Tube boost + overdrive running off a 9 volt battery

[kurtlives]

Why do you want everyone to use your layout?


I used it anyways...

[Renegadrian]

Well, I'm so proud of it...
Obviously I won't force anyone using it, but I'm glad someone did it and had good results...

Back to your circuit, well...I dunno...You say you got voltage but how's the sound? And the gain won't work...
Did you triple  check every connection???

[kurtlives]

It sounds pretty good... Has more gain than I expected (even though I cant tweak the gain)

[danielzink]

I saw a post somewhere in this thread that mentioned 150ma to run the pedal. Can anyone verify this ? I'm going to run my pedal with a PPII and it'll only make 200ma max with 18v Y cord (according to Voodoo Labs) - so I'm within spec - I just want to make sure.

Dan

[kurtlives]

I saw a post somewhere in this thread that mentioned 150ma to run the pedal. Can anyone verify this ? I'm going to run my pedal with a PPII and it'll only make 200ma max with 18v Y cord (according to Voodoo Labs) - so I'm within spec - I just want to make sure.

Dan

Mine was drawing 120mA yesterday.

[danielzink]

I saw a post somewhere in this thread that mentioned 150ma to run the pedal. Can anyone verify this ? I'm going to run my pedal with a PPII and it'll only make 200ma max with 18v Y cord (according to Voodoo Labs) - so I'm within spec - I just want to make sure.

Dan

Mine was drawing 120mA yesterday.

bee-yoo-tee-full

Thanks !

Dan

[liddokun]

[/quote]




"A 1M gain pot allows massive, saturated gain. A little mushy in the bass frequencies, but pretty cool. I'm considering putting a "more" switch in, whereby it adds a resistor in series to the regular gain pot."


[/quote]

Think I could toss in a 1m gain pot but change the input cap or coupling cap between the tube stages to tame the mushiness?  Or can I just up the value of the gain pot, but not to 1M, maybe something a bit less?  I have a 500K reverse log pot.  Would that work in increasing usable gain/saturated distorted sound?

[tranceracer]

I saw a post somewhere in this thread that mentioned 150ma to run the pedal. Can anyone verify this ? I'm going to run my pedal with a PPII and it'll only make 200ma max with 18v Y cord (according to Voodoo Labs) - so I'm within spec - I just want to make sure.

Dan

Mine was drawing 120mA yesterday.

I also found an interesting tone change when I changed my 9V regulated adapter from a 200mA to a 300mA. 
The tone was much more gritty with the 200mA but not as dynamic.  The 300mA is a more mild OD tone, a little brighter and has a little more dynamics.  I'll try to make a demo as soon as I get some time.

-bK

[kurtlives]

Gain is at the maximum when resistance is 0.

So going with a bigger value pot isnt really doing...just giving more "clean headroom" until you hit cutoff and the bias goes.

Higher value pots will also make it harder to dial in the right amount of gain for you.

[andrew_k]

Just picked up 8 7AU7 valves for $2.50 each (7v heater version of 12AU7) to try with this circuit, the Vibracaster and Pepper Shredder. With an LM317 regulator I'm hoping I can power them off 9v, as the LM317 spec states a 1.2v loss

Just another valve to look out for cheap deals on.

[comfortably_numb]

I'm a little confused by this circuit's gain control.  Reports are that gain is at maximum when resistance is at 0.  But what this control does (or should do) is alter the bias.  Center bias for this stage would probably be around 5k somewhere.  Increasing the resistance would push the stage toward cut off, sort of like lowering the forward voltage of a diode clipper.  Eventually, the entire negative side of the waveform would be gone.  In the other direction, decreasing resistance would warm bias the stage, heading toward 0 Grid volts, eventually making the triode a half wave rectifier.  This is what it looks like is happening with the second stage.  It could be grid leak biased I suppose, but 470k doesn't seem enough to give a proper grid bias (probably more like 10M!)

Can anyone offer some theoretical insight as to why this operates the way it does?

[MikeH]

I am using an unregulated 12V DC power supply...It can shoot upwards of 16.5V DC.

I'm a little late on this, but I'm pretty sure this thing needs regulated voltage.  I tried mine with an unregulated 12V power supply and it didn't work hardly at all.  Mostly just made noise; a little signal coming through.  But when I use a boss-style regulated 9v power supply, it works fine.

[Renegadrian]

The first I made was without the regulator - it worked but hiss was a nightmare - then a 7812 woked me up and hiss was gone...

[tranceracer]

Like FrequencyCentral's summary, I've just finished consolidating some notes and diagrams from this fine forum thread.  I was getting tired of opening and closing diagrams so decided to consolidate everything to one document and wanted to consolidate the mods for this pedal. 

Just thought other folks here may be able to use this rather than browse thru 34+ pages of this thread (which is excellent reading by the way) to find tips and mods.  Maybe it will inspire others to build one or two... or three..  or...   

http://www.aronnelson.com/DIYFiles/up/12AU7-6111_Valve_Caster_Summary.pdf

-bK

[frequencycentral]

I've just finished consolidating some notes and diagrams from this fine forum thread.  I was getting tired of opening and closing diagrams so decided to consolidate everything to one document and wanted to consolidate the mods for this pedal.http://www.aronnelson.com/DIYFiles/up/12AU7-6111_Valve_Caster_Summary.pdf

tranceracer, that is a superb piece of work!!

