BMC MCCI Phono

[Transient Design]

Ni som provat lite olika pickupper vet hur svårt det kan vara att hitta rätt last-impedans och få ut det bästa ur din puppa. Nu finns en annan lösning: BMC MCCI Phono! Helt balanserad och med äkta strömingång utan återkoppling trivs den som bäst med "omöjliga" pickupper på 1,8 Ohm.

When manufacturing units and assembly kits, B.M.C. implements unusual concepts in

order to reach a level of innovation and perfection that makes possible the kind of

transmission which truly does justice to your music.

The B.M.C. Phono MCCI is a completely balanced, passively equalized and degenerative

feedback-free moving coil phono amplifier with a current injection input and a LEF single

ended Class A output.

Amplifier circuit:

1. Balanced current injection input

2. Common base circuit as the most broadband basic circuit

3. Automatic gain adjustment

4. Degenerative feedback-free circuit with short signal path

5. Balanced circuit

6. Balanced LEF single ended Class A output

Equalization and adjustment options:

7. Passive equalization in the current-to-voltage conversion

8. Neumann constant (optional classic RIAA)

9. RIAA adjustments in deep bass and warmth range

10. Gain switchable in three steps

11. Subsonic filter switchable

High-end components and completion:

12. Special low-noise transistors with high hFE, ten each/parallel

13. “Balanced current” capacitors to ensure precision and richness of acoustic color

14. Non-inductively wound polystyrene capacitors

15. Metal film resistors in thin-film design with 0.5% tolerance

16. Gold-plated 4-layer circuit board

17. Copper-plated iron shield case covering the core module

Amplifier circuit:

“Current Injection” (CI) is a power input that makes the pick-up’s current immediately

part of the amplifier. The MC pick-up works as a generator by injecting its own current

into a system of balanced DC currents, the shift of which results in a notably higher

output voltage. CI uses the pick-up’s original current and the higher voltage corresponds

to the original quite exactly, so it is rather a current-to-voltage conversion than an

amplification. Loss of dynamics, distortion and discoloration of the signal are

considerably lower than with traditional circuits.

The current injection input circuit is an exceptional implementation of the principle of

the common base circuit. The common base circuit is the most broadband, low-

distortion, dynamic and therefore most musical of the three basic circuits, but, with a

low-impedance input and a high-impedance ouput, it also has two disadvantages.

Fortunately though, this circuit is a perfect fit for our best audiophile sources: MC

systems and D/A converters.

Some of the best MC amplifiers of the last decades employ this concept of the common

base circuit, but only when using an ungrounded, balanced input, the MC system can be

connected to such a circuit without compromising quality.

The current for the CI mode comes from the generator impedance and the impedance of

the CI input. This allows for basically automatic gain adjustment to different MC systems,

because a high-output MC system, on the one hand, provides a higher current, while, on

the other hand, the current is lowered by the higher impedance. Amplification happens in

two very short steps, and, as there is no degenerative feedback, no superfluous

amplification is needed.

Essentially there are many ways to construct voltage amplifiers pretty distortion-free,

but in the end a stable current driver is vital. When considering dynamics there are no

alternatives to single ended amplifiers. However, even those have disadvantages, such

as compulsory class A mode and higher even-numbered distortions. LEF single ended

class A prevents distortions due to the fact that the transistor driving the output does

not pass through its characteristic curve.

A completely balanced circuit keeps the supply voltage constant, because when a signal

passes through, additional consumption of one symmetric channel is compensated for by

lower consumption of the opposite hand symmetric channel. Accordingly, the supply

voltage is not modulated by the music signal. The fact, that any effect of supply voltage

variations is equiphase on both symetric channels but that in a symmetric chain only

differences are processed, constitutes another advantage.

When talking phono one hast to bear in mind that with high levels the output of a phono

amplifier produces some (few) volts, while the input has a sensitivity of uVolts. To make

things clear: if the output does not modulate the supply voltage (through a balanced

class A circuit) and, if, on the other hand, the effect of all persisiting interferences of the

supply voltage is equiphase on the inputs, that is a great accomplishment and enables

the listener to deeply delve into music!

