Can a off the shelf DAC, if engineered/implemented good, sound as good as a custom DAC?

The sonic character of a DAC or any other component is the result of the entire component…. All the subcomponents, design, materials, case. Power supply is a big deal. Typically a very high quality DAC will weigh 35 or 45 pounds. Much of that is the power supply and vibration dampening material.

Long ago I owned three different DACs, all with ESS DACs. The sound from each was completely different. The most inexpensive was simply terrible, tinny and shrill. It’s not just the DAC… it’s everything.

Can a off the shelf DAC, if engineered/implemented good, sound as good as a custom DAC?

There is NO generalization as it depends on each implementation. A custom DAC can sound good or bad. Also, manufacturers may use the same chip which usually has a general sonic character, but their implementation and thus Sonics will be different. 

The new Schiit Singular (Byggy) DAC is a custom implementation of delta -sigma designs. I owned it and it was the best Schiit DAC I have heard. I owned a few including LIM, MIB, OG. I no longer have these DACs.

My current DAC (and last) is less than 10lbs and uses a 2lbs external switching power supply (like a laptops). I may eventually try a battery power supply with this DAC.

There is so much more involved in designing and building a good sounding DAC, than the D/A conversion chips used.  My Mearson DAC1 MkII sounds great with its dual Burr Brown PCM1794A hybrid chips.  My Aries Cerat Helene sounds even better with its 8 Analog Devices AD1865N-K stereo ladder R2R DAC chips, or 8 D/A converters per channel.  

However, with each of those DACs there is so much more, such as:

• optimized USB input
• precision clocking
• multiple regulated power supplies
• discrete output stage
• well-damped chassis
• and more

Other considerations include how the DAC plays with your other equipment considering things like which input is optimal, whether it is optimized for a balanced or single-ended output, the output impedance, the output voltage, and more.  There are so many variables with both the DAC and with the rest of your system, that you simply need to try the different DACs you are interested in at your place and in your system.

@ted_b Great analogy!