New Effect: Bullitt

[The Tone God]

Hello everyone.

I posted a new effect called Bullitt. It is a low voltage tube tremolo using two 12AX7s and a dual opamp (not in the audio signal path). It has boost/distortion, Fender style three band EQ, wide speed range, and a very effective depth control. It can go from very slow to blindly fast, slight hint of modulation to full on chop, mellow to bright tone, and unity output to boast to mild distortion. A short article is included with some modification suggestions.

Enjoy.

The Tone God's Domain

Andrew

[puretube]

Just to keep things clear I did not claim this was "pure" tube tremolo. I doubt anyone, atleast not those who are high priests of "mojo", could argue that this changes the sound of the tremolo

what`s pure enough for you, is pure enough for me... 


`nother mod: switching the 2nd half of the (mod-)dualgangspeedcontrolpot
in series with the 1st half;
gives you the "Puretube half/normal/double speed-mod"
(not disclosed in a recent other thread...  )

[Unbeliever]

`nother mod: switching the 2nd half of the (mod-)dualgangspeedcontrolpot
in series with the 1st half;
gives you the "Puretube half/normal/double speed-mod"
(not disclosed in a recent other thread...  )

That is a really neat idea. No messing around with extra caps. Surely I'm not the only one thinking 'damn, so obvious - yet so cool'!!!! 

[brad]

Have I told you lately that I love you, Tone God  
Wait a moment...I'm getting a vision...

...it's getting clearer...wait for it...

A sequenced tube trem! 

[puretube]

oh, yes,
and the "Puretube-stepped-duty-cycle-mod" (un-sine, of course)
and the "Puretube-square-chop-mod"...

and last but not least: the "FullTube Pulsar re-issue Emulator"

                   

[MartyMart]

Bless you Andrew ...... you are indeed  ....  "A GOD OF TONE" 

Marty.

( I just knew that Ton would like this one  )

[puretube]

now on with the search for a suitable 2-tube chassis... (box)

[nelson]

I am putting this on my list, although I am replacing the LFO with a pulsar style LFO.

With a suitable tube cage you could fit this in a 1590B with the pots on the edge.

[zeta55]

I would love to hear some soundclips of it.

/Krister

[Mark Hammer]

oh, yes,
and the "Puretube-stepped-duty-cycle-mod" (un-sine, of course)
and the "Puretube-square-chop-mod"...

and last but not least: the "FullTube Pulsar re-issue Emulator"

Those all sound like wrestling holds.  "Oh, the Masked Dutch Crusher has Hurricane Hammer in a Puretube-stepped-duty-cycle-mod.  He's weakening....weakening.....OHHH, did you see that?  Its a Puretube-square-chop-mod to the solar plexus, and he's down.  One.....two....three.  It's over.  Folks, this match is over!  Send the kids to bed.  Pack up your bags.  Hammer is down and out for the count!!"

[puretube]

THE TONE GOD
will forgive me, I know,
for jumping on his thread.

I heard His voice - He called me... 

(those "holds" are only put here first in time,
to prevent self-entitled 3rd/4th party parties
to claim mods that have been thought of years ago
by others,
as being theirs, and making them feel like they are the only
ones that are allowed to take profit from it...)

[Mark Hammer]

Is there a difference between what is used in this circuit and what is generally referred to as "tube bias tremolo"?

Older-style tube tremolo is a wonderful thing and is instantly recognizable by its feel (which the Line 6 Tap Tremolo does a pretty passable job emulating digitally, incidentally, though I'm too ill-informed to know if any other pedals do it better).   But I can't honestly tell you what is being accomplished in such circuits that is different.  All I know is that it generally sounds and feels different from what you hear when the gain of a stage is being modulated (as with the old Pulsar) or when the attenuation of the input signal is being modulated (as with the Anderton Tremolo).  It doesn't sound like softer and louder.  It sounds like "giving up" and "getting stronger".  I don't know why, though.

So, what are the consequences to the signal when the bias voltage on the power stage is being modulated?  Is that the sort of thing you can ONLY do there, or is it possible earlier in the chain (e.g., preamp as in this Bullitt circuit)?  Can it only be done with tubes (in the analog domain) for some particular reason (and I don't mean that it sounds "better", but rather that it literally cannot be done) or can a well-engineered analog circuit do it with discrete or other components?

This is something that has perplexed me for a long time.  I'd simply like to unlock the mystery behind the principles of it.

[puretube]

not to interefere with Andrew,
but here`s a little side-comment:

most people I have experienced,
associate "Vintage Tube Tremolo" with something they heard
that is not tremolo in the true sense of the meaning,
but rather some kind of "timbre-tremolo" (Fender often used it),
where the Highs and the Lows are being accentuated/muted alternately,
such that apparently it sounds like alternating volume,
but in fact the average volume stays roughly constant
while the frequency-content is being varied.
Since this is being accomplished by alternately having the signal passed through a highpass and then through a lowpass,
some "phase-filth" is playing a role in there, too.

(Yet this is not a "Vibrato", either).

