This is your project, you can do anything you want. Also you may or may not change your mind about various aspects of the circuit as things progress. Projects seldom, if ever, remain exactly the same at the conclusion as when you started.
And you will learn more by building (and fixing) bad circuits than good circuits.
Very true. Keeping my goals in mind, I will endeavor to use AI and y'alls' help to achieve them in the smartest way possible. And I am sincerely grateful, from the bottom of my heart. There is no way to put a dollar value on the combined expertise and experience of this board.
Let me try to describe my goal amp in my own words:
A single-ended, common cathode tube-mosfet hybrid stereo headphones amplifier capable of delivering at least 1W/ch into 32Ohms and at least 300mW/ch into 300Ohms, with an inside-the-case potentiometer to adjust cathode bias. Regular 1/4" TRS is fine, but if a 4-pin XLR would fit into a Whammy chassis, that would be prefered.
That's my Mary Poppins wish list.
A single-ended, common cathode tube-mosfet hybrid stereo headphones amplifier capable of delivering at least 1W/ch into 32Ohms and at least 300mW/ch into 300Ohms, with an inside-the-case potentiometer to adjust cathode bias. Regular 1/4" TRS is fine, but if a 4-pin XLR would fit into a Whammy chassis, that would be prefered.
That's my Mary Poppins wish list.
That's pretty straightforward. Don't forget the power supply, which may take up more space than the audio circuitry.
True. I've selected an AS-1T150. It has a 150V .33A secondary to feed the tube, a 6.3V 3A secondary to feed the heater AC, and we'll rectify and use a voltage doubler to supply the mosfets.
Schottky diodes to rectify for the mosfets, 1N4007 diodes in a full-wave bridge rectifier for the tube.
That's amazing! I like the idea of inverting the tubes' pcb. Do you know if that's possible in a whammy chassis? What are your dimensions?
Most importantly, how does it sound? You've done a beautiful job, here, just going by looks!
Most importantly, how does it sound? You've done a beautiful job, here, just going by looks!
Here's my Bill of Materials. Do you see any mistakes, anything that was left out or should be improved, or was included but isn't necessary or helpful?
### **Bill of Materials
---
#### Resistors
- Bourns Potentiometer 3299W-1-103 (10kΩ, adjustable trimmer)
- Quantity: 1, Approx. Price: $2.00
- Vishay PR01 470R (470Ω, 1W for cathode bias resistor)
- Quantity: 2, Approx. Price: $0.20 each
- Panasonic ERX-2SJ0R22 (0.22Ω, 2W for MOSFET source resistors)
- Quantity: 2, Approx. Price: $0.50 each
- Vishay PR01 1kΩ (1kΩ, 1/2W grid stop resistors for tubes)
- Quantity: 2, Approx. Price: $0.10 each
- Vishay PR02 10Ω (10Ω, 1/4W gate resistors for MOSFETs)
- Quantity: 2, Approx. Price: $0.10 each
---
#### Capacitors
- Coupling Capacitors:
- WIMA MKP10 Polypropylene (100nF, 250V)
- Quantity: 2, Approx. Price: $2.50 each
- Power Supply Smoothing Capacitors:
- Nichicon UVZ2A101MPD (100µF, 250V electrolytic for tube B+ supply)
- Quantity: 2, Approx. Price: $1.00 each
- MOSFET Power Supply Capacitors:
- Nichicon UPW1J102MHD (1000µF, 63V electrolytic)
- Quantity: 2, Approx. Price: $1.50 each
- Decoupling Capacitors (for high-frequency decoupling):
- WIMA MKP10 Polypropylene (0.1µF, 250V)
- Quantity: 4, Approx. Price: $1.00 each
---
#### Diodes
- Rectifier Diodes for 150V Supply:
- 1N5408 (3A, 1000V diode)
