I have joined the Dark Side (well not really)

[Psycho Bass Guy]

AdmiralB,
..whatever. It's clear that you won't let it go, and that you'll go to any length to avoid it. I stand by what I've said, and unless you go back and edit your posts, your words are there for anyone else to read, so you can accuse them of putting those words in your mouth, too.

BTW, you ever think that maybe I didn't already try subbing V3 (and V4 at the same time) with a 12AU7 BEFORE posting this thread, did you?

 

[AdmiralB]

AdmiralB,
..whatever.

Whatever indeed. If that's how you answer specific, yes-or-no questions...I guess that's the end of that.

 

[K-Funk]

ok gentlemen, lets see if I (as a bassist that knows only the fundamentals of amp and tube function) can draw a FUNCTIONAL conclusion from the argument:

If I swap out V4 (the one behind the power and standby switches) with a good 12AU7, I'll lower the gain and increase my clean headroom. (I already did this, so it's proven true)

If I swap out both V4 and V3, the same will happen, but to a greater degree? (have not yet tested this)

And finally, if I replace ONLY V3 with a 12AU7, I will lower headroom and increase noise? (also haven't tested)

Just thought this scuff would be a good place to try and improve my 400+. Like I said, I already put a 12AU7 in V4 (which is the driver tube, right?), and whatever that socket/tube does (as I'm very uneducated as to amp function), it made my amp cleaner at higher volume levels.

Let's try to solve this debate and reduce the lowblows by explaining to me, an amp layman with a 400+ he needs to sound excellent, what to do to better the sound and functionality of my amplifier.

Gracias!

 

[Psycho Bass Guy]

ok gentlemen, lets see if I (as a bassist that knows only the fundamentals of amp and tube function) can draw a FUNCTIONAL conclusion from the argument:

If I swap out V4 (the one behind the power and standby switches) with a good 12AU7, I'll lower the gain and increase my clean headroom. (I already did this, so it's proven true)

The increased current headroom of the 12AU7 is more important here than the lower gain factor.

If I swap out both V4 and V3, the same will happen, but to a greater degree? (have not yet tested this)

No. Without the higher gain 12AX7 to drive V4 your amp will be significantly quieter but will not have any increase in headroom. Rather than more usable volume, the amp will distort sooner from more preamp gain (you'll have to crank the pre-gain to compensate) and you will have LESS headroom.

And finally, if I replace ONLY V3 with a 12AU7, I will lower headroom and increase noise? (also haven't tested)

Yep, and it may hum as well; at least mine did.

Like I said, I already put a 12AU7 in V4 (which is the driver tube, right?),

I say it is, but our new expert says otherwise.

 

[Chef]

With my 400+, I tried both 12au7, and 12at7 in the preamp slots.
For me, all it did was lower the gain stage; forcing you to turn it waaaay up...at which point it started behaving much as it did with the 12ax7's in it anyway.

Psycho's swap just flat works, for me, and I don't care why

 

[K-Funk]

I say it is, but our new expert says otherwise.

I agree with you.... but.. did anyone bother to call Mesa? and actually ask the people that made/manufacture the amp? If not, I'll call first thing Monday morning.

 

[Chef]

Good luck with that...
It's been my experience that the Mesa CS folks are friendly, and willing to try to be helpful, but are not so tech savvy.
(neither am, i past a point!)

Despite my owners manual saying that my 400 came with 6550's in it, they refused to acknowledge that.
Nor would they say that it was ok to run 6L6's in it.

So, my 400 isn't supposed to be running power tubes...

 

[quickervicar]

I agree with you.... but.. did anyone bother to call Mesa? and actually ask the people that made/manufacture the amp? If not, I'll call first thing Monday morning.

They're in the middle of the last production run for these things anyway. I doubt they'll be keen to change specs right now.

 

[K-Funk]

does anyone know the day and/or month they're terminating the 400+?

 

[Fealach]

FWIW, Psycho's comments on the 400PS led me to try it with Bag End 2X12 ELF cabs, and ended a long hunt for a great performing, portable solution for using all 3 outputs of said beast.

 

[TeenZombie01]

i saw on the mesa site that the power tubes for the 400+ are supposed to 6L6. i looked up some tungsol 6L6 GC STR power tubes on musician's friend and they have several different types; soft duet, soft quartet, medium duet, medium quartet, hard duet, and hard quartet. what is the difference in those types and which should i put into my 400+?

 

[greenboy]

FWIW, Psycho's comments on the 400PS led me to try it with Bag End 2X12 ELF cabs

Using that ELF cab as a conventional sealed cab, I take it, not as a ELF/INFRA processed sub.

