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ADVISES & CONSIDERATIONS
“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 “sachèm” as an honour on a senior warrior when he had distinguished himself with particular merit.
We have spent over two years in electrical and sonic research, listening at length to different components and circuit designs, in order to arrive at this final version, which “sounds” as unobtrusive as possible. Do not worry, we do think that the perfect amplifier must not add its own “sound” to the musical program! If you are a serious manufacturer, this must be your difficult target!
To achieve this superb sonic reproduction, we have adopted and developed an interesting all-discrete circuit, incorporating the most modern, high performance, top quality components, in a clean layout. The signal path has been optimised as well.
We have reduced the physical dimensions of the amplifier as much as possible and we hope that you like its professional look. 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 big difference in sound quality. Another benefit of our mono-block amplifiers is in bi/tri-amp stereo applications, or high-end home-theatre systems, where a Sachem V.2 can be dedicated to each channel or frequency range.
We believe that all “high-priced” amplifiers should be built to this configuration, because the use of long speaker cables, irrespective of price or make, always significantly degrades the sound. This is due to the complex impedance, and many other electrical parameters, of contemporary loudspeakers, which are anything but a pure resistor. By comparison, a good quality screened interconnect (low capacitance and resistance), between pre-amp and power amplifiers, does not appreciably affect the sound. Even in the very rare cases of signal degradation (some “funny” 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 all types of acoustical transducers with a nominal impedance of 3 Ohm or greater, mostly irrespective of the load complexity of the speaker. This peculiarity is absolutely essential to unlock the potential of your speakers, but unfortunately it is not necessarily present in every “exclusive” amplifier on the market today! That is why different 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. We have tested our amps driving a pair of 82dB (1W/1m) speakers at “crazy” volumes with fantastic results: very fast transients (for what it’s possible with this kind of speakers) and not a trace of clipping. No miracles; this is possible because the Sachem V.2 can deliver musical peaks of hundreds of watts without strain. We believe it is extremely difficult, perhaps impossible, to make a high-powered amplifier (about 200W RMS 8 Ohm, or more) with such a refined sound, so we opted for a mid-powered solution incorporating an "explosive" dynamic range. Furthermore, with the advent of active sub-woofers, the power-hungry “dinosaurs” of old are (finally and fortunately, I say) becoming extinct, in domestic settings.
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 class A at high current. Amplification of the output current is handled by 6 selected and matched Darlington devices, 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; by the way, these 6 Darlington devices are able to provide a RMS collector current of 60A and 90A peak!
Each mono-block is provided with an over-dimensioned 300VA toroidal transformer, feeding twenty audio-grade, very low impedance and low ESR capacitors, through a 35A full-wave bridge rectifier. These capacitors provide 66,000uF in total, paralleled with two exceptional WIMA polypropylene caps (MKP10 series). All other capacitors feature polypropylene or polystyrene dielectrics, while the most important of all is in solid aluminium with oxygen-free copper lead-out wires. This beauty resides on the feedback circuit, and, in its turn, is paralleled with polypropylene and polystyrene capacitors.
It is a fact that every capacitor in the signal path affects the sound negatively and most circuit topologies require many capacitors in this area. We managed to do things differently and, as far as we know, the Sachem V.2 is one of the very few amplifiers in the world, if not the only one, with just one capacitor in the signal path (on the feed-back circuit), and this capacitor is of the very highest quality. Having achieved our goal of using only one capacitor on the signal path, we believe we have made an important difference in sound fidelity. The full richness of harmonics, the incredible transparency and silky softness of the mid-high range and the “sculptural” quality of the bass depend to no small degree on this.
Our carefully considered grounding system eliminates internal loop-currents and hum in the signal ground-path and assures a high level of immunity to noise and mains interferences.
The Sachem V.2 is temperature-compensated, and the full performance 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.
The Sachem V.2 is a completely reliable piece of equipment. Every unit is deeply tested for 1 hour at full power into a 4 Ohm load (1V input, 1kHz).
