Lets talk tubes for a second

OUTLANDAH · April 05, 2012, 04:00:32 PM

So I know the difference when it comes to power tubes, but what about preamp tubes? And mixing different tubes. Such as on Dunwich's metropolitan I noticed for each preamp slot there is a different type of tube.

dunwichamps · April 05, 2012, 04:21:33 PM

Quote from: OUTLANDAH on April 05, 2012, 04:00:32 PM
So I know the difference when it comes to power tubes, but what about preamp tubes? And mixing different tubes. Such as on Dunwich's metropolitan I noticed for each preamp slot there is a different type of tube.

Well lots to talk here

Tubes in the 12aXX family (including 5751 and ECC832) have varying gain levels (12axy has mu of 100, 12au7 has mu of 17) as well a varying power dissipation, plate impedance, biasing, and grid current susceptibility (with 12at7 being a notable tube which is quite prone to this)

Just subbing in say a 12au7 or 12at7 into a stage designed for a 12ax7 will work technically but may or may not be optimized for that particular tubes bias point and voltages. However, that does not mean u will dislike the sound.

12at7 and 12au7 have much lower plate impedance compared to a 12axy and often they can darken an amp beyond just lowering the gain level. You may or may not like this. The metro 12au7 channel is dark and bassy and handles pedals way different than the 12ax7 channel even tho they both dont have much different levels of clipping

Beyond the 12ax7 compatible stuff there are small signal pentodes (EF86) and the 6nxP russian series of tubes which cannot be dropped in for a 12ax7 stage

Mr. Foxen · April 05, 2012, 05:39:00 PM

Gotta remember tubes are one component in a whole circuit, how they sound different to each other between brands depends on what the circuit is doing with them. So anyone who says 'JJ sound more something than Svetlanas' is basically not a useful person to listen to unless they are talking about the same or similar amp to you are. Is one of my pet hates right now, because I've just been pointing this out on loads of threads.

dunwichamps · April 05, 2012, 05:46:34 PM

Quote from: Mr. Foxen on April 05, 2012, 05:39:00 PM
Gotta remember tubes are one component in a whole circuit, how they sound different to each other between brands depends on what the circuit is doing with them. So anyone who says 'JJ sound more something than Svetlanas' is basically not a useful person to listen to unless they are talking about the same or similar amp to you are. Is one of my pet hates right now, because I've just been pointing this out on loads of threads.

i try to avoid brand talk because usually people are only sampling a super small quantity and that chances that you have a decent representation of a brand tube is small so judgments based on such a small sample are hardly applicable for the entire brand.

Fuhgawz · April 05, 2012, 05:55:51 PM

So, what's your take on using NOS/UOS 12AX7's? Some people pay insane amounts of cash for old tubes claiming that ALL modern tubes pale in comparison.

Mr. Foxen · April 05, 2012, 06:05:02 PM

Quote from: Fuhgawz on April 05, 2012, 05:55:51 PM
So, what's your take on using NOS/UOS 12AX7's? Some people pay insane amounts of cash for old tubes claiming that ALL modern tubes pale in comparison.

Not worth the money if you are playing music rather that using an inch and a half of glass to measure your dick against. Actually, most of my amps are loaded with old pre valves, because I have them. If an old valve still tests good, probably have a better chance of being good for a while than a new from the box one. As for sound difference, see above. The amp is the bigger deal to tone.

RAGER · April 05, 2012, 06:09:47 PM

Half the time when people pose this question, they don't post the amp in question. If you're asking generally, you'll get a general answer.

To the original poster; Ask specific questions about a specific amp. Research that amp and find out what tubes do what in what position. Do you know what V1 means? If not find out. Find out what type of circuit it is. Experiment on that one amp only then your ears will hear the differences of the tubes in reference to one platform. Go from there.

OUTLANDAH · April 07, 2012, 03:26:47 PM

I'm just playing out of a Sovtek mig 100. Ruby 6l6's and 12ax... something. Can't remember. Either way, when I first received the amp it had two Sovtek 6l6Gb and two Sovtek 6L6WXT+. Either Way I'm a newby when it comes to tubes. I just know I need 6l6 when I re-tube ad have not a clue on what the variations on 6l6 do.

dunwichamps · April 07, 2012, 05:31:30 PM

try not to concentrate on the variations IMO, any of the modern production 6l6s are 6l6s.

neighbor664 · April 07, 2012, 05:41:38 PM

Tubes?

Hemisaurus · April 07, 2012, 08:09:29 PM

Quote from: dunwichamps on April 07, 2012, 05:31:30 PM
try not to concentrate on the variations IMO, any of the modern production 6l6s are 6l6s.

Yeah and no, it's like carburetors, they all do the same basic function, you can group them by airflow, but, different brands are made different ways, and have different responses. Basically they all make you car go, but they all can make your car go differently, and what's a good carb for a circle racer, isn't the same as what's a good carb for a mudbogger.

It's a lot easier to quantify the other parts of an amp though, so if you're looking to alter you tone in a specific way, it makes a lot more sense to have the cicuit mod'd than start faffing about with tubes.