Sachem pure     high-end  preamplifier

 

     Please click here to read the very first review of the Sachem pure, made by Ashley Kramer on Witchdoctor hi-fi magazine.

 

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

 

 


 

                                                                                                         Sachem pure  -  preamplifier and power supply units

 


 

                                                                                                                               Sachem pure  -  top view 

 


 

                                                                                                                             Sachem pure - back panels

 

 

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

 

We have spent quite a long time in electrical and sonic research, listening at length to different components and circuit designs, in order to arrive at this final version, which sets a new milestone in the world of preamplifiers. It has been called pure for the simple reason that “pure” is the perfect adjective to summarise the peculiarities of its design, layout and sound!

Firstly, the pure doesn't have any timbre or sound: this simply means that it is completely neutral and does not add and mix its own “sound” to the original musical program. If you are a good designer, this must be your priority and challenging objective, but it seems that the majority of the hi-end manufacturers do not take this essential parameter into serious consideration!

To achieve this superior sonic reproduction, we have in the end decided to adopt and develop a minimalistic, capacitor-free IC circuit, incorporating the most modern, high performance, top quality components, in a hyper-clean layout. The logic and orderliness of the layout obviate the need for any wiring in the preamp and power supply units: they are totally wire-free.

Very much aware that preamps of large dimensions and messy wiring fly in the face of electronic rules (no matter the absurd price, the “noble” brand or the astonishing opinion of pathetic or biased reviewers), we have reduced to their smallest the physical dimensions of the preamp sections (shortening and compacting the tracks as much as possible), and abolished wiring, in order to minimize noise and possible radio interferences. Furthermore, the signal and ground path have also been optimised and shorted as much as possible. As a result, you can see in the specifications that the pure sets previously unheard of benchmarks in electrical measurements for preamps.

Even if many “esoteric” Audiophiles, hi-end "gurus" and reviewers say that such electrical measurements are not important for sound quality, I assure you that they are ignorant and wrong indeed. Real hi-fi is not a questionable religion, but just physics and the “numbers” are essential, unless you want to listen to a preamp that acts like an additional source of sound and/or like a limiter of the original harmonics, which, as said before, is the exact opposite of our objective! On the other hand, it's also true that there are many preamps and amps with very good “numbers” that don’t sound right. This does not mean that the “esoteric” people are right, but that these appliances probably have capacitors in the signal path. The caps (particularly the electrolytic ones) do not affect the “numbers”, but kill the sound. To me, this is the main reason why you can have a preamp (or amp) with good “figures” and poor sound.

Probably you have already recognised my “phobia” of capacitors in the signal path, because they are the only electrical components that affect and damage the sound. So, contrary to what the other manufacturers normally do, in the pure, the signal path is completely capacitor-free! I could be wrong, but, to my knowledge, the pure is the only preamp with this peculiarity and this surely accounts for a large portion of its unique sweetness, richness of harmonics, lightning response, "granitic" bass and uncoloured sound.

The pure is quite insensitive to external interferences, but due to its incredible frequency response (totally flat from DC, that means 0Hz, to 4MHz, that means 4 million Hz), if you live in an area saturated by radio frequencies and/or magnetic fields (these eventualities are quite rare in NZ), there could be the chance that the pure picks up some of them. In this case, we can try to stop them by putting a capacitor of tiny capacitance (47pF, in polystyrene) on the signal path, in order to limit the frequency response at 160kHz (-3 dB). The PC-board is already predisposed to take the small “intruder” and fitting it takes just a  few minutes. I don’t think that you will hear any sonic difference, because this component is of minimal capacitance and top sonic quality too.

