• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

haedphone amp. using 6418< NEED HELP

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briansune

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Joined 2011
I would like to try the 6418 tube in headphone amp.

And if it is possible to run the headphone(32-44ohms) without an op amp. or just use transistor MOS or NPN??

THANKS


6418-miniature-Tube-Preamp-Headphone-Schematic.png
 
roline

roline

Member
Joined 2010
I did a tube-MOSFET hybrid amp, and ran the output Mosfet as a class A follower with a CCS biased at 12Volts across the stack at 200ma. I increased the output bias and it would drive a 8ohm speaker.... backed it down to 200ma for headphone use.
Verify the output current drive on the Opamp, you would want around a 8 volt swing at 125ma or more....
 

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briansune

Member
Joined 2011
Really thanks for sharing Roline < The amp looks really good at all, but i wanna to use 6418 to drive a headphone via transistor. The reason is that i wanted to use it in hand carry(out door) beside of indoor using.

6418 is a really small tube with a fm 1.25V and 0.01A, max. P is about 30V, 0.5mA


OR a tube 6519 fm 1.25V, 10mA max. P is about 30V, 0.6mA

Would you have some ideas in this too?< Hope you can help@@ THZ
 
astouffer

astouffer

Member
Joined 2004
briansune said:
Really thanks for sharing Roline < The amp looks really good at all, but i wanna to use 6418 to drive a headphone via transistor. The reason is that i wanted to use it in hand carry(out door) beside of indoor using.

6418 is a really small tube with a fm 1.25V and 0.01A, max. P is about 30V, 0.5mA


OR a tube 6519 fm 1.25V, 10mA max. P is about 30V, 0.6mA

Would you have some ideas in this too?< Hope you can help@@ THZ
Click to expand...

That design does not look very good. At first glance R3 and R4 seem way too large. I don't think you can run two filaments from the same supply without getting a lot of crosstalk between the channels.

If you want to drive headphones with just a transistor take a look here HeadWize - Project: A Class A MOSFET Headphone Driver by Greg J. Szekeres
 
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briansune

Member
Joined 2011
Thanks astouffer< the site you posted can be used for an example.

The schematic is not my design, this is come from a kid, as you said some of the resistor might to high(This may be because the kid act the 6418 as pre-amp? and the op amp as the output?) So i am thinking use the 6418 tube as the op amp and replace the original pre-amp into transistor.

1.png
 
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