 

[fremenblue]

i saw on the mesa site that the power tubes for the 400+ are supposed to 6L6. i looked up some tungsol 6L6 GC STR power tubes on musician's friend and they have several different types; soft duet, soft quartet, medium duet, medium quartet, hard duet, and hard quartet. what is the difference in those types and which should i put into my 400+?

quartet=4 tube pack
duet=2 tube pack

Soft, medium, hard=dunno. Boogie wants you to use their tubes because they're biased for their amp. I've always thought of bias more in terms of hot/warm/cold than soft/medium/hard, but that has to refer to biasing, I would think.

 

[Psycho Bass Guy]

i saw on the mesa site that the power tubes for the 400+ are supposed to 6L6. i looked up some tungsol 6L6 GC STR power tubes on musician's friend and they have several different types; soft duet, soft quartet, medium duet, medium quartet, hard duet, and hard quartet. what is the difference in those types and which should i put into my 400+?

Those grades are what is technically known as "BS." Mesa uses them to specify different bias current amounts; it's a ludicrous idea, and is meant to sell more tubes because a natural part of tube aging is a shift in bias current needed. Mesa has a "rating system" which is supposed to allow replacement of power tubes by rating, so a rebias isn't required. It's not true, but Mesa says it, so people believe it.

The range they provide to "grade" bias current draw versus plate current only ensures that the tubes won't blow the fuse from overcurrent when they're newly installed. There are a couple of online tube dealers, Lord Valve at NBS Electronics and Bob Pletka at Eurotubes who can match tubes to Mesa's rating scheme, but it's no substitute for a good tech bias job.

 

[TeenZombie01]

Those grades are what is technically known as "BS." Mesa uses them to specify different bias current amounts; it's a ludicrous idea, and is meant to sell more tubes because a natural part of tube aging is a shift in bias current needed. Mesa has a "rating system" which is supposed to allow replacement of power tubes by rating, so a rebias isn't required. It's not true, but Mesa says it, so people believe it.

The range they provide to "grade" bias current draw versus plate current only ensures that the tubes won't blow the fuse from overcurrent when they're newly installed. There are a couple of online tube dealers, Lord Valve at NBS Electronics and Bob Pletka at Eurotubes who can match tubes to Mesa's rating scheme, but it's no substitute for a good tech bias job.

i'm sorry but i couldn't understand most of what you said. so should i not order those tubes and put them into my amp?

 

[Psycho Bass Guy]

i'm sorry but i couldn't understand most of what you said. so should i not order those tubes and put them into my amp?

The main thing I'm trying to say is that ONLY a tech should change your output tubes. They have to be calibrated (biased) to run properly in the amp, and the 'grades' of "hard" "medium" and "soft" are not reliable ways of avoiding that. No, you should NOT just order those tubes.

 

[AdmiralB]

No, you should NOT just order those tubes.

I don't see what harm it would do...since there are thousands of Mesa amps out there running exactly that way.

Mesa's grading system isn't current-based, it's a copy (and a refinement) of the Groove Tubes system - the same guy built them. They measure primarily headroom, that is they set the tubes up at a 'standard' operating point and start applying AC input signal. They measure the input voltage when the tube starts to distort, and group and rate accordingly. Plate current is a secondary concern for them, but my experience with Mesa tubes is that the matching is pretty good and also not variable with grade - that is, a set of "yellow" tubes, say, doesn't draw significantly different current than a set of "blue".

If you want more info about their matching, email Roy Blankenship - http://www.blankenshipamps.com/ - he was production manager for Groove Tubes for a long time.

Mesa biases their amps pretty cold, by "Respected Internet Amp Tech" standards, so the chances of ill effects from an outlier are pretty slim.

The current Mesa 6L6 (STR 440, I think they call it) is the same Chinese tube that Ruby sells as the 6L6MSTR. It's $42 a pair from Mesa; yes, you can get tubes a little cheaper from some of the other vendors, and as mentioned earlier there are some that will provide sets with similar current properties as the Mesas, but I doubt that over a matched...whatever you call a set of 12...you will save much.

The idea that you have to precisely bias an amp to some exacting specification is a little pedantic, IMO. You should verify that everything's inside a safe envelope, but that envelope is pretty large, and Mesa tubes, for any other faults, are pretty much guaranteed to get you there.

Further, since *most* bass players do not drive their tube amps into full-on power amp saturation, the tonal effects of differing bias conditions will pretty much be nonexistent, too.

