Sabaj A20a modification... worth the effort?

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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 :)

Post your modifications please and tell us:

1. what the improvement or the "improvement" was

2. what gave you the idea?

3. was it worth the effort?

Preferably with pictures in a reasonable resolution and a clear description what part/type numbers you have used. Avoid "blacker than black" to avoid the curse of the burned woofer that may come upon you!
 
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I have alraeyd mentioned it in another thread, but in case somebody else stumbles upon this thread: Not a modification, but turning up the input voltage (easy to do as the PS board can be unscrewed without removing any ribbon cables) makes the amp simply play more "grown up" - i.e. you get more of everything: timbres, soundstage, dynamics.
 
Sorry, I did not take a picture, but once you remove the PS board the tiny adjustment pot can be easily spotted - I just turned it to max as the power supply does offer just under 26V as maximum - hence just below the limit of the chip - and yes - output voltage of the PS.
 
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The German producer of the MA12070 states the following:

Description Features

The MA12070 is a super-efficient audio power amplifier based on proprietary multi-level switching technology. It supports a 4-26V supply voltage range, allowing it to be used in many different applications. Multi-level switching enables very low power loss during operation. In addition, it allows the amplifier to be used in filterless configurations at full rated power in a wide range of audio products.

"intended for portable" can not even be found. You are posting fake news, sorry.
 
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"Supply voltage 4 ... 26V" and high efficiency speaks about the field of application of these chips. The absence of output filters is a bonus of this technology and
significantly improves sound quality.
I have amplifiers A30 and TPA3255, both sound almost the same. Bass is better on TPA - more damping coefficient of acoustics. Therefore, a MA12070 chip is installed on each channel.
But the power is small compared to TPA3255.
 
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 :)
 
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)

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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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.
 
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Joined 2002
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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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 :wave:
 
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