Texas THS6012 used as a high quality amp.

[Malcolm Jenkins]

Hi, Malcolm here.
After reading Rod Elliot's article on the Texas THS6012 driver used as a headphone amp on his web site, I decided to try this chip as a differential driver for a horn loaded Lowther EX3. The power out from these chips is a max of 500mW so only high efficiency speakers can be driven. To make life easy, Texas supply an evaluation board, fully built and ready to go.
If you no nothing about this chip, here is a flavour. It's a digital driver for network line transmissions
Zero distortion at all power levels, well actually 0.0001%
dc-450 MHz bandwidth
-119db noise below full o/p
In short, the perfect amp.
So much for the hype. How did it shape up?
I have now taken delivery of the THS6012 evaluation board ($50 direct from Texas Instruments) and it looks promising.
The board worked without modification with each of the two drivers
providing the opposing phase of the signal via a pair of on board 12.4 ohm
resistors. Much more power was available when I shorted thes out.
This was a test setup only and I used a CD headphone output as the
source and a new EX3 which is being broken in (not in a cabinate), so it
is hardly a definative evaluation.
Once some of the roughness of the new EX3 was passed, it became clear
that there was no distortion caused by clipping and the volume was more
than enough to fill the listening room even without horn loading.
There was no hiss or hum eminating from the speaker, even with my ear
right up close to the cone.
I used BNC connectors and co-ax cable in the test setup because BNC
sockets are standard on the evaluation board.
The board itself is built to a very high standard and is totally stable
in operation. Everything you need is provided on the board, including an
additional op-amp to generate a ballanced signal from a an unballance
source. The only downside is the less than ideal
medium input impedance means that the board needs to be driven from a
pre-amplifier with a low (200 ohms) output impedance. This is not a
difficult proposition.
I will drive my boards from the Analod Devices balanced line driver
chips, which I am using with my current horn amps.
I estimate, from the graphs thst TI publish, to be able to deliver 1.8
watts into the 15 ohm EX3s with +-15 V supply.
Regards, Malcolm Jenkins