What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

McIntosh MA 7000

MA7000 has of course some flaws – it is an integrated amplifier after all and that means some limitations. I mentioned sound stage “in the window”. What I meant was that there is almost nothing happening outside the space between speakers. Same goes for elements out of phase, those are of course present behind and at both side of the listener but rather “by the way” than with clear intention to create “surrounding space”. Simply what matters is behind speakers. Another element worth mentioning is how the relations between basic sound and reverberations is built.. McIntosh “promotes” the first one, shortening the latter and thus slightly blurrs acoustics. I mean comparing it to the top high-end devices - the less expensive ones (with very few exceptions) don't do it better. But with outstanding sound stage you hear that as a weakness. I think this might be a reason why McIntosh is commonly associated with a distance, lack of dynamics and so on. In this particular case it is out of the question. Dynamics is outstanding, but is it the fact that the sound of instruments is not well differentiated, that they lack that little “something” that extents sounds when they are “in the air”, might give you, with the incorrect system setup, such a (wrong) impression.
MA7000 is like a dream when it come to its functionality. McIntosh simply knows how to do it right. I did not need to use tone control even once but I know there are some people who will like it. There is built in high quality MM phonostage – all you have to do is add some nice step-up transformer, use some high grade MC cartridge and then listen to your vinyl collection. There is also a head-amp available but I didn't like it too much – it sounded “mechanical”, but it was still better than what we find in most integrated amplifiers. Simply after using headphone output from MCD500 player (also from McIntosh) rather very few build in head-amplifiers could surprise me. Its design, long live and high prices for second hand devices are another elements of the whole puzzle. Not everybody will love the sound – that's obvious – but you should listen to it first to find out what you don't like. I am pretty sure that after an audition lot of you will go home with certainty that considering the price, you could live with this sound for the rest of your life.

MA7000 is the biggest so far McIntosh integrated amplifier. It is also one of the heaviest – almost 45 kg! It is classic McIntosh design. Front panel made of thick glass. In the upper part we can find blue illuminated power output Watt meters – calibrated to show even the smallest power output. Meters are there just to satisfy customers… Between them you will find two red LEDs that are indicators of one the the company's unique patents – Power Guard. This is a circuit that protects the device from overdriving the power. It doesn't simply cut the power but gently compresses power peaks so that the signal waveform, Power Guard is comparing, stays the same and there are no audible distortions. Below you will find a nice row of controls – two bigger ones at the sides, and five small in the middle. On the left side there is a balance control, on the right a volume control. Small controls in the middle are in fact complex equalizer controls. Equalizer is considered to be unnecessary or even harmful nowadays, but when correctly designed it might come handy surprisingly often. The real reason of avoiding equalizers is simple – no magic about it – well designed equalizer costs a lot, especially like this one with five frequencies: 30/150/500/1500/10000 Hz. There is no on/off button – it doesn't process the signal if control is in the middle position. Beneath there is a row of push-buttons – input selector (6 linear inputs and one MM phono input), mono, output (x 2) and ‘mute’. Rear panel connections are placed in two groups. One is located in the lower part of the chassis, and the other one in the upper part.. Lower part consists of gold finished RCA connectors and XLR preamplifier's output, and in the upper part two balanced XLR inputs with two RCA unbalanced right beside them, plus excellent WBT speaker terminals – like in tube amplifiers separate for different loadings - 2/4/8 Ω. Preamplifier and amplifier sections are connected via jumpers – I would prefer if it was done with electro-magnetic switch somewhere inside the device.

As already mentioned the inside is divided into two parts. Lower part is a preamplifier based on electro-magnetic switches of input selector, transistors and operational amplifiers NE5532. We can find there another circuit - TLC174 by Texas Instruments, eight-channel amplifier, working most likely as tone control. In the upper part of the device we will find power transistors fixed directly to huge radiators, that are visible at the side of the device. There are also four big capacitors – their task is to level current fluctuations for this part of device. The secondary winding is common for both power transistors. There is a separate one for preamplifier, hence advanced power supply in the lower part of the amplifier, where each section - input, driver, meters, safety circuits and so on have their on power supplies. The transformer (EI) itself is huge, packed in a metal case filled up with some dumping material. Autoformers (output transformers) were put into similar cases. All transformers are located in the front of the chassis. They are not hidden under the top plate of the chassis so together with beautiful front they make a nice, attractive design. There are twelve Power Transistors used in each channel of the MA7000Power Output Circuitry. Those are special elements called Thermaltracks. This allows for the instantaneous and accurate monitoring of the power transistor temperature. A specially designed bias circuit precisely controls and adjusts temperature of power transistors so that they always work in the same conditions. As mentioned before, balanced outputs (two pairs) are located separately in the amplifier's part of the chassis. XLR connectors are partnered by RCA ones, right behind the latter signal is symmetrized in inexpensive, low-noise NE5532 circuits. Signal goes from there to the lower part of the amplifier through computer cable.

Technical data:
Output power: 2 x 250W/8, 4 i 2Ω (20-20 000Hz)
THD: 0,005% (maximum rated power)
Frequency response:
(+0, -0.5dB) 20Hz-20 000Hz
(+0, -3dB) 10Hz-100 000Hz
Pre Amp Output: 2.5V (RCA, max. 8V); 5 V (XLR, max. 16V)
Input sensitivity (for 250 W): 250mV (RCA), 500mV (XLR)
S/N ratio (weighted) -100dB, -84dB Pre amp
Total harmonic distortion: < 0.005%
Wide band damping factor: 40
Input impedance: 20kΩ, Pre amp 47kΩ/65pF
Dimensions (WxHxD): 444,5 x 239,7 x 558,8 mm
Weight: 44,3kg

1 commento:

  1. Thanks for this complete info about the stereo systems.Well,what is working mechanism of the current transformers in this stereo systems?