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Aleph3 recap
Aleph3 recap
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Old 13th December 2011, 08:27 PM   #81
stereotype is offline stereotype
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Someone previously wrote: "...the smaller DC blocking caps in the signal path will cause a loss of low end when they start going bad..."

Last time I checked, the Aleph 3 is a directly coupled design. There are no caps in the audio path outside of the support circuitry. Also, I question changing the values of at least some of those smaller caps, as the actual purposes they serve are different in the different areas. For example, C-103 is to bypass noise, per NP. Not sure where NP is in all of this.

The audio path goes thru a resistor, mosfet, resistor, mosfet, resistor and to the spkr output. The rest of the circuitry is support, including a form of advanced feedback that includes ghost loading reaction.
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Old 13th December 2011, 08:44 PM   #82
Zen Mod is offline Zen Mod  Serbia
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do we agree that I can to disagree ?

C101 and C103 ( ref. Aleph 3 Service manual schematic ) are in signal path , at least in my book

all other are , say , filtering caps

these two are already over-sized in value , so no big fuss in decreasing them to 50%

off course - leaving them in original value is still better
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Last edited by Zen Mod; 13th December 2011 at 08:49 PM.
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Old 14th December 2011, 01:05 PM   #83
stereotype is offline stereotype
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Sure, I'll disagree with Zen Mod, as in fact, this is a directly coupled design. Perhaps you misunderstood my POV, since caps that off of the feedback loop, yet are not coupling the signal from the output to the input, are not necessarily in the audio path; at least not directly as far as amplified signal that travels directly from input to output. Having owned an A3, I claim a strong interest, a reasonable familiarity with its operation, configuration and most certainly, its extraordinary performance.

I previously provided the actual audio signal path, which is stands as correct. You may follow along with the schematic, if that would help you trace the path that I outlined as directly coupled with no coupling caps present, from the A3's input jack to output binding post; a total of three resistors and two mosfets. Any remaining circuitry is power supply related including CCSs, parametric support, and a special form of loading that enables a variable form of feedback.

Zen previously wrote: "through C101 and C103 you have signal flow ; C102 have sort of other role"

I might partially agree with a portion of your former statement above, although it would be limited to this: Audio signal flows through those caps via the feedback loop, yet these don't couple the signal to the input. C101 does have audio signal flow but not as "coupling" since it's technically a bypass cap; the same would be true for one of the other caps.

The audio signal that goes through C101 goes directly to ground. Please refer to the schematic to verify this fact. I will provide a more detailed explanation for those who might be unfamiliar: After the audio output is both attenuated and isolated by a total of 11K through two resistors, C101 bypasses that portion of the (attenuated) audio signal to ground, so this is a bypass cap that enhances the function of the diff. pair.
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Old 14th December 2011, 01:54 PM   #84
Zen Mod is offline Zen Mod  Serbia
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think whatever you want , that's your basic right .

I will continue to think that even caps in feedback are in signal path ;

on the other hand , in many circuits , even PSU caps are in signal path

I'm not saying that that's bad , just claiming a fact , per se .

anyway - did you ever tried to replace or bypass that cap in Aleph CS modulation ?

it's clearly audible , when you make a change

same case - when you place shortie instead of that cap in feedback node - it's audible change , and for my ears positive .

if signal is not flowing trough them , change in sound will be impossible .
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Old 14th December 2011, 03:22 PM   #85
Dukja is offline Dukja  United States
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Thanks for the discussion (even it is still beyond me at this point, but I will try to get it eventually).

I am very interesting in whether the change of those small cap values has + or - impact to sound. All the small caps were 220uF but now replaced by 470uF, so they are more than doubled.

Sonic-wise, after a about 50 hours of burn in now, the improvement on bass remains and it is the biggest improvement easily appreciated. The tremble and midrange are also changed but more or less in a mixed situation. The slight treble edge is gone, but at the same time the "air" feeling or the vividness/freshness is reduced a little bit. The midrange is still a little bit recessed and dry (but seems to be better after some burn-in). So I am observing its change.

Therefore, I am tempted to see how the SQ changes if I switch back to the original values of those small caps. Comments?

(I wonder if people put sockets for those caps so we can change them on the fly to see the change of SQ)

Thanks!

Last edited by Dukja; 14th December 2011 at 03:25 PM.
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Old 14th December 2011, 03:39 PM   #86
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there will not be change if you decrease value of these caps from from present one ;

I hope you put some nice 10nF (and upwards , to 220nF) MKC (polycarbonats) across them , as bypass ?

I think that I told you to do so , previously .

that way you'll gain some speed up - clearer sound .

I'm finding 10nF MKC of benefit , even bypassing Black Gate , put in C103 position ;
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Old 14th December 2011, 04:22 PM   #87
Dukja is offline Dukja  United States
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Yes, I am accumulating my mouser order to save some shipping.

As you knew that I am also hunting down a preamp project.
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Old 15th December 2011, 01:41 PM   #88
albertNL is offline albertNL  Australia
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After reading your story I am very scared what I will find if I open up my Aleph 3. Best to leave it closed for now!
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Old 15th December 2011, 02:30 PM   #89
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Quote:
Originally Posted by albertNL View Post
After reading your story I am very scared what I will find if I open up my Aleph 3. Best to leave it closed for now!
you know what to do then ........

send it to Authorized Facility for Proper Disposal of PL Products

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Old 15th December 2011, 02:42 PM   #90
albertNL is offline albertNL  Australia
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Originally Posted by Zen Mod View Post
you know what to do then ........

send it to Authorized Facility for Proper Disposal of PL Products

Sorry, Zen-mod, I cannot afford the shipping costs for proper disposal. I guess I will have to torture myself and keep listening to the Aleph 3!
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