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Pass Aleph P 1.7 preamp builders thread
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Old 16th July 2013, 10:06 PM   #21
sakellogg is offline sakellogg  United States
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amps are just bigger pearls or p1.7's.
they are more dough.!
i never did a X.
i started with a aleph. very cut and dry. good one to learn on.
a scope is very nice to have. a cheap one off of ebay will get you what you would need it for.
but i built my aleph 1.2 and hooked a scope to it and i didnt need it. it came out just fine.
if you decide to get one let me know ill scan my basic elec class manual on how to use one and send it to you.
i can talk u through it over the phone. not hard just a new tool to learn.

the 2k pot..... i dont know i dont remember. i would put it in the middle.
i did use a scope to ballance the chan on my 1.7 while tweeking the pot and looking at the signal.
proably could do it with a 60hz test tone and a fluke meter.
now that i think about it... i used my scope the most on my preamp.

anything i can do to help let me know. you will love them!
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Old 17th July 2013, 05:52 AM   #22
FormosaWest is offline FormosaWest  Canada
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Quote:
Originally Posted by generg View Post
As far as I remember, lower value of the 2k gives more gain and vice versa....
Thank you!
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Old 17th July 2013, 06:14 AM   #23
FormosaWest is offline FormosaWest  Canada
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Quote:
Originally Posted by sakellogg View Post
amps are just bigger pearls or p1.7's.
they are more dough.!
i never did a X.
i started with a aleph. very cut and dry. good one to learn on.
a scope is very nice to have. a cheap one off of ebay will get you what you would need it for.
but i built my aleph 1.2 and hooked a scope to it and i didnt need it. it came out just fine.
if you decide to get one let me know ill scan my basic elec class manual on how to use one and send it to you.
i can talk u through it over the phone. not hard just a new tool to learn.

the 2k pot..... i dont know i dont remember. i would put it in the middle.
i did use a scope to ballance the chan on my 1.7 while tweeking the pot and looking at the signal.
proably could do it with a 60hz test tone and a fluke meter.
now that i think about it... i used my scope the most on my preamp.

anything i can do to help let me know. you will love them!
Thanks!
If you could scan that basic elec class manual on how to use an oscilloscope id be super greatful. Ihave zero training or education in electronics (except first year university physics) and am learnng only as i go alng. So far no mistakes ...except ordering the wrong transformer once... Mostly i think im doing well so far.
What qualities or features might be needed to assess an amplifier for wave form distortion and clipping for example.

DjFormosa (at) hot mail (dot) com
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Old 17th July 2013, 04:13 PM   #24
sakellogg is offline sakellogg  United States
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ok ill see what i can get done today.
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Old 17th July 2013, 06:57 PM   #25
FormosaWest is offline FormosaWest  Canada
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Id love comments about the best way to proceed...

Im needing a balanced line-level output on the back of my preamp. This is important to me.
Ideally, this line out will be after the input switching and before the gain stage and volume control. This would enable source selecting but avoid unecessary gain or attenuation.

The purpose of this is line out is to patch my sources to my headphone amplifier for night time listening, and use the aleph as a source selector only, mute the speakers, and listen to headphones only.

I believe the attenuator im using has a mute funtion built in (joshua tree) ... Which would permit speaker muting, but im not sure if it is 100% muted. Im assuming it is at the bottom of the volume knob.

What would be the best way to wire this line out?

A) just split/tap the lines comming out of the input selector before they enter the gain boards and send each channel to a balanced out chassis connector directly. (Does splitting the line input have any possible drawbacks?)

B) insert a relay based switch in the line (instead of a tap) between the input board and the gain board, to allow selecting line out or pre out, or both. (Does adding another switch to the line in have any predictable negative inpact on sound quality?)
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Old 17th July 2013, 09:18 PM   #26
sakellogg is offline sakellogg  United States
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Imho I would run it like a pass trough.

All the inputs to the hinge of the relay, when the relay is off it goes to the 1.7.
On, it goes to a seprate set of xlr output.

By doing this you won't be changing the impedance the source see's.

Someone correct me if I'm wrong, but by tapping off it could half the input inpedance the source see's
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Old 18th July 2013, 01:46 AM   #27
FormosaWest is offline FormosaWest  Canada
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Thats what i was suspecting... Im leaning towards option two because of that. By adding a switch i can select the destination of the signal and not just rely on volume knobs to mute either the headphone amp or the speakers.
Relay on -> line out.
Relay off -> aleph p
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Old 18th July 2013, 02:18 AM   #28
sakellogg is offline sakellogg  United States
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Yah, I agree.

I did somthing like that for home theater.
I wanted to use the same amps for Fr/Fl that I would for lp quiet time spinning.
So I did 2 xlr and 2 rca in and a HT in rca.
Out I've got 1xlr 1rca and the pass trough rca.
I did the relays so if I turned off the 1.7 it would still pass the signal also 1 of the clicks on the input knob will also make it pass ht too.

I've got 10 total relays 2pole. 9 in the signal path.

Works like a charm! With test tones.... I haven't hooked it up to my HT yet but I know it passes audio like it should.

The 2 chan has been tested allot! Love it!

I didn't get to my office today to scan those pages ill try tomarrow.
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Old 21st July 2013, 03:53 AM   #29
FormosaWest is offline FormosaWest  Canada
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Originally Posted by sakellogg View Post
nice.

ive been there with the caps! trying to make them fit.
What did tou end up doing with the caps? Im thinking i might order a prototyping board and mount it above veterans board. I got the input caps on by wiring them over the sides with some left over leads clipped from some heavy resistors... It's the output ones that are a challenge.. id like to find something elegant if possible.

Did u use the same mkp4s as i?
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Old 21st July 2013, 03:55 AM   #30
FormosaWest is offline FormosaWest  Canada
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I like the sounds of your aleph setup! Ive elected to copy your idea with the relay based gain selector... Just received some spst relays, a pair for each side. Those should wire in no problem. ill have to mount them off board but thats ok..

Would sure like to build the aleph xa... Slowly gaining the nerve. Lots of things i dont understand though. Does anyone make a good board for the aleph xa that would allow something like 16 or 20 or 24 jfets to be easily wired in? I suppose it doesnt matter though since the fets need to be wired off board anyhow.

I cant seem to figure out how many heat sinks rated at 0.2c/w i would need to get anywhere near 0.06c/w to me to build a comfortable 75-80w into 8, that doubles right to 4 and at least to 3ohm, if not 2. .. I don't know if i understand the whole ac current gain thing and how to set it at say 60% or 50% or what the difference is... It seems that 60% provides a more efficient amp... But everyone talks about max 50 for class a.... Something im not understanding here.

So much to learn!

Last edited by FormosaWest; 21st July 2013 at 04:06 AM.
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