For the "true vintage poweramp-bias-tremolo",
the fact that the modulation is being applied to the power-section,
makes it sound different than when applied to a preamp section,
because while in a preamp you just modulate the amplitude of the signal,
which is being more or less being amplified "linearly" later on,
in a modulated power section, you quasi modulate the "SAG" by drawing varying amounts of "plate-juice" through the end-tubes at your desired tremolo rate,
no matter how high the amplitude of the actual signal is at that moment is, before it hits the grids.
In other words: the amp "pumps", even when you play at lower volumes, or even mute the strings...

of course, this is only my view...

[puretube]

p.s. to my previous post:
what do I know...

I have never played,
or wittingly heard an EA-trem, a CA-trem, an old Pulsar, nor an L6;
neither in real life, nor "clips".

[The Tone God]

I wasn't expecting so many responses.

Firstly thanks to everyone for the kinda words.  I thought I show you folks that is not all optocouplers, gates, and microcontrollers at The Tone God's Domain.

what`s pure enough for you, is pure enough for me... 

Yay! Now if anyone complains about it I can say it is a "Puretube Approved" design.

`nother mod: switching the 2nd half of the (mod-)dualgangspeedcontrolpot
in series with the 1st half;
gives you the "Puretube half/normal/double speed-mod"
(not disclosed in a recent other thread...  )

So simple yet so effective. I like it! I'll have to put that one on the books.

A sequenced tube trem! 

My word Brad, thats bordering on the brink of...insanity. Digital and tube analog existing in the same effect. Madness I tells ya! :::Starts to think about it::: Actually that would be kind of interesting. Maybe I'll save that for a lark some day. It would probably make me laugh watching it work. hmm...Vanishing Bullitt Point.

Bless you Andrew ...... you are indeed  ....  "A GOD OF TONE" 

Lets wait for some build reports before going off praising it. Praise me instead. The one I built does sound very nice I think.

( I just knew that Ton would like this one  )

Actually I'm fulfilling a previous commitment to Puretube with this. Sorry it is a little late.

http://www.diystompboxes.com/smfforum/index.php?topic=23996.0

now on with the search for a suitable 2-tube chassis...(box)

Hey you mean this could be built into one of those EH two tube chassis that someone here designed ? I never thought of that.

I am putting this on my list, although I am replacing the LFO with a pulsar style LFO.

You can do that. I will say that the LFO in the Bullitt was completely tick free even with all the messy wiring on the breadboard. The only time you could here anything when not playing was when the depth was cranked. It would do the "thump" sound but since tube amps do that too I thought it was acceptable. The LFO really performs nicely I think. I would suggest maybe trying both. You would be surprised at the amount of range that depth control has especially when used in conjunction with the gain control.

Another note is that circuit is running at 12v so you may have to recalibrate things. Also I'm not sure of the output swing the Pulsar so it may have mild interfacing issues. Nothing that can't be solved.

THE TONE GOD
will forgive me, I know,
for jumping on his thread.

You are forgiving. I understand for why you do this. In other words, it's all cool.

Is there a difference between what is used in this circuit and what is generally referred to as "tube bias tremolo"?

There three common types of tremolo circuits used by tube amps. One is the optocoupler circuit that is the most common. I could have done this but I would have consider that kind of lame way to go about this. Just my opinion. The CA tremolo would fall into that type of circuit.

The second type came before the optocoupler circuit and involved modulating the bias to the power tubes. Puretube already covered alot of the characteristics of that type. The EA tremolo would be something in that vain of circuit. I did try a low voltage version using a 12A*7 configure as a mu-amp and modulating the "lower" stage's cathode. It worked but not really spectacular sounding.

The third and less popular type is modulating the cathode of a earlier preamp tube stage. This is what I adopted in Bullitt replacing the tube LFO with the opamp and reusing the tube stage on the output. The tremolo tends to be alittle more even frequency-wise unlike the power tube/bias versions and softer I think. The softness can be tweaked by the cap on the cathode.

Thanks again all.

Andrew

[zeta55]

The third and less popular type is modulating the cathode of a earlier preamp tube stage.

I tried this in my tremler pedal, it's based on the circuit of Fenders Vibro-Champ. It produces (in my opinion) a very nice sounding tremolo. Shure hope you post some soundclips of yours.

/Krister

[brad]

My word Brad, thats bordering on the brink of...insanity. Digital and tube analog existing in the same effect. Madness I tells ya! :::Starts to think about it::: Actually that would be kind of interesting. Maybe I'll save that for a lark some day. It would probably make me laugh watching it work. hmm...Vanishing Bullitt Point.

I suppose it could also be done Tremulous Lune style by just having two tube stages with an LDR between them.  But that's not very exciting 

[rockgardenlove]

Damn!  I need more tube sockets

[dano12]

Thanks much for what looks like a very cool project.

It is so intriguing that I think I'm going to take the dive on this one and try my first ever PCB layout. I've got to learn how to do it at somepoint anyway

Will keep you posted!

[Peter Snowberg]

I'm a bit late to the party.

Fantastic job Andrew!