Probably the other bestselling high-end DAT recorder, the other being the DTC-2000ES.
Besides the very reliable 4-Motor mechanism, 4-heads for direct monitoring, a fully copper-plated chassis made of thick steel plates and two transformers make for the heavy hardware - see it here.
Sure : it isn't a DTC-1500ES or a DTC-2000ES but it still is built way better than the contemporary SV-DA10 or SV-D900 decks (and it sound better as well).
The drum assembly is that of the DTC-2000ES and the ultimate PCM-R700 : DOU-15A.
1-bit HDLC PULSE d-to-a (CXD-2552Q) converters and SCMS are here (the latter as inaugurated in 1990 with the DTC-55ES, aka DTC-75ES in the US), the build-quality is worthy of Sony tradition (massive), the overall finish and feel of use is worthy of Sony tradition (unmatched) and the features are... galore.
If Super Bit Mapping, 44,1Khz recording of analog sources and Advanced Pulse converters were for later units, the DTC-77ES made and still makes for eleven kilos of reliable and good-sounding digital recording machine.
The 77ES was a DTC-77ES in Europe, a DTC-77ES in Japan and a DTC-87ES in the USA.
In the pro world, the DTC-77ES was a PCM-2700 : dark grey with balanced XLRs, AES/EBU digital terminals, serial/parallel remote terminals (8P / 37P) and sans SCMS.
In japan and Europe available as DTC-77ES(N) (champagne) or DTC-77ES(B) (black), in the US only in black.