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Need some advice on a guitar pedal

vodka_cchhino

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Hello everyone. I made my first guitar pedal that uses a tube, as shown in the schematic:
the-circuit-diagram-of-Guitar-Preamp-over-drive.jpg

Here are my questions:
1-Could i use my pedal with 24 volts? If not, are there any modifications that should be done?
2-What changes should i make so that the tone control behaves closer to a tubescreamer? I am talking about the mid hump that tubescreamer offers and how can i get this pedal to do the same
Anyway, i would be happy to hear your suggestions. :)
 

barry

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I haven't worked with tubes in about 150 years. But I question whether this circuit will really work at 9V. Maybe it will, but I'm suspicious. But if you change your 9V to 24V it probably won't matter, because you'll burn out your heater and have to throw this all away and use a circuit with modern devices, like a 2N107 transistor.

Without knowing what response you're actually looking for, it's hard to offer any advice, but it sounds like you want some mid-range peaking, i.e., a bandpass response. What you have now is simply a low-pass adjustment.
 

vodka_cchhino

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I haven't worked with tubes in about 150 years. But I question whether this circuit will really work at 9V. Maybe it will, but I'm suspicious. But if you change your 9V to 24V it probably won't matter, because you'll burn out your heater and have to throw this all away and use a circuit with modern devices, like a 2N107 transistor.

Without knowing what response you're actually looking for, it's hard to offer any advice, but it sounds like you want some mid-range peaking, i.e., a bandpass response. What you have now is simply a low-pass adjustment.
I have it on 12 volts right now, and while its working, there is a high frequency noise when the pedal is on. Saw another schematic for a tube pedal, and someone said that this noise would leave if you feed it more volts. What i am trying to achieve is an overdrive that has a tubesreamer-like mid boost but feels more dynamic
 

barry

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The real Tubescreamer doesn't actually use tubes. It uses a lot of passive shaping circuitry to model the way tubes clip, as opposed to the way semiconductors do. Tubes clip 'softer' than semiconductors, which is why it seems more dynamic.

If you insist upon using this tube circuit, and you want to boost the plate voltage, then you're going to have to find some way to drop the voltage to the heater.
--- Updated ---

The real Tubescreamer doesn't actually use tubes. It uses a lot of passive shaping circuitry to model the way tubes clip, as opposed to the way semiconductors do. Tubes clip 'softer' than semiconductors, which is why it seems more dynamic.

If you insist upon using this tube circuit, and you want to boost the plate voltage, then you're going to have to find some way to drop the voltage to the heater.
Back in the old days, when everything was just plugged into the wall, they would just use a big ceramic resistor, or, more commonly, a transformer.
 

betwixt

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Like Barry, it was during the last ice age that I last used tubes but I'm curious how you are powering it. If the 9V is from a battery, do you realize how inefficient the circuit is: 150mA goes to the tube heater, about 7mA to the LED and only about 0.1mA to make the amplifier work. (about 0.05% efficient!)

From the values and voltage ratings in the schematic, it looks to be designed to work on a much higher voltage but with an independent 12V for the heater.

Brian.
 

vodka_cchhino

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The real Tubescreamer doesn't actually use tubes. It uses a lot of passive shaping circuitry to model the way tubes clip, as opposed to the way semiconductors do. Tubes clip 'softer' than semiconductors, which is why it seems more dynamic.

If you insist upon using this tube circuit, and you want to boost the plate voltage, then you're going to have to find some way to drop the voltage to the heater.
--- Updated ---


Back in the old days, when everything was just plugged into the wall, they would just use a big ceramic resistor, or, more commonly, a transformer.
So, i could use a voltage booster for the plates and a regulator for the heaters? I guess transformers are a bit expensive for a dyi pedal just to have fun, but let me know if i am wrong.
 

barry

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There’s a reason they don’t use tubes in portable equipment. Actually, there are a LOT of reasons.If you’re doing this to learn about tubes (why you would, I dont know) there would be better circuits. If you’re just interested in making a guitar pedal, there are a lot of better circuits.
--- Updated ---

Okay, I retract my previous comment about learning about tubes. Tubes have their place. Guitar amps is the only one I can think of, though. As a guitarist, I appreciate the tone of a good tube amp. As a guitarist with a bad back and no roadies, I appreciate a good solid state amp. I own solid-state amps.
 
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vodka_cchhino

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Like Barry, it was during the last ice age that I last used tubes but I'm curious how you are powering it. If the 9V is from a battery, do you realize how inefficient the circuit is: 150mA goes to the tube heater, about 7mA to the LED and only about 0.1mA to make the amplifier work. (about 0.05% efficient!)

From the values and voltage ratings in the schematic, it looks to be designed to work on a much higher voltage but with an independent 12V for the heater.

Brian.
I am powering it with a 12 volt dc, 1amp power supply. I really dont know about efficiency though.
 

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