Tube Screamer contained digital all along?

[Peter Snowberg]

I thought the title might get a few eyes pointed here.

One part of the tubescreamer has always been digital, and that's the JFET bypass switching control circuit.

Here, Ibanez (Maxon) used a pair of transistors to make a 1 bit memory circuit which then controls the state of the actual bypass transistors. This particular circuit is a "flip-flop" which in this topology can be though of as a divide by 2 counter. The effect is on every other time you push the stompswitch. Flip-flops have a pair of outputs, one normally is called "Q" while the other is called "/Q". When Q has voltage, /Q does not and vice versa. If one controls the passage of the dry signal and the other controls the passage of the wet signal, you will flip between one of them being active every time you trigger the flip-flop.

There really isn't too much difference between this two transistor flip-flop and one constructed out of a pair of logic gates; the latter of which is used to form every bit of storage in static RAM.

Think of 64K of SRAM as the same as 524,288 stompswitch circuits in one package. 

We normally avoid the digital here and go for true bypass for DIY, but I just wanted to point out that digital has been at the heart of some of our most cherrished ANALOG effects since day one.

[SeanCostello]

Of course, most of the schematics on the Internet, and many of the boutique clones out there, forego the JFET switching in favor of a "true bypass" solution. So, the TRUE analog diehards instinctively knew to avoid the digital content.

Sean Costello

"the future belongs to the analog loyalists. f*** digital"

- Steve Albini, back cover of Big Black, "Songs About F***ing"

[troubledtom]

what?

[SeanCostello]

Soooo...no Big Black fans out there? How about Shellac?

In all seriousness, the reference to the Tube Screamer switching being digital is probably going to make it into the advertisement of some boutique manufacturer that uses true bypass. A mods person could shoehorn a DPDT into a DS-1, and "remove the digital."

Sean Costello

[Jason Stout]

Soooo...no Big Black fans out there? How about Shellac?

In all seriousness, the reference to the Tube Screamer switching being digital is probably going to make it into the advertisement of some boutique manufacturer that uses true bypass. A mods person could shoehorn a DPDT into a DS-1, and "remove the digital."

Sean Costello

Shellac? man, I've been waiting for a new release for 5 years now, when do you think they'll do it? And, you forgot Rapeman

I'm a plane.

[phaeton]

DPDT and "remove the digital."

Technically, no they haven't.

[Eb7+9]

One part of the tubescreamer has always been digital, and that's the JFET bypass switching control circuit.

(!) good one Peter, but don't forget the battery - it's digital also ...

101 volts in base2   

[Dirk_Hendrik]

That's exactly what I thought when reading the first post Power supplies provide a continuous "one". last weekend I found out thet a 535 crybaby uses the principle by turning on logic gates of which the output powers the output stage. When not powered the stage is off and provides bypass...

[TELEFUNKON]

how about the good old stompswitch: I/0 : on/off   one whole bit, double throw!

[Alex C]

Flip-flops have a pair of outputs, one normally is called "Q" while the other is called "/Q".

How do you "say" or pronounce that?  "Slash Q?"

[Jason Stout]

Flip-flops have a pair of outputs, one normally is called "Q" while the other is called "/Q".

How do you "say" or pronounce that?  "Slash Q?"

I think the symbol Peter was trying to convey is normally written with a horizontal bar ABOVE the Q, pronounced QBar, or QNot. QNot's state is always opposite of Q's

[Peter Snowberg]

I say "not Q", so there's another way. 

The slash preceding the Q is the best we get in ASCII or ANSI text so that's the standard way of denoting the inverted Q output.

[Transmogrifox]

Another way I have seen the same thing expressed is Q and Q'

...sometimes called "Q prime"

When we get to the point of talking about the digital interpretation of DPDT mechanical switches, we just as well go to the other extreme and say the DSP's are analog.  They are.  The only thing that makes them different is our interpretation of the analog signals.  They're designed to be saturated to one rail or the other and we call it a '1' or a '0' though in the real world it's about 3V or 0.3V.

The important thing is that it sounds good, whatever comes out--and we DIY electronics guys know about that.  The average consumer is more easily suckered in by the analog vs. digital routine.  There are good sounds to be had in both worlds.