The Sachem pure, due to its low output impedance and high gain, is capable of driving any power amplifiers. The standard output impedance (purely resistive) is 150 Ω, which allows a perfect “marriage” of preamp and main amp(s) within a cautionary distance of 5 metres. If the distance between preamp and power amp(s) is more than 5 meters, on request and at the same price, we will prepare for you a version of the preamp with an output impedance of 8 Ω, which allows the use of very long screened cables, without any loss of quality. It is useful and important to know that, with very low output impedance, the quality of the interconnect cables becomes much less significant, with great joy for your wallet! However, even if the distance between the preamp and the power amp(s) is short, you can also ask for this version. It’s up to you, but be aware that, in this configuration, the preamp is no longer protected against short-circuits on the output sockets and, when connecting or disconnecting the cables between preamp and power amp(s), you may damage the ICs. If this happens, the warranty becomes void and you would have to pay for the cost of the replacement ICs. So, if you need to connect or disconnect anything to the 8 Ω version, before doing so, you must turn the power off and wait for 20 seconds.

The power supply is built in a separate cabinet and it’s a real beauty. It produces and delivers wonderfully clean DC to feed the ICs. The purity of the DC is of paramount importance for a “silky” reproduction of the high frequencies.

This unit features two over-dimensioned 15VA toroidal transformers, feeding twenty audio-grade, very low impedance and low ESR capacitors, through a 6A full-wave bridge rectifier. The block of capacitors features a total capacitance of 9,400μF and is integrated by two exceptional, high-speed WIMA polypropylene caps (MKP10 series).

On its back panel, there are two five-pin sockets (both named DC OUT), and you will use indifferently one of them to feed the preamp, using the cable provided. The remaining socket is intended to power any other Sachem device, if any in the future. NEVER use it with any different (not Sachem) appliances.

Another interesting feature of this unit is the USB power supply socket on the back panel. You may connect to it a transmitter dongle, in order to deliver the musical signal to any piece of wireless audio equipment, for example audio pro wireless speakers in other rooms.

 


 

                                                                                                                       Sachem pure - preamplifier interior

 


 

                                                                                                                      Sachem pure - power supply interior

 

 

In contrast to other preamps, the Sachem pure takes the problem of the bass range into very serious consideration. This issue torments (or rather, should torment) the large majority of Audiophiles, hi-end included. In fact, “booming” bass is a peculiarity of 90% (probably more) of the very expensive floor-standing "dinosaurs", particularly if they are positioned close to walls or in corners!

The pure delivers a unique tight, deep and fast bass-range, but this is not enough to remove the "booming" in those terrible speakers (once again, the “galactic” price is NOT a guarantee of serious sound at all). The Audiophiles negligibly try to solve this problem by buying crazily expensive, comical and probably “blessed” cables, but, if you want to get rid of this nasty "sound tragedy" comprehensively, you must feed the speakers a rolled-off signal and add a serious subwoofer to the system. There is always the opportunity to buy these cables and accessories later, but mostly for the peace of the "esoteric" part of your mind and to avoid any inferiority complex with friends!

Now, leaving the main subject for a moment, being a “bass-range paranoiac”, I’d like to tell you two words in this regard.

Subwoofers are the most difficult stuff in the hi-fi chain, but also the foundation of the musical reproduction. So, you surely need a subwoofer, but if you want to avoid throwing away your money and further worsen the already "not wonderful" bass of your system with some “esoteric”, expensive sub, equipped with tragically large (more than 10") woofer(s), please go to the page "school of sound" of this site and read the article regarding the subs; then it’s just up to you whether to buy a “subwoofer” or a “boom box” - forewarned is forearmed!

Returning to the previous subject, the Sachem pure has got a built-in electronic high-pass filter, which is essential to roll off and flatten the frequency response of the bass-range in your main speakers. This will also create the correct crossover point between the sub and the speakers, with the result that the whole infrabass-bass band will be deep, clean, tight and free of “boom”. Furthermore, the dynamic range of the main speakers will increase and distortion will decrease, because their woofers will no longer struggle (in vain) to reproduce the very low frequencies your sub is much better qualified to manage. Image and clarity in the mid-range and high-range will also improve as a result of the lower distortion of the whole bass range. The same happens in the main power amplifiers too, particularly if they are tubes amps: a real blessed gift to them!