So...my opinion is, the Mesa tubes will work just fine. The only thing you really lose is the ability to easily try different brands.

 

[hired hand]

The main thing I'm trying to say is that ONLY a tech should change your output tubes. They have to be calibrated (biased) to run properly in the amp, and the 'grades' of "hard" "medium" and "soft" are not reliable ways of avoiding that. No, you should NOT just order those tubes.

Hello Psycho -
Are you and I the only ones that understand what you are talking about?????
If I may try it one more time.. Tubes do not set, nor do they have anything to do with the bias of your amp. The bias for each, individual amp is set by your tech (or yourself if so inclined) usually with the aid of a trim pot that is part of the amp, or by changing resistors in the bias circuit. Your amp could be set to 0 MA on the meter and draw no current what so ever. Set to 100 and melt the tubes down as soon as you flip the on switch. Power tubes are designed to run within certain parameters. Your tech can play around within the high and low side of the specs to help determine where you think it sounds best.
Tube color codes, or a "grading system" of hard, medium, or soft is meaningless marketing language. I think Psycho Bass already mentioned this. Tubes (like everything in life) have a tolerance. So the tube companies "match" them, usually based on the milliamp amps that they draw. Some draw a bit more than others. So the tube companies will match them (again within a tolerance) so that they work closely together as a team. You can call the teams Red, Orange, and Yellow, or even Hard, Medium, and Soft. If you feel comfortable with that, then fine. Buy those tubes. install them in your amp and don't look back.
I prefer to get out the meter and check to make sure. What if a Yellow got mislabeled as Red. Or maybe a Soft got tossed in with a Hard. How do you know for sure? Also, the bias setting of your amp can drift. Not sure, but I think Psycho Bass Guy might have already mentioned this. It may need to be adjusted again. How do you know, if you do not check?
My fingers hurt, and I am out of things to say. I am not a tech, this has all been a generalization, and of course last but not least, is JMO.

 

[Fealach]

Using that ELF cab as a conventional sealed cab, I take it, not as a ELF/INFRA processed sub.

Yup.

 

[Psycho Bass Guy]

AdmiralB,
Since it seems you plan on making a habit out of arguing with most of what I say, I'll be sure and explain more than usual, so you'll have less 'ammunition' for your words games.

I don't see what harm it would do...since there are thousands of Mesa amps out there running exactly that way.

Suppose, like several Bass 400 and 400+ owners here, you discover those "settings" that Mesa specifies for tube bias are wrong. Or go even further, and compare the output power and symmetry on an oscilliscope between the supposed 'graded' tubes and a set that has actually been biased in the amp and see just how accurate their specs are.

Mesa's grading system isn't current-based, it's a copy (and a refinement) of the Groove Tubes system - the same guy built them.

...and they're BOTH BS. Both are measures of output current from bias voltage through a fixed resistor supplying a fixed voltage drop. They ARE current based.

They measure primarily headroom, that is they set the tubes up at a 'standard' operating point and start applying AC input signal.

Headroom implies a variable gain stage. By it's very nature, the rating system is invariable, so a more accurate description would be emission limitation.

They measure the input voltage when the tube starts to distort, and group and rate accordingly

...and you conveniently left out that the amount of input voltage needed to drive a tube to full output VARIES with its bias (and plate and screen voltage, and load... )

Mesa biases their amps pretty cold, by "Respected Internet Amp Tech" standards, so the chances of ill effects from an outlier are pretty slim.

...yet there have been several stories of people here and elsewhere having bias related problems with Mesa tube bass amps BECAUSE the specs are wrong. And maybe, just maybe, some people would like their amp to actually put out power near its rating somewhat cleanly.

The idea that you have to precisely bias an amp to some exacting specification is a little pedantic, IMO.

Really, and why is that? Do you work for Mesa or GT? I guess you think it's better to just trash a perfectly good set of tubes because their bias current needs have changed rather than rebias them for proper operation, too. How often do you recommend that bass players change their power tubes?

Further, since *most* bass players do not drive their tube amps into full-on power amp saturation, the tonal effects of differing bias conditions will pretty much be nonexistent, too.

You said elsewhere you were a guitar player, and you just told on yourself here. Bass players who use tube bass amps use them precisely to drive the crap outta them.

So...my opinion is, the Mesa tubes will work just fine.

If you feel so strongly, will you warrant the amp for repairs for any damage incurred by using Mesa's rating system as a sole guide for tube replacement? Chances are, the poster with the question doesn't NEED new tubes anyway!