Sachem v.2     hi-end  power mono-blocks

 

            Please click here to read the review of the Sachem system, made by Dr. Richard Varey on the Witchdoctor hi-fi magazine.

 

When, after more than twenty years of glorious service, I replaced my active audio pro A4-14 loudspeakers with a pair of passive Bravo FX-04, I started assessing many top amplifier options available on the local market, but I had tremendous difficulty in finding an amplifier able to deliver euphonic sound and lightening-fast-and-wide dynamics, in order to fully release the great potential of my new speakers, obviously helped by my "immortal" sub B2-50. So, quite disillusioned, I made the brave decision to develop and build my own amplifier. I embarked on this very challenging adventure because I could also count on the help of my very dear friends Rino Cieri and Allen Gill. Rino, who is an Italian old friend of mine, is a hyper-talented hi-fi technician and Allen is a no less skilled technician, with an eclectic knowledge in general electronics and digital technology. Anyway, it's been an exciting experience, even if hard and sometimes frustrating too, but absolutely interesting indeed! I have had the chance of discovering incredible things about electronic components in general and in particular about capacitors. In the end the result was more than rewarding and my new speakers fell in love with their new partners! The new "babies" have proved so good that we decided to produce a small series of 25 sets. In early 2003 the first set went on the market and was called Sachem, which is our statement design of how an amplifier should really be.

The Sachem has garnered critical acclaim driving any speakers, culminating in Martin Bell (the publisher of FFWD magazine at the time) calling it "the best 'sane money' power amplifier I have ever heard". Ashley Kramer, another famous name in NZ hi-fi magazines (now editor and reviewer of the online magazine www.witchdoctor.co.nz), in a Sachem review, said similar words of appreciation. It also seems that Martin and Ash really meant what they said, given that both bought Sachem for themselves. The same did Scott Bartley (head-reviewer of the late FFWD magazine), who, in my opinion was the most serious reviewer in NZ at that times. These are not just throwaway words, as evidenced by the long customer list of those who enjoyed and still enjoy the Sachem and/or audio pro speakers and subs at home; among them some of the most well-known names in NZ audio - Greg Vincent, owner of TONE magazine; Brent Burmester, reviewer of FFWD; Michael White, publisher of TONE etc. Also TVNZ bought for its “dreaming room” a big audio pro Bravo home-theatre system and people of the technical staff of TVNZ have bought similar systems for themselves too.

 

 


 

                                                                                                                        the original version of the Sachem

 

The success of the first lot of the original Sachem (shown in the picture above) has persuaded us to go on and release an upgraded version, the Sachem v.2, which can be purchased as a totally separate and discrete mono-block. This configuration, with independent mono-block units, has the advantage to allow a greater flexibility for custom installation, as their use in top home-theatre systems, where an odd number of amps is required.

The v.2 version features a totally redesigned PC-board with a layout as compact as possible and the addition of a large external heat-sink, which, in combination with the mica (instead of silicone rubber) insulators underneath the power Darlington devices, enable a much higher setup of the BIAS current. Furthermore, the original capacitors in the power supply have been replaced with "audio grade" ones, with larger capacitance too. Wires are employed only to connect the power supply and the in/out RCA sockets to the PC-board, which is the heart of the amplifier and totally wire-free.
What's more, this version features an internal micro-switch which allows to roll the bass response off, with a slope of 6dB/oct and three selectable -3dB points at different frequencies. This is essential to properly integrate a sub into your system or, if you don't have a sub, just to render quite listenable "boomy" floorstanders (not a rarity, but almost the norm).

Unlike many manufacturers of very expensive, hi-end amps, who prioritise the aesthetics of the cabinet, in the Sachem v.2 we have chosen to spend money on the audio substance. Probably you don't know that in many "noble" amplifiers the cost of the cabinet exceeds the cost of the electronic components, putting up the final price for nothing but the eyes. We are confident that our typical customer is the pure Audiophile, who mostly looks for exceptional sound at a quite affordable price, so we followed this philosophy. The technical and sound superiority of this upgraded Sachem easily makes up for the fact that it may not be quite as trendy-looking as our original product or many other amps as costly as a beautiful car. Anyway, we like its professional look!

So what can be said about the sound quality that the v.2 version provides?

