Pioneer
Pioneer sells quality audio electronics. Back in the late 1970's, electronics companies were hugely competive in producing electronic guided by one-upsmanship. In the stereo receiver lineup, they boasted producing the most powerful receiver with the SX-1980 model, which featured 270 watts rms/channel into 8 ohms 
. This and other models gave them a reputation of producing quality products. Some of their portable device models are listed below. Some Pioneer models also were marketed with the Centrex name.
- CK series
- CK-W50
- CK-W300
- CK-W700
- J-7 Disco Robo
- RK-111
- RK-113 ...................Centrex
- RK-114 ...................Centrex
- RK-222
- RK-304
- RK-305
- RK-306
- RK-355
- RK-356
- RK-444
- RK-777
- RK-888 ...................Centrex
- SK-1
- SK-5
- SK-6 .......................Centrex
- SK-6 II
- SK-7 .......................Centrex
- SK-8
- SK-11
- SK-21
- SK-21F
- SK-31
- SK-50
- SK-51
- SK-60
- SK-61
- SK-61F
- SK-70
- SK-71
- SK-80
- SK-95
- SK-101
- SK-111
- SK-200
- SK-210
- SK-212
- SK-222
- SK-300
- SK-303L
- SK-350
- SK-353
- SK-400
- SK-450
- SK-550
- SK-600
- SK-606
- SK-606L
- SK-650
- SK-700
- SK-750
- SK-757
- SK-800
- SK-808
- SK-900
- SK-909
- SK-Q10
- SK-Q10BK
- STEEZ NSP-D10P
- STEEZ STZ-D10S
- STEEZ STZ-D10T
- STEEZ STZ-D10Z-R
Did we miss something? Please advise us so we can update this list.