Anyone tried this tube pedal project?

[finkfloyd]

Hi,

Any one tried this and have any sound samples?
This actually looks like an easy build compared to other tube pedal projects ive been looking at, and using only 12v

Surely you can skip the "voltage regulator" "power transformer" parts and build the schematic as is, with a standard DC Jack and wallmart?

And that schematic design is how they all should be! So easy to understand

  http://www.hoffmanamps.com/projects/tube_box.htm
       http://www.hoffmanamps.com/projects/tube_box_4.htm

[Jered]

Surely you can skip the "voltage regulator" "power transformer" parts and build the schematic as is, with a standard DC Jack and wallmart?

Actually, you don't want to "skip" any part of that project. Its simple enough as is.
  Jered

[finkfloyd]

Surely you can skip the "voltage regulator" "power transformer" parts and build the schematic as is, with a standard DC Jack and wallmart?

Actually, you don't want to "skip" any part of that project. Its simple enough as is.
  Jered

Hi, Well if you have never messed with voltage regulators or chassis power transformers then it aint simple!

Although at least on the schematic dosent require them it seems

[JimRayden]

And that schematic design is how they all should be! So easy to understand

It might be easy to read if you're just building it, as it's more like a layout. Electrically, design-wise, it's pretty awful to read.

And yes, wallWart is okay, but I'd still regulate it. Nothing much, just three or four components.

--------
Jimbo

[brett]

Huh?
How do you get the B+ of 250V without a power tranny?

If you use a DC wall-wart, you'll need an oscillator capable of generating about 1W (100mA at 12V).

If in doubt, build the Real McTube.  It's a cracker!
cheers

[A.S.P.]

game over...

[finkfloyd]

game over...

Can you make some sense please?

I understand more than two words...

[The Tone God]

Will that circuit work at 12v ? Probably. Will it sound the same as the high voltage version ? I highly doubt it. In fact you will probably be disappointed.

There are other easier low voltage builds around if you do alittle searching.

Andrew

[JHS]

Hey floydman, go to school and learn the basic of tube amps or leave your fingers from this stuff, there are smarter ways for suicide.

The Hoffman-circuit is a  Marshall Plexi 1959 type preamp with 12V DC heating and 284V DC anode-voltage, so it's not that easy build.

Furthermore , you need a MU-metal capsuled tranny (if it's in the box) for such a project to prevent hum.

Sound?  1959 alike when connected to a tube power amp or the amps poweramp input, totally crap when conncted to the amps input.

JHS

[finkfloyd]

Hi,

First Im not stupid, thats why im spending most of my days studying posts on here, and im trying to find a tube pedal that takes a 12v wallmart, not internal transformers and UK mains voltage & such!

And at first glance the aforementioned schematic seemed what I was looking for!

[JimRayden]

Oh it's high voltage, not starved plate. Sorry, I guess I missed that. In that case, you either need an AC wall-wart and a tranny in the box or two trannies in the box. Or a tube amp power trafo.

JHS, don't be so rude, there are nicer ways to tell someone that high voltage kills.

High voltage kills.

See?

------------
Jimbo

[AdamB]

If you remove the transformer that supplys the plate voltage, the circuit *should* still work running as starved plate at 12V DC. However, it will not overdrive. Probably not at all. You need some form of solid state gain stage in there to bias the tubes with if you want any tube distortion (hence why starved plate pedals have a JFET or opamp at there input or output).

EDIT: By the by, the plate voltage of 250V is supplied by a 12V AC mains adapter, which runs through a toroidal power transformer, which bumps the voltage back up to 250V AC from 12V. This then goes through some diodes to form the magical DC we all know and love.

-Adam

[wampcat1]

JHS, don't be so rude, there are nicer ways to tell someone that high voltage kills.
High voltage kills.
See?

------------
Jimbo

Absolutely. This is a forum about learning, and the original poster is certainly more than welcome to ask questions and has a right to without being ridiculed in any way...we were ALL there once. 

[moosapotamus]

...im trying to find a tube pedal that takes a 12v wallmart, not internal transformers and UK mains voltage & such!

How about the Shaka Tube...
http://www.diystompboxes.com/smfforum/index.php?topic=35011.0

~ Charlie

[puretube]

http://www.hoffmanamps.com/projects/tube_box.htm

how long will those chassis be available...

[JimRayden]

I bet Shaka sounds far better than this marshall-preamp-in-a-box.

Listen to sound samples of both pedals and draw your own conclusions.

-----------
Jimbo

[brett]

My real McTube has some hum because it's very difficult to run the AC current from a wall-wart to a stompbox without generating a little hum. (Though my 12AX7 isn't shielded within the diecast box).  Looking back, it would have been just as easy to use two transformers in the box as one.

The real Mc Tube comes with lots of info about building it.  It offers high gain from a 12AX7 biased way off-centre.  It's a very good sound.  Similar to what you get from overdriving the input stage of most vintage amps (e.g. with a tubescreamer or a rangemaster).

cheers