• 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.

Uncle GAS Needs You: Help Design an All Tube Amp!!!

Status
Not open for further replies.
#301
Psycho Bass Guy said:
I have another request. Please make the head case tall enough that KT90's will fit in there. Lots of 6550/KT88 amps can't take 'em because they're too tall. BTW, the B15 sound on one channel and SVT on the other sounds cool. I've got a few of the Trace tube amps too. (I still have more tube amps than Tom Bowlus, but he's gaining quickly.) The V series is the Fender Showman tone stack. The VA/VR series is a solid state preamp that I usually bypass.

I'd REALLY like to hear a B15 feeding a clean 300 watt tube power section, and the SVT preamp is PLENTY gainy on its own. I don't think a more aggressive overdrive would be suited to the amp. The most successful modern tube amps have been more focused on tone than "everything for everyone." The Sunn 300T/Fender Bassman 300 took that route, and you'll notice Sunn is no longer around. ;) Aguilar is basically hi-fi Ampeg tone. Eden's VT300 is tube creaminess meets their s/s bass amps, and Sadowsky's amp refines that further. Even Traynor hasn't shied away from putting out a new amp that Pete Traynor could have made himself.

I would also like to suggest that you keep the output section VERY clean. Run those B+ rails at 750+ volts and an ultralinear OT, use an interstage tranny, and forget the power tube swapping. If players are going to gig this amp, they're going to need all the power you can muster. Bass cabs are usually inefficient and booty-shaking tone eats power very quickly. The power switch can drop volume and the preamp should be able to cover most of the overdrive needs above that. Even the SVT gets most of its grind from its preamp.

If I get a 300 watt tube amp, I want it to be loud as hell. Believe me, my standards are high.
Click to expand...

Would pairing up different trios of tubes really have that big of an impact on the power?
 
#302
Fretless5verfan said:
Would pairing up different trios of tubes really have that big of an impact on the power?
Click to expand...

Short answer: a HUGE yes. A 6L6GC has half the disappation of a 6550. To run them together, you'd be scaling the 6550's down to half power and having a 120 watt amp. 6V6's are even worse.

To complicate matters, to get full power out of a sextet of 6550/KT88's, they have to run at high plate voltages, usually over 650 volts. The only other tube that could even TAKE that kind of abuse would be a VERY good EL34, and even then you'd be reducing the amp to roughly 150 watts. Conceivably if you bias the amp cold enough, you can get away with it. (Music Man amps put over 700 volts on 6L6's and EL34's) but you are also putting the amp into Class B- not so good if you want clean power, and it also requires an output transformer with a much larger inductive value to "bridge" the crossover gap.
 
#303
Psycho Bass Guy said:
Short answer: a HUGE yes. A 6L6GC has half the disappation of a 6550. To run them together, you'd be scaling the 6550's down to half power and having a 120 watt amp. 6V6's are even worse.

To complicate matters, to get full power out of a sextet of 6550/KT88's, they have to run at high plate voltages, usually over 650 volts. The only other tube that could even TAKE that kind of abuse would be a VERY good EL34, and even then you'd be reducing the amp to roughly 150 watts. Conceivably if you bias the amp cold enough, you can get away with it. (Music Man amps put over 700 volts on 6L6's and EL34's) but you are also putting the amp into Class B- not so good if you want clean power, and it also requires an output transformer with a much larger inductive value to "bridge" the crossover gap.
Click to expand...

Very interesting stuff. :D
 
#306
Fretless5verfan said:
Would pairing up different trios of tubes really have that big of an impact on the power?
Click to expand...

It sure would, but this is all part of the flexibility of the amp. If you want HUGE power use KT88's, and if you want less power, use EL34's. Having the 300/200/100W switch will further let you tailor your tone and pick the volume/OD amount on a per gig bass-is. ;)
 
#307
jondog said:
With regard to the 2nd gain stage, all I'd really want is a footswitchable boost. This is what my B.K. Butler Tubeworks Blue Tube preamp has and it is very useful -- I get my tone dialled in and then when I need more of the same tone I step on the switch -- no knobs, simple and effective!

Another channel with different voicing and eq would also be cool, but it's not a requirement for me.

Happy Thanksgiving!
Click to expand...

Good point. :hmm: I'm still thinking on this one. I could certainly use more feedback on this one.
 
#308
Fealach said:
I'd imagine given the construction that it would be relatively easy for a pro to service, but easy access to tubes and bias controls is a big plus. I hate having to remove the chassis from the enclosure to get to the preamp tubes or bias pot.
Click to expand...

