Can I stop the hissing in my Valvecaster pedal?

[jaki54321]

I just recently built a Valvecaster with a 12AU7 tube running off 9 volts. Im getting some noise when i turn it on. I hear it happens all the time and to do it you must install a voltage regulator and an electrolytic capacitor on the DC jack.

If this is true, can anyone explain to me how to do this? Or give me a wiring diagram on how to do it like the diagrams on the Valvecaster thread? I have built mine using the PCB-less method, but with a 3PDT switch for true bypass. The pedal works fine, its just this noise that bugs me.

[earthtonesaudio]

"Some" noise is normal for any effect, tube or solid state.  You can eliminate "excessive" noise sometimes with a quieter power supply (like you are talking about with the filtering capacitor), or sometimes different part values, or more careful layout, or any number of things.

Also, it's possible (but much less likely) that you simply have a noisier than normal tube.

[darron]

i've never actually built this circuit, but i want to see you get a good answer.

to answer your question about regulation, i'd like to first ask what kind of power supply you are using to power it?

there are a couple of sorts. if you are just using a standard DC transformer pack then that CAN bring in noise... if you are using a power supply that says that it is already regulated then caps probably won't do much good (though they are a good build practice regardless!).




here is the schematic for the circuit you are talking about:



and the build layout:



taken of course from Beavis Audio Research: http://www.beavisaudio.com/projects/ValveCaster/


i hope that somebody can give you a good answer for the noise problem...

[PRR]

Bad power usually buzzes. Not hiss.

[jaki54321]

Bad power usually buzzes. Not hiss.

well i dont know how to explain the noise... I think it is buzzing... Its much more then hissing, its like this errrrrrrrrrrrrr.... sound. Like power.

[jaki54321]

i've never actually built this circuit, but i want to see you get a good answer.

to answer your question about regulation, i'd like to first ask what kind of power supply you are using to power it?

there are a couple of sorts. if you are just using a standard DC transformer pack then that CAN bring in noise... if you are using a power supply that says that it is already regulated then caps probably won't do much good (though they are a good build practice regardless!).


here is the schematic for the circuit you are talking about:



and the build layout:



taken of course from Beavis Audio Research: http://www.beavisaudio.com/projects/ValveCaster/


i hope that somebody can give you a good answer for the noise problem...

I am using a DC power jack I bought from small bear, I also wired a 9 Volt battery plug to it. Heres the link:

http://www.smallbearelec.com/Detail.bok?no=93

I also have used it without the battery plug and the buzzing still occurs. Im using it with a 9 Volt Wall wart. I do not think it is regulated at all. I was thinking about building a Huminator from Beavis Audio, so maybe it will help, or just find a way to fix it in the pedal, but i am almost certain it is the wall wart because well, its pretty old I guess, its from radioshack, and its probably not regulated. Any ideas?

[GibsonGM]

Idea 1....post your voltage right from the wall wart while the Valvecaster is turned on.  It should be just about 9V if it is regulated.  It's probably not, tho, like you suspected.   Does the wall wart have any specs written on it, such as "9V 200mA" or anything?  You might be exceeding the current rating...you could replace it with a regulated unit, or use an LM7809 to build your own in-pedal regulator with a higher voltage wall wart....

#2: Try a cap from the + terminal of the power supply input to ground (basically, put one across the power jack - from the top of the 220K resistor to ground, say).    Try something like 47uf, 100uF, 470uF - whatever is handy and rated more than 16V.   Does this help at all?  If so, you/we could probably come up with a scheme for a simple RC filter at the input to kill some hum.

Wires crossing other wires is bad....power lines running next to signal lines and such.  Try 'chopsticking' your wiring around with pedal on to see if it changes the noise.  If it does, you'd have a "lead dress" problem...the input wire is most sensitive to noise, so try to isolate it.   

I suspect the wall wart is letting noise in, tho.  It'll be a filter job. Shouldn't be hard.


