Circuit knowledge

Tuesday, September 9, 2014

Sound in the car

It is known that for many motorists machine evolved into something more than just a means of transportation. After all, the person conducting the wheel for several hours a day, not only wants to listen to the local news, but good music. However, high-quality automotive interior equipping reproducing unit, few who can manage only industrial products.

In recent years in the amateur literature appeared many publications devoted to independent manufacturing automotive audio equipment, mainly amplifiers. But even a good amplifier does not solve all the problems faced by the creator of Sound Hi-Fi class for its attitude avtomobilya.Skepticheskoe many motorists to leave such systems due primarily illiterate approach to installing speakers in the cabin.Unfortunately, in most cases, they are placed in the car according to the principle "to fit", not "where it is necessary." However, an unambiguous answer to the question - "Where else do you want?" - Does not exist. None of the known solutions does not give a guaranteed result. Much easier to answer the question "where it is not necessary?". Show rasprstranennaya error - placing powerful and high heads speakers in the rear tray. Front same state that have or nothing. Is the owner of this car prefer to sit with his back to the stage?

Contrary to popular belief, most importantly in the design of the car radio is not to achieve high power, low distortion, and not even getting a good frequency response. The main problem - the creation of a wide soundstage for listeners sitting on the front seat of the car. Its solution is directly related to the installation of the front head.

Under any reasonable version of their placement inside the difference in the signal path from the left and right radiators to the listener reaches unacceptably large. To reduce this difference may be reflected to use all or part of the signal from the windshield. So there setting with outdoor acoustics front (see Fig. 1).

Embodiment of a such a solution is quite difficult and time consuming, but the result is impressive. However, to cut the floor to install the heads dare not everyone. So really to install radiators in front passenger car is not too many places: the dashboard, windshield racks, doors, vertical bar at the bottom of the passenger compartment at the front wheels of the vehicle.

The dashboard allows you to set the emitters at a sufficient height, but head size is usually limited to 10 ... 13 cm, acoustic design is virtually absent, so low frequencies are reproduced in this case efficiently enough. To further advance the sound image can be installed on radiators racks on the side edges of the windshield, but in reality there are only fit tweeter (tweeter).

Popular because of its simplicity and low-frequency coaxial installation heads in the doors usually argued increase efficiency low frequency reproduction ready acoustic design. The result obtained is the opposite desired effect. For the reduction of phonograms most modern tools engineers is situated in the center of the bass sound stage, ie Sound signals of the left and right channels in the same frequency band are in phase and have almost the same intensity. Therefore, when installing radiators in the front door of the sound waves at frequencies 100 ... 150 Hz, critical for the subjective perception of bass attack reaches the opposite head of phase (as determined by the width of the cabin) and compensated. Hence - a dull, lifeless sound that did not fix any EQ. Installation heads in kikpanelyah decreases the difference in the signal path from the left and right radiators, but the sound picture falls unacceptably low. In addition, this embodiment carry the same effect, "blanking" bass attacks, although to a lesser extent as when installing heads in the doors, and organize a decent acoustic design easy.

It follows that the best results can be achieved, the use of multi-band dispersed front speakers. Bandpass emitters should be placed in locations where they will work with maximum efficiency. According to the author the best place to install the bass radiators - in buildings under the front Cedeno with the radiation of sound forward and upward. MF emitters best place on the front panel or in the upper front corner of the door, and HF - racks on the windshield (it picks up sound pattern).

Full bass reproduction is only possible using acoustic design of considerable size, so virtually all car audio sound frequency range is limited to the main channel 100 ... 120 Hz and lower frequencies generated by the speaker as the sum signal. Because at the lowest frequencies loudspeaker has a circular radiation pattern, the choice location for a subwoofer - question komponoki system. Most often, it is placed in the trunk. The problem is that the frequency response of the cabin, which plays here the role of acoustic design, has Wake up in the very low frequencies for each individual model of the body. Therefore, to obtain a uniform frequency response of the total system must be able to adjust only the level but also the frequency response sabfufernom channel.

