The No 523 is their finest one box preamp second only to the two box No 52(30k). The 523 exceeds all prior ML preamps. It is a sonic and ergonomic marvel. It sounds as good as it looks. There is a great Stereophile review of the No 526 which is a No 523 with a built in dac. The feature list is extensive including a great phono stage so please research the ML website for more info. I purchased this unit in Dec 2017 from a ML dealer. This was his personal 523. The unit works perfectly and is unblemished offerring much pride of ownership. Payment is to be by check or wire transfer. Paypal at my discretion requiring great buyer feedback. US sale only and be sure to check my feedback. **My apologies for the multiple photos of same image. Some glitch in program. The price is firm and very fair.