AxoClamp 900A

This week I installed a brand new Axoclamp 900A (Molecular Devices) in my rig.
The new amplifier has several neat features. One can save the setting of the amplifier as a configuration. This may be good for doing different kinds of experiments routinely in one rig.

They changed the headstages. This is really annoying.
The new headstage somewhat resembles that of Axopatch, but shorter. There is no rod and it is designed to be attached directly onto the manipulator. And, of course, it won’t fit on our manipulator. We use Siskyou’s micromanipulator. Siskyou provides a “dove-tail” headstage connector, which costs like $175 for each. This is a rip off.
So, I constructed two headstage holders by myself from scratch.


Photo: The old headstage (blue) and the new headstage (black).
The “dovetail” slide connectors were made from plastic plates cut out from the microelectrode box (Sutter). A wooden rod ($0.87) was bought at Home Depot. It was cut, carved, grooved, and epoxy-glued upon the dovetail plate. The tightness of the dove tail can be adusted by putting something under the headstage. I use a small amount of dental wax. The total cost is less than a dollar + my labor.

Another feature I don't like is that there are no knobs on the front face of the amplifier. You need to control the capacitance compensation using mouse, or type in, like 8 μF through your computer. It has to be all controlled by PC. Bridge balancing is automatic. This sounds good, but actually it is not. In a real E-phys experiment, you don't really balance the bridge that accurately, because I don't trust bridge at all for measuring input resistances. I mostly use the bridge to keep the output within the voltage range of your AD converter.

This was my first day of using it. I might change my mind after getting used to this machine. I don't like it so far, though.