Author Topic: Re-Tubing a Mesa 400+ (Read 598 times)

wcv · « **on:** April 30, 2004, 11:30:48 AM »

I am getting ready to re-tube my 400+. It came from MesaBoogie with 12AX7 & 6L6 tubes. The manual says use 12AX7 & 5881 tubes. I have visited many websites regarding tube characteristics, but they are all from a guitar point of view. Does anyone have recommendations for tubes for the 400+ from a bass players perspective?

alembic76407 · « **Reply #1 on:** April 30, 2004, 02:22:59 PM »

when I get home I will check my 400+ and see what Boogie sent me and let you know.

David T

son_of_magni · « **Reply #2 on:** April 30, 2004, 03:12:31 PM »

My understanding is that the 5881 is the industrial version of the 6L6. They should be better balanced, lower noise, and possibly more power. But they will most likely be harder to find and cost 30-50% more.

dnburgess · « **Reply #3 on:** April 30, 2004, 03:40:10 PM »

The reference manuals confirm magnis understanding. e.g.: http://www.mclink.it/com/audiomatica/tubes/6l6.htm

Also there are reviews of different tube types at: http://thetubestore.com/6l65881types.html

The JAN-Phillips models seem to get the best overall review:

Price considered, it's the best available NOS of this type; it's all there. Champagne tone with a beer price.

American made with the vintage sound! I switched between the other brands and even had someone else do the switching and re-biasing while I closed my eyes to keep the test blind yet my ears could always hear that little bit extra that told me it was the Phillips tubes driving the speakers. Even when biased rather cold the tone still came through. It's a subtle difference that you may not immediately appreciate but the more you play the more you smile. Treat yourself!

I should have realised that tube type could make a big difference. When I had my old Bassman retubed a couple of years ago I didn't think of researching the space and got whatever the repair man thought fit to put in. I'll have to dig it out and have a look.

alembic76407 · « **Reply #4 on:** April 30, 2004, 05:03:39 PM »

Mesa/Boogie sent me 12 Mesa/Boogie STR 425 tubes, they told me they will run better and last longer(and they have)and that was from Mr Boogie himself, and as far as preamp tubes I just replaced mine with what was in there, 12AX7 I guess, it's been awhile.
by the way, Welcome to the club!!!

David T

gbarchus · « **Reply #5 on:** April 30, 2004, 09:10:36 PM »

Be sure and check out Svetlanas. I think they have (RCA) NOS characteristics. I use a Mesa/Boogie 180 power amp with an F2B.

goatfoot · « **Reply #6 on:** May 04, 2004, 05:32:18 AM »

Hey guys,

How heavy is your 400+? And what cabs are you playing it through? How's the sound?

Found the perfect bass (Alembic, 'course) ... Still in search for the perfect rig.

Kevin

alembic76407 · « **Reply #7 on:** May 04, 2004, 05:47:10 AM »

Kevin, the 400+ is about 35lb and I play through 2x15s and 2x10s
(But there's allways Tornadic Thunder)for the speical gigs

David T (TLO)

wcv · « **Reply #8 on:** May 04, 2004, 09:41:29 AM »

First, thank you to all who responsed to my question regarding tubes for the 400+.

As far as my set-up, I play through one SWR 2x10 and one SWR Triad (1x15,1x10,1xTweeter). I have these 4 ohm cabinets wired in series to run at an 8 ohm load.

I was originally using a SWR Basic 350 (tube pre-amp & solid state power section)and found the Mesa
400+ (all tube with 12 power tubes)to have more headroom, punch, dynamic response as well as a more pleasing tone.

David Houck · « **Reply #9 on:** May 04, 2004, 02:06:53 PM »

Bill; just out of curiosity, why are you running your 4 ohm cabs in series? I see that the manual for the 400+ suggests that if you have two 4 ohm cabs you should connect them to the two 2 ohm outputs. I'm guessing you feel the 8 ohm load is safer. My initial thought was that running the cabs in series from one 8 ohm output would be less efficient.

wcv · « **Reply #10 on:** May 04, 2004, 03:20:54 PM »

Dave you are right, even though the manual said that I can run a 2 ohm load, I (and others I consulted) felt an 8 ohm load was safer. I did find out quickly, that you need to make sure the speakers are in phase. I am curious about your thoughts regarding the effeciency, can you elaborate?

I also have a third cabinet which is an 8 ohm cabinet that I was told I could combine with my existing set-up and run a 4 ohm load. Do you have any input regarding ohm loads and the quantity of drivers?
For instance, in this scenario, Cabinet One:1x15,1x10@4ohm and Cabinet Two:2x10@4ohm in series are connected to Cabinet Three:2x10@8ohm parallel (or the two 4ohm outputs at the amp) for a total 4ohm load, is there any kind of imbalance (sound or electrical) between the cabinets because of the differing quantities and sizes of speakers in the cabinets?

Thanks,
Bill

David Houck · « **Reply #11 on:** May 04, 2004, 04:39:28 PM »

Bill; the scenario you describe with the three cabs is beyond my limited ability to think. No matter how often I read up on this type thing, I just can't seem to retain the information. One question that immediately comes to mind is how this arrangement effects the power handling ability of each of the three cabs.

As to my comment about the efficiency; the specs of most power amps show that they output more power into a 4 ohm load than an 8 ohm load, and more into a 2 ohm load than a 4 ohm load. However, the manual for the 400+ says the amp will produce its full power at all of these impedances [8, 4, 2], provided that the total impedance of your speaker cabinets is matched to the output(s) used. So perhaps it doesn't make a difference with the 400+.

Again, this is beyond my technical expertise (or lack thereof). If Bob happens by this thread he's pretty good at this kind of stuff; as are a few others in the group.

hollis · « **Reply #12 on:** May 04, 2004, 05:41:00 PM »

Hi,

It seems to me that if you run all three cabinets in parallel you end up with an 8 ohm load......

go to: http://www.mikelights.com/speaker1.html

I think what he's saying is (R1XR2XR3)/(R1+R2+R3)

It looks like an 8ohm load to me........

hollis · « **Reply #13 on:** May 04, 2004, 05:44:49 PM »

By the way, thanks for the heads up about the tube store, I ordered a whole mess a tubes from them yesterday, and they're on there way today...very cool place.

wcv · « **Reply #14 on:** May 04, 2004, 07:52:41 PM »

Hollis and Dave,

Thanks for the input, this stuff is difficult for me also. And it looks like in this case I made it more complicated than it had to be. But now that I've seen the formula, I agree with Hollis, it looks like an 8 ohm load wired parallel.

Thank you to the Alembic Club, it's a great resource. I hope I be able to return the favor by helping someone in the future.

Bill