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

[tombowlus]

Would it be cool to have two channels with one that sounded more vintage like a B15N and the other more modern like say the SVT? The Modern channel would have more gain and it could be set as the gain channel and leave the Vintage channel as the clean channel.

This is just an idea, so shoot me down if I'm wrong.

This is pretty much what I would be after. I think that you could certainly do this with two seperate channels, but I'm wondering how close you could get with just one additional tube stage and a tonal balance control (use one side of a 12AX7 for each, maybe?). Of course, I'd love to see the whole crossover idea, too, but that might be more work.

My guess is that it might be worth while to at least sketch out both options and see how much work is involved each way. But of course, the proof is in the pudding (or is that "prototype"?).

Tom.

 

[Biker4Him]

I would tend to agree. I would jsut want to make sure the gain boost can be set so that the volume would be the same, when it's on or off. Although.. the two channel idea is intriguing. It would allow for more and interesting options.

Either way.. I think Brad can see what we are after.. and it seems like he's going to do everything in his power to deliver.

And we can all say we had a small part in it.

I meant more in the way of did he say that as a dig or...

And i think the two channel thing isn't necessary anyway with the boost idea

 

[cabcreaser]

Regarding the "could be a guitar amp" discussion. So far, nothing in this amp's design seems to make it necessarily bass specific (a guitar player that wanted massive clean headroom might like it). One thing I always liked about the B15 is that it also produces a great guitar sound.

If the amp preserves all aspects of the sound of the instrument put into it, but gently adds that nice tube mojo, any instrument requiring clean amplification should sound great through this type of amp.

The additional gain stage would only sweeten the deal (or SVT channel/ B15 channel, for that matter).

 

[tombowlus]

I still have more tube amps than Tom Bowlus, but he's gaining quickly.

Heh, I have been fortunate in the gear that I have been able to acquire recently, but I am a total noob compared to Sir Psycho! I'm glad to see him chiming in here. You can add a big +1 to pretty much all he has said so far.

Tom.

 

[jokerjkny]

what exactly do you mean?

hehe, what B4H said,

there's no two channel guitar amp in his lineup. pull the amp down to 100 or even 50 watts, and VOILA, add another notch to Brad's belt.

actually wouldnt mind hearin' that one for myself.

 

[Fretless5verfan]

So what is it exactly that makes the SA200, Trace V8, 400+, SVT, etc. bass specific? Or are they just super guitar amps too?

 

[jokerjkny]

very good question...

well, voicing for one thing. again, IMHO, an EQ section on a guitar amp just isnt correctly voiced or "Q"ed in the right freq's like a true bass amp.

also, while smaller power tubes are fine for most guitar amp, IMHO, the 6550 is still king to my ears, tho the SA200 is slowly changing that idealogue within me.

 

[Fretless5verfan]

I agree totally about the EQ, but we haven't even started on the voicing yet...and the SA200 is already changing your mind about the tube. So i'm thinking we're safe from becoming traitors anytime soon

Once the OD/Channel thing is settled i think the EQ voicing should be next on the list. I think that might be the single most important part of the amp.

 

[JacksonAmpworks]

This might make things easier.

Jackson Ampworks Bass Amp Poll.

http://www.talkbass.com/forum/showthread.php?t=214746

 

[JacksonAmpworks]

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.

Yeah I think it's really an either or kind of thing. One things for sure, if I add the second channel, the amp will be larger, so factor that into your thinking. The second channel will have NO effect whatsoever on the tone of the first channel. If we decide to make a two channel amp, I'll use relays to swap the channels that way each channel is kept completely isolated from the other.

Just by looking a the circuit at a glance, it seems like the SVT circuit would have plenty of gain if I were to install a MASTER control on that channel and allow the user to vary the gain my using the volume control. Is this in keeping with your experience guys?

 

[JacksonAmpworks]

Traitors the both of you!

And that idea sounds good to me brad.

Glad you dig it! I have a feeling that it would be more useful in a gig situation that just a gain boost because while the second channel could be set for a gain boost, having a separate channel that you could set clean and EQ for a different response would be cool too. The second channel doesn't HAVE to be used as a high gain channel.