- Quantity: 4, Approx. Price: $0.25 each
- Schottky Diodes for MOSFET Power Supply:
- 1N5819 (40V, 1A Schottky)
- Quantity: 2, Approx. Price: $0.10 each
- Zener Diodes for MOSFET Gate Protection:
- BZX55C15 (15V Zener for gate protection)
- Quantity: 2, Approx. Price: $0.20 each
---
#### Relays & Protection
- Soft-Start Circuit Relay:
- Omron G2R-1-E-T130 DC12 (12V, 10A, SPDT relay)
- Quantity: 1, Approx. Price: $3.50
- Headphone Output Delay Relay:
- Panasonic TX2SA-LT-12V (12V, DPDT signal relay)
- Quantity: 1, Approx. Price: $2.50
- NTC Thermistor for Inrush Current Limiting:
- Amphenol CL-60 (10Ω, 5A thermistor)
- Quantity: 1, Approx. Price: $1.00
---
#### Other Parts
- ALPS RK27 Blue Velvet Potentiometer (50kΩ volume pot)
- Quantity: 1, Approx. Price: $20.00
- Kingbright WP7113SRD (Red LED)
- Quantity: 1, Approx. Price: $0.10
- Schurter OGN-SMD (SMD fuse holder)
- Quantity: 1, Approx. Price: $2.00
- Littelfuse 37211000000 (1A fuse for MOSFET section)
- Quantity: 1, Approx. Price: $0.20
- Littelfuse 37221500000 (2A fuse for tube section)
- Quantity: 1, Approx. Price: $0.25
---
#### Chassis Components (with XLR Connector)
- Neutrik NC4FXX (Female 4-pin XLR connector for headphone output)
- Quantity: 1, Approx. Price: $4.50
- REAN NYS367-0 & NYS367-2 (RCA input jacks, black & red)
- Quantity: 2, Approx. Price: $1.50 each
- Parts Express 240-2218 (Aluminum knob)
- Quantity: 1, Approx. Price: $7.00
- Schurter DD12.9111.111 (IEC filtered PEM with integrated switch)
- Quantity: 1, Approx. Price: $12.00
- Harwin R30-3002502 (M3 standoffs, 25mm)
- Quantity: 4, Approx. Price: $1.00 each
- McMaster Carr 92000A114 (M3 screws)
- Quantity: 8, Approx. Price: $0.10 each
- McMaster Carr 90695A033 (M3 nuts)
- Quantity: 8, Approx. Price: $0.05 each
---
#### Transformer
- AS-1T150 (Toroidal transformer, 150V secondary, 6.3V taps)
- Quantity: 1, Approx. Price: $45.00
---
#### Tube
- 12AU7 Tube
- Quantity: 1, Approx. Price: $35.00
---
#### Chassis
- Whammy Chassis
- Quantity: 1, Approx. Price: $120.00
---
### Total Estimated Cost
- Total Cost: $320 - $350 (excluding PCB manufacturing and paying the electrician to test it)
---
### **Bill of Materials
---
#### Resistors
- Bourns Potentiometer 3299W-1-103 (10kΩ, adjustable trimmer)
- Quantity: 1, Approx. Price: $2.00
- Vishay PR01 470R (470Ω, 1W for cathode bias resistor)
- Quantity: 2, Approx. Price: $0.20 each
- Panasonic ERX-2SJ0R22 (0.22Ω, 2W for MOSFET source resistors)
- Quantity: 2, Approx. Price: $0.50 each
- Vishay PR01 1kΩ (1kΩ, 1/2W grid stop resistors for tubes)
- Quantity: 2, Approx. Price: $0.10 each
- Vishay PR02 10Ω (10Ω, 1/4W gate resistors for MOSFETs)
- Quantity: 2, Approx. Price: $0.10 each
---
#### Capacitors
- Coupling Capacitors:
- WIMA MKP10 Polypropylene (100nF, 250V)
- Quantity: 2, Approx. Price: $2.50 each
- Power Supply Smoothing Capacitors:
- Nichicon UVZ2A101MPD (100µF, 250V electrolytic for tube B+ supply)
- Quantity: 2, Approx. Price: $1.00 each
- MOSFET Power Supply Capacitors:
- Nichicon UPW1J102MHD (1000µF, 63V electrolytic)
- Quantity: 2, Approx. Price: $1.50 each
- Decoupling Capacitors (for high-frequency decoupling):
- WIMA MKP10 Polypropylene (0.1µF, 250V)
- Quantity: 4, Approx. Price: $1.00 each
---
#### Diodes
- Rectifier Diodes for 150V Supply:
- 1N5408 (3A, 1000V diode)
- Quantity: 4, Approx. Price: $0.25 each
- Schottky Diodes for MOSFET Power Supply:
- 1N5819 (40V, 1A Schottky)
- Quantity: 2, Approx. Price: $0.10 each
