• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

I have joined the Dark Side (well not really)

#82
The Tungsol 12AU7 that I put in mine is not the currently-made Russian tube. It is an old stock US made 12AU7. Before you spend money on all your preamp tubes, just try replacing the driver (furthest preamp tube to the left when facing the front of the amp). It is the tube type more than the brand that is important for this swap.
 
#83
Vanni said:
Anderbass, I use the DI, and no one told me it sounds bad or distorted... maybe is only the bias correct setting (BTW I don't play very loud... so I don't push hard pre or power amp).
Click to expand...
My 400+ DI has always sounded pretty good when I've ran the pre/master at lower settings too.

I just gave my DI another shot with my full band at a live recording session this past weekend. The amp settings I ended up using on this session once again resulted in an unusable and very distorted signal to the recorder. I tried serveral different (known-good) mic/line preamps (inputs set to both mic and line level) and even tried inputting the recorder directly from my DI again.

My amp still sounds wonderful, but there's definitely a malfunction in mine or (what I truly think) a basic design flaw causing something to overdrive in this amps DI when used at loud volume levels.

My cab tone was fairly clean and very punchy.
My amps knob settings were:
mid-10
bass-6 (this was the only knob I pulled)
treb-0
master-6
I only used input one, and it was on 4-1/2.
(eq was switched off)

Bass was a 98 Fender P-Deluxe with a known good battery and its on-board 3-band EQ was set flat in the middle.

My 400+ DI sounds absolutely amazing at lower volume levels, and Its not that its output is to high (db wise) its just flat distorting. My resent mods helped a bit, but there's still a problem going on somewhere. (the DI ground float switch didn't make any difference)

Got any thoughts on all these (unusable-distorted) 400+ DI reports that've been floating around for years Psycho?
 
#84
My 400+ is fairly recent and still has the original Mesa power tubes but I replaced the preamp 12AX7s with JJs, which made a considerable improvement. I have just ordered a JJ 12AU7 to try for the driver, so will post as soon as it arrives. For me one of the great advantage of tube amps has always been the sheer enjoyment of tweaking them and experimenting like this.
 
#87
Psycho Bass Guy said:
pad down its primary
Click to expand...


If my tech were to install a some sort of user adjustable pad, (pot with a knob?) would you take an educated guess and recommend a likely candidate for the actual pot he might try first?

If an adjustable pad/pot is even a possibility here, I'd like it to still enable unaffected DI operation at one rotation extreme and then probably offer more than enough attenuating in the other direction.

Thanks Psycho.
 
#91
Hi Chef, that is good to hear. I am still waiting for my JJ ECC82/12AU7 to arrive. From your experience it sounds like it will do exactly what I am hoping. I assume that the amp still has the same overall volume but just does not dirty up on the higher input settings as it used to?
 
#92
If there was a drop in overall gain, it was small.
I'm gigging it tonight; gonna take a Lakland Scheff, MM Stingray, and a Schro 410L
(as opposed to the two Mesa 115 Diesel's I usually use with this head; lazy today!)

I'll report back, but for sure, the 400 takes active basses without turning to grit waaaay better, in both channels, than before.

Waaay better.
 
#94
OK, so, I lied;)
Took the Stingray HH4, and a Reverend Brad House 5...so, I had one passive, and one active.
The BH5's stacked JJ pups are really hot tho, and the 'ray ain't so hot, for an active bass.
At any rate, I played them both thru channel 2, the higher gain channel. EQ set flat (mids at 10, treble and bass at 3), with the graphic set to take a little out of 40 hz.
Master on 10, input on 2, horn on the Schro 410L at 50%.
It was massive, and awesome, and *clean*

Thanks to PBG for the tip!
 
#95
PSYCHO BASS GUY IS A GENIUS!!! My JJ12AU7 arrived today and I rushed home at lunchtime to give it a whirl. First impressions in my band room by itself are clean, clean, clean. I swapped between the two tubes as I wanted to see what the gain difference was and there is a slight loss, but it is more than compensated for by the extra amount of headroom so that you can turn the master up much more (not that you need to with this amp). Practical improvements are that I can use the input gains much more freely without worrying about the amp overdriving and my band mates asking if my speaker is distorting, and the sound is so clean with all that headroom that for the first time I might have to be careful not to pop a speaker. Before when I dug in I had to be careful not to have the inputs set too high, now there is no problem. I could imagine perhaps a metaller preferring it the original way but for this old bluesman it's like coming home.
Don't mean to rave on too much, have to get back to the classroom so am a bit rushed. Will do a gig report later. BTW, I ended up using my Goliath 410 and my MesaDiesel RR 215 for the test - I had forgotten just how good the Diesel 215 was with the 400+. For a fifteen it has tremendous midrange.
 
#96
Well, having got over my initial gushing euphoria above I can now give a more objective response after gigging at a medium (250 odd) sized venue last night. Let me say first that I was quite happy with my 400+ originally, but the key thing is that the 12AU7 has made it much more user-friendly. It does not sound like distortion any more when I dig in during those moments of over enthusiasm we all share when eyeballing the young lassie in front, and with the input gain being less sensitive setupseems so much simpler. The overall sound, while still similar to the original, is a little smoother and "creamier"at the bottom end. Not sure, but I think that the mids bark a little less. With my Diesel 215 it continues to sit sweetly in the onstage mix. Cannot comment on the DI as I always use a Sansamp as a DI. Certainly there is no apparent loss at all in practical, useable volume, although as I stated above a metaller might prefer the easily accessible grind of the original 12AX7. For me, the 12AU7 is a keeper.
 
#98
Did any of you try a 5751 in the driver position? I've got in a Sovtek 5751 to swap, I'll post my results tonight.

On a related note, I retubed my Ampeg SVP-BSP preamp with a Tung Sol 12ax7, what a sweet lil tube! Nice. . ..the clean side sounds soooooo good and the drive side is much more manageable now. I will retube my 400+ with Tung Sol 12ax7's when I can.
 
#99
fremenblue said:
Did any of you try a 5751 in the driver position? I've got in a Sovtek 5751 to swap, I'll post my results tonight.
Click to expand...

Let me give you a preview: you will barely notice ANY difference. The big reason the 12AU7 "cleans up" the amp so much is that it has a much higher plate current capacity than the stock 12AX7. A 5751 has the same plate current rating as a 12AX7, so aside from the neglible loss of gain, it won't really change anything. The swap affects the driver stage, not the a preamp gain stage.
 
#100
Psycho Bass Guy said:
Let me give you a preview: you will barely notice ANY difference. The big reason the 12AU7 "cleans up" the amp so much is that it has a much higher plate current capacity than the stock 12AX7. A 5751 has the same plate current rating as a 12AX7, so aside from the neglible loss of gain, it won't really change anything. The swap affects the driver stage, not the a preamp gain stage.
Click to expand...

I'll prepare myself for disappointment then. :) I guess when I read this thread I keyed in on mgmadian's comment that he'd used a 5751 in a Kern and had experienced a small loss of gain but had cleaned up the sound as well, and also that you thought that a 5751 wouldn't mess up the tone controls the way a 12au7 did.

My conclusion from that was that a 5751 might be a better choice than a 12au7. Ah well. . . .
 

Latest posts

Top Bottom
Back