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

[JacksonAmpworks]

Two questions. Like F5Fan, I am wondering about an overdrive section (Gain 2, maybe? Using 12AX7 and/or EL84?). Also, in this fixed bias design, how do you adjust the amp for different tubes (6550's/KT-88's from a different brand, not a different tube type)

Tom.

I can certainly add a gain stage if ya'll (yes I'm from Texas) like the idea. I might be able to make it footswitchable. Hmmmmm

Regarding the Bias Question, let me introduce you to the most innovative bias systems ever created.

The Jackson Ampworks Omni-Range Bias Adjustment.

The OMNI-RANGE BIAS ADJUSTMENT, or ORBA for short, is a completely new fixed bias system developed by Jackson Ampworks that provides a level of flexibility and performance unequaled in any guitar amplifier. The ORBA, which uses the Current Method for setting the bias point, measures the actual current flow through the output tubes, and is therefore the most accurate method of determining and setting the bias point.

As an additional benefit, the ORBA will allow the use of previously unmatched output tubes. Because of this, the Jackson Ampworks Atlantic is exceptionally quiet as the push-pull output section is able to work together to completely rid the amplifier of unwanted output section hum.

In an EXCLUSIVE FEATURE, the Jackson Ampworks Atlantic, as a result of the ORBA now allows users to run dissimilar output tubes and match them perfectly! Because of the ORBA, users can now use a KT88 with a 6V6, an EL34 with a 6L6-GC, a KT66 with a EL34 etc! The tonal possibilities are endless!

The Omni Range Bias Adjustment system consists of 6 key components that are essential for the precise measuring and adjusting of the bias setting for each amplifier.

These components are as follows:

BIAS CHART – This bias chart contains the correct bias setting for each output tube listed here. Notice that output tubes that range from the 6V6 to the KT88 can now be safely used as a result of the ORBA system.

RANGE – This locking control is used as a course adjustment for setting the current flow of both output tubes at the same time. The inclusion of this control adds a great deal of flexibility to the ORBA, thus allowing a full range of output tubes to be used. If this control were eliminated, the user would only have a small range of adjustment when biasing tubes and many popular output tubes such as the KT88 and the 6V6 could not be used. Therefore the inclusion of the RANGE control allows a full range of output tubes to be used with the Jackson Ampworks Atlantic, thus expanding the users’ tonal range!

DIGITAL METER – This meter is constantly measuring the idle current of the selected tube and provides immediate feedback on the condition of the output tube. Please note that the protective film over the meter was still in place during the photo shoot.

V1 TRIM – This locking control is used to fine tune the current flow for V1, or the left output tube and is completely independent of the V2 control.

SELECT SWITCH – This control is used to select which tube the Digital Meter is viewing. By placing the select switch to the Left, the Digital Meter is now measuring the Left Output Tube or V1. By placing the select switch to the Right, the Digital Meter is now measuring the Right Output Tube or V2.

V2 TRIM – This locking control is used to fine tune the current flow for V2, or the right output tube and is completely independent of the V1 control.

 

[Fretless5verfan]

Personally i'd like to have a gain and a master type set-up so i could drive the tubes to get a littly gritty without killing myself via sound pressure (though that doesn't mean i still might try it ).

And as far as the switches, what exactly is a resonance control? I use both my bright and ultra high switches on my SVP for different reasons. E.G. if i'm trying to go for a grinding rock tone i might pop the bright on, but not the U-high. But if i'm going to slap, i'll put on the U-high and not the bright. And i use my ultra low quite a bit for crappy rooms and what not, but if this and the resonance control do exactly the same thing, it'd definately be redundant.

A footswitch would be GREAT! Good idea! And tom's idea of a gain 2 would be incredibly cool as well. With all these options the amp will be so simple, yet versatile at the same time.

 

[jokerjkny]

Okay, here's the recap just to make sure that I didn't forget anything.

01.) 6SL7 front end
02.) 6550/KT88 power tubes (300W)
03.) 3 Band EQ (Treble - Mid - Bass) with MID Shift
04.) Resonance and Presence controls
05.) Direct Out - Selectable PREAMP (post FX Loop) or SPEAKER Tap
06.) Tone Stack Bypass
07.) Tube Buffered FX Loop
08.) Fixed Biased with Bias Meter
09.) 2-4-8 Ohm Selector Switch
10.) Speakon Connectors (1/4" and Speakon)​

Again these items are all preliminary, and are a starting point for development.

hmm... so there's no XLR DI? cause, it'd be nice to drive a slave power amp / cab setup, while also sending something to the house PA for those big outdoor gigs.

also, i'd rather just have straight up speakons. for an amp this nice, "speakon only" seems a good way to go.

