Univox Tremolo..

[Jack_Hester]

http://www.el34world.com/charts/Schematics/files/univox/univox1221.pdf

I was recently sent a copy of this schematic, and am curious as to the function of the 12AU7 connected to the Intensity pot.  The triodes appear to be paralleled, but flipped.  Thanks for any info.

Jack

[sluckey]

Think of the plate to cathode as a variable resistance. The tremolo signal on the grid varies that resistance from a low to high value at the tremolo rate. That resistance is parallel to the guitar signal path and varies the guitar signal by shunting it to ground.

[Jack_Hester]

Thanks, Steve.  I'll have to experiment with this configuration.  Any special reason why they would use this over a typical oscillator setup?  And, what about the cathode to plate connections on this tube?  Why not just parallel plate-to-plate and cathode-to-cathode?  Steve_P was the one who showed me this schematic, over on the Guild site.  He's now posted it here, under my Guild 66-J thread. 

I like circuits that don't follow the norm.  I wonder how the sound compares.  Thanks again,  for your response.

Jack

[kagliostro]

Hi Jack

if you like unusual circuits, you'll like this

give a look at how the tremolo is joined to the signal

Franco

[Jack_Hester]

Hi Jack

if you like unusual circuits, you'll like this

give a look at how the tremolo is joined to the signal

Franco

That is unique.  Thanks, Franco. 

Where did you manage to find those schematics?  I'm not familiar with the brand. 

Jack

[sluckey]

I like circuits that don't follow the norm.

You'll love Univox then. They travel to the beat of a different drum. Sometimes good, sometimes not so good.   

[kagliostro]

Playmaster was an Australian brand

I didn't remember well but it seems to me that the brand published schematics to be build

like this article (that you can download if you want)

http://www.mediafire.com/view/9k73f3uy1vrv8va/Playmaster%20102.pdf

Here you can find news about those amps

http://www.ozvalveamps.org/playmaster.htm

(http://www.ozvalveamps.org/)

Franco

[HotBluePlates]

...  And, what about the cathode to plate connections on this tube?  Why not just parallel plate-to-plate and cathode-to-cathode?  ...

At first I saw that and said, "Dafuq??"

You see where the ground connection is. Look at the other end of the tube, and follow the non-grounded plate/cathode to see where they go. They connect to the output of a tone circuit and a tube grid with no other ground reference.

So current can flow through the 12AU7 if the signal at that tube grid (6AN8 input) is positive-going, but would be blocked when it switches to negative-going on the other half-cycle. So the other 12AU7 triode has to have its cathode pointing to that 6AN8 input to allow current to flow on the negative half-cycles.

...  Any special reason why they would use this over a typical oscillator setup?  ...

They wanted to prove folks wrong about never seeing a 12AU7 in a guitar amp?

Maybe they got a kick-back from their 12AU7 supplier for follow-on tube sales?

Fender already had a patent on the neon-optoisolator trem and they wanted to stick it in Leo's eye?

Who knows. Try it and see if it sounds good. I probably won't be wasting a tube socket and heater current like this, but I do have a metric sh!t-ton of 12AU7's just begging for something to do...

[Jack_Hester]

HBP -

Very interesting response.  Thanks for the insight, and I don't think that it would be a waste of a tube/socket.  I usually build things that don't necessarily need building.  Sometimes I do it just to prove it out. 

For the most part, every discussion here is a concept of a sort.  Usually ending in a build that inspires others to go off on a tangent with an idea inspired from the discussion. 

Thanks to Steve_P for bringing the odd circuit to my attention. 

Jack

[Steve_P]

I like weird stuff.

So much so that I joined an Australian amp forum because they used a bunch of odd tubes over there...

[Willabe]

Ok, but where do you live, in the US?

         Brad   

[Steve_P]

Ok, but where do you live, in the US?

         Brad   

Yeah. I have to stand on my head to read the forum. 

[Willabe]

Yeah. I have to stand on my head to read the forum.