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Old 5th May 2006, 03:06 PM   #1
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Default the sound of DIY aleph X

Hi, for an 3-4 days I am listening for my 4 x new aleph x amps. Inspite of some different materials used(PS caps) and different bias 1-1.3A per mosfet.voltage ios 25V. I am concerning about sound of it. My others aleph 5 even built with cheap chineese electrolytic sounds better than aleph x in most aspects. From expierence I know that bass is weakest thing in new borned amps is bass. After 2-3weeks it appears ƒº but in this case there no ablsolutely bass with my speakers my speakers is 3 way with 2x 8inch ¦woofers each 92db sensitivity 1x 7¡nch midrange 89db and 1inch ¨ tweeter. 94db All drivers are 8ohms. impedance about 6ohms from 130hz to 15khz and several dips in 80hz and 30hz (3 and 2.5 ohms respectively) real system sensitivity pretty high -around 91db

The problem that is almost no low frequencies. I measure spl.vs frequency . And the low FR is lower than aleph 5,especially playing louder. The aleph 5 has much better low frequency control and quantinity.

The other problem is with musical enjoyment aleph x is more technical sounding amP, with less focused soundstage and less enjoyable sound. .. I was expecting from aleph x aleph 5 sound with much more dynamic and control.. maybe its just my amps? How other opinions?

And question, what amp can drive these spekers? Maybe I can crank up bias, add more pairs mosfet? To feed higher voltage? And how to do this? In can usevery big heatsinks. Or I should look to another amps? I spent mamy thousands euros when making these aleph so it will be suicide

any help or expierence are very welcome..
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Old 5th May 2006, 04:25 PM   #2
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The bass has less control in the aleph-x than in my aleph 30, if it´s less in quantity, than just a little bit. But less focus? The aleph-x has more focus for my ears, single voices or instruments are better focused in their position in the room and the three dimensions of their shape. And the aleph-x is a bit cleaner sounding too. But sometimes it seemes, that it´s more hifi and less emotion The aleph has more sound, it adds something to the music that can be nice, but not for a single voice or a violin, than the alph-x is a big advantage. As you can see in my thread "Aleph-x running, but a little problem" i´m looking for some modifications too.
Oliver
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Old 5th May 2006, 04:44 PM   #3
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yes aleph x is clearer sounding and more transparent, soundstage is bigger more three dimensionall etc. just for my ears(I and my friend for example understand focus very different) it is lees focused. too big soundstage especialy with my speakers which has huge 3dimensional soundstage, the sounstage it just too big. I think i gat get use to it, BUT from 30kg 2x120w amp with 16 power mosfets I just expecting litle bit more low frequency quantinity especially ant lower impedanse..

I am not bass freak, I like fast qualitty bass, but I know my spekers potential and they are wall shaking speakers with xm max 29mmm of 4 x woofers at 22sq m room..and now they even dont moove at loud and very loud volumes even
should I try krell ksa50 amp? or beef aleph x?
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Old 5th May 2006, 05:22 PM   #4
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I'm wondering if it is a power problem. The standard Aleph designs output more power into higher loads. Whereas the AlephX has peak power output into a certain load dictated by the bias setting.

With a 2.5 to 3 ohm load, the power maybe falling off dramatically if the AlephX to biased for 8 ohms.

Just a thought.

-David
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Old 5th May 2006, 05:31 PM   #5
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I thought it too. also I saw aleph xa160 review on stereophile and at 8ohm it has 160w and at 2ohm about 15Wor so! so how to rebias amp for 4 ohm impedanse? I always wondering how krell mark levinson makes amps both bass killers and pretty ok sounding.bipolar better mosfet in LF? nelson suggested double mosfets on output. I can do this but how? I need just paralel mosfet or extra parts(220ohm resistors,source resistors etc)
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Old 5th May 2006, 05:37 PM   #6
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Try to reduce R12 and R34, that helped in my case. I use 800 ohm instead of 1.2k
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Old 5th May 2006, 05:43 PM   #7
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good idea, but probbaly yours resitors numberinga are far away from mine I using this shematic and pcb from kritijan

http://www.kk-pcb.com/alephx.html

which of theese resisitors are in my schematic and what theese resitors do?
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Old 5th May 2006, 05:59 PM   #8
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There are 220uF that see the output, they are connected to 1.5K resitors, these are the wright ones.
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Old 5th May 2006, 05:59 PM   #9
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Quote:
Originally posted by elviukai
I thought it too. also I saw aleph xa160 review on stereophile and at 8ohm it has 160w and at 2ohm about 15Wor so
Logically an amplifier which has 160 watts into 8 will have
at least 40 watts into 2, even if it's limited by current.

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Old 5th May 2006, 06:17 PM   #10
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sorry my mistake , xa160 has 28w at 2 ohm load regarding stereophile. I am not familar with electronic nuances but is this mean that if I am driving 8ohm speakers which has bass woofers of 3ohm at low frequancies so spl diferency are quit big. no wonder why bass is weak.

as I understang from endless searching in posts that I need reduce source resistors tu up the bias if I want to drive 2.5-3ohm.

uping the rail voltage will only up power.the more power at high impedances and still low impedanses starving. all I need is 50-80w amp which delivers the same 50-80wats at 2.5-3ohms. the problem with my speker is in itself inspite 2 musle bass in 50lltr vented box with fb of 30hz and woofers fs at the same region the bass start down already at 70hz . vey slowly like in closed box and in room it somewhat compensates but still there is very little bass from such muscle drivers.
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