Connections and Installation
On the back panel of each amplifier unit there are the connection sockets: the red input socket receives the line-level signal from your pre-amp. The black socket is an 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 facility of our amplifier: the possibility to select a flat response or a “cut-bass” response, with many different selectable roll-off points at –3dB (see the attached explanation). You must choose one of these possible 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 the low frequencies your sub is better qualified to manage. Image and clarity in the mid- and high-range will improve as a result too.
NOTE: you could also use the roll-off option of the amplifier in case your floor-standing speakers have a tendency to “boom”: try it and you will probably be amazed about the transformation in these speakers in the bass department.
As standard, the Sachem V.2 is set up to deliver the full signal range.
For safety reasons, you are not allowed to open the amplifier, so, if you wish to change the default setting you will need to contact your authorized Sachem dealer to have the job done.
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. People 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 audiophiles believe that a sub will muddy the sound of a good system, and they are very often right, but this usually happens because of poor integration of the sub, so that “booming” bass from the main speaker pair is only worsened by the sub’s additional output. The second reason is that the large majority of these sub-woofers do not have acceptable sound-accuracy (no matter the brand, the high price and the astonishing review of some incompetent or biased reviewer). We only use and recommend audio pro sub-woofers, which, thanks to their patented ACE-bass technology, achieve a completely “unusual” bass. When an audio pro sub is correctly tuned along side the main speakers (properly cut and possibly driven by Sachem V.2), low frequencies are very deep and almost undistorted, virtually carved out of the air.
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 advisable to cut the bass response in the Sachem V.2 for the high frequencies, setting up the highest possible roll-off point.
With each Sachem V.2 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 importer 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 realise fully the potential of your speakers.
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 NEUTRIK connector to reach the screws which lock the cable. Please, be totally sure to connect the new cable exactly the same as in the original, in order to maintain correct polarity and phase.
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. Obviously, in order to connect the cable to the speaker with the correct polarity, connect the marked one to the red (+) binding post of the speaker and the smooth one to the black (-). To finish, you must test the cable for a possible short-circuit, which will “kill” your amplifier.
In this connection, be aware that 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 beginners” - will connect their speakers with the requisite care.
Before disconnecting the speaker cables, always ensure that the amplifiers have been switched off for at least 30 seconds. We also recommend that the amplifier ends of the cables be disconnected 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 Sachem V.2 is 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. If everything seems properly connected, replace this fuse with a new one of exactly the same type and rating. If that solves the problem, keep enjoying the music, but, if the fuse blows again, a more serious fault is likely, so 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, in order to understand if the problem is serious or fixable without returning the amplifier to us.
Dust build-up inside the enclosure should be removed annually by blowing compressed air through the ventilation holes. Canisters of compressed air can be bought at photographic supply shops. Make sure the amplifiers are switched off and disconnected beforehand, and keep around 10 cm. between the air-nozzle and the electronics.
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-fi system.
Please remember, though, that a Sachem V.2 will not perform miracles. These amplifiers will reveal any weaknesses in your speakers and source components. Until all your components are as good as your new Sachem V.2, your quest for sonic perfection will remain unfulfilled.
Please do not hesitate to contact us if you need any assistance or advice in connection with the installation or use of our products, or if you have any hi-fi related questions.
SPECIFICATIONS
Rated continuous power (RMS) 8 Ohm (20Hz ~ 20kHz) > 80 W
Rated continuous power (RMS) 4 Ohm (20Hz ~ 20kHz) > 140 W
Rated non continuous power 2 Ohm > 220 W
Output impedance < 0.1 Ohm
Power bandwidth @ -3dB 3Hz ~ 160kHz
Phase linearity 20Hz ~ 20kHz max 3º
THD at rated power 8 Ohm 1 kHz < 0.03%
Input sensitivity @ 1 Volt
Input impedance 12kOhm
Hi-pass filter (–3dB roll-off points as per attached sheet) 6dB/oct
Unweighted signal-to-noise ratio (input shorted) > 100dB
Dimensions (W-H-D) 320 -145 - 205 mm
Weight 7.0 kg
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