If none of the above works, post your voltages at each tube pin.  And any pics you could provide of the guts might help, too.
You should expect some Hiss....tubes do that.  But not to an annoying level!! 

[jaki54321]

Idea 1....post your voltage right from the wall wart while the Valvecaster is turned on.  It should be just about 9V if it is regulated.  It's probably not, tho, like you suspected.   Does the wall wart have any specs written on it, such as "9V 200mA" or anything?  You might be exceeding the current rating...you could replace it with a regulated unit, or use an LM7809 to build your own in-pedal regulator with a higher voltage wall wart....

#2: Try a cap from the + terminal of the power supply input to ground (basically, put one across the power jack - from the top of the 220K resistor to ground, say).    Try something like 47uf, 100uF, 470uF - whatever is handy and rated more than 16V.   Does this help at all?  If so, you/we could probably come up with a scheme for a simple RC filter at the input to kill some hum.

Wires crossing other wires is bad....power lines running next to signal lines and such.  Try 'chopsticking' your wiring around with pedal on to see if it changes the noise.  If it does, you'd have a "lead dress" problem...the input wire is most sensitive to noise, so try to isolate it.   

I suspect the wall wart is letting noise in, tho.  It'll be a filter job. Shouldn't be hard.


If none of the above works, post your voltages at each tube pin.  And any pics you could provide of the guts might help, too.
You should expect some Hiss....tubes do that.  But not to an annoying level!! 

The specs of this wall wart are 9 Volt 300mA. I think its just letting in noise or something, because I tried a 9 Volt battery, and there was MUCH less noise. It didnt last long tho(the tube ate the battery) But while I was playing, i only heard a small little hiss, which i think is the tube because i always hear tubes make small amounts of noise, more/less then others.

I have a 100uF Electrolytic capacitor left over from a broken circuit board, it still works because I have used it before, and its kind of brand new, its maximum voltage is 16 Volts. Could I use it? And when i put it on, how do I do it? Do i just solder the positive leg to the positive terminal on the DC jack, and solder the negative onto the negative terminal?

[tubelectron]

Hi
GibsonGM and Darron are right : you probably have a hum noise, not a hiss noise - so yes, use your 100uF cap as you described it, but I think that a 1000uF or more would be much more efficient at this place, due to the 250-300mA heating current which alters the damping provided by the filtering capacitor. Or you may choose a regulated DC PSU - in 12VDC instead of 9VDC, to have the correct heater voltage, except if 9VDC is compulsory for this circuit.
A+!

[jaki54321]

Hi
GibsonGM and Darron are right : you probably have a hum noise, not a hiss noise - so yes, use your 100uF cap as you described it, but I think that a 1000uF or more would be much more efficient at this place, due to the 250-300mA heating current which alters the damping provided by the filtering capacitor. Or you may choose a regulated DC PSU - in 12VDC instead of 9VDC, to have the correct heater voltage, except if 9VDC is compulsory for this circuit.
A+!

I think what I am going to do is attempt to run this pedal on 12 volts, add a filtering Cap, and a 7812 Voltage Regulator. I have been told that it is probably the best method to kill the buzzing.

[darron]

the regulator idea sounds good. more satisfying than buying a new power supply to DIY one....

what you need however is a 7809. this will take the +12v and regulate it to 9V. the regulator needs a few more volts on the input than the output.

i'd put a nice size cap on both sides of the regulator too, for good measure. if you're feeding it DC then a smaller one on the input side and then anything from 100uf to 1,000uf on the other side.

[jaki54321]

the regulator idea sounds good. more satisfying than buying a new power supply to DIY one....

what you need however is a 7809. this will take the +12v and regulate it to 9V. the regulator needs a few more volts on the input than the output.

i'd put a nice size cap on both sides of the regulator too, for good measure. if you're feeding it DC then a smaller one on the input side and then anything from 100uf to 1,000uf on the other side.

