Quietest amp you ever owned ?


A few years ago I had the little Antique Sound Labs MG SI 15 DT integrated and was impressed how quiet it was; in other words with the amp on and no music playing it was dead quiet when I put my ear right up to the drivers on the speaker. I am curious what other amps out there are as dead quiet since most amps have a slight hum or hiss that can be heard when music is not playing. At the time I was using Coincident Conquest speakers which are pretty efficient.
bobgates
The degree to which an amp will be perceived as quiet or noisy depends to a certain extent upon how efficient (or inefficient) the speakers it is used with are, e.g, a 92 db/watt efficient speaker will make upstream components sound noisier than an 86 db/watt efficient speaker. In fact, the noise level with highly efficient speakers, like horns or many single-driver speakers, can be intolerable unless partnering components are chosen with an eye toward their noise characteristics.
Elevick I never knew the Dynaco ST-80 was that quiet; I had a ST-120 way back in the early 70s. The reason I am asking this question is that I am running a pair of modified Klipsch KLF-20s in a second system and, as Raqual has pointed out, the more efficient the speaker the more the amplifier noise comes through. Speaking of Dynaco I had a ST-70 at one time with the Sutherland front end board and it was dead quiet; on the other hand the stock amp with the 7199s was pretty noisy. Thanks everyone for your input; I've learned a great deal.
Yamaha MX1000U
(1979 - solid state, 760wpc @ 4ohm; 960wpc @2ohm; 460wpc @8ohm) which I still use with fabulous results. I am amazed that for the power output and the cheesy original power cord that this monster does not put out ANY noise. Totally clean.
Even my CR-1020 (1978 - 90wpc @4ohm; 70wpc @ 8ohm) which is in a separate system performs in the same quiet manner.
A while ago I sold my much newer Mac and a Krell but kept the Yamahas. Do it again Yamaha ... where'd you go.