A single supply, 2 transistor DAC-IV stage.

[Brian Guralnick]

This is not a simple question to answer.

I am designing with this philosophy. In the audio path, the least amount of silicon, the better. Then, for powering the circuit, use floating / isolated supplies if it means to lower the transistor count.

For my AD1955 board, I will use an insulated low voltage 1Mhz toroid switcher for the +/- 15v IV stage, isolated 5v dac analog supply, isolated digital 5v for dac & clock oscillator. (The design is not this simple, certain things need to be done to make the switcher perform as clean & consistent as an analog supply. The main digital logic has a completely separate standard analog supply.)

Little overkill?
Well, it’s intentional…

 

[dice45]

Brian,
dont let Jocko discourage you too much, i know a guy complaining in same way about Jocko's easy-to-build I/V stage, particularly about thermal instability and two CCS wrestling with each other (maybe glueing all transistors on the same heatsink helps? insulated of course), as Jocko complains about your I/V stage.

I would just try it out to find out how good it works. The only way to get a definite answer.

 

[Jocko Homo]

The difference is......

I know what works. Because I have built it, and most anything else like it.

So there.

Jocko

 

[Brian Guralnick]

Brian,
dont let Jocko discourage you too much, i know a guy complaining in same way about Jocko's easy-to-build I/V stage, particularly about thermal instability and two CCS wrestling with each other (maybe glueing all transistors on the same heatsink helps? insulated of course), as Jocko complains about your I/V stage.

I would just try it out to find out how good it works. The only way to get a definite answer.

Well, the MAT02 has both matched transistors in a single metal case. In fact, the metal case makes a great shield for the gain stage.

 

[kiwi_abroad]

Something I havn't verified, and may not apply to the Analog devices DAC's, but I heard that Burr Brown DAC's have internal protection diodes on their current output pin to limit the output voltage to + or - 0.7 volts, just in case someone leaves off the I/V stage. If there is 0.7V on the output pin, these internal diodes will start to conduct, and there goes any musical fidelity.

Like I said, it may not apply to AD DAC's, but it would be worth checking out.

Cheers, Adrian

 

[Brian Guralnick]

Again, this circuit was designed to operate with a floating supply. It should not apply any DC current on the DAC I output unless my 'I' negative input is tied to an incorrect reference voltage.

 

[Jocko Homo]

The AD current-out types will fry without a load.

Jocko