The Overdrive USB DAC is coming along nicely. The first revision circuit board is being fabricated and I should have a pile of them mid-week. The USB module that is used on it is already in production at a contract assembler. Still procuring some parts for the Overdrive. Very eager to get one built and listen to it. New chassis are on order too for it. Front and back panels are design complete and ready to be ordered.
My plan is to try it first with three wall-warts driving the DC input connector directly. Then I will try three wall-warts driving a filtering section and then the DAC. Finally, I will design a same-size chassis battery supply using three sets of LI batteries and chargers. This will have IEC inlet.
The base unit will be offered with either three wall-warts or three wall warts and a filtering chassis with umbilical. May also put some regulation in the chassis and start with 18VDC rather than 12VDC.
I plan to offer the base Overdrive DAC with only one option: Superclock4 for the USB module clocking. The battery power supply can of course be combined with the base unit.
A second fully hot-rodded Overdrive will also be available with:
1) point-to-point internal wiring
2) Superclock4 for USB clocking
3) upgraded signal coupling caps
4) Black Gates for power decoupling
I had planned to debut the Overdrive at RMAF, but not sure now. My room partner has opted out, so the only way I will go is if he can get a room last-minute. Not likely at this point.
This will give me more time and money anyway to get the Overdrive and two other new products finished and into production. These products will replace all of my mods. Planning to stop modding by end of year.
Overdrive features:
Inputs:
1) USB
2) I2S
3) S/PDIF coax
4) DC power
Outputs:
1) RCA left and right channel single-ended
2) XLR left and right channel balanced - fully balanced from the D/A
Front-panel Controls:
1) manual volume knob
2) input select toggle
3) digital filter select (3) toggle
4) volume/line-level select toggle
5) Deemphasis toggle
The outputs are high-drive, so it can drive headphones directly.
The XLR and RCA outs are not independent, so only one set should be used at a time.
Analog signal path is super simple:
op-amp I/V -> Transistor driver -> coupling cap -> 30 ohm resistor
There are no resistors in the signal path, except the output series resistor, which is necessary for transmission-line effects. All Class-A operation and fully balanced from D/A chip out, 4 separate signal paths.
The volume control has 3 profile settings and 3 max amplitude settings via internal jumpers. This volume method is unlike any other ever tried in a DAC or preamp. It does not change in any way the resolution nor does it insert any devices, active or passive, into the analog signal path. It is just like driving your amps directly from the line-out. The prototype that I have mocked-up has unprecedented clarity. Better than any preamp I have heard, even my own modded ones.
A waiting list has been established and there are a few customers on it already. Not taking orders or payments quite yet.
Steve N.