Im having an issue running the pedal on 12 volts tho. when i plug in the pedal with my 12v adapter, it does not work. Well the tube lights up, but the pedal doesnt effect my guitar. When its off, its true bypass so my guitar goes right through, when its on, the LED indicator does not turn red and nothing can be heard at all. But with 9 volts it works just fine, any ideas on how to get this workin?

[darron]

first, me saying that you need a 9V regulator does not mean that you have to match the transformer. 9volts is just the output, so you'd regulate your 12v transformer down to 9v, but you can't regulate a 12v transformer to 12v.


that's a strange issue with not being able to run a 12V. the LED should light up regardless, so something funny is going on. are you sure you are plugging in a 12v DC transformer and not AC? that would still light the tube up but not run.

[jaki54321]

first, me saying that you need a 9V regulator does not mean that you have to match the transformer. 9volts is just the output, so you'd regulate your 12v transformer down to 9v, but you can't regulate a 12v transformer to 12v.


that's a strange issue with not being able to run a 12V. the LED should light up regardless, so something funny is going on. are you sure you are plugging in a 12v DC transformer and not AC? that would still light the tube up but not run.

hmm... I'm guna give you as most of details as I can. This is what my wall wart says: plug in class 2 transformer, model number: AM-12500. Input: 120VAC 60Hz 12W. Output: 12VDC 500mA.

Judging the term transformer, I'm assuming it, well is a transformer xD I have the positive terminal of the DC Jack inside my pedal, connected to pin 5 of the 9 pin tube holder, and pin 4 to ground, the sleeve of the input stereo Jack. I also have the positive terminal running to the 2.2k resistor that goes to the led, then to the 3pdt switch. And the negative terminal on the Jack is connecting to the input jacks ring. After I changed to 12 volt, I added 4.7k resistor to the led, either way it still didn't work. What should I do?

[darron]

the 2.2k and the 4.7k resistors shouldn't matter. both should be very good.

i suppose the obvious thing to check is that the polarity is in fact correct? have you got your multi meter out yet and checked that polarity of your 12v supply compared to your 9v supply? it could be reversed which is the simplest problem that you can hope for...

[jaki54321]

the 2.2k and the 4.7k resistors shouldn't matter. both should be very good.

i suppose the obvious thing to check is that the polarity is in fact correct? have you got your multi meter out yet and checked that polarity of your 12v supply compared to your 9v supply? it could be reversed which is the simplest problem that you can hope for...

EDIT: ok I think I got something here...  I ran the positive leg on my volt meter to positive terminal on the Jack, and negative the same, I got a negative value of about 15 volts(my volt meter is a lil inaccurate sometimes idk y, but I hope it is 12), so then I swapped the legs, and I got a positive number, the same... So does tat mean the polarity has been reversed? An if so, wat should I do now?
EDIT2: I think I got more... I plugged in the 9volt and put the positive leg to positive terminal on DC Jack and negative to negative as well and I got positive! 10-11 Volts (kina crappy meter, it's old but digital atleast.) and then I swapped the legs, I got negative. I think you were right, the polarity may be switched with the 12 volt. Hmm... So should I swap the cables to the opposite terminal and confirm tat is the issue?

[GibsonGM]

Place your negative probe on a KNOWN negative point from the schematic (ground).   Probe the DC jack.  Where you think is positive should give you a + value.  Reversing the probes will of course give you a "-" value.  Probing ground should give you 0.0v.    Sounds to me like swapping the  2 wall wart wires will get your polarity correct.  Hopefully nothing has fried.....probably not, tubes are very forgiving as long as you don't pull much current thru the grid!

You should go back to the original thread you started (this one is kind of about the hiss issue, sounds like a new one developed!).    PRR over there was working with you, and he knows a LOT about your problem - just post your tube socket voltages!!  That way someone w/the same problem can find the topic.   Looking from the bottom,  pin 1 is to the left of the tube key.    Keep your "-" probe on a known ground.