However, if you don’t believe me and belong among those who think (very wrongly) that the addition of a serious sub to the system is a bad thing, leave out the sub (for now) and, if you have connected the power amp(s) to the pure's OUT1 sockets, just switch between flat and cut response (F and C on the back toggle switch): you will probably be amazed at the transformation of your big floorstander speakers, when in C position. Even if the pure's standard cut (100Hz, Butterworth curve) is not right for this job, it's already enough to let you understand the huge potential of this facility! The booming disappears (or at least decreases) and the mid-high becomes clearer and cleaner. This way, you are totally losing the pathetic infra-bass that the floorstanders try to deliver, but the bass, mid-bass and all the rest of the audio-band becomes another story! This happens because the roll-off lowers the “bulge” in the frequency response between 100 and 200Hz, which is in the “DNA” of the large speakers, and the cause of booming. Anyway, for the perfect result of this application, you should choose the Bessel roll-off curve, with the -3dB point between 130Hz and 250Hz, depending on the degree of "booming" of the speakers. We can do that for you, using a spectrum analyser, which is an essential instrument in order to achieve a perfect result.

Now a word on this selectable and very versatile built-in electronic second order high-pass filter (12dB/oct), which can be set up with either Butterworth or Bessel roll-off curves. The cut-off -3dB point is continuously adjustable and its range depends on the type of curve: for the Butterworth curve, the range is 65Hz → 300Hz and, for the Bessel curve, is 90Hz → 400Hz.

Furthermore, each channel is independent and can be set up with different roll-off points and curves. This is particularly useful if the speakers are positioned in a not symmetrical room, or if the room has less than ideal layout (e.g. one speaker in a corner and the other one in open space or just with a wall at its back, etc.). In such cases this will result in each speaker producing a different frequency response from the mid-bass to infra-bass range. In this connection, please visit the "school of sound" page and read the article regarding this nasty, but normally underestimated and neglected problem (practically the two speakers sound differently!), and what must be done to solve it.

Connections - The preamp output marked OUT1, depending on the position of the toggle switch on the back panel (F or C), respectively delivers a flat response or a rolled-off one; the output marked OUT2 is fixed and always delivers a flat, full range response. So, if you have a subwoofer, you connect the sub to the OUT2 and the main amp(s) to OUT1. As standard, the Sachem pure leaves the factory with the -3dB crossover point at 100Hz and Butterworth curve.

For example, if your speakers are not “booming” and your sub is (hopefully) audio pro, follow these simple steps and enjoy the sound: connect the sub to OUT2 - the main amp(s) to OUT1 – switch the micro-switch on the back to C - setup the Low-Pass knob of the sub to 50HZ and to finish adjust the volume of the sub.

However, if you use Sachem or Sachem v.2 amplifiers, you also can roll-off the frequency response of the main speakers by the passive crossover inside these power amps and use the pure flat. Just connect the “rolled-of” mono-blocks to OUT1 and the sub to OUT2 or directly to the output socket of each Sachem v.2, but, in this configuration, be ascertain to set up the pure's toggle switch on F, which means “flat”.

 


 

                                                                                                                    another open view of both the cabinets

 

 

The Sachem pure features another interesting facility: the BYPASS option. This function is intended only for the owners of advanced home-theatre systems, who also want to enjoy high-end stereo system too.

For example, there are those with a serious home-theatre system made up of a 5.1 receiver - a high-end stereo amplifier (or better two mono-blocks), driven by the receiver’s PREAMP OUT, for the front channels - two high quality main speakers - top sub(s) - centre and rear speakers driven by the amps of the receiver. When they want to listen to stereo CDs, they select STEREO mode, on the receiver, but the quality of the preamp section in such receivers is commonly not high-end. Practically, the weak link is the preamp, which is good and more than acceptable for home-theatre use, but not for hi-end stereo. Now, finally, they can solve the problem using a Sachem pure.

You insert the pure between the receiver and the main amps, connecting the receiver’s output sockets (FRONT L and FRONT R) to the BYPASS socket of the pure and its OUT1 to the main amp(s); be sure to select F on the crossover toggle-switch, because the position C doesn’t work in this configuration.

So, if you want to listen to the 5.1, switch on the pure (compulsory) and select BYPASS: this way, the pure doesn’t exist and your home-theatre is exactly like before, but if you select any of the other three inputs, it’s now the turn of your receiver to drop out of existence, and you have a glorious stereo system!