To have an idea, you could start reading the "testimonials" page of this web site, but, to fully discover its superiority, and to help you appreciate what we have achieved, we highly recommend that you compare the Sachem v.2 to any hi-end amps on the market by listening, without any "inferiority complex" and any price limits (the more, the funnier) and possibly using very dynamic and well-recorded CDs. Differently to other amps, the v.2 loves very complex loads, so compare it using so called "difficult" speakers, and ... enjoy!

 

an overview of the Sachem v.2 mono-blocks and considerations

Please note that the text below has been partially copied from the instructions we put in every Sachem amplifier. They are useful to understand the "philosophy" of this amplifier and also to learn technical and hi-fi related issues, which you will never read in any magazine and will never told in a hi-end shop.

 

 


 

                                                                                                                 Sachem v.2 metallic dark silver - front view

 

Sachem (pronounced Sakèm) is the general Chief of all the American Indians, and the word comes from the Algonquian language of a tribe, who lived close to Lake Michigan. The Indians also used to bestow the epithet “sachem” as an honour on a senior warrior when he had distinguished himself with particular merits.  

We have spent over a year in electrical and sonic research, redesigning and compacting the PC-board and listening at length to different top components and testing small modifications of the original circuits, in order to arrive at this v.2 final version, which “sounds” as unobtrusive as possible. We do think that a perfect amplifier must not be, in its own turn, a musical instrument, adding its own “sound” to the musical program and this should be the ultimate target of any serious manufacturer of such machines!

To achieve this superior sonic reproduction, we have adopted and developed an interesting all-discrete circuit, incorporating the most modern, high performance, top quality components, in a totally clean and wireless layout, where the signal path has been optimised as well.
We have reduced the physical dimensions of the amplifier as much as possible and, as a result, you can place the amplifier very close to each speaker, on a nearby support. This is the greatest advantage of mono-block amplifiers, for it allows you to minimize the length of your speaker cables to yield a substantial difference in sound quality.
We think (sadly in vain) that all “hi-priced” amplifiers should be built to this configuration (mono-blocks), because the use of long speaker cables, irrespective of price or make, always significantly degrades the sound. A speaker is a very complex electrical load (anything but a pure resistor, unfortunately) and the cable (due to its own electrical parameters, which vary with its length) interacts to modify the electrical parameters of the total load "seen" by the amplifier. By comparison, a good quality screened interconnect (low capacitance and resistance), between preamp and power amps, does not appreciably affect the sound. Even in the very rare cases of signal degradation (some “funny” hi-end preamps, due to the high output impedance, are not able to drive long cables properly and/or using cables of very poor quality), the loss would be significantly less than that of using a long speaker cable. 

The Sachem v.2 is capable of driving any types of acoustical transducers, irrespective of their load complexity, nominal impedance and efficiency. This peculiarity is absolutely essential to unlock the full potential of your speakers, but unfortunately it is not necessarily present in every “exclusive” amplifier on the hi-end market today! That's why amplifiers can sound so different when driving a given pair of speakers.
Regarding power, many Audiophiles believe that an 80W amplifier cannot drive a low-efficiency speaker properly, but, if the amp is a Sachem v.2, they are wrong indeed. We have tested our amps driving a pair of 82dB (1W/1m) speakers at “unusual” volumes with fantastic results: very fast transients (for what it’s possible with this kind of "conceptually wrong" speakers), and not a trace of clipping.  No miracles, this is possible because the Sachem v.2 is able to deliver, without strain, peak-currents of 20A, resulting in instant musical peaks (on a load of 8Ω) of more than 3000 Watt!

On the other hand, we believe it is extremely difficult, perhaps impossible, to make a hi-powered amplifier (about 200W RMS 8Ω, or more) with such a refined sound and speed. So, we opted for a mid-powered solution, incorporating a "lightning" dynamic range and monstrous current delivery. Furthermore, with the advent of active sub-woofers in domestic settings, for driving the main speakers, there is no longer need for very powerful amps, but for well sounding and very fast ones! So, my personal advice to the Audiophile who looks for sound perfection is to buy a Pure, a pair of v.2, and an audio pro sub, and replace his useless power-hungry “dinosaurs” with better sounding, smaller speakers, which, differently to the "dinosaurs", always have many more chances of delivering coherent and accurate sound. In fact, if not designed by someone stupid, the smaller dimensions of their cabinets, at least, allow the adoption of interesting shapes, with a much smaller front panel, more respectful of the basic rules of physics-acoustics, for diffraction, reflection, phase etc.  To know more about this topic, visit the page "school of sound".