You may like to add the information from this thread: http://www.diystompboxes.com/smfforum/index.php?topic=70212.0

If you're reading this you'll already know that I'm obsessed with 6111 submini dual triodes!

I'm looking at ways of powering a single 6111 heater from a 12 volt supply. The 6111 requires 6.3 volts (300ma) ideally, but 6 volts should be fine.

The only example I have to go on is Dano12's way of powering the Subcaster, which uses an LM317 and associated parts.

I'm thinking a simple resistor voltage divider would do the trick a little more elegantly.

Just looking at the math:

6 volts divided by 300mA = 20 Ohm

6 volts multiplied by 300mA = 1.8 Watts.

So - I'm looking at a voltage divider using two 20 ohm/1.8 watt resistors. Is this correct?

Next: I only have 10 ohm/3 watt in my parts bin. Am I right in assuming two of these are more than enough?

Finally: Most voltage dividers I've seen for 'vref' purposes include an electro cap (say 10uf) between the vref and earth, should I include one in my voltage divider?

Thanks!

The tubes' heaters allow 300ma to pass when there is 6.3V across them, and they are resistive. That means, as you properly compute, that the resistance of a heater is 6.3V/0.3A = 21 ohms. If you have 12Vdc and want to drive 300ma into you heaters, you can do that easily enough without using a voltage divider by putting a resistor in series with the heater. The resistor is R = V/I = (12-6.3)/0.3 = 5.7/0.3 = 19 ohms. It would dissipate 5.7*0.3 = 1.7W and you'd need to use a 3W resistor to keep it from runnig at about 200C surface temp.

A 20/20 divider will not give you what you think. A divider composed of 20 ohms / 20 Ohms from 12V will gie you 6V only when there is no load on the 'Y"s. This produces 6C only when it's not loaded.

Thank you again R.G., that's just great! Amazingly simple solution. 

Summary: Running a 6111 submini tube heater at 6.3 volts from a 12 volt DC supply.

Put a 19 ohms 3 watt resistor in series with the heater.

So - no need for the LM317/220 ohm resistor/1K trimpot.


EDIT: I tried it - it works. I had two 10 ohm 3 watt resistors in my parts bin which I scavenged from an old T.V. set. With 5% tolerance, they add up to 19 ohm in series. They get HOT! But then so does the tube, or an LM317 for that matter! They actually get too hot to touch for more than a few seconds - much hotter than the tube.

[danielzink]

I've benn obsessing over this pedal also......

One thing I'd like to add - I contacted Jimmy H re: the tone stack PCB. It wasn't making sense to me how it was laid out vs his Pepper Shredder PCB on page (25 ? 26?) which has -right on the PCB TS-A (tone stack in) and TS-B (tone stack out).

Here's his reply:

I see what you mean (and it was in Dutch).
And you should discard the volume pot in the layout of the tonestack (because there is already a volume pot on the shredder)
So Connect A with in
                 B    with middle tap of the treble pot
                Aarde with Ground from the pepper shredder.

I also have used this layout for an amplifier of mine, that's why the volume pot is on the layout of the tonestack.



HTH, Dan

[ehofherr]

Thanks Tranceracer......I'm looking to build this pedal.....must get parts.

[tranceracer]

Rick, thanks for the additional tips!  I've updated the .pdf.  I've also added links to the diagrams to the authors in the thread.

Thanks Tranceracer......I'm looking to build this pedal.....must get parts.

No problemo!  It's the great members of this forum who actually did all the work!    I just consolidated it.

Enjoy!
-bK

[FlyingZ]

Very small review:
I tried it out at an outdoor gig last weekend. I stomped all configurations I could think of and it ended up as a semi-clean lead pedal for songs like sweet Home Alabama. It could slightly overdrive my clean channel without the typical solid-state wimpness.

I tried boosting it with MXR, TS9, and CS-3 which all failed. It worked best alone as a clean channel boost.

I'll give it a try next weekend at another outdoor event but as for now it likely wont make my rig 

[tranceracer]

Very small review:
I tried it out at an outdoor gig last weekend. I stomped all configurations I could think of and it ended up as a semi-clean lead pedal for songs like sweet Home Alabama. It could slightly overdrive my clean channel without the typical solid-state wimpness.

I tried boosting it with MXR, TS9, and CS-3 which all failed. It worked best alone as a clean channel boost.

I'll give it a try next weekend at another outdoor event but as for now it likely wont make my rig 

Yea I use it by itself to overdrive my amp sim.  It doesn't play well with my other pedals either.  Right now it's the main pedal for the tone I'm looking for.

Here are some sound clips:
Valve Caster boost kicks in at about T-24 seconds. Recording setup: Humbucker (bridge position), valve caster (stock setup), amp simulator, recording rig.
http://www.aronnelson.com/gallery/main.php/v/bK-diystompbox/ValveCasterRiff+001.mp3.html

TranceRiff using ValveCaster Pedal. Valve Caster kicks in at T-23 seconds.
http://www.aronnelson.com/gallery/main.php/v/bK-diystompbox/TranceRiff+003.mp3.html