It looks very easy, and it is, but if you have a sub it’s no longer quite so; in this case, there are many different configurations that can to be considered.

1) if you have a sub (or subs) already connected to the receiver, keep it/them and the perfect, comprehensive solution is to buy another sub to connect to the pure, as explained before. This way, you really have two completely independent systems with completely independent subs too; furthermore you can perfectly tune each sub with the respective system.

2) in the case that you have two Sachem v.2 or any other main amp with an incorporate crossover, you roll-off the frequency response in them and connect the sub in parallel to the inputs of the main amp(s). Now, connect the pure as in the previously mentioned system without sub(s). This way the systems have the sub(s) in common, but it’s not a problem at all. However, if you adopt this solution, please go to the “speaker set-up” menu of the receiver and set the front speakers to “LARGE”, Subwoofer to “NO” and the CENTRE and SURROUND speakers to “SMALL”. To finish set the crossover switch of the pure to F.

These are two of the most common situations, but, as I said before, there could be many others. Anyway, I cannot consider them all here, but, don’t worry, there is always a solution: if anyone should have any particular problems in this regard, I do prefer talking directly with him, so … just call me!

The contemporary technology brings out on the market new astonishing electronic components every moment, so hi-fi equipment becomes obsolete in quite a short time and this is the miserable end of the ordinary preamps on the market (no exceptions for the very expensive ones too), but the pure does not belong to this category and your preamp was thought out so that it will last a long, long time. In fact, you can upgrade it any time, investing very little money. At the heart of the apparatus are the ICs and if any better ones come on the market, you can purchase them and replace the old ones. It is very easy and you can do it yourself, but it could be better to contact us if you are unsure.

Anyway, at this point you have probably realised that, buying a pure, you don’t buy a preamp, but an advanced machine capable of continuous evolution!

Speaking about ICs, I have chosen the specific ones mounted as standard in the pure, following my personal criteria. I do think that nowadays they are the best neutral sonic option on the market and I have chosen them because, with my live recordings, they are simply astonishing and natural: perfect dimension of the instruments, with precise localisation of the performers and stable image; the bass is as tight, fast and deep as I’ve never heard before and the high-band “silky”, ethereal, incredibly refined and with all the original harmonics. Not for nothing, I use them in the preamp-crossover-mixer I have built for my “trinity” of Schöps microphones too. Anyway, if you read the opinions of the hyper-happy customers in the "testimonials" page, it seems that I made the right choice!

However, I know that many Audiophiles (unfortunately, I say) are not looking for the “absolute sound”, but for something that suits their taste: the pure is the perfect machine to give them the possibility to “experiment” or, using a more appropriate verb, to "play". If asked, I will tell you about the sound of some different ICs.

Someone noted that I have not furnished the pure with balanced inputs and outputs, so I’m going to explain why. Let me start telling you that balanced lines are specific to “professional” gear, but be aware that the adjective “professional” is NOT synonymous with high-quality sound. I can affirm that normally (a few exceptions apart) the "professional" stuff is never hi-end.

Back to the subject, the only purpose of balanced lines is to avoid the possibility of inducted noise in long cables. For example, in a studio or in a concert hall, the cables of the mics are usually very long (often more than 20m/30m), and sometimes found in places saturated with radio frequencies and/or magnetic fields. In such circumstances, balanced lines are a must, in order to avoid interferences.

In the hi-fi world, on the other hand, the interconnections are very short, very well screened too, and the line level is normally higher than in a mic line, so it is veeeery unlikely that there will be induced noise, so you won’t need balanced lines at all. Anyway, it's more than easy to check if you are affected by inducted noises or not: select the input you want to check, turn on (but not playing) the appliance connected to that input, set the volume as high as possible and listen.

