I decided to build my own amp when my very old 80’s amp broke down for good. Until then I summed up some major Hifi-components in living room, such as a Bluray/DVD player, an Apple TV (Gen. 1) and of course a 90’s CD-player. By upgrading to a flat-screen TV I imagined that a new sound-system should be installed.
From my old speaker-building days when I used to design and build sets of speakers I knew what to expect from good speakers. Lacking time, space and tools I bought a set of classy Nubert speakers and an active Yamaha sub-woofer. But still I was looking for a decent amp. So I went into different stores and read mags but could not find a suitable amp. To be honest I literally got fed-up by the huge amount of brands and functions I really did not need. But what did I need?
- very good sound reproduction
- enough volume for a party
- hassle-free operation
- minimalistic design which blends into my living room
- an eye-catcher but still subtle in design
Unfortunately I could not find any match in a realistic and acceptable price-range which could meet my demands. I certainly got inspired by a fruit-branded computer manufacturer whose product ease of use is IMHO legendary. After some hard thinking and research I came up following demands:
- very good sound reproduction
- a tube pre-amp
- IC-based power-stage
- as little as possible silicone in the sound-signal path
- enough volume for a party
- IC-based power stage
- well dimensioned toroid transformer
- a booster-stage of Caps to deliver enough power
- hassle-free operation
- just only one single button to choose the input-channel and mute the amp
- a small graphics display and one LED to show the status
- one volume knob
- one bias knob
- minimalistic design which blends into my living room and a subtle eye-catcher
- a good choice to re-use a very old and out-dated SCSI-drive housing
- all in white with the button and the knobs in “metal”-colour
- the graphics LCD with a green backlight which fades out after a while
- one green status LED
- a window displaying the pre-amp tube
- the tube which is lit by a blue LED in her socket which emphasizes the contrast of the bright red colour of the tube’s filament.
After about half a year of designing and building the Hybridamp was ready.
I inserted my favorite Dire Straits Album “Love over Gold” which I have been using as a reference for my sound projects into the CD-Player and listened to the first title “Telegraph Road” and then “Private Investigation”. The sound coming out the speakers was powerful, voluminous and crisp. Nearly no hum was audible. Of course I turned the volume straight up to the max. The amps Volume was really, really loud, but still clear and with no audible distortion. Read ahead to get into the technical details.
I have divided the technical details into two parts: The analog part, in which I describe everything which is related to analog electronics in the Hybridamp. The second part refers to all digital electronics in the Hybridamp.
Here are some major technical details:
- Tube: ECC82 double triodes (ECC81 or ECC83 possible with minor changes, see schematic)
- Powerstage: 2x LM3886 “Gainclone”
- Inputs: 4, selectable by only one button on the front panel
- Outputs: two speakers
- Output Power: around 68 Watts @ 4Ω, 50 Watts @ 6Ω and 38 Watts @ 8Ω per channel
- Sub-woofer control for my active Yamaha sub-woofer
Here are some pictures…