 

 


 

                                                                                                                               Sachem v.2 - back panel

 

technically speaking

Sachem V.2 features a fully complementary design, with a dual differential input stage, followed by a dual complementary differential single-ended voltage gain stage, operating in A class, at high current.

Each mono-block features an over-dimensioned 300VA toroidal transformer, which, through a 35A full-wave bridge rectifier, feeds twenty audio-grade, very low impedance and low ESR capacitors of 3,300μF each. The two blocks of capacitors provide an impressive total capacitance of 66,000μF and are integrated by two exceptional, high-speed WIMA polypropylene caps (MKP10 series). We are very aware that the purity of the DC provided by the power supply is of paramount importance for a "silky' and accurate final sound, so we have taken great care in designing it.

The power final stage is handled by six selected and matched complementary Darlington devices, in order to achieve low open-loop output impedance and linear high-current capacity. This ensures very smooth output transitions, without any audible crossover or switching distortion, even under high-current output conditions. The whole power supply and the darlingtons of the final stage are so over-sized that the result is a terrific peak max transient current of 20A on the speaker, equivalent to peaks of 1.6 kW @ 4Ω and 3.2 kW @ 8Ω !!

The other four current-filtering capacitors inside the circuit feature polypropylene dielectric, while the only one in the signal path (in the feedback circuit, where its use is compulsory) is in solid aluminium, with oxygen-free copper lead-out wires, and, in its turn, integrated by WIMA polypropylene capacitors, MKP10 series.

It is a fact that every capacitor in the signal path affects the sound negatively and most circuit typologies require many capacitors in this area. We do things differently and, in our knowledge, the Sachem v.2 is one of the very few or the only amplifier with just one capacitor in the signal path, and this capacitor is of the very highest quality and audio-grade too. Furthermore, and this surely happens only in our amp, if you set up the amp for a rolled-off output (for example, when you have to join a sub to the system or just to "humanise" the booming in floorstander speakers), this electrolytic capacitor is bypassed and the signal "sees" only polypropylene (high-speed WIMA MKP10 series)! Having achieved our goal of using only one capacitor on the signal path, we do believe we have made an important difference in sound fidelity. The v.2's euphonic sound, the full richness of original harmonics, the incredible transparency and the silky softness of the mid-high range, the endless and lightning dynamic range and the “sculptural” quality and speed of its bass range, depend to no small degree on this. Anyway, this uncommon silky softness of the mid-high range of our amplifier is also due to its total absence of crossover distortion.

The carefully considered grounding system and the state-of-the-art PC-board eliminate internal loop-currents and hum in the signal ground-path and assures a high level of immunity to noise and external interferences. I'd like to point out that the only wiring in a Sachem v.2 is for the connection of the PC-board to the transformer and to the input and output sockets: it's almost impossible to avoid these wires and totally useless too. On the contrary, and this is very important, the signal and its amplification is handled by a totally wire-free PC-board (see the picture below). Be aware that the internal lay-out and wiring of an amplifier is the "business card" of its designer and manufacturer, and it tells you a lot about their technological level. Nowadays it's unpardonable to build an amp with messy wiring or just with a lot of wiring: there is no reason and it could also cause problems! Nevertheless, many very high-priced amps on the market are poorly designed and built that way! So, in order to avoid buying one of these "jewels", my strong advice is to go to "Google Images" and check out if the interior of the amp of your dreams is as nice and clean as its external look. You don't need to be a technician to understand on the spot if the "baby" is a joke or has got the chance to be serious stuff! An astute Audiophile should always act this way before buying some piece of expensive equipment, particularly preamps.

The Sachem v.2 is temperature-compensated, and the perfect performance and sound of the amplifier is assured after a quite short warm-up period of around fifteen minutes, so there is no need to leave these units permanently powered-up, in respect of the environment and energy efficiency.

The Sachem v.2 is a completely reliable amplifier. Every unit is deeply tested for 2 hours at full power into 4Ω load (1V input, 1kHz) and for 12 hours at 25W, into 4Ω load, with "pink noise".

Regarding its reliability, the first Sachems went on the market in early 2003 and we don't have any failures reported so far. Furthermore, the Sachem Guitar combo, when on stage, seems to enjoy "shooting out" more than two hours of killing sound, without any strain, and you probably know that this kind of performance is not advisable and achievable with so-called hi-end amplifiers!

