Pass HPA-1, what do we know?

[Hikari1]

Jeff,

Interested to hear your impressions of HPA-1 as a line amp. Let us know if you are able.

 

[JeffYoung]

@Hikari1, will do. It was built to feed a pair of these:

But as I don't have the Beefcakes built yet I might compare it to the pre-amp section of my Rogue Cronus Magnum....

Cheers,
Jeff.

 

[Hikari1]

Beefcake front end is quite interesting.

 

[JeffYoung]

It's essentially a J2 modified to handle +/-50V rails.

Here's the latest version of the front end with its shunt regulators:

Cheers,
Jeff.

 

[PiotrL]

So how's it sound?

(...)

The SEX was more fun than the T3, but if I was listening seriously I'd be annoyed by the loss of detail. The Pass consistently gave me goosebumps where the other two didn't. For me? The Pass without a moment's hesitation.

Jeff, would you mind to share what source was feeding those amps?

 

[JeffYoung]

Nothing special -- a 20-year-old NAD CD player that I've been using for all my auditions.

In use they get fed by Roon -> Metrum Ambre -> Metrum Onyx, but I can't easily get to the cables of my main system for comparison tests.

I'm in Louth if you want to drop by for a listen....

 

[PiotrL]

Sounds great Jeff, however I'm in the process of building one myself, I guess it may be interesting to see if they will sound different

Inspiring build!

 

[JeffYoung]

Cool! Let me know when you get it done and we'll have to meet up somewhere....

Cheers,
Jeff.

 

[Markw4]

Jeff,
Any chance to compare the sound of the original to your version?

Can't think of any difference except possibly the power transformer, but who knows?

-Mark

 

[xrk971]

Wow, superb work!
Very very nice!

 

[JeffYoung]

Mark, Jam said he spent a lot of time working on the transformer, so I suspect there is some difference there. There aren't a lot of HPA-1s in Ireland, though, so I'm not sure I'll get a chance to compare.

Hmm... Srajan lives in Ireland, doesn't he? Anyone know where-abouts?

Or maybe someone on the States could build one and then do a comparison....

 

[ItsAllInMyHead]

Inspiring build, Jeff. Congratulations!

 

[Manolo47]

Liscarney, Co Mayo, Ireland

according
to his bio in 6 moons..... hope I wrote it ok, but you’ll know... it kould be an interesting visit and story.

 

[Manolo47]

Liscarney, Co Mayo, Ireland

according
to his bio in 6 moons..... hope I wrote it ok, but you’ll know... it kould be an interesting visit and story.

 

[phase]

Just saw this, WOW!!
Nice project.

 

[Pars]

So here's my clone of the HPA-1.

BIG CAVEAT: This is based on Jam's descriptions earlier in the thread, hints from others, and some long hours studying not-quite-good-enough photos to discern connections and resistor values. Also, I'm an amateur in the analog domain, so while I now comprehend most of this circuit at a basic level, I certainly don't understand it well enough to know whether or not I got things wrong.

I'll post the Kicad files and/or Gerbers once I find out if it works or not.

Oh, and if you see issues with the design, please tell me! While I've already started building, I've got enough hours in the casework that I can do another board if necessary.

Cheers,
Jeff.

Were these ever posted Jeff? I thought I had seen them, but can't find them now...

 

[JeffYoung]

There's a zip of them on my hard disk, which would suggest that I posted them. I thought it might be in the "Pictures of your diy Pass amplifier" thread, but I couldn't find them there, so who knows.

Anyway, here they are (possibly again).

 

[Markw4]

Thanks, Jeff.

Say, any progress on the power amp? It should be very good if built

 

[JeffYoung]

I've been a drillin' and a tappin', a drillin' and a tappin'. Lots of progress, but it's fairly uninteresting to show.

Funny thing I discovered: mono blocks are twice as much work.

 

[Pars]

Thanks Jeff. That is a large board

What specs did you use when you ran yours? Given the size of these, my initial thought had been 2mm board thickness with 2 oz. copper.

Funny, you share your name with my younger brother, but he isn't in Ireland

Very nice work on this and on your build, BTW.