DÆ v3.0 Dual Mono-block Preamplifier

The DÆ v3.0 Preamplifier is a dual mono-block preamplifier housed in two totally separate aluminum and acrylic enclosures. The right channel is housed in the upper enclosure in the stack and the left channel is in the lower enclosure. It is not necessary to stack the enclosures one on top of the other; in fact any arrangement that suits the application is equally good. It really only depends on the cabling to an from the preamp.

A Bluetooth radio connection is maintained between the two channels to synchronize the volume, power and source selection of the two channels. When the volume control knob on either of the two channels is rotated the other channel automatically moves to the same volume setting. While the look and feel of the volume control is totally analog, behind the scenes a stepped attenuator maintains precisely the same volume on both channels. The DÆ v3.0 stepped attenuator is totally unlike other stepped attenuators because it’s operation is silent without the clicking noise associated with relay based stepped attenuators. Bluetooth is also used for the remote control.

Power is provided by a battery pack with six, 6-volt valve regulated lead–acid (VRLA) batteries, also known as a sealed lead–acid (SLA) batteries. When fully charged, the battery pack provides low noise power to the analog electronics for a six hour playing time. Once the battery power is depleted, the Battery Charger/Power Supply switches over to re-charge the battery-pack and power the electronics from a wall plug. it is still possible to continue listening while the battery is recharged with a (very) minor increase in noise level. The switch over from battery to wall power is seamless and the only indication that wall power is being used is the blue light of the voltmeter will be switched off while the other panel lights remain on.

Each channel of the preamplifier includes the following sub-assemblies that are described in previous blog posts and webpages as noted:

• One v2.1 Phono Preamp (blog post dated May 23, 2020). I know it is a confusing number system with the DÆ v3.0 preamplifier having having v2.1 phono preamplifier circuitry - sorry. The phono preamp is optimized for high output moving coil cartridges and is a low noise/low distortion with an ultra precise RIAA curve;

• One CD input and two auxiliary inputs. Each of these inputs includes a single ended RCA input and an XLR differential input. The inputs use multiple opamps to achieve very low noise (blog post dated October 23, 2020);

• One DÆ v3.0 stepped attenuator. This is a unique reed switch based, motor operated volume control with ultra precise levels (DÆ v3.0 stepped attenuator webpage);

• One v0.1 “Sort of Analog Panel Meter” (blog post dated May 19, 2020). This custom designed meter employs a computer controlled stepper motor providing a non-linear voltage scale to properly portray the battery pack state-of-charge.

• One v3.0 Battery Charger/Power Supply (blog post dated September 9, 2020). The Battery Charger/Power Supply is computer controlled by a microcontroller to avoid over discharging the battery pack.