Pass X2 Rev.1

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Mad_K

Mad_K

Member
Joined 2002
It seems a lot of people are eyeing the Pass Labs X2 preamplifier.
I have buildt the discontinued Rev.1. I stayed with the original schematics for the most part. Some changes where needed to accomodate some of the parts from my (ever growing) junkbox. This was probably the biggest reason I undertook the project -to put some of my precious junk box parts into service again. Another reason was that I needed a reference preamp to judge my own designs against.
The changes I did was to double the capacitance in the psu (along with RC filtering to be able to use my existing trafos), and some additional filtering/decoupling because of the separate boards/boxes. I found the outputrelays and voltage headroom circuit excessive for a diy unit. It is a extreme design; it runs hot as a racecar (so be warned) and nearly as dangerous with unregulated rails of +135/-45VDC!

Ever since the manual ( http://www.passlabs.com/downloads/old product/x2serv1.pdf ) was graciosly made available through passlabs.com I was faschinated with the design of this pre, and immediately wanted to build one.
This is a extremely nice sounding preamp, thank you very much Nelson! I am very grateful for your efforts and continous contributions to the diy community, you're a true inspiration!

I snapped some pictures today, sorry for the poor quality, but you get the idea ;)
 

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Mad_K

Mad_K

Member
Joined 2002
Thank you Steen, maybe I'll consider bringing it up from the basemaent for a little while :)

Thanks Jürgen, yes, how DOES it sound? I don't like to talk about sound, I like to talk about music. What I can say is that it plays music very, very, very well :D It allows me to play any record I want, soft or loud, doesn't matter. Simply a wonderful preamp..
 
Mad_K

Mad_K

Member
Joined 2002
Thanks William,

Didn't the volume control show in the pictures? Anyways, it's a DACT CT2, and the input selector is a CT3. I've compared it with BZLS and XBOSOZ and lot's of other designs I've made for myself. Not in the same period in time (read setup), so it's very difficult to compare directly. No specs or measurments besides the ones in the manual, sorry. It's such a simple circuit, so when the DC-figures are correct, and it works, I don't bother with additional measurments. I made it for my own personal enjoyment, so measurments doesn't have any value for me.
 
steenoe

steenoe

Member
Joined 2004
Thank you Steen, maybe I'll consider bringing it up from the basemaent for a little while
Click to expand...
Yep, you better do that Mads:D I think the X2 is a bit hard to beat;) Hey, come to think of it, I have one of those nice Italian boxes too:) My headphone amp sits in a chassis just like yours;) Beautyfull stuff, indeed. I have to repeat myself, Very good job:) How did you go about designing those boards?? Its over my head for sure;)

Steen:cool:
 
Mad_K

Mad_K

Member
Joined 2002
jacco vermeulen said:
Mads,
very elegant.
Getting the units that slim is really nice, and pretty difficult i think.
Mind telling how you attached the supply cable to the powersupply on the bottom of the preamp chassis

Mmm, ever heard of Buell ?
Click to expand...

Thanks ;)

Buell Motorcycles? Yes, very nice machines..

I simply fastened the supply cable with 3-4 cable ties. The cables are individually isolated, with a jacket, then I put some heat-shrink tubing in the area where it is entering the box. I had bought a second AMP-connector, but since I recycled an old box with pre-drilled holes I didn't bother..
 
Mad_K

Mad_K

Member
Joined 2002
steenoe said:
<snip> How did you go about designing those boards?? Its over my head for sure;)

Steen:cool:
Click to expand...

I do a lot of pcb design at work, and also for myself. I think it was really straight forward, and I'm not particularly proud of the design. What is nice about the boards are that they are designed to fit in the (limited) mechanical space, and are optimized for those nice Italian boxes (I think they're great). I also used some layout ideas from the original pcb design.
I have most experience with dual layer SMT boards, but I'm designing more and more and more single sided HMT boards for my self. It gives me some kind of strange satisfaction to fiddle with the old, large hole mounted components, compared to the 0603 and 0805 SMT componets I have to work with on the HF boards at work. To get some challenge (and ease of manufacure) I make single sided boards whenever possible.
 
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