- Zener Diodes for MOSFET Gate Protection:
- BZX55C15 (15V Zener for gate protection)
- Quantity: 2, Approx. Price: $0.20 each
---
#### Relays & Protection
- Soft-Start Circuit Relay:
- Omron G2R-1-E-T130 DC12 (12V, 10A, SPDT relay)
- Quantity: 1, Approx. Price: $3.50
- Headphone Output Delay Relay:
- Panasonic TX2SA-LT-12V (12V, DPDT signal relay)
- Quantity: 1, Approx. Price: $2.50
- NTC Thermistor for Inrush Current Limiting:
- Amphenol CL-60 (10Ω, 5A thermistor)
- Quantity: 1, Approx. Price: $1.00
---
#### Other Parts
- ALPS RK27 Blue Velvet Potentiometer (50kΩ volume pot)
- Quantity: 1, Approx. Price: $20.00
- Kingbright WP7113SRD (Red LED)
- Quantity: 1, Approx. Price: $0.10
- Schurter OGN-SMD (SMD fuse holder)
- Quantity: 1, Approx. Price: $2.00
- Littelfuse 37211000000 (1A fuse for MOSFET section)
- Quantity: 1, Approx. Price: $0.20
- Littelfuse 37221500000 (2A fuse for tube section)
- Quantity: 1, Approx. Price: $0.25
---
#### Chassis Components (with XLR Connector)
- Neutrik NC4FXX (Female 4-pin XLR connector for headphone output)
- Quantity: 1, Approx. Price: $4.50
- REAN NYS367-0 & NYS367-2 (RCA input jacks, black & red)
- Quantity: 2, Approx. Price: $1.50 each
- Parts Express 240-2218 (Aluminum knob)
- Quantity: 1, Approx. Price: $7.00
- Schurter DD12.9111.111 (IEC filtered PEM with integrated switch)
- Quantity: 1, Approx. Price: $12.00
- Harwin R30-3002502 (M3 standoffs, 25mm)
- Quantity: 4, Approx. Price: $1.00 each
- McMaster Carr 92000A114 (M3 screws)
- Quantity: 8, Approx. Price: $0.10 each
- McMaster Carr 90695A033 (M3 nuts)
- Quantity: 8, Approx. Price: $0.05 each
---
#### Transformer
- AS-1T150 (Toroidal transformer, 150V secondary, 6.3V taps)
- Quantity: 1, Approx. Price: $45.00
---
#### Tube
- 12AU7 Tube
- Quantity: 1, Approx. Price: $35.00
---
#### Chassis
- Whammy Chassis
- Quantity: 1, Approx. Price: $120.00
---
### Total Estimated Cost
- Total Cost: $320 - $350 (excluding PCB manufacturing and paying the electrician to test it)
---
Last edited:
AI is getting kinda scary smart. But it will make weird mistakes and sometimes double-down to the point of completely breaking itself if you call out its mistakes. Such as insisting out of the blue that the 12au7 was an 8 pin tube. I copy-pasted the wikipedia page into the prompt to try to correct it, since it couldn't read the datasheet for the tube. even so, it would not move from that. so, i had to open a new chat and prompt it from the beginning, "We are working on a project..." then it was ok again.
It's weird to work with, but it is what's making all this possible for me. Before I started talking to AI about this project last week, I had no idea what really would be involved, how the components work, what they do. So we have had a lot of conversations just teaching me about what a capacitor is, what the different composition materials of a capacitor do (polypropylene, electrolytic, film). That sort of thing. And now, when someone comes at me with a lot of higher-level jargon, I can understand (or get AI to translate) and keep in the conversation.
There's absolutely no doubt in my mind that I need your human expert input and advice on this project. But I'm also amazed at what AI has been able to teach me, and help me get done so far. Just walking me step by step through learning kicad has been an amazing help. Last week, I couldn't have told you what a diode did. And this week, I'm drawing a schematic.
