Adjusting the quiescent current of the transistors of the output low-frequency stage. Setting up a Lanzar power amplifier - circuit diagram of a power amplifier, description of the circuit diagram, recommendations for assembly and adjustment. Basic Amplifier Settings

How to properly configure a car amplifier? I'll tell you about setting up a car amplifier step by step. The principle of amplifier tuning.

Setting up midbass.

Please note that the tweeters will need to be turned off, and if a subwoofer is installed, then that too, either from the head unit or manually. We do not cut off the midbass from above with filters.
We divide our path into two parts:
1. Head unit;
2. Amplifier.
Each of these parts of the path introduces its own distortions into the signal, including distortions due to signal limiting (). For this we, for the ultimate fine tuning When matching the head unit and amplifier, this process should begin with determining their capabilities. We will not focus on abstract concepts about the position of the maximum..., or so many percent of the maximum permissible...
Tuning is done using the 315 Hz track.
We will need a setup (test) disk Denon Audio Technical CD.
We can download the disk here:

Http://rutracker.org/forum/viewtopic.php?t=2258371

We will need the following tracks:

46. ​​40Hz Sine Wave (0 dB L+R) (0:30)
48. 315Hz Sine Wave (0 dB L+R) (0:30)
50. 3149Hz Sine Wave (0 dB L+R) (0:30) - dome tweeters
51. 6301Hz Sine Wave (0 dB L+R) (0:30) - horn tweeters

Green for SUBWOOFER
Red for the Ministry of Foreign Affairs
Blue for TWITTER

To burn a disc, download the program from the Internet.

You can create the necessary sines yourself using the SoundForgeAudioStudio program, but you must pay attention that their level is ZERO dB.

Please note that you should not listen to the speakers on the test sine for a long time!!!

Set the Gain (Level) control on the amplifier counterclockwise to minimum. By this we prevent the possibility of introducing distortion into them by limiting the signal.
We disable all additional (set by us) settings on the GU!!!
- We put a track with a frequency of 315 Hz (track No. 48 on the disk) and by adjusting the volume knob we determine the level of signal amplification when a tone appears stepwise in the region of 1 kHz (1000 Hz). This will be the level above which there is simply no point in turning the knob, since further distortions simply follow. You still need to focus not on this level (already audible distortion), but on a step or two below the volume control, depending on the level adjustment step grid on the head unit.

If, in the process of determining the maximum possible pure level of the signal from the PG, partially subtonal changes in the tone of the frequency 315 Hz appear somewhere, then this is a reason to think about the quality of the PG.

All! The maximum possible clean (with minimum distortion) amplification level of the head unit has been sorted out, and it will be possible to proceed to harmonizing the identified maximum level output signal of the head unit (GU) with the level of amplification that the amplifier can provide.
- We also set the track with a frequency of 315 Hz, and set the GU volume level knob to the position that was already determined at the first stage of setup, and by changing the position of the amplifier’s GAIN (Level) control, we find the level of the maximum possible (pure) signal amplification by the amplifier, without distortion , which this amplifier is capable of delivering. We again focus on the appearance of an audible transition to a frequency of 1 kHz (1000 Hz).

I remind you! Do not use sinusoidal signals for a long time to avoid mechanical damage dynamics!!!

Now the Head Unit and the Amplifier are coordinated with each other. !!!

And the following happened.
Here is an example of a graph of distortion versus power. We see that up to 100 watts the distortion was within 0.01%, and after 100 watts sudden jump up. This is what we hear in the presented videos.

Next, set the volume of the head unit to maximum value volume without distortion, already in a coordinated path.

Setting up the tweeter.

Tweeters, for the most part, are louder than midbass. More precisely, not even that. Due to the way they are installed and directed, they are louder. For this reason, we adjust their volume level to the midbass.

You can also use a sinusoidal track of 3149 Hz (disk track No. 50) for dome tweeters and a 6301Hz track (disk track No. 51) for horn tweeters. And using the method described above, we repeat the whole process. But without a complete understanding of the process (what we ultimately do), the tweeters may fail to work! Since the maximum signal distortion, as a rule, occurs within their range.

To tune dome tweeters, set a second-order filter in the region of 2.5 - 3 kHz, and for horn tweeters, set a second-order filter in the region of 5-6 kHz. To avoid damaging the tweeters.

Setting up the subwoofer.

We take a 40 Hz sinusoidal track (track No. 46 on the disk) and use the method described above for midbass to match the sub amplifier with the head unit.

If you have additional equipment, it is possible to coordinate without sound.
An example of such a setting:

1 kHz sine distortion 0,03% link to listen

Http://music.privet.ru/user/eterskov/file/310328286?backurl=http://music.privet.ru/user/eterskov/album/310327806

Amplifier low frequencies(ULF) is a device whose purpose every music lover knows. This component of the audio system allows you to improve the sound quality of the acoustics as a whole. But like any other electronic devices, the AC can fail. Learn more about how to repair car audio system amplifiers yourself in this article.

[Hide]

Typical faults

Before you repair, install and configure the ULF in your car, you need to understand the breakdown. It is simply impossible to consider all the faults that can be encountered in practice, since there are so many of them. The main task of repairing a sound amplification device is to restore a broken component, the failure of which led to the inoperability of the entire board.

In any electrical equipment, including amplifiers, there can be two types of faults:

  • contact is present where it should not be;
  • There is no contact in the place where there should be contact.

