Unless you are comfortable with re-biasing the output stage of your amp, the best voltage would be 36V. These were delivered with Sony VFETs that were biased to run with the included SMPS brick. There is little to be gained by adding a couple extra volts to the supply.
The case runs warm, but not hot with the default voltage and bias. Switching to a linear supply may offer better performance, but only if you are willing to provide some better separation of power between the two channels. Dual-mono can be a good way to go, or separate banks of capacitors for each channel can help as well.
The case runs warm, but not hot with the default voltage and bias. Switching to a linear supply may offer better performance, but only if you are willing to provide some better separation of power between the two channels. Dual-mono can be a good way to go, or separate banks of capacitors for each channel can help as well.
Thanks!
There are limits to any piece of gear, I believe.
I was hoping to pull a bit more out of the amp. Aside from the end result, there is always the benefit of trying something and then learning from doing a direct comparison.
I’ve had a few projects where I really wanted a change to make a difference for the better, but that’s not always the case…
P
There are limits to any piece of gear, I believe.
I was hoping to pull a bit more out of the amp. Aside from the end result, there is always the benefit of trying something and then learning from doing a direct comparison.
I’ve had a few projects where I really wanted a change to make a difference for the better, but that’s not always the case…
P
I am sure Nelson spent many hours determining the optimal operating point of the amplifier.
Perhaps common drain is not to your liking, and you prefer the higher distortion of a common source amplifier.
There is a simple thing that you can try. Add a 1000uF capacitor to the power rail on each channel. That was my first tweak to the DIY Sony VFET, pt 1. The brick SMPS handles this easily. This begins to offer better stereo separation through some independence of power supply per channel.
If this tweak sounds good, it may be a start to building a linear supply for your amp.
If this tweak sounds good, it may be a start to building a linear supply for your amp.
There's a PCB project here on the Forums which provides two linear voltage regulators (one per channel) for VFET and Theseus amplifiers. It's called "Tuba". The board includes an LRC filter to remove SMPS HF noise (prior to regulation), followed by a pair of 5 ampere voltage regulator ICs, the ST Microelectronics LD1084. These remove noise at DC and below-SMPS frequencies. Just the ticket for those who demand flat FFT curves with no blippity glivvets at f_mains and 2xf_mains.
Nice!
Don't lose sight of the fact that most of the magic of this amp comes from the SONY VFETs themselves as implemented in Nelson's design. Experimenting can be fun. However at some point you are faced with the law of diminishing returns when it comes to sound quality, in some cases very soon.