Threshold UHP-1200

[R-K Rønningstad]

Attached is a picture I took of the Threshold UHP-1200 at the 1983 CES in Chicago. The novel thing with this machina was that the mains was rectified dirctly. In other words: No mains transformer. I remember our quiet question regarding output power, Mr. Pass thoughtfully replied "Well, it depends on the wall." UHP = Ultra High Power. So in the U.S. of A. 1.2 kW in 8 ohms and 4.8 kW in 2 ohms should be possible....

Sorry the pictures are not very good. The original negatives are long gone, I think. The pictures are from a long gone Norwegian audio journal.


Rolv-Karsten

[R-K Rønningstad]

Here is the other photo I took of the THreshold UHP-1200. Please note the mains transformer being substituted by four giant electrolytics, each 11.000 uF/200V.
As I remember, these amplifiers had an input line level transformer from Sowter.
My excuses if the old notes from the magazine on this construction should contain some errors.

Rolv-Karsten

[steenoe]

So in the U.S. of A. 1.2 kW in 8 ohms and 4.8 kW in 2 ohms should be possible....

Think about 230V here in EU This is the true Pass Monster

Steen

[Zen Mod]

Originally posted by steenoe
Think about 230V here in EU This is the true Pass Monster

Steen

ya gonna build one?

[steenoe]

ya gonna build one?

I dont think so, on the other hand it kind of gets the thinking going It gives a whole new meaning to unregulated supplies One could really shake the neighbourhood with that one....

Steen

[R-K Rønningstad]

If someone does this, please be careful. I think Nelson made this 23 years ago to show what was possible. I do not remember, but I doubt he really planned to put it into production. Amplifiers and equipment in general, without mains transformers is nothing to fool around with! ;-)

RK

[steenoe]

Correct indeed
On top of my wishing list is a fully balanced J-fet amp around 2x50 watt's I am not gonna start a new build before NP spoils us with a circuit like that. Nothing wrong with preparing the chassis allready though

Steen

[Nelson Pass]

Originally posted by R-K Rønningstad
Attached is a picture I took of the Threshold UHP-1200 at the 1983 CES in Chicago. The novel thing with this machina was that the mains was rectified dirctly. In other words: No mains transformer. I remember our quiet question regarding output power, Mr. Pass thoughtfully replied "Well, it depends on the wall." UHP = Ultra High Power. So in the U.S. of A. 1.2 kW in 8 ohms and 4.8 kW in 2 ohms should be possible....

Actually, because the amp was bridged, it would swing about
+/-260V, which is about 4 KW into 8 ohms.

At CES, everyone was afraid to touch the volume control, but at
the end, we drove it full power into Martin Logan Monoliths...
and nothing broke.

BTW, the input transformer was a Jensen.

[R-K Rønningstad]

Yes, I remember you had the Monoliths there. But the transformer was a Jensen. Excuse my memory. 23 years....

RKR