Hello all. I have working on this on and off for a few months. Last couple of hours I have been refining this more and more. Posting to see if any of you who are more experienced see any glaring issues that I do not.
What results do you get? Gain, freq response, that sort of thing?
BTW, no use to sim two channels, they are identical and only slow the sim down.
Jan
BTW, no use to sim two channels, they are identical and only slow the sim down.
Jan
Is it a preamp?? Not sure what you're aiming for with a KT88 output running at 2.5 mA. Here's a screenshot so others can see.
Also once you have discusses the goals - what are your thoughts for the power supply?
It’s a good start and people appreciate you’re putting in the work. @6A3sUMMER has some very valid points about what is the end goal which will guide much of the advise.
It’s a good start and people appreciate you’re putting in the work. @6A3sUMMER has some very valid points about what is the end goal which will guide much of the advise.
Sorry, the version I posted was mainly to show how I plan on doing everything including the sub channel. The file I run the simulations on is only a single channel. The photo is at the output (not sub)
Phono stage has 100ma output. looking to build a preamp and power amp in one package and hopefully also have a LPF at the output for a sub channel.
Power goal is open. I mainly want to make a working unit on my first go, after that i can start building /refining designs for power.
8ohms per channel is the impedance I am looking to use
I intend to drive the speaker directly, there will be a 1:1 transformer at the output then 8ohm speaker
Power supply: I plan on taking the 110v AC and stepping up to 220v then rectifying. Unsure if I will used a Full Bridge or go with a tube rectifier for looks.
You can't drive a 8r load with a 25k plate resistor.
OK, you "can", but: you will get less than 8/25008 or 0.00032 of your supply voltage as swing at the load. Taking 200V supply, that is 0.06 volts. Peak. That is 0.000,25 Watts, or 36dB down on 1 Watt. Taking typical speaker as 88dB SPL/Watt that is 52dB SPL on the loudest peaks, and probably 40dB SPL average. That's near the ambient noise level of a house. (Mine touches 35dBSPL but I am a mile back in the woods.)
Probably mV not mA.
So the usual way of working is to understand the output and work back to fit with the input. Remember that a tube is a voltage to current converter.
If you know the rough voltage (peak) input and the voltage output required with the speaker load (assuming a consumer line level input, 100mV as pointed out?) then you will want to work out the gain required. Break that up for each stage (and include feedback as needed).
It is important to understand that each stage is not isolated and will see the the input and output - hence PRR’s point about the transformer.
Work out the voltage peak required (and therefore current etc) for the speakers you have. That will the start shaping the conversation and suggestions for the transformer (power amp) - i would avoid OTL for your first amp.
If you know the rough voltage (peak) input and the voltage output required with the speaker load (assuming a consumer line level input, 100mV as pointed out?) then you will want to work out the gain required. Break that up for each stage (and include feedback as needed).
It is important to understand that each stage is not isolated and will see the the input and output - hence PRR’s point about the transformer.
Work out the voltage peak required (and therefore current etc) for the speakers you have. That will the start shaping the conversation and suggestions for the transformer (power amp) - i would avoid OTL for your first amp.
Last edited:
So if you've not read the beginner's thread for tubes(https://www.diyaudio.com/community/threads/on-line-tube-learning-for-newbies.38278/) , there's a number of great reasources. One is Merlin's web page: https://www.valvewizard.co.uk/ even if you don't take his precise design, it will take you through the steps required.
Also that 100mV isn't the cartridge output? If so you will need a network such as an RIAA equalisation network.
Also that 100mV isn't the cartridge output? If so you will need a network such as an RIAA equalisation network.
Last edited:
The 100mv is coming out of the phono output of my turntable, measured with my scope. I picked up this book and have been designing as go though the book as well (Link 1). Also I may have misspoken. I will not be driving the speaker directly off the tube. I will be using an output transformer. which I have not chosen. But lets just say for now I will use the one in Link 2. So then how would I simulate this in LTSpice? Here is the datasheet of the speakers I plan on using as well (Link 3).
When I put this amp together in LTSpice it was done from the input to the output, the goal was to have a clean output at the wattage I was looking to get. Figured if I ran into wattage issues when built I could put a load in LTSpice that made the simulation match what I was seeing with the scope then adjust the values of capacitors and resistors then swap what I needed out then. Basically any kind of output would make me happy, then adjust parts by using trial and error to get the result I wanted. Super rough prototype then refine over and over until desired result is achieved.
Link 1
https://www.amazon.com/Valve-Amplifiers-Morgan-Jones/dp/0080966403
Link 2
https://s3.amazonaws.com/tubedepot-com-production/spree/attached_files/1750A.pdf?1611850448
Link 3
https://www.focal.com/sites/www.foc.../document/aria_906_specification_sheet_gb.pdf
When I put this amp together in LTSpice it was done from the input to the output, the goal was to have a clean output at the wattage I was looking to get. Figured if I ran into wattage issues when built I could put a load in LTSpice that made the simulation match what I was seeing with the scope then adjust the values of capacitors and resistors then swap what I needed out then. Basically any kind of output would make me happy, then adjust parts by using trial and error to get the result I wanted. Super rough prototype then refine over and over until desired result is achieved.
Link 1
https://www.amazon.com/Valve-Amplifiers-Morgan-Jones/dp/0080966403
Link 2
https://s3.amazonaws.com/tubedepot-com-production/spree/attached_files/1750A.pdf?1611850448
Link 3
https://www.focal.com/sites/www.foc.../document/aria_906_specification_sheet_gb.pdf
Last edited: