Speaker posts to headphones

[john & Jake the dog]

hi,
Is there a way of attenuating the speaker outputs of the Kel84 to enable me to attach my headphones (600 ohm) directly to the speaker outputs.
I did see mention of such a box on the forum but can't find any details.
Anyone done anything similar and willing to share details please ?

cheers

[Grog]

I think the easiest way would be to use a 50w 8 or 10 ohm resistor as the load and connect the headphones in paralell. this could all be put in a box with the headphone jack.
the only thing is i'm not sure if the kel84 will like having both negative outputs connected together?? i'll go check the circuit diagram

[Grog]

just checked and both negative outputs are grounded so there should be no problems.

[john & Jake the dog]

hi George,
Thanks for your reply,
Is it possible for you to sketch out your description for me to make it easy for me to understand Parralell etc

Found this,
http://sound.westhost.com/project100.htm

Seems to be similar to your description but it warns it is not to be used if the neg of the amp can't be grounded, you imply that this is the case.
Is it safe for the 84again, not difficult.
cheers

[Grog]

the problem with that circuit is that it doesn't load the output transformer correctly this means that the output valves will swing too much voltage, which isn't good long term.
the output stage expects to see a load of 8ohms (4-16 ish) to work correctly.
you could add a loading resistor (15w would be ok but get hot, 50w would stay nice and cool)
i've added that resistor to the diagram you posted

[john & Jake the dog]

many thanks George.
That's given me a project to give to myself for Christmas, sad isn't it

I have a nice pair of phones that are good at mimicking speaker listening (AKG 240 df ), I dont listen to them enough but I think that will change when connected to the 84.
cheers

[john & Jake the dog]

Hi I'm just about to go to Maplins for the bits.
I have posted the diagram again with some values for r1 and r3.
These values give an output at 119 ohms.
Is there a value please that would give a 600 ohms output which would be perfect for my phones.



cheers