MESA Boogie 400 preamp ?'s

TaylorO' · #1 03-23-2010, 01:37 PM

the preamp is driven by 4 12AX7's... they are all in a line.. which one do i switch to a 12AU7 to get some headroom?

anyone?

thanks in advance...

t.

RCCollins · #2 03-23-2010, 01:56 PM

you're using a 400 and you don't have enough headroom? jiminy crickets!

TaylorO' · #3 03-23-2010, 02:03 PM

i want more than enough.. haha.. i just got the amp so im trying to make sure i get everything out of it possible. ive been using the y cord and it has a great sound. still learning the EQ and stuff, and i was curious if anyone knows much about the KT88 swap...

lem8r · #4 03-23-2010, 02:07 PM

Try 2nd tube (preamp section), or 3rd (phase inverter).
I think it's 3rd too hot.

TaylorO' · #5 03-23-2010, 02:10 PM

Quote:

Originally Posted by lem8r

Try 2nd tube (preamp section), or 3rd (phase inverter).
I think it's 3rd too hot.

are you saying 2nd and 3rd looking from the back of the amp, or looking from the front?

Grooveman1961 · #6 03-23-2010, 02:13 PM

this pdf should clarify for you

lem8r · #7 03-23-2010, 02:13 PM

If You use Y-cord just roll of some gain on both channels, may be that's why there is lack of headroom)?

TaylorO' · #8 03-23-2010, 02:25 PM

Quote:

Originally Posted by Grooveman1961

this pdf should clarify for you

Ok. i have the 400, not the 400+... i assume that would be the same though...?

yeah maybe the y cord is causing the over distortion.. if the volumes arent up then im not loud enough..

DaZombieWoof · #9 03-23-2010, 02:31 PM

Maybe 400 is different. With 400 plus I could get death looks from the guitarist with regards to volume. Most fun was running an SVT box to just below destruction volume and running a wireless because 20 feet was too close for comfort.

Krügmeister · #10 03-23-2010, 02:36 PM

I read that the actual tube to switch was the 2nd from left when facing the front of the amp? can we clarify this?

Hollywars · #11 03-23-2010, 02:36 PM

400+ has a lot more power I think. It has like 500 watts at 2, 4, and 8 ohms.

Just kidding, 12 times 25 is not 500. Caca is right.

Caca de Kick · #12 03-23-2010, 02:42 PM

Quote:

Originally Posted by DaZombieWoof

Maybe 400 is different. With 400 plus I could get death looks from the guitarist with regards to volume.

No, volume wise it isn't any differen't. I've enjoyed sending guitarists crying home to mama with my 400. Same with SVT owners.

Caca de Kick · #13 03-23-2010, 02:44 PM

Quote:

Originally Posted by Hollywars

400+ has a lot more power I think. It has like 500 watts at 2, 4, and 8 ohms.

False. It does not make 500w. 12 6L6 tubes can only top out at 300w if biased hot.

Caca de Kick · #14 03-23-2010, 02:46 PM

Quote:

Originally Posted by TaylorO'

the preamp is driven by 4 12AX7's... they are all in a line.. which one do i switch to a 12AU7 to get some headroom?

anyone?

It's the preamp tube furthest away from the input jacks.

TaylorO' · #15 03-23-2010, 02:49 PM

Quote:

Originally Posted by Caca de Kick

It's the preamp tube furthest away from the input jacks.

ok cool. do you think this is a dumb idea?

i read somewhere you were in a punk band, which one? i play for Rabid Reaction, from Cleveland..

lem8r · #16 03-23-2010, 02:51 PM

Quote:

Originally Posted by Krügmeister

I read that the actual tube to switch was the 2nd from left when facing the front of the amp? can we clarify this?

yup!

Or 3rd from the left when facing the back of the amp

Grooveman1961 · #17 03-23-2010, 02:59 PM

Quote:

Originally Posted by TaylorO'

Ok. i have the 400, not the 400+... i assume that would be the same though...?

yeah maybe the y cord is causing the over distortion.. if the volumes arent up then im not loud enough..

yup

same same. put a 12au7 in that position, and you'll be a happy camper. It's a popular mod around here.

TaylorO' · #18 03-23-2010, 03:02 PM

Quote:

Originally Posted by Grooveman1961

yup

same same. put a 12au7 in that position, and you'll be a happy camper. It's a popular mod around here.

ok cool. the ideas of where it goes seems a little "conflicting" on here....

Grooveman1961 · #19 03-23-2010, 03:03 PM

Quote:

Originally Posted by Hollywars

400+ has a lot more power I think. It has like 500 watts at 2, 4, and 8 ohms.

500 peak watts, more like 250 rms. thats what mine did.

despite what people say, these things are not massively loud.

Calaverasgrande · #20 03-23-2010, 03:12 PM

Most folks talk about swapping out the last tube in the preamp/first before power section. Going to a 5751 will give lower gain but more current, so more headroom/bass.
Thats the one farthest from the input jacks. The one closest to the input jack is where you get your most gain/tone. So put your fancy telefunken/mullard/RCA there.

The 400 does about 150-180 watts on 6L6's maybe 200-230 with 6550 or KT88.
The 400+ is 500 watts PEAK. Its really more like 300-350 watts. Either amp could put out more watts if they had more volts on the tubes or bigger output transformers. Mesa runs tubes kinda cold. Thats the mesa sound, get your distortion in the preamp and run the power amp cold, with headroom.