The balanced mode therefore immensely increases the sound’s inner sereneness, which

creates space for fine details, dynamic leaps, ease of performance combined with threedimensional

spatial reproduction.

RIAA equalization and adjustment options

Since all B.M.C. analog-circuits work without degenerative feedback, “active”

equalization is of course out of the question for the RIAA equalization. Precise RIAA

correction is achieved by “quasi-passive” equalization in two uncoupled stages, that

means in a frequency-dependent current-to-voltage conversion. This concept steers

clear of required over-amplification (accompanied by high reserve of the power supply)

of frequencies that are subsequently lowered, which is a disadvantage of traditional

passive equalization. The B.M.C. Phono MCCI integrates the neutrality of passive filtering

and the avoidance of superfluous amplification.

Traditional RIAA equalization peters out with infinite attenuation towards high

frequencies, this implies that records would have to be cut with infinite amplification

towards high frequencies, which is of course impossible. Insofar, the traditional RIAA is

always wrong. The cutting machine manufacturer Neumann introduced a quasi-standard

for the limit of high frequencies decades ago. The difference the Neumann correction

makes in the level is small, but definitely distinguishable. Phase correction at the top end

of the transmission range is even more important. You may turn off the Neumann

correction and easily perceive its advantages: there is just more air and openness in the

music.

Correction of recording deficiencies or pick-up/tone arm combinations with too little

bass can be performed by elevating the lowest deep bass as well as the warmth range.

Even though some pick-ups automatically adjust the amplification, there are still designrelated

differences in their levels. Because of that the Phono MCCI offers three

switchable levels of gain.

Ideally, tone arm and pick-up should fit each other and be sufficiently attenuated. If that

is not the case, you can activate a mild subsonic filter.

High-end components

The special transistors of the Phono MCCI have a very high hFE and a typical noise figure

of 0,3 dB, which is today’s achievable value. In the Phono MCCI ten transistors work

parallel, reducing fluctuation noise by approximately another 10 dB! Obviously, there are

virtually no solutions for MC phonos that are even more low-noise.

The balanced current electrolytic capacitors have a completely symmetric characteristic

curve for both polarities, and the tonally important ESR frequency range is far superior

to conventional electrolytic capacitors. This becomes evident soundwise through unusual

musical clarity, precision, definition and beauty, commencing in the deepest depths and

covering the whole spectrum.

Non-inductively wound polystyrene capacitors have no natural resonance, hence they

are able to create a very open, melodious high range.

SMD metal film resistors in thin-film design with 0.5% tolerance are the most high-end

parts, and their capless design makes them non-inductive.

New standards

The rise of digital technology has challenged analog technology by pressuring developers

to take their work to higher levels, which has led to new and better phono devices. This

process should not be arrested by any traditional standards. For example, unbalanced

phono inputs and layouts are not up to date anymore, because they are too interferenceprone

and therefore cannot produce the fine resolution that is demanded in order to

really enjoy music playback.

Furthermore, all aspects of a circuit are to be designed to achieve dynamic

differentiation capability across the whole frequency range, thereby allowing to take

advantage of the actual benefits of vinyl playback. Part of this is abandonment of

degenerative feedback, even in the RIAA equalization, since only a circuit which does not

loop is sufficiently quick and sensitive to detach pick-up interferences far enough from

the music so that the human brain is able to blank them out. Not until then will music be

ready to unfold in a way that is at the same time emotionally gripping and relaxing, that

takes you to different spaces or even worlds, that touches and seduces.

Om det var nåt som var svårt att förstå ovan eller om nån vill diskutera detta som varmt välkomna!