 

[JacksonAmpworks]

ya know,

if i didnt know better, this could be a 300 watt guitar amp.

Ha! You're right really. The only difference between a guitar amp and a bass amp is the power and of course you pass a lot more of the low frequencies in the preamp stages.

 

[JacksonAmpworks]

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

Baxandall all the way baby!

Regarding the 6SL7, it is a much better tube for bass because it has an extended low end range and a really smooth high end. Think Vintage Bass Tone.

I can't wait to hear this amp while using my 1966 Candy Apple Red P-Bass. Funny story, I thought that bass was a 1972 for some reason, so last week I popped the neck off and it's a 1966!

 

[JacksonAmpworks]

Well... two channels.. one clean.. one for overdrive....

sounds like a guitar amp to me..

Remember the second channel CAN be used for overdrive, but it will most likely be used a separate channel that can be re EQ'ed for your taste.

I think this would be the most flexible configuration.

 

[JacksonAmpworks]

I meant more in the way of did he say that as a dig or...

And i think the two channel thing isn't necessary anyway with the boost idea

I don't think it's completely necessary, as the first channel will be great by itself, but I'm just trying to gauge which is more useful. I can personally see people using the second channel more than they would an added gain stage, but that's just me. I'm really open to your thoughts and wants.

If we're going to do this thing, let's do it once and do it right!

 

[JacksonAmpworks]

This is pretty much what I would be after. I think that you could certainly do this with two seperate channels, but I'm wondering how close you could get with just one additional tube stage and a tonal balance control (use one side of a 12AX7 for each, maybe?). Of course, I'd love to see the whole crossover idea, too, but that might be more work.

My guess is that it might be worth while to at least sketch out both options and see how much work is involved each way. But of course, the proof is in the pudding (or is that "prototype"?).

Tom.

Actually I've been working on both units during the entire life of this thread. I use Microsoft Visio to layout a chassis and once it's done I export it to AutoCAD and send it to the sheet metal shop in Fort Worth. Using this software really makes my life easy when designing a chassis. Can you believe that the first chassis that I had made I had to draw using a pencil and paper!

 

[JacksonAmpworks]

I would tend to agree. I would jsut want to make sure the gain boost can be set so that the volume would be the same, when it's on or off. Although.. the two channel idea is intriguing. It would allow for more and interesting options.

Either way.. I think Brad can see what we are after.. and it seems like he's going to do everything in his power to deliver.

And we can all say we had a small part in it.

Heck yeah I'm going to deliver! And you guys are going to deliver gut busting bass tone to the masses!

We're all in this together!

 

[JacksonAmpworks]

Regarding the "could be a guitar amp" discussion. So far, nothing in this amp's design seems to make it necessarily bass specific (a guitar player that wanted massive clean headroom might like it). One thing I always liked about the B15 is that it also produces a great guitar sound.

If the amp preserves all aspects of the sound of the instrument put into it, but gently adds that nice tube mojo, any instrument requiring clean amplification should sound great through this type of amp.

The additional gain stage would only sweeten the deal (or SVT channel/ B15 channel, for that matter).

Very cool! I was actually thinking the other day. Since I'm a guitar player and I'm naturally bent toward liking output tube distortion, I was thinking that I could use one of my amp heads and run it into a load box (Weber MiniMASS) and crank the amp. I would then take the line out tap from the MiniMASS and then run that into the FX Loop Return on the Bass Amp and be able to have Output Tube Distortion at any volume level.

 

[JacksonAmpworks]

Heh, I have been fortunate in the gear that I have been able to acquire recently, but I am a total noob compared to Sir Psycho! I'm glad to see him chiming in here. You can add a big +1 to pretty much all he has said so far.

Tom.

Don't worry Tom, you'll have a new bass amp soon.

 

[JacksonAmpworks]

hehe, what B4H said,

there's no two channel guitar amp in his lineup. pull the amp down to 100 or even 50 watts, and VOILA, add another notch to Brad's belt.

actually wouldnt mind hearin' that one for myself.

Actually this is part of my thinking. Why design the same wheel twice? I might be able to use this same size chassis on a new guitar amp that I've been thinking on. It always plans to think ahead.