Check out the Omni-Range Bias Adjustment information that was posted earlier. I think you'll be very pleased. :D
I'd vote for keeping the face as clean and vintage looking as possible, keeping its looks in line with your guitar amps, which look very cool. Modern features such as DI I'd prefer to have in the back. For me, weight isn't an issue. I think most people who are into 300 watt tube amps know that they aren't light. Perhaps if it could be squeezed into a rack mount format, again like the 400+, it would keep weight down, and a custom rack housing could be made for the amp so that when together it would have the look of a more conventional head for those that prefer it.
Click to expand...

I think in the future, provided that their is interest in the idea, I'll make a rack mounted version. For now I'm going to make a head that is in the same style as my other amplifiers.
 
#310
Psycho Bass Guy said:
I have another request. Please make the head case tall enough that KT90's will fit in there. Lots of 6550/KT88 amps can't take 'em because they're too tall. BTW, the B15 sound on one channel and SVT on the other sounds cool. I've got a few of the Trace tube amps too. (I still have more tube amps than Tom Bowlus, but he's gaining quickly.) The V series is the Fender Showman tone stack. The VA/VR series is a solid state preamp that I usually bypass.
Click to expand...

I'll look into the KT90's. I think they'll work as of now, but I'll check into it to be sure.

I'd REALLY like to hear a B15 feeding a clean 300 watt tube power section, and the SVT preamp is PLENTY gainy on its own. I don't think a more aggressive overdrive would be suited to the amp.
Click to expand...

I certainly want to hear this as well, I'm just trying to get a good feel for what users will actually use/need. As always, more feedback regarding the 2nd channel idea, or simply just an added gain stage on the existing clean channel.

I would also like to suggest that you keep the output section VERY clean. Run those B+ rails at 750+ volts and an ultralinear OT, use an interstage tranny, and forget the power tube swapping. If players are going to gig this amp, they're going to need all the power you can muster. Bass cabs are usually inefficient and booty-shaking tone eats power very quickly. The power switch can drop volume and the preamp should be able to cover most of the overdrive needs above that. Even the SVT gets most of its grind from its preamp.
Click to expand...

I was thinking about the same voltage myself and also thinking about using a UL OT. I'll have to test this to make sure the tone is there, but again these are all ideas that need to be tested. :)

If I get a 300 watt tube amp, I want it to be loud as hell. Believe me, my standards are high.
Click to expand...

300W = LOUD :bassist: :p
 
#312
Looks very interesting so far. A full 2nd channel does give more options, but the gain boost as described sounds cool too.

For me, the important thing is if the goal for the clean channel is a B15 at 300 watts. This hasn't been done before. There are a variety of choices for powerful tube heads, my own personal thought is a new one should stand out, like this one has the potential to. Sure, it would be great if it could ALSO sound like an SVT, but not if it compromises the clean channel - anyone who wants an SVT can just buy an SVT. I personally prefer to get my distortion from guitar heads anyhow, but that's just me. Well, me and The Ox.
 
#313
Fealach said:
Looks very interesting so far. A full 2nd channel does give more options, but the gain boost as described sounds cool too.

For me, the important thing is if the goal for the clean channel is a B15 at 300 watts. This hasn't been done before. There are a variety of choices for powerful tube heads, my own personal thought is a new one should stand out, like this one has the potential to. Sure, it would be great if it could ALSO sound like an SVT, but not if it compromises the clean channel - anyone who wants an SVT can just buy an SVT. I personally prefer to get my distortion from guitar heads anyhow, but that's just me. Well, me and The Ox.
Click to expand...

Traitors the both of you! :p

And that idea sounds good to me brad. :D
 
#316
Brad, in your recap of the specs you say Bass/Mid/Treble controls. Would that be a modified Baxandal setup, or a Fender stack, or something different again?

BTW, I read this thread just today. Very very interesting, especially because I've been planning my own valve amp for the last few weeks - basically a B15N with a pair 6550s in cathode bias. I'm not interested in 300w, this amp would be for jazz/blues/roots gigs. I have a S/S amp for louder gigs.

The mention of the difference between 6SL7s and 12AX7s is particularly interesting. I've built/designed guitar amps before but never tried these valves, always used 12A*7s. Looking at the specs they are pretty much the same. Is the 6SL7 that much better for bass amps?

John
Canberra, Oz
 
Status
Not open for further replies.

Latest posts

Top Bottom
Back