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X-250 /X-350, DIY possible?
X-250 /X-350, DIY possible?
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Old 28th November 2003, 06:08 AM   #1
lovemov is offline lovemov  United States
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Default X-250 /X-350, DIY possible?

Love these apms but tooo expensive...is DIY possible? Is there a place selling complete kit?
I remember someone told me Pass Labs actually has kit for sale, but I have checked their site and can't finad anything.
Sorry if this question was asked before, I am new member here. Thanks!

(if x-250/x-350 is not available, is there any other option for me? I'd like to DIY a true class A, 50-100w apm, preffer full kit...I head x-250/x-350 is true class A when output is less than 50w, right?)
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Old 28th November 2003, 03:16 PM   #2
Hans B is offline Hans B  Denmark
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Hi and welcome to the forum

Petter has made a version of the x100, which can be found here:


And it can be scaled for higher output, however this might be some work. Also no kits exists for this design, so my suggestion would be, to go for another amp.

Passlabs does not have kits as such, but they do sell PCBs of a non commercial power amp, which is designed by Nelson Pass. The amp is called the penultimate zen, and can be found at:


If you look under "amplifiers" you can download the zen-V4.pdf and see the PCB and a complete components list.

Regarding commercial products - Passlabs is probably not going to provide PCB or complete kits for their commercial amplifiers.

Hope it helps

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Old 28th November 2003, 03:48 PM   #3
GRollins is offline GRollins  United States
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There isn't a kit for any of the X amps. As Hans B noted, Petter did a nice job of reverse engineering the circuit to produce a 100W version. Other variations are possible.
The X amplifiers run class AB, which means that they are class A up to some arbitrary point (depending on where the bias is set), then operate in class B. There was a thread where folks were speculating on the level at which the transition occurred, but I don't remember what the final figure was. You're using the phrase 'true class A' to describe the circuit you want to build, but if you're speaking in terms of an X amplifier, it's not actually class A.
I gather that you're new to DIY. If you're serious about building a class A amplifier, I think you'll find the Aleph amplifiers to be a lot easier to deal with. Quite a few people have been down that path. As far as I know, Mark Finnis and I were among the first to go that route. I've got a thread here on building the Aleph 2, and Mark has a web page. I think he built a 4. If you're interested in pursuing the Alephs, go to www.passlabs.com, go to Products, then to the bottom of the page. There's a link there to the full service manuals (including schematics).
If you want a class AB amp, particularly a large amp, there aren't too many places you can go. I think there's one on the ESP pages, and certainly you should at least look over Anthony Holton's stuff, as I know he's got some monster amps. Roam the links in the project amp area listed here on the DIY site.

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Old 28th November 2003, 06:23 PM   #4
moe29 is offline moe29  United States
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Default Zen is it...

If you want to learn to build amplifiers, and you are a first timer, i
strongly reccomend that you start with the Zen articles on PassDIY.
Don't get hung up on the number of watts, or the class
of amplification, etc. Building something that works, and sounds
good is a great feeling.

What you can learn from those articles and the huge amount of
information contained in this forum - you have a great chance of
success. All i can say is that if i could do it - so can you!!

good luck!
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Old 28th November 2003, 08:18 PM   #5
till is offline till
Join Date: Apr 2002
Location: Germany, Clausthal
In case power is enough ZEN V4 has my vote. If you need more power, be quick and order some alephx PCBs from hifiZen: http://www.diyaudio.com/forums/showt...threadid=22334

And read a lot in this board, you will remark the Master himself listens to lighbulb - Zens!
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Old 28th November 2003, 08:32 PM   #6
grataku is offline grataku  United States
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Now wait a minute!
_ULI_ has an excellent, fully tested AND in operation at the moment in his system.

Homework: find the link using DIYAUDIO serach engine...

So the answer is YES, and although there is no "kit" the circuit has been fully worked out and I believe a 250 or a 350 verision would be easier to implement than a comparable AlephX.
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Old 29th November 2003, 02:58 PM   #7
LBHajdu is offline LBHajdu  United States
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In order to build a true x-amp you need to get the service manual. I have read of one account of a man by the name of David Smith ordering a service manual for his X350 on www.audioreview. He says ďI contacted the factory and obtained a service manual.Ē I wonder if Mr. Pass would send me a service manual for some type of fee.

I would be uncomfortable building an amp from Petters circuit. It may be 99.99% the same as the true x-amp, however one inappropriate resistor value will take away from the sound of the amp. Petter gave little info on the sound of the amp and I donít know of anyone else who has built his circuit. After about 10 good reviews I would opt to build it. Everyone seems caught up by XA madness. I canít think why. A good size XA amp uses up so much power.

Uli has also built an X-Amp from his own circuit. Itís a little more stable and better documented compared to Petters circuit. Just look up the ďnormal X-AmpĒ thread.

Iím also donít know if the lower bias amps like the x5 with an idle dissipation of 40 watts per channel sound as good as the bigger higher idle dissipation amps like the x350.

Iím driving my self mad trying to pick which amp will suit my needs best. My current choice is Anthony E Holtonís N-channel Amplifier; however I may change my mind on that. It packs a little bit more punch on the bottom then the Aleph and the dissipation is only 46watts.
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Old 29th November 2003, 06:47 PM   #8
cocolino is offline cocolino  Germany
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The Link of the previous post from LBHajdu don`t work (for me).
I hope this one does it:

I wonder if Mr. Pass would send me a service manual for some type of fee.
I wonder too!!
But I doubt it.
I believe only actual X-350 owners may have a service manual
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