Mvh Lasse

Edited November 22, 2010 by Transient Design

[Transient Design]

Och här kommer en lite grövre guide enligt BMC:s egna prov och tester på vad som fungerar bäst ihop:

A short description of the B.M.C. Phono MCCI innovative technology regarding MC-Pick-Up

cartridges:

Many of the Phono Cartridge "Pearls" couldn´t show their full performance in the past. With our

innovative CI (current injection) B.M.C. Phono MCCI the efficiency of the MC-cartridges can now

perform to the utmost. And this without any transformer!

An example: (Lyra Delos, 0,6MV at 8,2 Ohm)

Lets assume the B.M.C. Audio Phono MCCI input resistance plus cable plus plug is in total app. 5

Ohm. Together with the Cartridge it is 13,2 Ohm and 0,6mV/13,2 Ohm=45uA. This means that the

BMC Phono MCCI in the first stage delivers already more than 0,3V! (without RIAA)

Another example:

(Cartridge 0,3mV at 38 Ohm, like a very popular and expensive Cartridge-lets call it BMRG). The

result is (same calculation as above) 7uA! At "ordinary" Phono Amps the Lyra and the BMRG

differ usually 6db - but here it is 16db! The BMRG works fantastic at the BMC Phono MCCI but the

very efficient cartridges go along with all their advantages, which they usually can´t show at

others!

3rd Example:

Lets take a Dynavector Te-Kaitora Rua (0,26mV at 5Ohm --> 26uA)

The cartridge is much less quiet as one would expect it to be, very low noise and it even doesen´t

need a shield at the phonocable!

4 th :

A positive extremum: MY Sonic Lab, (Hyper) Eminent 0,5mV at 1,8Ohm --> 73uA!!!

Conclusion:

The energy produced from the cartridge generator is being transformed at a CI-Phono very

positively and should be a criteria of selection. If the current is high enough, a CI-phono amp will

produce a very high voltage with remarkable low dynamic losses. Accordingly the following

voltage amplifier has less work to do.

Examples of cartridges:

Group A+ (super efficient):

- Air Tight PC1 (0,6mV; 2,5 Ohm)

- MY Sonic Lab, (Hyper) Eminent (0,5mV; 1,8 Ohm)

- Transfiguration Orpheus (0,77mV; 2,5 Ohm)

Group A (very efficient):

- Lyra Titan i (0,5mV; 5,5 Ohm)

- Lyra Delos (0,6mV; 8,2 Ohm)

- Ortofon MC A90 (0.45mV; 5 Ohm)

and many others...

Group B (efficient)

- Dynavector Te-Kaitora Rua (0,25mV; 5 Ohm)

- Dynavector DV-20XH (2,8mV; 150 Ohm) High Output MC

- Denon DL 103 R (0,25mV; 14 Ohm)

- Denon DL 160 (1,6mV; 160 Ohm) High Output MC

Group C (standard)

- Benz-Micro MC Ruby 3S (0,34mV; 38 Ohm)

- EMT XSD-15 SFL (0.21mV; 24 Ohm)

- Van den Hul Condor XGP-MO (0.35mV; 36 Ohm)

Cable:

At above named impedances a technician would not wonder that the shield is not so important.

The lower the cartridges impedance the more important is a low inductivity of the cable! This

also makes the cable more resistant against magnetic influences -means Trafo-humming

influences.

Also this criteria differs from others (and also invites for happy experimentation!)

Everybody wants to optimise his cartridge, what usually is the covering of weaknesses (e.g. some

more bassy cables to reduce a dynamic loss in a phono-amplifier). But this is usally a compromise

and if a component in the system has not those weaknesses the harmony in the system of Audio

Components is harmed. The B.M.C. Audio Phono MCCI is totally different and innovatively

engineered in its design and characteristics that one should absolutely implicitly adjust his very

own system following the personal taste.

[Bebop]

Intressant ...

Skulle du kunna kompletterar med Koetsu Rosewood Signature Platinum (0,2 och 5 ohms internimpedans) blir det ännu mer intressant...

[Transient Design]

Bebop: 0,5 och 5 Ohm? Finns den i två olika versioner menar du? Enligt BMC så har de uppnått en smått fantastisk ljudkvalitet just med lågimpediva pickuper. Så denna Koetsu platsar säkert som handen i handsken med MCCI. Vill du låna och se om det funkar?

