If I did not want to use the CODA or KRELL to drive the RAAL SR1a. I could get a dedicated SR1a headphone amp such as the following.
Schiit Audio: Audio Products Designed and Built in California and Texas
This is the lowest end one, but I am looking to get a used one for my bedroom. Notice the headphone connection is opposite of normal headphones. I cannot use the Benchmark HPA4 with the RAAL SR1a and you can only use the SR1a with the Schitt Jotunheim R that I linked above.
Designed Especially for Raal/Requisite Headphones
Let’s be clear. If you have other kinds of headphones, this amp isn’t for you. This amp was designed for one kind of headphones only: the Raal/Requisite ribbon headphones. Delivering up to 13A (amps…yes, amps) per channel into the Raal’s extremely low impedance load, and including the baffle compensation needed for the SR1a, the Jotunheim R is completely unique. It means you can leave your speaker amp behind, forget the Raal/Requisite interface box, and, if you buy it with the optional True Multibit™ DAC, you have a one-box system that’s easily transportable.