14-09-2016, 11:40 AM
It's to double the current drive available. Some headphones are 32 ohms...
Taking the negative feedback from the junction of the two 47 ohm resistors ensures that the amplifier is a good voltage source. The two 47 ohm resistors ensure the two op-amps share the current nicely. Theoretically they provide current limiting, but the op-amps themselves are no-doubt doing that themselves.
It's not a terrible circuit, despite appearing to be unconventional. Well, the op-amp part, at least - I can't really comment on the valve bit.
If you have a couple of spare tubes of NE5532s, you can scale this up to drive loudspeakers. Douglas Self published a design that used 32 of them!
Taking the negative feedback from the junction of the two 47 ohm resistors ensures that the amplifier is a good voltage source. The two 47 ohm resistors ensure the two op-amps share the current nicely. Theoretically they provide current limiting, but the op-amps themselves are no-doubt doing that themselves.
It's not a terrible circuit, despite appearing to be unconventional. Well, the op-amp part, at least - I can't really comment on the valve bit.
If you have a couple of spare tubes of NE5532s, you can scale this up to drive loudspeakers. Douglas Self published a design that used 32 of them!
