Tube boost + overdrive running off a 9 volt battery

[Renegadrian]

That' s what Rick - frequencycentral posted a while back, using a stock ckt.

Here's voltages taken from my working Valvecaster, which I run at 12 volts:

Pin 1: 3.02v
Pin 2: -0.518v
Pin 3: 0.00v
Pin 4: 0.00v
Pin 5: 11.97v
Pin 6: 8.21v
Pin 7: -1.285v
Pin 8: 0.00v
Pin 9: 5.91v

Nice to know you got no hum! bingo!

[drbob1]

I'm really sorry for not reading this WHOLE thread, but has anyone tried this build with 12U7 dual preamp tube designed to actually run at a full voltage of 12V?

[iccaros]

@drbob1
yes.. lots... starting about page 2. Mine is running @30V with a 317 regulating the heaters at 12v

@everyone
my pedal is for the most part quiet as longs as I have a good clean power strip. But twice tonight I started to hear radio when the pedal is engaged. So while its nice to keep up with the baseball scores.. everything has its time.. any suggestions on how I could supress this? maybe add a cap to the input jack?

Thanks

[PlaidBicycle]

Nice to know you got no hum! bingo!

Well I've got no hum, but also no signal from my guitar when this thing is on. Can you or someone else take a look at that circuit I posted and verify if that layout is even correct?

I've went over it quite a few times and still can't find issue with the connections or components (most of which I replaced already once and will do again while trying a new layout).

Anymore suggestions, like how to get my pin6 and pin7 values a little closer to ricks? (change resistor values?)

[PlaidBicycle]

I'm pretty sure that schematic was just missing a ground wire on one of the tube pins 

Tried out the "no-tone" version and it worked with my breadboard, so I tried my tube socket with the parts soldered directly and it worked. Unless one of the few other components involved were bad, I can't see why it didn't work previously. I might try to correct the schematic later so that others won't toil endlessly...

Little noise maker sounds great, just need some white paint and I'll post a few pictures. Not too shabby thanks mangs! 

[Renegadrian]

Can I say BINGO now!? 

[zambo]

@ iccaros you could try a cap from + to - on the input jack. I would use like 500pf or so. maybe smaller.

[drbob1]

@iccaros:

I'm not sure you realized that wasn't a typo? The thread (I read the first 10 pages or so) discusses using a 12AU7, a tube designed to run a 12v heater and 200+ volt  B+. Running at even 30v is considered a starved plate design and is far out of the operating range for the tube, resulting in most of the pedals I've played having a harsh type of distortion.

The 12U7 tube, along with the 12K5 power tube, were designed for car stereos, to run at 12v heater and 12v B+ in "space charge" mode. So I wondered if anyone had used a 12U7, not a 12AU7 in this circuit? I did try a search, but so far all the mentions I've seen of the 12U7 are typos for 12AU7.

Thanks for your patience...

[zambo]

it seems like i saw something about a 12u7 but i cant remeber what. I think their was an issue with the amount of current through it??? maybe?? I just cant remeber though. i know the sopht amp uses something like that though.

[iccaros]

@iccaros:

I'm not sure you realized that wasn't a typo? The thread (I read the first 10 pages or so) discusses using a 12AU7, a tube designed to run a 12v heater and 200+ volt  B+. Running at even 30v is considered a starved plate design and is far out of the operating range for the tube, resulting in most of the pedals I've played having a harsh type of distortion.

The 12U7 tube, along with the 12K5 power tube, were designed for car stereos, to run at 12v heater and 12v B+ in "space charge" mode. So I wondered if anyone had used a 12U7, not a 12AU7 in this circuit? I did try a search, but so far all the mentions I've seen of the 12U7 are typos for 12AU7.

Thanks for your patience...

@drbob1
Got ya,
If I can get my hands on one I am willing to try...
But all Pre-amp distortion can sound harsh. I changed to a 5751 and it killed a lot of harshness but I am working on a tri-pedal based on the firefly amp design but at 30 - 60 volts. In this case the final tube is on more of a power amp configuration and power amp overdrive is the nice "tube" overdrive most people are looking for. 

