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Any problems with the "Aleph" (5, to be specific) architecture ?
Any problems with the "Aleph" (5, to be specific) architecture ?
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Old 4th January 2019, 10:44 PM   #1
teodorom is offline teodorom  Italy
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Default Any problems with the "Aleph" (5, to be specific) architecture ?

Hi,
I'm trying to understand how the whole stuff works.
Sorry about that, but to do that I'm using a simulator (less danger and less smoke).
Let's have a look on the original Pass design for "Aleph 5": http://www.kk-pcb.com/a5serv.pdf that I have reproduced this way:
Click the image to open in full size.
My question is threefold and always related to the C5 capacitor.
  1. My simulations says that the input impedance on the XLR+ and XLR- is very different: 14.7kOhm and 5.3kOhm, respectively. Is this a "fake" result or it's real? and, if it's real, does it have any consequence on the SQ?
  2. If I replace C5 by an appropriate resistance I can get the two impedance's identical. For sure I have to recheck the OFFFSET and, to get the original gain, I need to raise the NFB resistance R7.
  3. The "Aleph" architecture is said to be "capacitor free": is anybody worried by the presence of C5 on the XLR- line?
Thanks
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Old 4th January 2019, 10:45 PM   #2
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Any problems with the "Aleph" (5, to be specific) architecture ?
try using original schematic
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Old 4th January 2019, 10:52 PM   #3
teodorom is offline teodorom  Italy
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Quote:
Originally Posted by Zen Mod View Post
try using original schematic
Sorry about that, but, as I mentioned, this is the ORIGINAL schematics: https://scontent-mxp1-1.xx.fbcdn.net...f7&oe=5CC5D6BA.
Perhaps there is something better, among the many schematics I could find on the web. But, who knows?
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Old 4th January 2019, 10:56 PM   #4
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Any problems with the "Aleph" (5, to be specific) architecture ?
R8 is 1K
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Old 4th January 2019, 11:01 PM   #5
teodorom is offline teodorom  Italy
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Quote:
Originally Posted by Zen Mod View Post
R8 is 1K
My mistake, thanks.
Now the two impedance's are 10.9kOhm and 9.1kOhm.
Let me guess that I should be satisfied.
But ... a huge capacitor on the XLR- line doesn't worry you?
Thanks
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Old 4th January 2019, 11:06 PM   #6
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Any problems with the "Aleph" (5, to be specific) architecture ?
I believe I already pointed you to my Babelfish J thread , where you can see what worries me

anyway , Aleph series was , in general , very successful series of amps , primarily due to sound quality , exquisite craftsmanship and longevity ........ which means that many satisfied customers didn't had nothing to worry about

suddenly , there we are , Greedy Boyz and Grand Tweakers , having doubts about Papa's constructions

if you're worried with that capacitor - just short it ; but only after you make entire amp and prove with DBT that you're able to hear when it is in circuit
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Old 4th January 2019, 11:10 PM   #7
wayne is offline wayne  United States
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Any problems with the "Aleph" (5, to be specific) architecture ?
The original Alephs didn't have symmetrical input impedance.
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Old 4th January 2019, 11:12 PM   #8
teodorom is offline teodorom  Italy
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Quote:
Originally Posted by wayne View Post
The original Alephs didn't have symmetrical input impedance.
This is what I suspected.
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Old 4th January 2019, 11:17 PM   #9
teodorom is offline teodorom  Italy
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Quote:
Originally Posted by Zen Mod View Post
suddenly , there we are , Greedy Boyz and Grand Tweakers , having doubts about Papa's constructions
Me, I would only to be helped to understand.
I have no faiths or misconceptions.
No phase rotations on T2 (see my schematics)? tell me that and I shall trust you.
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Old 4th January 2019, 11:21 PM   #10
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Any problems with the "Aleph" (5, to be specific) architecture ?
Quote:
Originally Posted by teodorom View Post
......
No phase rotations on T2 (see my schematics)? ......
clarify "phase rotation"
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