Tube boost + overdrive running off a 9 volt battery

[Ark Angel HFB]

Sound samples and effect of the boot strap?

[esdiezy28]

I don't have a good recording rig, so I'll have to charge up my video camera recorder. Sound samples soon. Though I apologize in advance for my playing skills, be forewarned!

[Ark Angel HFB]

I'll say this much... after a little testing I'm just very very shocked that no company does this kinda simple pure pedal... they sound so much better then diode clipping and what not.

Tubes for the win...

Also, and this has more to do with general pedal construction... If you are not using regulated power supplies I highly suggest that every pedal you built has the following in the circuit.

(V In) -> 100ohm resistor -> 470uF cap to ground (Optional 220uF cap to ground) -> (V Out to circuit) Add this to the start of every circuit and power supply noise will be a thing of the past... Also don't forget that until you get something inside a box... it can have hum/hizz/buzz from junk signals that are in the air... so it might hum/hiss/buzz just from being outside the box.

[esdiezy28]

I think everyone who's built this project has a better understanding of power supply hum issues than before they started. I've had hum probs in non-tube pedals, fizzy and whatnot. But if you don't filter the power for tube heaters, you get some REAL HUMMERS! My first build got all the dogs on the street barking at once before I dropped a 7812 in there to regulate the power.

[fastcar123]

I built mine with the exception of no volume pot and I have no signal. what can I do?

[HerrUlder]

Hi Guys,

i've build the BoobTube Twin from Juansolo with the Charge Pump from Renegadrian. Here are the schematics:





It's not running very well, Tone Knobs and the Master Volume are working great but if  i turn the gain knob, i only get a weird buzzing noise.

Here are my results:





Thanks,
Jan

[Ark Angel HFB]

well off hand I'd ssay something is wrong when you have that kinda voltage on pin 7 of tube 2.

Look I don't know what the dude who drew up the boobtube is thinking, not in an insulting way as I honestly don't know everything about these designs... but from what I know you should be drawing you out sig from ether pin 6 or 2 then through a cap and out to the tone stack or volume.

I only understand some of what is going on with V2B's pin 8... but what I do know is that you may want to try adding a cap(10nf to 1uf) between vb2's Pin 7 and va2's Pin 2.

[J0K3RX]

Yeah, I believe Ark Angel HFB is right... I think you need another 100k resistor from the power rail to pin 6 of V2B. In between the 100k resistor and pin 6 connect to the 33k and 470pF cap of the tone stack. You also may want to replace the 100k resistor from pin 8 of V2B to ground to 820 ohm or so..? Maybe a 22n cap from pin 6 on V2B to the tone stack?

[Ark Angel HFB]

btw way guys... has anyone tried much lower value for the plate resistors?

I've been having some really lovely crunch tones from about 22k to 33k.

I'm making one for a buddy of mine and with the profit from selling it I'll be sure to grab some more jumpers(I don't like bread boards...) and will fully jumper a tube socket up so that I can test every component.

I'll try drawing signal from the pin 3/8 side but I've only every seen that on this last boobtube design so it may be a mistake.

also I think if we pay some careful attention to the bass in the circuit, there may be a way to get true high gain out of one tube without it sounding flabby... I'm if we limit bass and tweak the values for cathode resistance and plate resistance we might just get a really great hard od pedal that could be used as some kinda awesome crunch pedal and then a solo booster.

I still have not tried the double version but I'll pick up some larger cases and have a go at it. ^_^

[rutabaga bob]

If you're wanting a higher-gain pedal, check out the Tube Star...

[Ark Angel HFB]

IDK man two valve caster into each other is a crazy great gain pedal.

[Ronan]

That Boob Tube twin schematic looks like a Marshall 2204 preamp, the V2b is a DC-coupled cathode follower therefore the high voltage on pin 7. There is nothing wrong with it that I can see.

[Ark Angel HFB]

so you can draw signal from the pin 8/3 side of triodes... learning new crap all the time. XD

[Ronan]

Yes its similar in principle to the tranny emitter-follower, it doesn't boost voltage (there is no voltage gain), but it can drive a bigger load (lower output impedance). In that schem they are using it to drive the tone stack.

The more I learn the less I know, these forums are good at doing that to a person

[Ark Angel HFB]

Yes its similar in principle to the tranny emitter-follower, it doesn't boost voltage (there is no voltage gain), but it can drive a bigger load (lower output impedance). In that schem they are using it to drive the tone stack.

The more I learn the less I know, these forums are good at doing that to a person

lol I know... it like you learn something and you are like ok these are the guide lines... then the learn a little more and all your guide lines fall completely away are "Not always true."

So basically the last bit in the boobtube is like a buffer too drive the tone stack and lower the impedance so that pedal that come after it are not crap sounding.

[juansolo]

That Boob Tube twin schematic looks like a Marshall 2204 preamp, the V2b is a DC-coupled cathode follower therefore the high voltage on pin 7. There is nothing wrong with it that I can see.

Yup. All it is is the pre-section of a JCM800 with a little bit of filtering on the end of it to tame the top a little that dealt with by the presence control later in the amp.

Not sure what's up with the OPs build.

[esdiezy28]

I built mine with the exception of no volume pot and I have no signal. what can I do?

From the negative side of the 1uf output capacitor, where your output is connected, place a 100k resistor to ground. This will work as if you've cranked your 100k Volume pot to max. That should give you an output signal

[Ark Angel HFB]

I built mine with the exception of no volume pot and I have no signal. what can I do?

From the negative side of the 1uf output capacitor, where your output is connected, place a 100k resistor to ground. This will work as if you've cranked your 100k Volume pot to max. That should give you an output signal

I'm probably showing a startling amount of noob-ishness but as to your statement above... WHHHYYY?

No really... wy would the resistor give him an output signal?

is it an impedance issue. (Still barely grasp anything about impedance at all btw.)

[esdiezy28]

I just tossed the pull-down resistor in there to simulate a volume pot. I'm not exactly sure why that is. This page here has some great equations http://www.aikenamps.com/Equations.htm.

I see the resistor plays a part in output impedance. It sets the load resistance, or the input resistance of the following stage (for me, thats right into my amp). Though the output impedance (Z) is = to the plate resistor if RL is not added. Also, the plate resistor (RP), output capacitor, and load resistor form a high pass break point. Why this is keeping you from getting an output signal without the load resistance, I'm not sure

[Alfie]

Trying to troubleshoot my valvecaster. I am getting a lot of gain and the volume and tone pots don't seem to do anything. I have checked the wiring a million times but can't see a problem, why might I be getting these results?