 

 


 

                                                                complete PC-board (without darlingtons and power supply) - it is the state-of-the-art heart of Sachem v.2

 

Connections and Installation

On the back panel of each amplifier unit there are the connection sockets: the red input socket receives the signal from your preamp. The black socket is a line output that can be used to feed the signal to other units or to drive an active sub-woofer alongside the speaker. At this point I have to introduce you to an interesting and very useful facility of our amplifier: the possibility to select a flat response or, via its passive high-pass filter, a 6dB/oct “rolled-off” response, with three selectable -3dB points at different frequencies (we provide every customer with a detailed explanation). You must choose one of these roll-off options (possibly, the right one for your purpose), if you use a sub-woofer.
Doing so will create the correct crossover point between the sub and your main stereo pair, so that the bass will be clean and free of boom. Furthermore, the dynamic range of the main speakers will increase and their distortion decrease, because they will no longer struggle to reproduce (in vain) the low frequencies your sub is better qualified to manage. Image and clarity in the mid and high-range will improve as a result of the lower general distortion of the loudspeaker.
NOTE: if your speakers are floorstanders and have a tendency to “boom” (it's in the "DNA" of this kind of speakers), try the roll-off option and you will probably be amazed about the transformation in the bass department and in the rest of the audio band too. Please call us for a better explanation of this powerful facility.
As standard, every Sachem v.2 leaves the factory setup to deliver the full signal range (flat response).

 

 


 

                                                                                      internal view - note the gain stage (operating in A class) and the power stage

 

Now we would like to digress and give you our point of view about the much-discussed subject of sub-woofers.
Given for sure that bass instruments do not deserve to be treated like ugly ducklings (they are the foundation, and an essential part, of a musical composition), we do recommend the use of high quality subwoofer/s with any system. Audiophiles usually "forget" that, by definition, a hi-fi system must reproduce frequencies across the whole audible range, from 20Hz to 20kHz ± 3dB.  So, if you like to listen to a genuine hi-fi system, you must have a dedicated sub-bass speaker, as NO traditional full-range speaker can achieve decent infra-bass.

Many esoteric hi-fi lovers believe that a sub will muddy the sound of their systems, and they are very often right, but this usually happens because of poor or wrong integration of the sub into the system, so that “booming” bass from the main speaker pair is only worsened by the sub’s additional output. Another reason is that the large majority of the sub-woofers do not have acceptable sound-accuracy (no matter the noble brand, the "galactic" price, and the astonishing review of some inept or biased reviewer). We only use and recommend audio pro sub-woofers, which, thanks to their patented ACE-bass technology, achieve a completely “unusual” infra-bass. When an audio pro sub is correctly tuned alongside the main speakers (properly cut and possibly driven by a Sachem pure and a pair of v.2), low frequencies are very deep and almost undistorted, virtually carved out of the air and ... NO trace of "booming"!

 

 


 

                                                                                                                     a completed Sachem v.2 - open view

 

Back to the previous subject, if you plan to bi-amp your speakers with a second pair of Sachem v.2, connect your pre-amp to the red RCA input of the amps driving the low spectrum, then connect its black socket to the red socket of the mono-blocks handling the mid-high. It is a must to cut the bass response in the Sachem v.2 used for the reproduction of the high frequencies, selecting the highest possible roll-off point.

With each mono-block you will find a metre-long speaker cable terminated in a NEUTRIK Speakon plug. The cable provided is NORDOST 2 FLAT.  Although we are not the distributor of this brand, in all our trials of speaker cables up until now, we have found this to be superior to all others (some crazily expensive too) in clarity, bass control and speed. We reckon that this cable is the best (or amongst the best) choice, in order to fully transfer the Sachem's huge potential to your speakers and it's cheap too!
Anyway, you are free to try other brands/types of cable, but whatever cables you decide upon, keep them as short as possible.
Connecting them to the amplifiers is straightforward via the professional NEUTRIK Speakon connectors, with an electrical current/contact rating of 30A RMS – just the best. If you want to change the cable, you have to open the Speakon plug to reach the screws which lock the cable. Please, be hyper-sure to connect the new cable exactly the same as in the original, in order to maintain correct polarity.
To discover the polarity of the accompanying NORDOST cable, you have to look carefully at the external white plastic cladding. You will note that the plastic cladding of one wire is completely smooth and that the other one carries a line in relief along the middle - this marked wire is the positive and the smooth one, the negative. To finish, you must test the cable for a possible short-circuit, which will “kill” your amplifier. In fact, Sachem v.2 is NOT protected against speaker cable shorts. Invariably, protection measures introduce sonic compromises, so we have refused to adopt any, in the reasonable expectation that our customers - who are unlikely to be hi-fi neophytes - will connect their speakers with the requisite care.
Anyway, before disconnecting the speaker cables, always ensure that the amplifiers have been switched OFF for at least 30 seconds. We also recommend to disconnect the Neutrik Speakon plug before the speaker ends.
Please note that the warranty will NOT cover the cost of addressing any problem caused by a short on the speaker cables.

