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Sabaj A20a modification... worth the effort?
Sabaj A20a modification... worth the effort?
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Old 18th September 2021, 10:34 PM   #11
denbret is offline denbret  Canada
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Quote:
Originally Posted by zek View Post
Has anyone listened to and compared the A20a and the little brother A10a?
I remember on ASR a representative from Sabaj wrote that the A20a had much better SMSP than the A10, that the sound is superior.
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Old 20th September 2021, 10:49 PM   #12
daniboun is offline daniboun  France
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I decided to completely disassemble the Sabaj A20a so that you can see the entire PCB.


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Last edited by daniboun; 20th September 2021 at 10:51 PM.
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Old 22nd September 2021, 02:07 PM   #13
ceausuc is offline ceausuc  Romania
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Quote:
Originally Posted by jean-paul View Post
This little MA12070 "Merus" based amplifier that could... Can it be modified? Does it need to be modified? And what do we do to the poor creature then? Nah, we just do it like we always do
someone from ASR changed op-amps with opa1656 on a dual Merus (AO200, but probably the same board inside) with (very) positive results.

these amps are really good and when Infineon will release a more powerful version of this chip.. well, TPA's can retire
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Old 22nd September 2021, 02:21 PM   #14
scholl is offline scholl  United States
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HEllo

What was the original rail voltage before adjusting to 26V? It looks like a single rail voltage so in a balanced configuration would would peak at only 48watts.
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Old 22nd September 2021, 02:49 PM   #15
daniboun is offline daniboun  France
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Quote:
What was the original rail voltage before adjusting to 26V? It looks like a single rail voltage so in a balanced configuration would would peak at only 48watts.
For the Sabaj A20a, the Morsun PSU gives about 24/25V. But you can increase the PSU @ 26V by turning the small potentiometer on the edge of the PCB completely to the right (see picture)

Quote:
someone from ASR changed op-amps with opa1656 on a dual Merus (AO200, but probably the same board inside) with (very) positive results.

The OPA1678 is already very good, not sure the update worth it considering how difficult it is to do :

Low noise: 4.5 nV/√Hz at 1 kHz
• Low distortion: 0.0001% at 1 kHz
• High open-loop gain: 114 dB
• High common-mode rejection: 110 dB

I sincerely think that out of the box, the Sabaj is just sublime.
The only thing I would do is : insulate the cables and increase the voltage of the Morsun PSU. It's easy to do.

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Last edited by daniboun; 22nd September 2021 at 02:52 PM.
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Old 22nd September 2021, 03:20 PM   #16
ceausuc is offline ceausuc  Romania
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Quote:
Originally Posted by daniboun View Post

I sincerely think that out of the box, the Sabaj is just sublime.
The only thing I would do is : insulate the cables and increase the voltage of the Morsun PSU. It's easy to do.
thank you, I might try to open it one day.
Not only it sounds good but it has a nice case, tone controls and a remote
all this for less than 200$...
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Old 25th September 2021, 02:36 PM   #17
douede is offline douede  France
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To be sure, I shorted the terminal & output HP cable block, by soldering directly my HP cables on the bottom of the PCB...

So :
Quite balanced. Homogeneous, detailed.
But:
Lacks energy, depth, and bass definition.
Lacks body and density.
The sounds and textures should be more differentiated; general Polyester cap (MKS) coloration.
Lack of vigor, rhythm, full-bodiedness, glitter..., thus lacks emotion.
I am not impressed.
Is it the chip, a coupling capacitor ?.

Despite its limits (noise, kinda simplification), i prefer my super tweaked FDA (STA326).
Still a believer in FDA (open loop), dreaming of an improved STA326.

Last edited by douede; 25th September 2021 at 03:06 PM.
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Old 25th September 2021, 03:15 PM   #18
jean-paul is offline jean-paul  Netherlands
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Soldering cables directly to PCB's is a choice but it is really best avoided. It does not bring much and it can lead to service unfriendliness and peeled off PCB tracks.

The Sabaj was sold although I really liked it. I will wait for the FDA version (if that will come out that is). Being used to FDA and its benefits I could not go back to an analog chain and single input despite all the goodness the A20a brings.
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Last edited by jean-paul; 25th September 2021 at 03:21 PM.
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Old 25th September 2021, 03:47 PM   #19
douede is offline douede  France
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Hi Jean-Paul,
Soldering directly to the PCB is to check...In fact, i solder directly on the PCB pieces of the same HP cable i use too go to my speakers and inside them (twisted Neotec OCC). The binding is made with dominos. To my ears, bypassing cheap binding posts (of cheap amps) usually brings a lot.

"Being used to FDA and its benefits I could not go back to an analog chain and single input despite all the goodness the A20a brings".
I am not alone; happy

Last edited by douede; 25th September 2021 at 03:54 PM.
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Old 25th September 2021, 03:49 PM   #20
jean-paul is offline jean-paul  Netherlands
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Better binding posts also is an accepted solution
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