**Edit**

Instead of leaving this post with info what will slightly disagree with the updates I’ve decided to correct it to follow the design changes.  The new Amp fits in as Amp8S (even numbers are balanced, odd numbers are SE).

With the success of Amp1S and the enjoyment I got out of the process, the build and the customer feedback I received, I’ve decided to step it up and develop a higher end battery powered balanced desktop amplifier.  The electrical design for this amp has been in the works for years, now it’s time to make it a reality.

Unlike Amp1S where they sold before I was able to keep one for myself, this time the amp is as much for me as anyone else.  This will be the amp I want with the design and features that I’m looking for.  As it happens, I’m probably not the only person who this will appeal to.  Target quantity is only 5 pieces possibly 6 (0 of 5 will be mine) with each having the number engraved either on the front or back.. 1 of 5, 2 of 5 etc… if I do make the 6th unit it will be 0 of 5 and the unit I keep.  Given the roadmap I have for various amplifier designs and styles, and price ranges, this will likely become Amp8S.  The S refers to the Stepped attenuator and Special edition nature of this amp the same way it did in Amp1S, the 8 is where it fits into my master plan.

Design goals:

– Lithium battery powered
– 50+ hour battery life
– Automatic built in battery charging
– Standard RCA and 3pin XLR balanced inputs
– 1/4″ and 4pin XLR outputs (I’m doing some final testing of a dedicated 3.5mm IEM output jack with low noise, low gain)
– High output current (would drive small speakers)
– Drive headphones like the HE-5/6, LCD2/3 with authority/clarity
– Use balanced stepped attenuator
– Simple, solid, attractive enclosure
– Dual mono balanced construction, including separate battery packs and a physical division between the channels.

The Amp1 enclosure was based on cost effective design, simple assembly, inspiration derived from Bosch Rexroth extruded aluminium.  I still love the design, of course it’s mine, however with more freedom I think I can create something much more interesting.  I love the look of machined aluminium, a recent piece I milled for a new charger I’m building for the Electric Porsche has revived my interest in designing a nice thick aluminium face.

cooling plate finished

With a target quantity of 5-6 units instead of a small production run in the 100’s I have more freedom from cost, and it’s within the means of my CNC router that is normally reserved just for prototypes.  This means I will have complete control over the finished product, but it also means it could take awhile.

I have a pair of Amp1 Upgrades that I use for my personal use, and for the past year they’ve been powered by a lithium battery.  This battery appeared in my first blog post and is something I use for all of my testing, the final revisions to Amp1S were done powering it with this battery.  The problem is that even though Amp1S sounds wonderful with the included power brick, it actually sounds better when powered by the battery.  I contemplated turning this stand alone battery into a product, however it’s better to simply incorporate it into the amplifier design from the start.  Amp8S will not have a battery that plugs in the back in place of the power brick, the amps entire power supply will be designed around the battery being an integral part of the Amplifier.  Actually two batteries to be specific, each channel will have a separate battery, when used with the balanced 4 pin xlr output the two channels will be physically and electrically separate.  Due to the battery monitoring and charging system I was unable to keep the batteries separate, but the single battery is twice the size and very stable.  They will share the same face plate and volume control (Quad stepped attenuator), however the enclosure will be constructed from physically independant “boxes”.  One advantage of the dual mono approach is simplicity of execution, I design one balanced channel/battery/power supply and build two of them to make an amp.

Battery

 

 

The PCB/Battery/Enclosure designs are all underway, I will post the progress as I have more to show.  Pricing will be announced once I have a firm handle on both the PCB design, Enclosure and BOM.  Although the price will be quite a bit higher than any of the versions of Amp1 it will still provide very good value for money.  And like Amp1S, once they’re gone they’re gone!