Model 5000 uses a tube output stage with a single 6922 and tube-rectified power supply with two 6CA4s and one 6X4. Doesn’t upsample or oversample, the digital darlings of the day. Instead, Zanden uses a proprietary analog filter designed and patented by Mr. Yamada.
This filter, Zanden contends, is one of the crucial ingredients of the unit’s especially fine sound.
The Mk IV a little quieter, allowing more music to emerge. There's ever-so-slightly greater detail. The difference is certainly not staggering, but for someone who is seeking the best sound regardless of price, it’s relevant enough to take seriously.