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Hello swagatam,
I’ve been looking at the Korg Volca Nubass and more specifically its supposed “vacuum tube VCO”. This really intrigues me but I was unable to find any available schematics or information on how this was done and I was wondering if you knew. Thank you!
Hi Emerson,
actually this “vacuum tube VCO” thing in Volca Nubass is not like those big old glass tubes we see in vintage synths or guitar amps, not that type. Korg Volca Nubass is using this small thing called Nutube, it is actually a real vacuum tube only but very tiny and low power, so it can run inside this small Volca box without heating or high voltage drama.
Now the company never released schematics, so nobody outside really knows the exact circuit but from what Korg itself says and from people who opened it, the tube is sitting in the oscillator sound path and also in the sub bass and drive part. So the oscillator is analog but the Nutube is there to add that tube like uneven harmonic feeling, not some fake digital effect.
So yes, it is a real vacuum tube, but done in modern style, not old school tube VCO like 1970 lab equipment, more like clever compact tube flavor added into an analog synth.
That’s so cool thanks for sharing.
Thanks, glad you liked it….
Hey Swagatam, I’m a big fan of your website and your audio circuits.I was wondering if you could help me out with a project Idea I have. I’m trying to make an analog pitch shifter guitar pedal with two pots. One pot goes from an octave lower than the sound source to an octave higher than the sound source, and the second is the ability to blend the original signal and the modulated signal. I’m not sure doable this is but I thought I’d reach out anyway in case you were able to make a schematic for this. Thank you!
Hey Emerson, thank you very much for liking my website and audio circuits.
About your idea, I must say that proper analog pitch shifter which can smoothly go from one octave down to one octave up using a pot, is not really possible with simple analog circuits. Pitch shifting needs time stretching and compressing of the signal which is why most good pitch shifters are digital.
With analog circuits, we can do octave down and octave up effects separately, using rectifiers, dividers or bucket brigade ICs but the sound will be rough, noisy and the range will be limited. Clean sweeping pitch control like modern pedals is not feasible using pure analog.
The blend control part is easy, we can mix original signal and effected signal using an op amp and a pot.
However, minus one octave to plus one octave with analog pots is not practical.
Thank you for the reply! I understand that this is likely not possible, but would a circuit that’s fixed at say a fifth (the music interval) be possible? I built your robot voice modulator and it seemed to have pretty defined fifth harmonics.
Yes now this is more doable, because fixed intervals like a fifth can be made with analog tricks. What you can do is use full-wave rectifiers, frequency dividers, and mixing to create harmonics at a specific interval. Like in my robot voice modulator, the circuit creates extra harmonics and when you mix them with the original signal, you get a defined interval effect, for example a fifth.
Hi Swagatam,
I’ve noticed that in your health related circuits the “Blood electrification unit” from Bob Beck isn’t included.
I think you will be interested.
But if you share this circuit, It is very important that the protocol is also followed. The effects of i.e. medical drugs can get 10x stronger during the electrification process.
I think the importance of this Device stands in one line with such like Joule Thief or Bedini SSG
Thank you so much Waldemar, for this interesting suggestion…
I will definitely investigate this concept, and if it is feasible i will include this concept on my website.
Many thanks again.
Dear Swagatham
I am looking for PCB kit for 1000Watt amplifier you published, do you know where can i get that kit ordered, Thanks.
Thank you Swagtham truly appreciate your response.
You are welcome Suresh!
Dear Suresh,
PCB kit may not be available readymade, you may have to contact a PCB manufacturer and get it fabricated for you. There are many PCB designers online whom you can contact and check who offers the most reasonable price.
sir how are you home was work
I have driver board circuit sg3525 lm 358
which is do ups transformer or ferried core transformer
which MOSFET is quality for power
please I need diagram for this circuit inverter circuit
Abdulkarim,
You can use UPS transformer or ferrite transformer as you like by adjusting the operating voltage, PWM etc of the circuit accordingly..
MOSFET will depend on the battery, load, transformer specifications…
Hello Swagatam,
I am looking for a circuit or circuits to run a 2 phase 4 wire stepper motor from a camera(low power stepper).
