Good Morning Audio people.
I did my usual perusal of the local equipment ads today. I noticed a relatively low priced super amp in there. It was a SUMO Andromeda. Big and black and it looked really heavy.
It was about 1/2 to 3/4 of the usual price for this type of thing, so interested I became. It reviewed well in the 90's, and gained favor in several magazines. I looked further into it. SUMO was another incarnation of James Bongiorno's businesses.
His name is either Good Morning in Italian or a homonym (or is it homophone) of that. So good morning!
He started at Marantz in the golden NY era. Then moved to New Jersey with Dynaco. Then California with SAE and then GAS, and eventually SUMO. Each step was further down the road of his quest for electronic perfection. Each stop produced notable products. A quest does not have to be linear or even successful.
I must remind you that JB was one of the three big golden age designers who gained respect even fans among the audiophile world. The other two being Nelson Pass, and Bob Carver.
Anyway back to the SUMO. The documents for this Amp, an Andromeda II, were interesting. They talked about separate power supplies and robust hardware. It was also one of the Early big FET amps. Stereophile sorta liked it in certain systems. When it was good it was very good. Both good and FET. It was priced about what I could get for my Franken-amp if I found a buyer. Wheels started to turn.
So I dig further. As per usual I looked up the circuit schematic. Holy shit! This was an electronic maze. I imagined service techs throwing themselves off of tall buildings if this showed up. It looked like each channel was made from two complete amplifiers bridged to act as one amplifier. That apparently is exactly what it was.
In the normal application many stereo amps can be bridged to act as one monophonic amp at about double the power. Good things usually happen. So why not, they thought, do that right in the box with four amps to make 2 bigger ones. Twice as many parts!
In my opinion one benefit of bridging amps is you have two completely separate devices so there is no cross talk. It is physically impossible. Putting two already bridged amps in a box would be fine if they had their own power supply like Harmon Kardon and others do. SUMO didn't do that.
They did a weird thing in having two tiers of power supply one for the low level Class A front end and a second (smaller one!) for the big output transistors. Well he was in California, he may have been smoking something. If these power supplies could be cleaved apart for each channel and the big outputs given more umph capacitors things could look good.
Hey I am not an electronic engineer. BUT things were screaming at me why did they do that!
The only cool thing they did was to have the power stages biased so that they acted as Class A up to a couple dozen Watts. 95% of your listening is at very low Wattage. So a Class A Bias is generally a good thing though it makes it run kinda warm. Cool to be warm.
It looks like he went down a "lets try this" rabbit hole. Yes MOSFETs were involved but dear me. Interesting the Mr Pass went the route of simplicity. He also moved to a mountain forest.
All these things have a voice. The Stereophile review discussed how it sounded really good with some speakers and less so with others. Interesting that made such a difference. Obviously it was reacting to the speakers impedance function. Why else would it sound different? You shove a big electrical signal down the throat of any speaker it should just put out sound. But sometimes they argue. Sometimes the amplifier does not like arguments. Maybe if the power stage had more umph behind it?
So after being intrigued I thought give it a miss. I am sure someone will buy it and like it, until it breaks.