Need some advice on a guitar pedal

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.

barry said:

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.

Click to expand...

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

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.

barry said:

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.

Click to expand...

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.

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.

barry said:

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 Sep 22, 2021 ---

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.

Click to expand...

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.

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.

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.

betwixt said:

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.

Click to expand...

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