To all,
I just finished building one of these amps for my desktop near-field system in the basement. If you have not heard of it, it is a design for a simple single-ended MOSFET amplifier by Nelson Pass that can be done in a day. Looks alot like an Aleph from a circuit standpoint. It is available as a kit from DiyAudio.com, for around $350, which includes a nice chassis. Power supply is a 20V/5A switcher from MeanWell. You can read all about it on DiyAudio.com. I built it stock, with the exception of an upgrade of the output capacitor from the stock 3300uF/50V CDC industrial snap-in electrolytic, to a Nichicon KG(M) Gold electrolytic of the same value, about $4.50/channel upgrade, available from Mouser. It is a 8W/ch ampifier for 8 ohm loads, and 5W for 4 ohm loads. For a desktop amp is probably does not need to be very much.
The sound, as it breaks in, is very nice for a near field setup. I have had a much more powerful tube/MOSFET hybrid amp and a pair of 2A3 SET monoblocks in the same system (powering a pair of Aria 5R MTM 4ohm monitors). Compared with both of these amps, it produces a much more expansive soundstage and a more warmth to the sound that even the 2A3 amps provided. No doubt a bit of second order distortion in the profile, it does sound like a single-ended tube amp. Detail is nice, can really hear instruments and their locations. Instrument colors are spot on. Listening to a recording of Rachmananoff Symphony No. 4 with the Philadelphia Orchestra under direction of Yannick Nezet-Seguin, at 24/96 recording on Qobuz, and is beautifully full bodied, expansive and engaging.
It is not a headphone amplifier, there is no volume control (though some have modified the design to add both). I am driving the amplifier using my computer as a source through a Topping D50s DAC and companion A50s headphone amp/preamp (using the P50 linear power supply). Plan on having something that can provide addition gain, the amp only has 14dB of gain, so needs 3 to 4 volts at the input for full output.
I have another on order (have the parts kit already, waiting on the chassis), so I can hear what it does as mono amplifiers. There is a lot of flexibility, as a mono amp you can run it with balanced input, bridged (for more power at 8ohm and 16ohm) or parallel (for more power at 4ohm loads).
Anyway, I am really pleased so far with how it sounds. It is a relatively cheap project if you have a need or purpose for it, or just want to have some fun building something that does not take a lot of planning or effort (an instant gratification project). It is obviously not an end-all amplifier, when I build my second one, I will try it in my main system just out of interest. But if you want to put together a nice little system for a bedroom, computer workstation, or a small little hideaway, it could fit the bill. Obviously, a companion project would be a pair of nice high efficiency single driver full range speakers if you were setting up a system.
David
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