I want to use a single pole 2 way switch to set direction of motor.
I want motor to run for 2 to 5 seconds then turn off motor until switch is thrown again.
Can this be done without a micro-controller?
Any help would be appreciated
Hi David,
yes it is possible using the ICs A4988/DRV8825, for optimal performance.
Thanks Swagatam, Do you have any circuit diagrams showing this please?
Hi Swagatam, That is fabulous, thank you so much.
It is the best explanation of the stepper motor control that I have found anywhere.
Now to get parts and build it.
Regards and thanks again
David
Hello, thank you for the information. I am doing home appliance board repair. I am thinking of a circuit to test an air conditioner compressor. I want to drive the IGBT module directly. I have such an idea. If you want to help, I can send the detailed module. I would be happy if you can assist. Our Turkey will advance and develop. Regards.
Sure, please send the details, if possible I will try to help!
No Problems David, all the best to you, and let me know if you have any issues with the circuit…
Hi David, I have designed it now, please check the following article…the diagram is on the bottom end of the article:
https://www.homemade-circuits.com/a4988-motor-driver-circuit-diagram-with-ic-555/
Thanks David, It is quite easy and I will design it for you, and let you know soon, please give me 1 days time..
need an electronic circuit using 555 timer, which is fed with 12VDC via a switch for 1 hour. The output of 555 circuit must be a short pulse of 1 sec generated immediately when the switch is pressed..
You can try the following circuit, just replace the BC547 transistor with a push button switch:
https://www.homemade-circuits.com/wp-content/uploads/2022/08/555-monostable-with-trigger.jpg
Thanks for your replay but the switch must be ON for 1 hour and cannot be a pushbutton.
You can make it ON for 1 hour, no problem, and until it is released the circuit will not reset and its output will continue to be inactive and off.
I am looking for a device I can buy or make to do the following:
12 volt for auto use
When the ignition is turned on to start the car it sends a signal to a timer to light a light for an adjustable time.
When the timer times out the light will go off; and the light will remain off while the ignition remains on and the car is running.
When the ignition is turned off the timer will reset itself. Each time the car is started the sequence will happen again.
Sure, you can build the following circuit for the proposed application, it will do exactly as per the requirement:
https://www.homemade-circuits.com/wp-content/uploads/2025/10/lamp-timer-for-vehicle-ignition.jpg
I have used 3nos of 1 watt LEDs here for the lamp. If you want to use an external high power lamp then you may have to add a transistor driver at the pin#3 output of the IC..
I am having trouble with the diagram as I am not electronic literate.
1. I have searched for IC 1555 and have found them with only 5 and 10 connections and many letters and numbers after the 555.
2. The capacitors at the top of the diagram shows two capacitors on the 12V battery to ground with no details on the capacitance.
Thank you for your patience.
You can use any version of the IC 555, all will have 8 pins.
https://www.homemade-circuits.com/wp-content/uploads/2019/06/IC-555-timer.png
Those two capacitors at the top positive rail near the IC pin8 and pin4 are 100uF/25V and 0.1uF/50V capacitors.
Thanks for the quick rely.
How do I adjust the time the light stays on?
The delay time can be fixed by adjusting the 1M potentiometer or preset, if preset is used instead of a potentiometer….
sir need fan Regulator dimer PCB curcuit AC 220 volt
Waqas, sorry, I do not have PCB for this project..
Hello Swagatam,
I’m looking for a high-power inverter design (220VAC, 10kW or higher) using 48V batteries as input. I’d appreciate any recommendations or guidance on suitable topologies and components.
Regarding design approaches, I’m considering a transformerless design using MOSFETs to potentially increase efficiency. However, I’ve come across information suggesting that transformers may be necessary for optimal performance. Could you please clarify the pros and cons of transformerless vs. transformer-based designs for high-power inverters?
Hi Masoud,
I think transformerless is more efficient because a transformer can have inherent core losses.
However, for 220V transformerless design, you may need a 310V DC supply for the inverter. (7nos of 48V batteries in series)
Thank you for the information.
