Q: headphone amp with variable distortion

[vladn]

I'd like to build a simple tube-only headphone amp that has an adjustable level of tube-specific low order harmonic distortion. Something that can be adjusted with a pot from fairly linear 0.1% (or lower) to about 10%. It will be used exclusively with 600ohm K240M headphones so output impedance is not a big issue. Should have good voltage swing without hard clipping and other high order junk though.

 

[Gordy]

This design has variable feedback and variable tail current in the long tail pair. Perhaps a design such as this may give you the adjustability that you seek?

http://home.swbell.net/acavalli/ima...iable_CCS_and_Delay_and_Smart_Regulator_2.gif

I am not sure where the original article is. Maybe a search for ' cavalli lovell ' might help.

Good luck.


[ edit : I just noticed that you said that you wanted simple. Oops ]

 

[pmillett]

It's pretty hard to make the distortion adjustable without changing the gain quite a bit along with it.

This might be interesting:

http://www.pmillett.com/etf_sod.htm

I used a 6BN6 gated-beam discriminator to do the distorting, but had preset operating conditions so I could match the gain at the different distortion settings.

Pete

 

[vladn]

Interesting circuit - is the 6BN6 hard to get ?
I think it may be possible to use ganged pots to compensate for gain change (at least to some degree) when changing the transfer function profile.