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Mesa Boogie Bass 400 (not +) tube rec.

C

crapshack

Dec 17, 2008
34
0
47
Portland, Oregon
#1
Howdy peoples.

Picked up an old Mesa Boogie Bass 400. Sounds great.

But im thinking of changing the preamp tubes and wondering if any of you have a some sort of magic combination of mixing and matching that you find to be gold.... or if I should stick to a one manufacturer thing only?

It's now running stock 6550's for power and what looks to be standard issue stock 12ax7 mesa tubes for pre as well.


Serial # B241 if you wonder.


Side note* - if anyone has a manual for the 400 not the 400+ and could shoot me a link or email that would be much appreciated.


thanks for your time!

jrdn
 
#3
The Bass 400 will sound better with NOS or similar tubes due to being originally voiced for them. The 400+ was voiced around cheap Chinese tubes available at the time, and therefore sounds better with them.

So basically, get NOS tubes if you can. I've owned both the 400 and 400+, and I did a lot of experimentation with pre tubes. RCA's and GE's work great for the gain stages, and I used an EH Gold 12AU7 for the driver. However, my old tubes were used, and ended up dying fairly quickly, so I had to go back to Mesa tubes.
 
#4
I've been using JJ/Tesla 12AX7 and 6550's, no magical mixes, just straight.

I actually do have a copy of the 400 owners manual. My scanner is on the fritz, but I can fax it tomorrow from work you have a number somewhere.

#B559 here.
 
#6
Try the reissue:
Genelex KT 88 's ' instead of 6550's. More bottom & top end.
& Tungsol gold tip 12ax 7s.

NOS CIFTE 12AU 7 in driver stage. I bought a pricey one. NOS stock. not cheap! :hmm:

Thats what I have in mine.

Found some old telefunken 12AX 7's too- so I 'm experimenting with them too.
So far the one in 3rd socket ( from the left socket being #1 --- to right most #4 )---
if you looking at the amp face plate) has made
the most difference. along with the Tungsol 12Ax 7's.

I really notice the difference when I plug my F bass 6' r fretless thru it!
 
#7
after looking at the schematic, i see that the driver is v3 and the buffer is v4. when i'm looking at the top of the head, which tube is it? i have two of 'em, and i'm dying to try out something new.

both of mine are running 6 x JJ 6L6s, and 4 x JJ 12ax7s. at times, it's a bit too much on the crunchy, heavily overdriven side for me. with some careful tweaking, though, they break up really nicely, just when i'm getting heavy.

thank you.

jz
 
#9
Correct, the preamp tube everyone was experimenting with is the one furthest away from the input jacks.

Earlier this year I had two Bass 400's, one was loaded with 6550's and the other with 6L6's. It was a pretty obvious difference volume wise, and the 6550's sounded a bit 'bigger' and of course stayed much cleaner.
Right now I'm down to my mainstay 400 with the 6550's.

(when I say 6550's, I actually mean JJ KT88's)
 
#10
K-Funk said:
The Bass 400 will sound better with NOS or similar tubes due to being originally voiced for them. The 400+ was voiced around cheap Chinese tubes available at the time, and therefore sounds better with them.

So basically, get NOS tubes if you can. I've owned both the 400 and 400+, and I did a lot of experimentation with pre tubes. RCA's and GE's work great for the gain stages, and I used an EH Gold 12AU7 for the driver. However, my old tubes were used, and ended up dying fairly quickly, so I had to go back to Mesa tubes.
Click to expand...

That's interesting. Did Mesa first start using Chinese preamp tubes in 1989 when the 400+ came out?
I'm in no way disputing the results you got rolling your 400/400+ preamp tubes, but have you been able to find any confirmation that Mesa did indeed make changes and "re-voice" the origanal 400 preamp section for the 400+?

I always thought the 400/400+ shared the same preamp sections but I'd be very interested in learning exactly what changes they made to re-voice the 400+ for Chinese tubes. (I was thinking it might be a cool to have my 400+ modded back to the origanal 400 design)
 
#11
I'm just going by what Psycho told me, and what I read in his posts. And I'm pretty sure it was a theory of his, and not solid fact. Regardless, both he and I got similar results between the two different amps; with the newer Chinese tubes sounding better in the 400+ (i.e. losing their "icepick" top end and smoothing out a bit) and the vintage tubes sounding good in the 400.
 
#13
Been a while! Have been wondering about the drastic volume diff. between channel 1 and 2. It's about 50% overall volume when driving same settings through the first compared to second. I know that there is some sort of gain reduction or something for active\passive basses, but the more I mess with it the more I wonder if something isn't quite right? I live in Portland Oregon and Eurotubes is 20minutes from my house - has brand new matched kt88's and all new pre tubes. Older Tobias standard active 4 string bass is my main plucker.

What I really want is a Aguilar GS412 to pound on - but finding one for a decent price in my neck of the woods is like pulling teeth. Who's got one gathering dust?

Anyone ever find the schematic for the orig. 400 and not the plus.

PS: if you put 6l6's in this head you really aren't getting what you could!
 
#14
I used to have a faxed version of the owner's manual (wish that I had a pdf). Channel one is a lot different (quieter) than channel 2. I have two of these amps, and this sounds like normal behavior (and a lot cheaper than a re-tube). The manual says something to the effect of "pick whichever one you like". On my passive basses, I use channel two for more grind. On my Robin with a loud preamp, it works a lot better with channel one, because it drives the amp's preamp pretty hard.

Hope that helps.
 
#16
I've never done an a/b with a plus and a non-plus. I've actually been thinking that I need to get rid of one of my mesas. I love 'em to death, and they've essentially served me well for about 5 years, but both of my bands aren't loud enough to merit 200 watts of anything. I know that I'd love to play a plus, but I really don't require that sort of power.
 

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