 

[JacksonAmpworks]

Personally i'd like to have a gain and a master type set-up so i could drive the tubes to get a littly gritty without killing myself via sound pressure (though that doesn't mean i still might try it ).

And as far as the switches, what exactly is a resonance control? I use both my bright and ultra high switches on my SVP for different reasons. E.G. if i'm trying to go for a grinding rock tone i might pop the bright on, but not the U-high. But if i'm going to slap, i'll put on the U-high and not the bright. And i use my ultra low quite a bit for crappy rooms and what not, but if this and the resonance control do exactly the same thing, it'd definately be redundant.

A footswitch would be GREAT! Good idea!

I'm told that the resonance has to do with dampening. Again this is a feature that I will have test through. It may be redundant, but only testing will prove that.

 

[jokerjkny]

Do you guys think that an extra gain stage would be cool? I can certainly do that since we're starting from scratch on this build.

Regarding the Ultra-Hi and the Ultra-Lo, I'm still not sure if I will use them since I've included the Presence and the Resonance controls. Including both seemed a bit redundant. Again this will be an issue for testing. Like they always say, "The proof of the pudding is usually written on the label."

hmm... good question. but in this case, i like your idea.

it would be redundant to have both, and i'd much rather have a knob that gives me greater flexibility than having an all or nothing kind of switch setup.

and holy crap! love your bias mechanism.

 

[JacksonAmpworks]

hmm... so there's no XLR DI? cause, it'd be nice to drive a slave power amp / cab setup, while also sending something to the house PA for those big outdoor gigs.

also, i'd rather just have straight up speakons. for an amp this nice, "speakon only" seems a good way to go.

I might not have worded it correctly, but the Direct Out - Selectable PREAMP (post FX Loop) or SPEAKER Tap was my way of saying DI with an XLR.

I think you're right. Two Speakons will work nicely.

 

[JacksonAmpworks]

and holy crap! love your bias mechanism.

I thought you'd like that.

 

[jokerjkny]

woah,

so, the output of the DI can send to the house either the signal coming from the preamp OR send a signal coming straight from the power section!?!?

how'd i miss that post?

 

[Fretless5verfan]

hmm... good question. but in this case, i like your idea.

it would be redundant to have both, and i'd much rather have a knob that gives me greater flexibility than having an all or nothing kind of switch setup.

and holy crap! love your bias mechanism.

True, but do they actually do the same thing? Would turning the presence knob to full give you that big boost in the extreme high freqs? Cause i thought it was more of a really high mid type freq boost. Same thing for the other two (in the lower freqs of course)

Testing is definately the way to go on this one i think.

 

[tombowlus]

Okay, now I may have to buy two!

Your bias control setup is fantabulistic! I can't wait to try it out! Very nice.

A second, footswitchable gain stage would be very cool.

Some control over the damping factor (if that's what your Resonance control does) is also way cool.

You go, Brad!

 

[Biker4Him]

Your bias control setup is fantabulistic! I can't wait to try it out! Very nice.

A second, footswitchable gain stage would be very cool.

Some control over the damping factor (if that's what your Resonance control does) is also way cool.

You go, Brad!

Wow... I walk away for an hour, and there's an entire new page of posts... with great info.

Yes.. a second gain stage would be greatly appreciated... and making it footswitchable makes it a lot more user friendly.

That ORBA is off the chain!! wow...

I'm not sure of the difference between the presence and resonance.. and the bright and deep switches... normally, when I think of a presence knob, I think of it adding some mid/upper mids. Which is not the same as a bright switch. And for resonance vs. a Deep switch... I don't know. However; I'm guessing you will work it all out in testing.

 

[DEVILMAN]

...count me in for one of the 50 or so...

~S~

 

[cabcreaser]

I love the philosophy behind the amp (using 60s bass sounds as a reference). So far, the idea looks fantastic (IMO more bass amps should use 6SL7s for the preamp tubes). In fact, the bass tone that inspires me most is a really well maintained mid-60s B15 before it breaks up-unfortunately, that is pretty early.

