much any preamp tube without modification.
Yup. I knew that already. My example was just to point out that if you want your Mesa to sound like with the old "mesa" tubes, you just might have the best luck with Sovteks.

As for the biasing projects, check out the Bias Master. I've seen one in action, and it makes biasing VERY quick and easy. All you need is the gizmo and a screwdriver!

If I remember correctly, 6550s were used in Marshall amps that were imported from UK to US. The EL34s couldn't take the overseas travelling, and were replaced with 6550s in the US. The EL34 is of British design and was not at the time widely available in the States; or something like that.
 
#19 ·
"One tube sounds better than another" statements are BOGUS. First of all one needs to define "better". There are several criteria that make a tube objectively "better":
1. Build quality (mostly affects microphonics)
2. Filament shielding/hum cancellation
3. Vacuum strength - affects tube life

Any decently built tube (say a Sovtek or JJ or Svetlana) does well on all three thus making it nearly impossible to tell which one is better.

There are a couple factors that make tubes different (not better or worse):
1. Gain
2. Transfer curve shape (which in part defines gain, too)
3. Capacitances between electrodes (in real life circuits this is affected by gain, too - see the definition of Miller effect).

These three will affect the tone, but there's NO WAY to tell if any given tube is better or worse unless you try it IN YOUR particular amp. For example tubes with higher interelectrode capacitances may do better in some stages of high gain amps, because these capacitances are used (along with Miller effect and high resistance on anode) to tone down the "sizzle". Yet they can make your amp sound worse if used in other amplification stages. Same thing with gain. Higher gain tubes can be detrimental or beneficial to the tone of your amp depending on the amp (and channel, and stage) in which the tube is used.

Guitar player must also NOT expect any dramatic change from changing from one tube to another. If you're swapping a non-faulty tube for another brand the change in tone will most likely be purely psychological. Your ear fatigue affects your perception of guitar tone a lot more than even $80 NOS Telefunken tube.

Do not rely on rhetoric of tube sellers, remember, they're SELLERS, their only goal is to get you to buy more tubes to "try them out".

:lol:
 
#21 ·
microdmitry said:
"One tube sounds better than another" statements are BOGUS. First of all one needs to define "better". There are several criteria that make a tube objectively "better":
If I didn't make it clear in some cases I meant some people find Brand A better that Brand B because............. (statemenst about filament noise, frequwncy response, output and gain here!)

I have just looked at a few sites. I will try and finfd the scope readings for some tubes and explain them!! :twisted:
 
#24 ·
microdmitry said:
Guitar player must also NOT expect any dramatic change from changing from one tube to another. If you're swapping a non-faulty tube for another brand the change in tone will most likely be purely psychological. Your ear fatigue affects your perception of guitar tone a lot more than even $80 NOS Telefunken tube.

Do not rely on rhetoric of tube sellers, remember, they're SELLERS, their only goal is to get you to buy more tubes to "try them out".

:lol:
Well, I thought preamp tubes didn't make that much difference until I had a chance to do some swapping between chinese, Sovtek EHX and JJ 12AX7s in my own amp. I noticed differences when it came to character, noise and gain. It didn't make the amp become something totally different, it just seemed that different brands emphasized different aspects of the sound. I was quite suprised that the changes were so obvious, I wouldn't give credit of them to ear fatigue, paranoia or some weird psycho-acoustical phenomenon.

But it's true that you cannot save a lousy sounding amp by buying expensive tubes. If it's good, it'll sound good.
 
#25 ·
And the thing is, there's no way to tell that, say, Sovtek will be better for all amps for all players. There's even no way to tell if you will like the tube you like today tomorrow. Have you ever had this experience when you totally love your amp one day and hate it the next day? You play the same guitar, through the same cabinet using the same settings and the same cable, yet one day your amp sounds smooth and the other it seems that somebody is sanding your brain with coarse sandpaper. I've even measured the voltage in these two situations - the voltage was the same both in the outlet and on the tubes.

The only difference is that one day I was relaxed and the other day I was tired. :lol:
 
#26 ·
Yes! Indeed!

And the problem of induction! If all A are B, and C is A, then C is B; but how do we know that C is B tomorrow? What if the current paradigm changes while we're asleep?

My intention isn't to get personal by any means, but all these arguments are getting to a territory where we're sort of walking the fine line between relativism and nonsense, to use a vai-ish expression.

I don't deny the existence of psychoacoustics but hey, come on... That fact that our mindset(or mood or headspace or whatever term you wish to use) affects every damn thing we do will not survive as an argument for making everything subjective and relative. You might love your wife today, but hey, you might hate her tomorrow so go ahead and screw your neighbour's wife. You might be better off with her... Or maybe she'd just be different, not better or worse. :lol: But in a way, it is very subjective. There are millions of valid guitar tones.

I'd say, try out stuff. Stick with what you like. See what floats your boat. Goes for preamp and power amp tubes, dogs, gorillas, amps, guitars, chicks and _________________(fill in the blanks, folks). Unless you are a very religious person and believe that God will eventually direct you to the things that are the best for you. :lol:
 
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