Help With Provenance: Pass Labs Zen

[SiliconTi]

Hi All,

I tripped across this amp the other day, but passed on it until I could confirm some info on it.

It is a Zen, that I know. I was led to believe that is was built by Pass Labs (not a kit) and that it won some HiFi competition in the 1990's.

Can anyone shed some light on it? There are no markings on the case, only on the board as pictured. Thanks!

 

[gary s]

Certainly does not look like a Pass Labs in house quality build. The Zen amps were designs released by the master and were built by hobbyists all round the world. Your photo quite clearly show it was built "at home" by someone.

Could be a Pass Labs derived pcb, although I don't remember it as such.

 

[gary s]

Looking at the Zen amp article, there was a published pcb by Nelson - not sure where one could get it though.

Maybe Mr Pass can shed more light on it for you, 25 years or so ago since the design came to light.

The builder has added more PSU caps and inductance to make it a CLC PSU - not as per original design either.

You can find the amp article at Pass Diy and download it if needed.

 

[Michael Rothacher]

Looks like a possible genuine prototype to me. Built in a NEW chassis. Could be the real deal.

 

[wayne]

Looks like an experimental prototype that walked out the door.

 

[gary s]

Gee Wayne - very experimental. I bet your current prototypes are put together way better than that one. As long as it works, that's all that matters, I suppose.

 

[twitchie]

Wow, never seen blue Vishay RN55D before! Cool!

 

[Dennis Hui]

Yeah, those blue RN55D look pretty nice.

This looks to me like the "Return of Zen": https://firstwatt.com/pdf/art_zen_redux.pdf

 

[gary s]

Thanks Dennis, I see from the schematic in your link that there is a CLC PSU - something not seen often in Pass designs. Maybe the amp is a true Pass prototype as Wayne has mentioned, if so it would be worth having because of that.

 

[SiliconTi]

The board does say Pass Labs right on it, so they must have at least made some "official" boards.

 

[SiliconTi]

Here is a link to a similar one. Same case, slightly different build:

Pass Labs Zen Amplifier - Price Reduced For Sale - US Audio Mart

 

[Michael Rothacher]

I'd love to get my hands on one of these artifacts. I think prototypes are little works of art.

 

[SiliconTi]

If it can be proven to be a prototype or Pass built unit, I'll acquire it.

 

[SiliconTi]

I think we need some wisdom from @nelson pass

 

[Dennis Hui]

I'd love to get my hands on one of these artifacts. I think prototypes are little works of art.

You might want to contact Tom V. One was found in storage and
brought to BAF last year.

Cheers,
Dennis

 

[Zen Mod]

pcb definitely original PL pcb, parts adequate for era, assembly looks Papastyle veeeery much

 

[vdi_nenna]

Looks like a Zen v2, based on the parts placement and the use of inductors in the power supply.

 

[Zen Mod]

yup , I forgot to confirm that - Zen amp, Audio Amateur 2&3/94

will -post articles, if needed

in fact, I'll not , find them here : FIRST WATT

 

[vdi_nenna]

My first amp.

 

[Dennis Hui]

I just had a look at my zen amp pcb from Old Colony Sound Lab and it also
has the "PL27 Rev 0" marking, but lacks the green solder mask.