Tweakers' Asylum: REVIEW: Borbely Audio Servo-50 Amplifier (SS) by ccd

Model:	Servo-50
Category:	Amplifier (SS)
Suggested Retail Price:	$varies
Description:	Kit amplifier/100wpc
Manufacturer URL:	Borbely Audio
Manufacturer URL:	Borbely Audio

Review by ccd on December 22, 2001 at 18:27:09
IP Address: 66.31.148.46

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The amp has been completed thanks to the assistance of Peter Noerbaek of PBN Audio. Moral of the story: do not change the output devices on a Borbely amp (I changed the amp from MOSFET to BJT).
Second moral: do not assume, as I did, that all BJT amps make good subwoofer amps. They don't. This amp is VERY smooth, almost tube-like. I've never heard a BJT amp like this one. Because of this quality, the Servo-50 is being used to power the Mangers. Compared to the BK Electronics amp modules which it replaces, the Servo 50 adds a layer of depth to the music which I never knew I was missing. The overall presentation is very musical while still being accurate and really shines with better recordings. However, there is a third moral.
Third moral: better equipment sometimes highlights shortcomings in other parts of your system. With an amp like the Servo 50 powering the Mangers, my PPI Pro 8 woofers simply cannot keep up. Most of the problem is that the PPIs simply do not go low enough to integrate with the Mangers. The matter is made worse by the other improvement to my system, the Millenium which is powering (or should I say overpowering) the woofers. You can hear the PPIs bottom out as they try to reproduce the lower bass register. Simply put, the woofers need help. I tried two woofers per cabinet, but that muddied the bass. Within their limited range, the PPIs are the most transparent woofers I've ever heard.
With material with limited bass content AND if it is a good recording, the combination of the Servo 50 with the Millenium is magical. Poor recordings and/or too much low bass content break the spell.
The Servo 50 would be a good combo with speakers that tend to be too analytical or sterile in their presentation. Even drivers which are not analytical such as the Mangers seems to be enlivened by the Servo 50.
A word of caution: I have no idea how the Servo 50 sounds with MOSFETs instead of BJTs. Also, I cannot recommend that anyone substitute BJTs for MOSFETs. The only reason why this amp is working now is because I shipped it to California to the only person in the country with extensive experience with Borbely amps, Peter Noerbaeck of PBN Audio.

Product Weakness: VERY hard to build
Product Strengths: Smooth musical amp. Deceptively powerful.

Associated Equipment for this Review:
Amplifier:	Borbely Millenium amp
Preamplifier (or None if Integrated):	Marchand PR-41/XM-9
Sources (CDP/Turntable):	Denon CD player
Speakers:	Custom bi-amped 2 way, Manger/PPI Pro 8
Cables/Interconnects:	nothing special
Music Used (Genre/Selections):	jazz/classical
Room Size (LxWxH):	30 x 13 x 8
Room Comments/Treatments:	none
Time Period/Length of Audition:	several hours so far
Type of Audition/Review:	Product Owner

Product Weakness:	VERY hard to build
Product Strengths:	Smooth musical amp. Deceptively powerful.