Pass X600, 600.5, 160 & 160.5

[RobertS61]

Patents of NP:
https://patents.google.com/?inventor=Nelson+S.+Pass
1. Active bias circuit for operating push-pull amplifiers in class A mode: Threshold 800A
2. Active low frequency acoustic resonance suppressor: TubeTraps
3. Amplifier with gain stages coupled for differential error correction: Super-Symmetry, all Pass X power amplifiers.
4. Opto-isolated bias circuit for operating push-pull amplifiers in class A and Class AB modes: introduced in Threshold 'optical bias' models S/200 - SA/1.
5. Amplifier having an active current source: Aleph series??
6. Constant voltage - constant current high fidelity amplifier: introduced in Threshold Stasis 1, 2 & 3.
7. Efficient high fidelity audio power amplifier: floating cascode, not implemented?

2. Correction: implemented in Phantom Acoustics Shadow

 

[RobertS61]

Just saw this above the serial number of my Pass X600.5:
What does that mean in practice?
Probably for Active Audio France.

 

[Zen Mod]

there is mains input?

 

[RobertS61]

there is mains input?

Haha, thanks! Now I know I have to insert an AC cable to get these things fired up.

 

[RobertS61]

To Zen Mod:
Saw a mentioning on your website of one of my alltime favorite novels:
Piersig M. Robert - Zen and the Art of Motorcycle Maintenance . An inquiry into Values
I strive to be the main character on the Honda but in reality I’m the guy on the BMW that has little or no cognition of the working of his motorcycle and keeps kicking his kickstarter wondering why his machine won’t start, clueless.

 

[Zen Mod]

I'more likely that stuck screw on engine cover

 

[Nelson Pass]

Just saw this above the serial number of my Pass X600.5:
What does that mean in practice?
Probably for Active Audio France.

Yes. Occasionally.a distributor will feel the need for a little boost on the label.

😎

 

[RobertS61]

Yes. Occasionally.a distributor will feel the need for a little boost on the label.

😎

Aha, like the former German importer WBS of Threshold or the Japanese loving the 'Limited Edition' badges...
It was probably Active Audio Vertrieb GmbH in Germany that wanted the label.

 

[RobertS61]

I'more likely that stuck screw on engine cover

Keeping the whole thing together...

 

[Nelson Pass]

Aha, like the former German importer WBS of Threshold or the Japanese loving the 'Limited Edition' badges...
It was probably Active Audio Vertrieb GmbH in Germany that wanted the label.

Yes Werner Barden, unfortunately deceased. When I started Pass Labs in '91 he was my first customer, and made the company successful in its first year. He could have any label he wanted...

 

[RobertS61]

Yes Werner Barden, unfortunately deceased. When I started Pass Labs in '91 he was my first customer, and made the company successful in its first year. He could have any label he wanted...

Yes indeed. We collected a pair of Acoustat Sixes at his place in Stephanshausen Germany and of course Thresholds. He had a very beautiful Threshold prototype pre-amplifier PCR-1 that complemented the Stasis 1 mono amps. In Germany Threshold was relatively popular due to his efforts in the first place. These kind of figures are long gone from the scene...