As another matter of interest, you may like to know how you obtain a balanced input/output from unbalanced ones and vice versa: just by adding an extra electronic circuit to the output stage of the "sender" appliance and another circuit to the input stage of the appliance that receives the signal, in order to reconvert it in unbalanced again. Usually these circuits consist of IC amplifiers, plus resistors and capacitors. These capacitors are in the signal path and normally have a capacitance around 10μF, which renders the use of polypropylene caps practically impossible, due to their big dimensions; so, they normally are cheap bi-polar electrolytic capacitors! Please note that electrolytic caps are the absolute worst quality capacitors made. A good audio designer tolerates them only because, for some things, they're the only capacitors that will work (as in the power supply), but only the most starry-eyed audio technician will tell you that putting electrolytic caps in an audio signal path is a good idea!

So, by utilising balanced interconnections, you are listening to two additional, not sonically accurate, electronic circuits to NO advantage. I don’t know how much they will affect the final sound, but they obviously do.

The photo below shows the additional unbalanced-to-balanced circuit of the Sachem microphones preamp-crossover-mixer. I had to provide it with balanced XLR connections, just because some professional recording machines feature only XLR sockets. However, my Tascam recorder has got unbalanced RCA inputs as well and I always use them.

I do think that in a “serious” hi-end system, it would be better to avoid balanced lines and, where balanced and unbalanced sockets are on offer, my strong recommendation is to use the unbalanced ones!

Now you can fully understand why I didn’t fit the pure out with a balanced input/output option: it’s because I wanted to maintain the signal path as “capacitors-free”, in order to keep calling it “pure”.

 


 

                                                                                  typical circuit to convert an unbalanced output into a balanced one (two channels)

 

Looking after the Sachem pure is easy: just avoid positioning the cabinets in direct sunlight or in a damp place. Regarding the layout of the two cabinets, feel free to set them up as you like, side by side or in a pile.

If the blue light around the ON/OFF switch, on the front panel of the power supply unit, goes out, it means that the internal fuse has blown. DISCONNECT the AC power cable from the unit and, with a screwdriver, remove the four screws and the top panel. Replace the fuse with a new one of exactly the same type and rating (T315mA - 250V). Close the cabinet again and reconnect the power cable. Turn the power ON and, if the blue light shines, be happy and keep enjoying the music. In the improbable case that the light goes out again, a serious fault is likely, so DISCONNECT the power cable from the unit or from the AC socket and, at this stage, it would be useful to contact us. In New Zealand, power voltage is very unstable and power surges are quite frequent: these two occurrences are very bad for any electronic equipment and they may cause damage.

We hope you now feel ready to use and care for your Sachem pure. So, turn the power on and … no sound at all! No worries, the delay circuit is doing its job and you have to wait for further twelve seconds to fully enjoy the pure’s unobtrusive sound!!

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

Please do not hesitate to contact us if you need any assistance or advice with the installation or use of our products, or if you have any other hi-fi questions.

A curiosity about the name: “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.

To finish, thanks indeed to my very dear friends Allen Gill, who designed the remote control and Rino Cieri, who is a very talented Italian hi-fi technician. They helped me more than once to solve big problems! Also thanks to Kevin Munt, who machined the cabinets to perfection.

 

SPECIFICATIONS

Nominal Input Sensitivity                                                                                  200 mV

Input Impedance (referred to the IC)                                                             5 x 1011Ω

Output Impedance (purely resistive)                                       150 Ω  (8 Ω on request)

Slew Rate  (Rload =1 kΩ, G = +1)                                                                  140 V/μs

Bandwidth @ 0dB                                                                                     DC ~ 4 MHz

Phase Deviation  DC ~ 2 MHz                                                                                   0º

THD (Total Harmonic Distortion) at 1 kHz                                                    0.00003 %

Input Voltage Noise (referred to the IC)                                                       12 nV/√Hz

Settling Time to 0.1% (0V to 10V Step, Av = -1)                                               150 ns

Gain                                                                                                                 16.1 dB

Hi-pass Filter Slope (Bessel or Butterworth - see instructions)     12dB/oct @ xxx Hz

Signal-to-Noise ratio (input shorted)                                                  no audible noise

Cross-Talk between different inputs (one input shorted)             no audible cross-talk

Dimensions of each cabinet  (W-H-D)                                            220 - 60 - 250 mm

Shipping weight                                                                                                  4.5 kg

 

  

Sachem pure  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".