Atma-Sphere Gem Amplifier

The Gem is a Push Pull class A tube amplifier meant for bedroom, desktop, headphone or main system use. It uses many of the concepts we use in our other amplfiers. Its fully differential from input to output (although has RCA inputs only). It is overbuilt with precision parts; for example the output transformers are rated for 10 Watts so the amp can't get in trouble should a power tube fail. It can drive 4 or 8 Ohm loads and does well with 16 Ohm loads too (on the 8 Ohm taps). If you do a search, one thing you find out quickly is that tube amps of this size aren't also built to be high quality. This amp uses the same parts quality of our highly regarded OTLs and has power supply capacity found in many amps of 5x more power. 

This was originally designed as an amp for a bedroom system where reliability is paramount. Its low noise suits headphone use as well, and is attractive and small enough that it is suitable for use in a good quality desktop or home main system (if the latter has higher efficiency speakers). 

We considered building a Single-Ended Triode (SET) amp for this project and so a number of designs were tried. SETs have a strong following; their proponents claim they sound better than push-pull amps. But output power and class of operation are never the same in any comparisons so far... So we found that if just these two variables are eliminated, SETs have no advantage over a properly designed and built push-pull amp, if faithfulness to the music is the determining factor. We were able to get the same power in a smaller space with wider bandwidth (most easily heard in the bass region where SETs are at their worst) with lower distortion, which translates to 'more transparent' since distortion obscures low level detail, and smoother for the same reason.