How many preamp tubes in Fender Bassman 100?

kodax · #1 10-03-2010, 02:23 PM

I don't have the amp here, and from the picture I have it looks like it has two preamp tubes, one phase inverter?, and four power tubes.
Is this correct? It's a two channel amp..

I'm thinking of getting JJ 6L6GC for the powersection.
Any recomandations for NOS preamp tubes?

craig.p · #2 10-03-2010, 03:16 PM

That looks right. A pair of 7025s and a 12AT7.

Sorry, can't help you with the tube-choice question except to say a) wait for the tube heavies on this board to answer, because b) what's best may not necessarily be what has the highest name recognition or what the popular amp manufacturers are using.

BassmanPaul · #3 10-03-2010, 03:22 PM

What's wrong with the tubes that are in there??

toprekoms · #4 10-03-2010, 03:28 PM

I would recommend using NOS RCA's or GE's. That's most likely what it came with when new. Look for a matched quad of 6L6GCs, a matched pair of 7025"s, and a matched (both grids) 12AT7.

T-Bird · #5 10-03-2010, 10:48 PM

Hi.

Quote:

Originally Posted by BassmanPaul

What's wrong with the tubes that are in there??

Perhaps he has bought the "GT is evil" thought people seem to have

.

Could be the camera, could be the lighting, could be anything, but if that's the actual color of the GT logos (dark, deep, brownish red), those tubes are indeed toast. Or at least in dire need of biasing.

If the logos are bright red, no loss of power or tone, there's no need to change the power tubes. IMHO/IME only of course.

While tube rolling is fun, it's a vicious circle that never ends.

Regards
Sam

kodax · #6 10-03-2010, 11:16 PM

Quote:

Originally Posted by BassmanPaul

What's wrong with the tubes that are in there??

The amp works ok, but was last serviced and retubed with Ruby tubes in '91. I guess it sounds ok, but maybe it can sound better? (I'm a guitarist. The amp is used for bass, and my experience is limited..)
Futher I'm told that regular service/new tubes will reduce the risk of the amp suddenly breaking down (?).
I have experienced with other (guitar) amps that changing to NOS GE preamp tubes have made a huge difference in terms of clarity, headroom, response, smooth breakup etc.
Sum; I'm changing the tubes both because of curiosity and for precautionary reasons. Maybe it's a waste of money (maybe the mudbucker on the EB-0 never will clear up

), but then at least I can say my experience with bass-gear is a little less limited..

kodax · #7 10-03-2010, 11:21 PM

Quote:

Originally Posted by toprekoms

I would recommend using NOS RCA's or GE's. That's most likely what it came with when new. Look for a matched quad of 6L6GCs, a matched pair of 7025"s, and a matched (both grids) 12AT7.

I know that power tubes should be matched, but I believe preamp tubes don't? And a matched singel tube?? (Are you pulling my leg, saying that I'm to eeger to change the tubes

)

JimmyM · #8 10-03-2010, 11:23 PM

you do not need to match or bias preamp tubes...only power tubes.

kodax · #9 10-03-2010, 11:26 PM

Quote:

Originally Posted by T-Bird

Hi.

Perhaps he has bought the "GT is evil" thought people seem to have

.

Could be the camera, could be the lighting, could be anything, but if that's the actual color of the GT logos (dark, deep, brownish red), those tubes are indeed toast. Or at least in dire need of biasing.

If the logos are bright red, no loss of power or tone, there's no need to change the power tubes. IMHO/IME only of course.

While tube rolling is fun, it's a vicious circle that never ends.

Regards
Sam

Those are Ruby tubes, and I don't think there is any loss of power, but I'm anxious that they will soon break down, (and probably on stage.)
...and I'm allready caught in the wonderful circle of tubeswapping

will33 · #10 10-04-2010, 12:17 AM

I have the 135 version of that. From my experience, don't get caught up in the "must need tubes" thing. A good tech will test them and let you know. And yes, you can swap preamp tubes all you want with out having it rebiased or checked out. If you run across an old Mullard, I like those in there. Also try jumping the channels and remember the fender tone stack, bass and treble only boost and mid only cuts. Oh....and leave the deep switch off. That's something like a 10db boost at 50hz. Might sound cool in your house but you'll be washed away with the band. Use the bass knobs instead. Lots of good tones to be had in there if you don't need 'em loud. Hanging with a band in someplace bigger than your local blues bar or whatever need cabs that are high SPL or just plain have a lot of speakers.

kodax · #11 10-04-2010, 01:30 AM

Quote:

Originally Posted by will33

I have the 135 version of that. From my experience, don't get caught up in the "must need tubes" thing. A good tech will test them and let you know. And yes, you can swap preamp tubes all you want with out having it rebiased or checked out. If you run across an old Mullard, I like those in there. Also try jumping the channels and remember the fender tone stack, bass and treble only boost and mid only cuts. Oh....and leave the deep switch off. That's something like a 10db boost at 50hz. Might sound cool in your house but you'll be washed away with the band. Use the bass knobs instead. Lots of good tones to be had in there if you don't need 'em loud. Hanging with a band in someplace bigger than your local blues bar or whatever need cabs that are high SPL or just plain have a lot of speakers.

I don't want to hear "I dont need new tubes"

You might be right, but my tech only have Ruby, TAD and some NOS Sylvania. I'm curios about those JJ's, and I will get tubes far cheaper than my tech will sell them for. Futher I don't trust all techs; they might know how to bias, change caps etc. (and of course a lot also knows how amps should sound), but they don't necessary knows what I want. In this case I don't either, but I believe JJ's would be interesting.
Thanks for the info on the amp settings! I've noticed the deep switch issue, but didn't know how the eq worked.

kodax · #12 11-01-2010, 02:47 PM

JJ 6L6 GC, NOS GE 12ax7 & 12at7.
The gruff is gone (witch is usually a constant challenge playing an '76 EB-0), more headroom, and much smoother overdrive.
Sounds good, allright!

BassmanPaul · #13 11-01-2010, 03:00 PM

Quote:

Originally Posted by kodax

maybe the mudbucker on the EB-0 never will clear up

There's nothing much wrong with the EB0 humbucker. Check if your EB0 has a square black plastic plate under the hand rest. Both my EB0F and EB2 had one. Underneath is what Gibson called the "tone Coil". It was wired across the pickup and shunted all treble frequencies to ground. If you disconnect the thing in the control cavity the bass comes alive in a most pleasing way. Being a little creative with serial and parallel connecting the coil gave me six different tone colours.