To clarify, I’ll be using two 110VAC split-phase outputs to achieve 220VAC. My current battery setup consists of two 48VDC strings, each with a 300A output. While I have some flexibility to adjust the battery configuration, connecting seven batteries in series might not be feasible.
Do you have any suggestions for inverter designs or configurations that could work with my existing setup?
Specifically, I’d appreciate guidance on:
1. Suitable inverter topologies for high-power applications
2. Potential modifications to my battery configuration
Any recommendations or resources you could provide would be greatly appreciated
Sorry, I have no idea how to get split-phase AC from H-bridge transformerless inverter design, in that case it is better to use a transformer…
Hello and thank you for generous offer to help others.
My issue I am trying to solve may be an interesting for you.
I am wanting to simulate a pwm 12 vdc signal to a variable displacement ac compressor solenoid which operates with 12 vdc and 1 amp.
The original driver is via an auto ac control driver module which varies the duty cycle of the solenoid valve from various ic inputs.
I just want to use a ntc temp probe on the evaporator ac core for feedback and use a cpu pwm temperature fan control readily available and a n type felt to switch the ground to the valve.
The hiccup which I foresee is that a cpu 4 wire fan controller frequency is around 10ths and the solenoid valve requires around 400 hz to supply enough torque on its plunger so how do I tap into the cpu driver to change RC timing to achieve 400 hz.
Any help appreciated.
Hi, thanks for your interesting question.
However, you cannot change that CPU fan driver frequency because that PWM is fixed around 25 kHz inside the controller, so no RC can make it 400 Hz. So we can just take that PWM signal and make it control another circuit which gives 400 Hz output. We can do it by filtering that fan PWM with RC to get DC voltage and then feed that into a simple PWM generator or into one small Arduino or ATtiny chip. That chip can read the voltage or temperature from NTC and then make a new 400 Hz PWM for the compressor solenoid. We must drive the solenoid through a logic level MOSFET with one flyback diode and one fuse for safety.
I really like the work you’re doing. I also create small electronics projects, videos, and circuit designs (555 IC, sensors, and other components).
I’d love to contribute to your website for free—whether it’s project tutorials, circuit diagrams, or student-friendly content. My goal is simply to share knowledge and help more students learn electronics in a practical way.
Looking forward to your reply.
Sure! You can contribute guest posts, but without any external links. I will post them on this website…
Hi,
My children have expressed a desire to create a home made chicken coop automatically opening door system for our coop.
The basics of it are: sun light opens the door then when the sun sets the door closes.
I am thinking a solar panel, drives a motor/servo the rotation of the shaft reels in the door opening cord. (this would open the door) then a switch gets actioned when door fully open which cuts power to motor. I would assume a relay could be used so that when the solar panel gets no power (sun sets) it switches over to a battery which then drives the motor/servo the opposite way (closing door) then either the same or new switch kills power when at the full closed position.
Some considerations for the project:
– when door open full and solar panel still generating a way to shift this power to charge the battery (you battery charger circuits is how I found your blog)
I am still working out the power requirements of the motor and the locking the door open function but help understanding a circuit so that I can then teach it to my kids and then create it would be an amazing help.
Hi, I think I already have a similar kind of concept available on this website. You can check out the following link to know more about the details of this design:
https://www.homemade-circuits.com/automatic-door-circuit-for-hen-house/
The solar charger section is not difficult, and can be easily configured using an LM338 IC.
Let me know if you need any further modifications in the aforementioned concept.
hi, i have a sua2200xl APC tower type smart ups. problem is on ac mains it works but has an abnormal 34.5 volts charging the batteries and when when the mains goes off it clicks some relays and goes off . please help. +254772722582 whatsapp
Hi, without checking the circuit board or the circuit diagram it can be difficult to understand the fault.
Here’s the correct diagram for the 4093 buffer stage which you can used for triggering your 4017 IC correctly:
https://www.homemade-circuits.com/wp-content/uploads/2025/07/4093-gates-as-buffer-circuit-diag.jpg