Safeguarding the Sachem v.2 from overheating is simple. Do NOT place the amplifiers within an unventilated enclosure, such as a closed cabinet or cupboard. The amplifiers are best kept out in the open, on a hard surface, not a carpet or other yielding surface that might block or even just restrict the underside vents. Finally, and most importantly, ensure that the mono-blocks are kept out of direct sunlight.
If these conditions are not met, there is an almost certain risk that the amplifier will not run at its optimal temperature and it may suffer “thermal runaway”, leading to breakdown.

If the blue LED on the front panel goes out, it means that a fuse of the power supply has blown. This can happen and it's normally due to a power surge (quite common in NZ). Replace the fuse with a new one of exactly the same type and rating and if that solves the problem, keep enjoying the music, but, if the fuse blows again, a serious fault is likely. In this eventuality, TURN THE POWER OFF as soon as possible and DISCONNECT the power cable from the AC socket too. At this stage, it would be useful to contact us.

 

 


 

                                                                                                         a brand-new Sachem v.2 is ready to enjoy someone

 

We hope you now feel ready to use and care for your Sachem v.2, and we are confident you will enjoy the improved performance of your hi-end system.

NOTE: Please remember, though, that a pair of Sachem v.2 amps will not perform miracles! These amplifiers will mercilessly reveal any weaknesses in your hi-fi chain, and, in turn, their full potential will be “obfuscated” by any other component(s) of poor selectivity, speed or sound-clarity. Until all your components are as good as your new Sachem v.2 amps, your quest for sonic perfection will remain unfulfilled.

Please do not hesitate to contact us if you need assistance or advice with the installation and use of our products, or ... just if you have any general curiosities or questions.

 

 

SPECIFICATIONS

 

Rated continuous power (RMS)   8Ω  (20Hz ~ 20kHz)                                                        >  80W

Rated continuous power (RMS)   4Ω  (20Hz ~ 20kHz)                                                      >  145W

Rated not continuous power       2Ω                                                                                >  220W

Peak max. transient current on load  -  see note below (**)                                                 >  20A  

Output impedance (also called Internal impedance)                                                           <  0.1Ω

Input sensitivity                                                                                                                       ~ 1V

Input impedance                                                                                                                    12kΩ

Power bandwidth @ -3dB   (top-band limited by a filter 6dB/oct)                            3Hz ~ 160kHz

Phase deviation  20Hz ~ 20kHz                                                                                              <  3º

THD @ rated power  8Ω  1kHz                                                                                        <  0.03%

Crossover distortion                                                                                                         NO trace

Hi-pass filter slope  (see instructions)                                                                6dB/oct @ xxx Hz

Signal to noise A-weighted  -  input shorted                                                                        120dB

Dimensions  (W-H-D)                                                                                    205 – 140 – 330 mm

Shipping weight                                                                                                                       8 kg

(**)  Please note that a current of 20A is equivalent to peaks of 1600W @ 4Ω and 3200W @ 8Ω

 

 

Sachem v.2  is on display at the following dealers:


AV World - Auckland

Signals - Auckland

Computer Lounge - Auckland

HiFi Auditions - Hamilton

Soundhaus by Schuler - Napier

Tone Electrical - Paraparaumu

Russell Roberts - Christchurch

(you'll find their contact details in the "partners" page)

 

PLEASE NOTE:  If you are not living in an area covered by one of our local dealers, please contact us and we will "invent" an alternative solution, in order to let you experience and enjoy the Sachem "difference".