Here I will publish a Headphone Amplifier with 6N1P and 6AS7
based on the optimized Morgan Jones circuit with OTL output.
Here is that circuit https://headwizememorial.wordpress.com/wp-content/uploads/2018/03/cmoy5_1a.gif
There will be one circuit for 300 Ohm headphones and one for 32 Ohm.
You are all welcome to follow and discuss 🙂
Here is the 300 Ohm version. It has lower distortion.
based on the optimized Morgan Jones circuit with OTL output.
Here is that circuit https://headwizememorial.wordpress.com/wp-content/uploads/2018/03/cmoy5_1a.gif
There will be one circuit for 300 Ohm headphones and one for 32 Ohm.
You are all welcome to follow and discuss 🙂
Here is the 300 Ohm version. It has lower distortion.
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Your simulation shows quite optimistic THD. My LT Spice gives 0.27% at the same signal level.
I have built one OTL headphone amplifier with 6AS7G using normal AC-heaters. No hum problems at all.
Your value is surely more like the real THD.
Yes, I get optimistic numbers.
But do you get best value with 510 Ohm?
I did not searched the best value, just used the circuit you posted. There R2 + R10 is 510 Ohms.
That circuit should be modified. For example the grid voltage of 6N1P is unhealthy low, just less than -0.4 V. Should be -1 V minimum.
Yes, I know the purpose of this resistance, but was just musing that the value seems high for such a hefty valve. For comparison, the optimized Morgan Jones uses around uses 120-ohm for ECC88.
A quick search reveals the optimum value to be 1/gm or rp/mu.
At 510-ohm, you drop about 51V in that resistor and end up with less than 100V across each half of the 6AS7. This will function, of course, but may not be the most linear way to operate the valves. The datasheet will tell the tale.