Mvh Lasse

[Bebop]

Bebop: 0,5 och 5 Ohm? Finns den i två olika versioner menar du? Enligt BMC så har de uppnått en smått fantastisk ljudkvalitet just med lågimpediva pickuper. Så denna Koetsu platsar säkert som handen i handsken med MCCI. Vill du låna och se om det funkar?

Mvh Lasse

Det finns tre Koetsu Rosewood där Signature Platinum är den främsta men också den knepigaste. De andra två har högre utspänning och mer normala internimpedanser. Det skall vara 0,2 mv utspänning och 5 ohm internimpedans. Jag var lite otydlig.

Jag kommer eventuellt att köpa en begagnad Rosewood Signature Platinum som förre ägare av min Simon Yorke ägde. Problemet är bara att det inte går att köra i min ARC PH 5. Antingen måste jag ha ett nytt RIAA som klarar den eller en step up transformator som passar pickupen.

[Transient Design]

Det som gör att BMC MCCI är så unikt bra till puppor med extremt låg inre impedans (fast trots detta mycket hög verkningsgrad!) är att den inte alls förstärker en spänning. Vad den istället gör är att den mäter inkommande ström och förstärker strömmen med 16 par perfekt matchade lågbrusiga transistorer. Och strömmen ut från en 5 Ohms pickup kan vara ganska stor (relativt sett) vilket då gör att nivån in till nästa steg sedan sker utan problem.

Man kan välja att se på det så här: I vanliga fall så mäter man strömmen genom ett (lågt...) motstånd på ingången och så får man fram en liten, liten spänning som man sedan förstärker massor av gånger för att nå upp till en normal nivå. Det gör att hela energin som kommer från din pickup försvinner ner till jord via ett litet motstånd.

Vad Carlos Candeira hos BMC upptäckt är att det finns en annan väg att göra det på! En transistor (eller rör) kan kopplas på 3 olika grund-sätt. Två används överallt och används av alla. Men det finns ett tredje sätt som nästan ingen använder någonstans. Varför, jo för det har en mycket låg ingångsimpedans (lågt motstånd) och när man normalt "bara" skickar en spänning så skapar det jättestora problem. Fast det finns ju undantag till detta och det är källor som har jättelåg inre resistans och spänning ut men istället kan lämna lite ström, tex MC-pickupper, vissa DA-omvandlare och bandmickar. Vad man då kan göra är att ansluta en trafo som omvandlar låg spänning och lite ström till högre spänning och mindre ström. Detta för att göra signalen lättare för nästa spänningssteg att jobba vidare med. En anpassning.

Eller så gör man som BMC. Man kopplar en hel massa transistorer parallellt tillsammans (noggrant matchade!) för att få ner bruset så långt det bara går och så kopplar man dem i denna special-koppling så att ingångsimpedansen är låg och strömmen förstärks ett hel massa. Sedan kan man lätt låta detta driva en sk ström-spänningsomvandlare (I/V) så att vi får ut en hel del spänning att jobba vidare med. Detta görs för övrigt helt balanserat (fungerar klart bäst då!) och helt utan återkopplingar. Alltså, ingen billig liten OP om nån nu trodde det.

Sedan sker en helt passiv RIAA-kompensation och ytterligare lite förstärkning och anpassning av signalen, bla en lätt avrullning ovanför 20kHz. Det finns ytterligare möjligheter att anpassa steget internt med små "jumpers" för högre eller lägre förstärkning och även högpass och lite annat.

Flera har frågat mig hur BMC (gäller alla deras produkter!) låter. Och jag har svårt att svara fastän jag brukar ha lätt att svamla (vet ni som känner mig...) eftersom jag har så svårt att peka på et BMC "hus-ljus". Det låter liksom inget! Transparant, dynamiskt och ändå lite fylligt på nåt vis.

Prova och se själv!

Mvh Lasse