4049 gating

[johngreene]

The MXR uses decoupling.

http://www.montagar.com/~patj/mxrhott.gif

OK, WHY am I not decoupling? 

Me thinks you mean 'coupling' capacitors? Decoupling is what you do to the power supply, coupling (as in AC coupled) is what you do in the signal path. You are DC-coupling the stages.

--john

[aron]

uh yeah - coupling. 

[aron]

From what Puretube said, shouldn't there be series resistors as well? Too bad I can't try it tonight. Anyway, I will find out tomorrow.

[johngreene]

From what Puretube said, shouldn't there be series resistors as well? Too bad I can't try it tonight. Anyway, I will find out tomorrow.

The series resistor allows you to set the amount of gain just like you would for an inverting amplifier. If you use the series resistors in this way I would get rid of the series resistor in the power supply because this also lowers the gain of the invertors.

--john

[puretube]

some call them coupling caps coz they link 2 stages,
some call them de-coupling caps coz they de-couple 2 stages DC-wise,
some call them blocking caps coz they block DC between 2 stages.

series-input-resistors make the stages more predictable.
series-input-caps serve as frequency-dependant resistors here, too.

the lower the power-supply voltage, the higher the max-gain
(AN-88, fig.5).

don`t expect a max gain of more than 30 to 50 times per stage in practical circuits...

[Mark Hammer]

The MXR uses coupling.

http://www.montagar.com/~patj/mxrhott.gif

OK, WHY am I not coupling? 

Quick!  Kill it before it spreads!!!

The Electro-Harmonix Hot Tubes, NOT MXR.  That was RG's old typing error that ended up being in mirror sites around the world that used the LEPER's schematic archive from Jaimie Heilman.  Honest to god, it couldn't be worse if he had had some youthful indiscretion and briefly appeared in a nudie flick.  It's like one of those bad dreams that will simply not go away.

Now, apart from that brief panic attack, yes THAT one, and it does use a combination of coupling caps AND input resistors.

[puretube]

Never trust a schematic on the web!

and: make that the so-called "Vintage E-H Hot Tubes"...

(the current, not: "re-issue" E-H Hot Tubes works on 2x 12AX7).

And to answer another question from a different thread:
those both have plate-/cathode-/& grid-resistors... 

[Mark Hammer]

Yes.  My bad.  I'm usually good about noting that, and missed it this time.

Of course, it's an even bigger source of misunderstanding when the "old" HT doesn't use tubes, the current one does, the company that makes them  in the new form continues to produce catalog items from the same era as the old HT essentially unchanged (e.g., Dr. Q, BMP), and the NAME of the pedal has the word "tubes" in it.  Yeesh!!  How many potential sources of misunderstanding can you get in one place?!

[johngreene]

some call them coupling caps coz they link 2 stages,

Right AC-coupled

some call them de-coupling caps coz they de-couple 2 stages DC-wise,

Never heard this before.

some call them blocking caps coz they block DC between 2 stages.

Yes, I've heard it referred to in this way as well.

series-input-resistors make the stages more predictable.
series-input-caps serve as frequency-dependant resistors here, too.

agreed.

the lower the power-supply voltage, the higher the max-gain
(AN-88, fig.5).

But not when it is lowered through a current limiting resistor without heavy de-coupling caps on the supply pin. (forgot that part before, my bad)

don`t expect a max gain of more than 30 to 50 times per stage in practical circuits...

Yes, for the unbuffered version.

--john

[puretube]

most circuits discussed here for these kinda purposes are talking bout unbuffered...

note: 

in practical circuits

... 

Aron`s schemo doesn`t mention "buffered" or not...

I automatically thought they were intended to be... 

btw:

Quote from: puretube on Today at 07:50:36
some call them de-coupling caps coz they de-couple 2 stages DC-wise,

Never heard this before.

from an old tube-book (1937)

[puretube]

Yes.  My bad.  I'm usually good about noting that, and missed it this time.

Of course, it's an even bigger source of misunderstanding when the "old" HT doesn't use tubes, the current one does, the company that makes them  in the new form continues to produce catalog items from the same era as the old HT essentially unchanged (e.g., Dr. Q, BMP), and the NAME of the pedal has the word "tubes" in it.  Yeesh!!  How many potential sources of misunderstanding can you get in one place?!

`

I`s just joking... 

[aron]

I believe the DC blocking caps worked. It seems to work fine, but there's massive amounts of distortion. So much so that I can't really prototype on my breadboard. There's too much oscillatiion.

I'm going to move toward perfboard.

[MartyMart]

I'm glad that worked aron, the few that I have problems with DO have blocking/coupling whatever caps
too and still have gating / farting issues ..... 
Still, I have a working Red Lama and a ROG double D !

MM.

[JisforJustin]

Yep, mine have coupling caps as well and I still get the gating at the end of notes, or when the input is below a certain threshold. Since it is oscillating at a low threshold, wouldn't pull down resistors between stages do the trick?

Justin

[puretube]

then which circuit do You use?