Sound image formed without using surround izluchatalay certainly be incomplete. Their main value - "the creation of the hall effect" by simulating the reflected sound. Spectrum Signal rear channels (Fig. 2) for this should be limited [2], and the signal can be both traditional ("left-right" channel), and the sum or difference, or a combination thereof. Power rear channel nevilika (no more than 10% of the total capacity of the system), and in some cases, for its realization will require additional amplifying devices. The simplest case - anti-series connection of the rear head between the amplifier output left and right channels through a simple filter.

On the influence of connecting cables and sound quality lately written so much that this subject can not apply here. Wire size than the power supply current consumption and the length of the wires themselves. In any case, the voltage drop in the supply of power at maksimaonoy should be no more than 0.1 ... 0.2 V

Damping parasitic resonances and sound elements salon are also important. Noise absorbing material should be applied to all available panels and plastic body parts, focusing on the panel, located near the head speakers, or those used as part of the speaker enclosure.Resonances usually disappear when the cover 25 percent or more of the area. To absorb road noise noise canceling material should cover polsalona, fireproof bulkhead area and wheels.
Original article source cxem.net

Valve Sound Converter Wiring diagram Schematic

‘Valve sound’ is not just an anachronism: there are those who remain ardent lovers of the quality of sound produced by a valve amplifier. However, not everyone is inclined to splash out on an expensive valve output stage or complete amplifier with a comparatively low power output. Also, for all their aesthetic qualities, modern valve amplifiers burn up (in the full sense of the word!) quite a few watts even at normal listening volume, and so are not exactly environmentally harmless. This valve sound converter offers a cunning way out of this dilemma. It is a low cost unit that can be easily slipped into the audio chain at a suitable point and it only consumes a modest amount of energy.

A valve sound converter can be constructed using a common-or-garden small-signal amplifier using a readily-available triode. Compared to using a pentode, this simplifies the schema and, thanks to its less linear characteristic, offers even more valve sound. For stereo use a double triode is ideal. Because only a low gain is required, a type ECC82 (12AU7) is a better choice than alternatives such as the ECC81 (12AT7) or ECC83 (12AX7). This also makes things easier for home brewers only used to working with semiconductors, since we can avoid any difficulties with high voltages, obscure transformers and the like:the amplifier stage uses an anode voltage of only 60 V, which is generated using a small 24 V transformer and a voltage doubler (D3, D4, C4 and C5).

Since the double triode only draws about 2mA at this voltage, a 1 VA or 2 VA transformer will do the job. To avoid ripple on the power supply and hence the generation of hum in the converter, the anode voltage is regulated using Zener diodes D1 and D2, and T1. The same goes for the heater supply: rather than using AC, here we use a DC supply, regulated by IC1. The 9 V transformer needs to be rated at at least 3 VA. As you will see, the actual amplifier schema is shown only once. Components C1 to C3, R1 to R4, and P1 need to be duplicated for the second channel.

The inset valve symbol in the schema diagram and the base pinout diagram show how the anode, cathode and grid of the other half of the double triode (V1.B) are connected. Construction should not present any great difficulties. Pay particular attention to screening and cable routing, and to the placing of the transformers to minimise the hum induced by their magnetic fields. Adjust P1 to set the overall gain to 1 (0 dB). The output impedance of 47 kΩ is relatively high, but should be compatible with the inputs of most power amplifiers and preamplifiers.

For a good valve sound, the operating point of the schema should be set so that the audio output voltage is in the region of a few hundred millivolts up to around 1.5 V. If the valve sound converter is inserted between a preamplifier and the power amplifier, it should be before the volume control potentiometer as otherwise the sound will change significantly depending on the volume. As an example, no modifications are needed to an existing power amplifier if the converter is inserted between the output of a CD player and the input to the amplifier.

Tuesday, September 9, 2014

Sound in the car

Saturday, August 16, 2014

Valve Sound Converter Wiring diagram Schematic