Pass Aleph P 1.7 preamp builders thread - diyAudio
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Old 12th July 2013, 06:40 AM   #1
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Default Pass Aleph P 1.7 preamp builders thread

Ive begun the process of crafting a preamp following the fine design of the pass aleph p. the idea of building m own stereo was never something id ever considered possible except in my dreams. Thanks to this community and the generosity of nelson pass, ive been able to slowly learn bits and pieces about audio component design structure and function.

After finishing the pass labs pearl 2, designed by wayne at pass labs, and falling head over heels in love with records, i couldn't help but want to build a matching preamp/control deck to pair with it and my turntable.

This forum is to discuss the challenges and success in building a copy of the aleph p for personal enjoyment and education.

Last edited by FormosaWest; 12th July 2013 at 07:14 AM.
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Old 12th July 2013, 07:07 AM   #2
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Just about finished the attenuator boards, relay driver and control deck. My veteran preamp boards are almost complete. What a tight fit! Vishay dale RN60s and RN65s are great but the cmf would have fit better on these boards.
Ive selected the 250v wima mkp4 polypropylene capacitors for input and output, as im under the impression that they sonically may outperform polyester type caps or electrolytics. They dont fit on veterans boards at all, but a little creative mounting and point to point wiring should be just fine.

Im building a loopbreaker and ground protection with a 35 amp bridge rectifier just as i did with the power supply for the pearl2, and housing the power supply seperately... But im not sure how ill manage the connection yet. 3 distinct power supplies and a ground will require a good safe connection... Im considering dsub or 8pole speakon connectors... Any thoughts? ...fitting ti all in one box wont be easy and besides, id like to stack my control unit on my pearl2 and hence need to avoid the transformer hum.

Im selected paired DPDT omron low signal relays for input switching, and wiring the coil voltage to a rotary switch mounted to the front panel. Im hoping this will work and allow quiet input switching...

Last edited by FormosaWest; 12th July 2013 at 07:12 AM.
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Old 12th July 2013, 02:33 PM   #3
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Without pictures it didn't happen. Let's see what you've done.
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Old 12th July 2013, 06:11 PM   #4
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Well, there is the Aleph P1.0, and the Aleph P1.7, and the Balanced Zen Line Stage (aka BOSOZ) and countless CCSXYZ versions. I have played with all the Pass versions. The one I found most worth trying again is suppoorted by this statement from the 1997 article, "Balenced Zen Line Stage":
"This is a particularly good sounding circuit, and I think it sounds
significantly better than the Bride of Zen, although I would be hard
pressed to explain why. It seems more liquid and has greater depth,
while BOZ is a bit dry by comparison. It might be distortion cancellation
in the balanced circuit, or it might be the greater dynamic range afforded
by quieter balanced operation and higher output swing. As always, I
encourage you to build it and decide for yourself." N.P.
And as many others, I applied more voltage, more Iq, etc. etc. But now, we have the Semisouth R550 device and I'm ready to do it again...
In the true Pass Zen spirit, why would you want more?
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Old 13th July 2013, 03:54 PM   #5
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I actually had a hard time choosing which one to build of the two! Bosoz or aleph.
So whats the r550 device?

Ill post photos soon.
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Old 13th July 2013, 07:24 PM   #6
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An interesting SiC Enhancement Mode JFET from Semi South which should replace the 610 device nicely. If you can find some.
Attached Files
File Type: pdf SJEP170R550_rev1.3.1.pdf (160.9 KB, 360 views)
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Old 15th July 2013, 01:33 AM   #7
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formosawest:

i did almost the same thing. you shouldnt have any issues with the relays, i didnt.
i did a xono and aleph P1.7 with a seprate power.

i used 8 pole mill style conectors for mine. both duel mono.

you dont need high current. so prettymuch anything will work. i tend to like heavyduty solid built but nothing fancy.
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Old 16th July 2013, 05:53 AM   #8
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Quote:
Originally Posted by sakellogg View Post
formosawest:

i did almost the same thing. you shouldnt have any issues with the relays, i didnt.
i did a xono and aleph P1.7 with a seprate power.

i used 8 pole mill style conectors for mine. both duel mono.

you dont need high current. so prettymuch anything will work. i tend to like heavyduty solid built but nothing fancy.
Thanks sakellogg! Im glad to hear it worked out for you. Im thinking a dual deck switch so i can run a set of led input indicators as well. ... What do you think?
I kinda wish my pearl had balanced output so o could take advantage of the common mode noise rejection of the balanced type circuit for my record playback.
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Old 16th July 2013, 06:11 AM   #9
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Quote:
Originally Posted by FormosaWest View Post
Thanks sakellogg! Im glad to hear it worked out for you. Im thinking a dual deck switch so i can run a set of led input indicators as well. ... What do you think?
I kinda wish my pearl had balanced output so o could take advantage of the common mode noise rejection of the balanced type circuit for my record playback.
dual deck will work for sure. could also put the led's and resistors in paralel off the coils of the relay.

i dont know if the balanced output makes it sound any better or not. but it was there so away i went. i wouldnt loose sleep over it for sure.

what did you use for vol control.

back emf might fry the led's. i know the relays at work are huge so maybe small ones wont matter?
maybe someone smarter than me will know.
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Last edited by sakellogg; 16th July 2013 at 06:14 AM. Reason: im dumb..maybe...
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Old 16th July 2013, 06:19 AM   #10
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Ive just build the Joshua tree stepped attenuator by pear tree audio. Its one of them newfangled relay based attenuators. I believe it has a roughly fixed output impedence. Im hoping its well suited to this build. Im pretty ignorant about this new hobby of mine! What did you use?
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