Ampdog
R.I.P. 23 June 2022
This flagship has been under discussion before. I have just finished refurbishing one for a member, and I must say that it was the first amplifier where I found all the characteristics to measure as claimed and the valve design optimal. Only slight change necessary was in the main NFB circuit to cure some drastic h.f. damped oscillation. (I presume these things are checked in the final execution; then why oh why can't the designer get it right first time? I find that in many valve amplifiers, and it is mostly rectifiable fairly simply.)
There are a great many adjustments available, more than are really necessary. I guess it was designed when the folks over in the east thought all those were desireable. High and low pass filters cut off sharply, not the double RCs found in some designs. As stated before, it is only the third design I found to use the distributed load output stage with local feedback (a la Quad II) configuration. The output transformers are massive for the claimed output; as it is now an easy 40W/channel is obtainable.
The only other thing that needed attention were the (flimsy and corroded) output slide switches, giving an 8 - 16 ohm output impedance choice, and a phase reversal option. After consultation with the owner they were simply bypassed to 8 ohms and standard phasing.
I have no general experience of Sansui products, but if this one is representative, they could be purchased with confidence.
There are a great many adjustments available, more than are really necessary. I guess it was designed when the folks over in the east thought all those were desireable. High and low pass filters cut off sharply, not the double RCs found in some designs. As stated before, it is only the third design I found to use the distributed load output stage with local feedback (a la Quad II) configuration. The output transformers are massive for the claimed output; as it is now an easy 40W/channel is obtainable.
The only other thing that needed attention were the (flimsy and corroded) output slide switches, giving an 8 - 16 ohm output impedance choice, and a phase reversal option. After consultation with the owner they were simply bypassed to 8 ohms and standard phasing.
I have no general experience of Sansui products, but if this one is representative, they could be purchased with confidence.
