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-   -   haedphone amp. using 6418< NEED HELP (http://www.diyaudio.com/forums/tubes-valves/203875-haedphone-amp-using-6418-need-help.html)

briansune 6th January 2012 08:21 AM

haedphone amp. using 6418< NEED HELP
 
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


http://i1206.photobucket.com/albums/...-Schematic.png

roline 6th January 2012 11:08 AM

1 Attachment(s)
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....

briansune 6th January 2012 09:59 PM

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 7th January 2012 04:22 AM

Quote:

Originally Posted by briansune (Post 2850000)
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

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

briansune 7th January 2012 08:18 AM

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.

http://i1206.photobucket.com/albums/...riansune/1.png

astouffer 7th January 2012 04:41 PM

That won't work either. The tubes have to drive the transistor, and the transistor drives the headphones.

briansune 7th January 2012 04:50 PM

how about adding a small output transformer without the transistor driving?

Could you give the formula of the output gain?


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