It's weird to work with, but it is what's making all this possible for me. Before I started talking to AI about this project last week, I had no idea what really would be involved, how the components work, what they do. So we have had a lot of conversations just teaching me about what a capacitor is, what the different composition materials of a capacitor do (polypropylene, electrolytic, film). That sort of thing. And now, when someone comes at me with a lot of higher-level jargon, I can understand (or get AI to translate) and keep in the conversation.
There's absolutely no doubt in my mind that I need your human expert input and advice on this project. But I'm also amazed at what AI has been able to teach me, and help me get done so far. Just walking me step by step through learning kicad has been an amazing help. Last week, I couldn't have told you what a diode did. And this week, I'm drawing a schematic.
I am missing the resistors from tube grid to ground. Without ground reference the grids will charge and pinch off the tube. Standard 1M.
Great catch! Thank you!
Updated BOM with Grid Leak Resistors
Resistors
- Grid Leak Resistors:
- Vishay PR02 1MΩ (1MΩ, 1/2W grid leak resistor for tube grids)
- Quantity: 2 (one per channel)
- Approx. Price: $0.10 each
Schematic Update
- Add the 1MΩ resistors from the grids of the 12AU7 (pin 2 and pin 7 for the two triodes) to ground in your schematic.
Yeah, it's a whole new world. AI is enabling complete ignoramuses like me to get things done that usually only an electrical engineer can get done. And hopefully, in maybe 6 months or less, I'll have the headphone amp that is just perfect for me.
Pretty soon, all this will be over, though. I'm maybe one of the few humans who will get to use AI in this way, still having to actually learn what everything is and how it works, and doing the work myself once you and AI have helped with the design. In a year or two, I'll be able to just tell the AI want sort of amp I want, and it will design the entire thing, do the schematics and assign footprints, print the pcb, and have a robot assemble it and ship it to me. And it probably won't cost too much more than the parts. Probably, the money that I'll spend on getting an electrician to test this thing would become the manufacturer's profit, so it would end up costing me about the same. But I'd be left with an amp, and no knowledge or experience of designing and building it. I really want that knowledge and experience, though. This is as much about me as it is about the amp, for me. I am a retired, disabled veteran, and I need something to stretch my brain and keep me busy and creative.
Pretty soon, all this will be over, though. I'm maybe one of the few humans who will get to use AI in this way, still having to actually learn what everything is and how it works, and doing the work myself once you and AI have helped with the design. In a year or two, I'll be able to just tell the AI want sort of amp I want, and it will design the entire thing, do the schematics and assign footprints, print the pcb, and have a robot assemble it and ship it to me. And it probably won't cost too much more than the parts. Probably, the money that I'll spend on getting an electrician to test this thing would become the manufacturer's profit, so it would end up costing me about the same. But I'd be left with an amp, and no knowledge or experience of designing and building it. I really want that knowledge and experience, though. This is as much about me as it is about the amp, for me. I am a retired, disabled veteran, and I need something to stretch my brain and keep me busy and creative.
Added to BOM:
Bleeder Resistor
- Vishay PR02 100kΩ, 2W Metal Film Resistor(Mouser Part Number: 594-PR02-100K)
- Resistance: 100kΩ
- Power Rating: 2W
- Tolerance: ±5%
- Voltage Rating: 500V (suitable for handling the high voltage in your tube amp's power supply)
- Quantity: 2 (one for each capacitor that needs to be discharged)
- Approx. Price: $0.50 each
The problem that I currently see with AI is that it can only answer a question, it cannot teach a broad spectrum of things like what you personally go through a learning curve and experience. Yes shure it can probably design an amplifier to a set of requirements or specification, but you still have to tell it exactly what you want. Now the fact that you have to tell it, is the engineering task in anyway. Lets say I give a technician my broad scribbled schematic and what I need it to comply with, there is little difference, it is the technicians task to make my engineering ideas work.
Can AI come up with new innovation because there is no published data on it in existence yet, I doubt it very much it can only do from what is known.
Can AI come up with new innovation because there is no published data on it in existence yet, I doubt it very much it can only do from what is known.