What I do not like about this design is that is changes bias of the tube to create a situation where the grid is less negative than the cathode. The bias should be fixed with the "gain" between stages. 
I use it currently to drive my Carvin Vintage 15 into more of a metal realm, so I can do more with the amp.
With the firefly design I am hoping I can place this in front of any amp and get from a clean tone, the distortion I want.

So back to your thought, If the tube is made to run @ 12 volts.. Then I would place the gain control between the anode(pin 1) and the Grid (pin 7) and I would probably make a two tube design, with the second being driven to overdrive by the first.

[iccaros]

@drbob1
now you have me intrested
I found this site
http://www.sophtamps.ca/mambo/index.php?option=com_content&task=view&id=25&Itemid=37
and Tubedepo has the tubes.. All NOS, so that means I would have to buy a few to ensure I had enough when they die....

This runs so low it could be a pedal or a small amp, I guess a impedance switch would be needed. but I'm game.. but this is off topic for this thread, so should we start another? 

[PlaidBicycle]

  Thanks Renegadrian

[Renegadrian]

Hell yeah!  me likes it!!! 

[a soBer Newt]

could I run this off 48v phantom power; If I used a 12v voltage regulator for the filament?

[frequencycentral]

could I run this off 48v phantom power; If I used a 12v voltage regulator for the filament?

I very very much doubt 48v phantom power would have enough juice to power the tube heater which requires 150ma. In fact, I do more than doubt.....

[Ratbones]

Hey guys, I'm slowly acquiring all the parts to build this. Just waiting on some sockets and an enclosure. I'm planning on building a single valvecaster with a switchable pentaboost into one enclosure. My plan is to run it all off a 24v Electro Harmonix power supply from Amazon. It doesn't state the amperage, but I assume since it is made for their beefier pedals, like the memory man and worm, that it should be fine in this application. (do you suppose that since it's expressly manufactured to power pedals that it would be well filtered and regulated straight away?)

I'm wondering, since the 5672's require 1.25 volts to the heaters, can I go:

24v --> lm7812 -->12AU7 heaters
                        `--> lm317 --> 1.25v --> 5672 heaters

With the 24v going to the plates of both tubes? I think I can track down a 7824 to regulate the 24v.
Does that sound... sound? I'm assuming that putting 24v into the lm317 and regulating it way down to 1.25v would require a ton of heat dissipation, right?

EDIT: Also, is it just the lm317 that requires at least 3v over its output to work? Or are the 7812 and 7824 in the same boat?

(by the way, I went to my local brick and mortar electronic supply to see if by chance they had any tubes, and the guy of course said their stock of 12AU7's and the like have been long gone; just for kicks, I asked if they had any 5672's, and lo and behold, they actually had two NOS Tung-Sol tubes! for 7 bucks a piece no less! These should be rad!)

[Ratbones]

Sorry to bump this, I just don't wanna buy those 7824's tomorrow if they'll do me no good.
Thanks for all the awesome support throughout this thread guys.

[waltk]

Also, is it just the lm317 that requires at least 3v over its output to work? Or are the 7812 and 7824 in the same boat?

2 volts for the Fairchild LM7824.

[Ratbones]

Blast! Thanks for the info though!

For nice, quiet, behaved sound from this tube design, I'm going to need a nice regulated voltage going to the plates, right?
So would using an unregulated 24v to the plates for headroom's sake be better or worse than 18v regulated?

[Dongle]

Just try.
You dont need it regulated. Stabilized is enough. So just put an LC filter there and it should be fine.
I dont know, why so many people are trying to "filter" with 7812 and similar stuff...
7812 is not a filter! You still can get ripple voltage out of this. I agree, in most cases ripple is reduced, but its much more effort than just putting an L and a C somewhere...