It sounds like that really clean (in a tubey sense) but fat sound (though not grindy or muddy) you hear on countless older recordings is the goal, and if that is achieved I would definitely want to buy one. In fact, if you need any local bass players to check out prototypes, I live in Dallas and would love to help you in any way possible.

Though I have nowhere near the tube bass gear collection that many have on this forum, I have or have had prior to separate bouts of GAS: the Trace Elliot V6, Demeter VTHF-300M, Demeter VTBP-201, Kern IP-777, mid 60s Ampeg B-15, mid 70s SVT, and my personal favorite, the Aguilar DB680 (which has become pretty much the only thing I ever use for recordings).

The only features I don't think I have seen mentioned that would appeal to me, I apologize if these have, is the ability,like the new Sadowsky head has, to use different power tubes and also a switch that can cut the power in half (preferably by reducing the number of tubes used as opposed to the pentode/tetrode switch like the Demeter power amp has). I love KT-88s/6550s for live applications, but I really love what 6L6s do to a bass sound for recording. In addition, since you have been convinced to bring the power up to 300 watts (which is a great thing for a 3000 dollar amp), the option of cutting the power in half as well as variable fan speeds could make it a perfect amp for the studio.

sorry this post is so long

ps- how is the naming process coming?

 

[Fretless5verfan]

i've never had the pleasure of using a tube head in the studio sadly, but what are the benefits of running half power? I'm sure it's quieter (more quiet?) but is there anything else?

Variable speed fans would be a very nice touch.

How IS that naming process coming?

 

[Kelly Lee]

On the rackmounting thing again here... just for reference the Trace Elliot HexaValve uses six 6550 powertubes, puts out 380 watts, and mounts in a 4sp rack case.

 

[JacksonAmpworks]

woah,

so, the output of the DI can send to the house either the signal coming from the preamp OR send a signal coming straight from the power section!?!?

how'd i miss that post?

Yeah, that shouldn't be too hard. I'll just add a switch that selects from either point and then convert it to low impedance. But as always, saying something is easy and actually doing it are two different things.

 

[JacksonAmpworks]

True, but do they actually do the same thing? Would turning the presence knob to full give you that big boost in the extreme high freqs? Cause i thought it was more of a really high mid type freq boost. Same thing for the other two (in the lower freqs of course)

Testing is definately the way to go on this one i think.

You're right on this one. From what I understand, most Ultra-Lo switches just shunt some of the highs to grounds so you "perceive" an increase in bass. I'll have to test all of this.

 

[JacksonAmpworks]

Okay, now I may have to buy two!

I'll make sure to check with you guys before I punch the chassis to make sure that I have each of you covered.

Your bias control setup is fantabulistic! I can't wait to try it out! Very nice.

I think people will really respond to that one. I've never seen anything like it. On this amp, since I will have 6x ouput tubes, it would be a complete circus to set the bias on EACH tube so I will set the left 3 and the right 3. That will help to balance the push pull output section and keep the amp as quiet as possible.

A second, footswitchable gain stage would be very cool.

This is a great idea. I'll certainly look into it, but if it changes the tone of the amp, I may have to pass on it. I'll still give it a solid look though.

Some control over the damping factor (if that's what your Resonance control does) is also way cool.

That's my understanding of what the Resonance control does.

You go, Brad!

I try.

 

[JacksonAmpworks]

Wow... I walk away for an hour, and there's an entire new page of posts... with great info.

Yes.. a second gain stage would be greatly appreciated... and making it footswitchable makes it a lot more user friendly.

How much extra gain are we talking here? Like obvious overdrive, or just a little hair on it?

That ORBA is off the chain!! wow...

That was my first thought when I thought of the idea. It's nice to see that you agree.

I'm not sure of the difference between the presence and resonance.. and the bright and deep switches... normally, when I think of a presence knob, I think of it adding some mid/upper mids. Which is not the same as a bright switch. And for resonance vs. a Deep switch... I don't know. However; I'm guessing you will work it all out in testing.

You're right. If they are extraneous, they won't make the cut, but if they help the amp, then they'll be there.

 

[JacksonAmpworks]

...count me in for one of the 50 or so...

~S~

You got it! So far I have 5 people that want one. Do I hear anymore?