The design idea is to use this power amplifier with a DAP as source. It’s almost like a Nintendo Switch concept, with the amp being the dock. Use this amplifier with your speakers and a DAP, or use your DAP with some headphones instead. One DAP can perform double duty. You could save money with this approach, or splurge on a truly awesome DAP. DAP not included.

Effectively, this is a hybrid power amp which provides enough gain so that is doesn’t require a preamp. It is self-powered via the internal battery. Battery powered provides some benefits: no AC line noise and batteries can deliver more power faster, when needed. It also provides some insurance in areas with electrical instability.

This amplifier is composed of 2 separate DIY kits: PASS Labs B1 with Korg Triode (NuTube) and the Bottlehead Quicksand—both are inside of this one chassis. In most cases, the kit components were upgraded with higher quality parts. The chassis is a powder-coated and modded Dynaco ST-120 clone made by DAL Audio. The batteries are 24v NiMHs. There is an extra battery included (grand total of 2). Batteries can be charged while inside of amplifier or externally. Both batteries have a capacity of 4.5Ah, they play for a very long time. Though, one battery is a little stronger than the other. The built-in battery meter doesn't light up during amplifier operation, but it could be reconfigured to do so.

Can this amplifier be used with a preamp? Yes. But this amplifier has roughly 36dB of gain built-in, which is a lot. So it would need to be a passive preamp that doesn’t add further gain.

Can it be used with AC powered components, like a DAC? Yes. I’ve done it and had no issue.

Can it be charged while in use? No, the current configuration does not allow that. Charging and amplifier operation are separated. When switch is in up position, amplifier is operational. When the switch is in the middle position, the amplifier is off. When the switch is down, the battery meter is on and the amp can be charged (charger must be plugged to do this).

Is there a volume control on the amplifier? No. The idea is to use the DAP or other source for volume control.

The B1 with Korg Triode has built-in adjustments to shape the tube sound--this requires a small screwdriver and voltmeter to dial in your preferred sound. NuTubes tend to be microphonic--this is an open chassis, so a loud clap within 1 foot of the amplifier will result in a short ringing.

XLR is used for charging--RCA is the only input.

The amp sounds great. Cosmetically, the amp is a 9. Again, the idea is to use it with a DAP.

Everything included: padded box, amplifier, extra battery, charger, extra IC chip, external meter.