Functionality check

Repair of car amplifiers first begins with ULF diagnostics:

  1. First you need to open the case and carefully inspect the circuit, use a magnifying glass if necessary. During diagnostics, you may notice damaged components of the circuit: resistors, capacitors, broken conductors or burnt out board tracks. But if you find a burnt-out component, you need to take into account that its failure may be a consequence of the burnout of another element, which in appearance may seem intact.
  2. Next, diagnose the power supply, in particular, check the output voltage. If burnt out resistors are identified, these elements will need to be replaced.
  3. Apply power to the ULF and the Remout output, then you need to short-circuit the system to positive and look at the PROTECTION diode indicator. If the light comes on, this indicates that the device has been protected. The reason may be poor power or its absence on the board, a broken transistor, or problems with the operation of the voltage converter. In some cases, the reason lies in the breakdown of the transistor power amplifier for one of several channels.
  4. If, after power has been applied, the fuse element does not burn out, you need to check the voltage level at the output. It should be approximately 2x20 in or more.
  5. Carefully inspect the transformer device of the voltage converter; it may have burnt out turns or broken circuits. Smell this element, it may smell burnt. In some ULF models, a diode assembly is installed between the PN output and the amplifier - if it fails, the assembly can also include protection.

Troubleshooting

Do-it-yourself repair of a car amplifier is carried out in accordance with what problem was identified during its operation:

  1. If a transistor in a car amplifier breaks down, then before directly replacing it, it is recommended to diagnose the power supply safety element. You also need to make sure that the diodes on the buses are working. If everything is in order with these parts, the installed transistors need to be changed.
  2. For more specialized repairs, you will need an oscilloscope. By installing the device probes on pins 9 and 10 of the generator board, you need to make sure that there are signals. If there are no signals, then the driver is changed; if there are signals, then the field-effect transistor elements are replaced.
  3. Capacitors are changed much less frequently during the repair process - as practice shows, this happens infrequently (the author of the video is the HamRadio Tag channel).

Basic Amplifier Settings

Now let's move on to the question - how to set up a car amplifier? There are several configuration options - for use with or without a sub.

How to properly configure the ULF without a subwoofer - first you need to set the following parameters:

  • bass boost - 0 decibels;
  • level - 0 (8V);
  • The crossover must be set to FLAT.

After this, adjusting the audio system settings with an equalizer, the system is configured to suit your preferences. The volume must be set to maximum and turn on some track. How to set it up for use with a subwoofer - the procedure is also not particularly complicated.

For correct settings It is advisable to use the following parameters:

  • Bass Boost should also be set to 0 decibels;
  • the level is set to 0;
  • the front crossover is set to the HP position, and the FI PASS control element must be set in the range from 50 to 80 Hertz;
  • As for the rear crossover, it is set to the LP position, and the Low control must be set in the range from 60 to 100 Hertz.

It is very important to observe these parameters, since they determine the quality of the adjustment and, accordingly, the sound of the audio system. In general, the setup procedure is similar, using a level control to ensure a more harmonious sound. The sensitivity of the rear and front speakers should be adjusted to each other.

If you don’t understand anything about this, it’s better not to go there, because repairs will cost more after you burn or break.

Sorry, there are no surveys available at this time.

Depending on the type of cascade, change the quiescent current of the cascade, either the base current of the transistor, or the bias voltage on the lamp grid.

To create a base current in a common-emitter transistor, use a resistor connecting the base to either the supply rail or the collector. The second is preferable from the point of thermal stabilization. The lower the resistance of the resistor, the greater the opening base current, and the quiescent current of the cascade. There are other, more advanced bipolar thermal stabilization schemes that involve the use of several resistors.

To create a bias voltage for the lamp, connect its control grid to the wire through a high-resistance resistor (its value does not need to be changed), and connect a resistor between the cathode and the common wire, with which the bias voltage will be regulated. Bypass it with a capacitor (if it is electrolytic, connect it with the positive side to the cathode). The greater the resistance of the cathode resistor, the greater the blocking voltage on the grid, which is negative relative to the cathode (but not the common wire), and, accordingly, the less the quiescent current of the cascade.

If the stage is used for AC amplification, feed it the input signal through a very low leakage capacitor to avoid disturbing its DC mode. Also remove the output signal from the load through a capacitor.

Regardless of whether the cascade is tube or transistor, first take a resistor that sets the quiescent current, of high resistance, so that this current is small. Apply a signal to the input of the cascade through a capacitor so that its distortion can be easily detected by ear or on the screen of an oscilloscope. Also remove the output signal through a capacitor and feed it, respectively, to a control amplifier or oscilloscope. Install the transistor on the heat sink in advance.

Connect a milliammeter in series with the load resistor. Only then apply power to the cascade. The quiescent current will be small, and the distortion will be large.

Whenever you first turn off the power to the cascade, place a resistor of lower and lower resistance in it. The quiescent current will increase and distortion will decrease. When they stop falling, stop lowering the resistance. Do not try to find out in practice what will happen if it is further reduced - take my word for it: the gain will begin to fall, the quiescent current will increase to an unacceptable level of great importance, the active element may fail.

If you are satisfied with the increased power consumption of the cascade, leave the quiescent current at the blue level, and if you want to sacrifice amplification quality for the sake of economy, reduce the quiescent current to the desired level.

Before adjusting the ULF, you should touch with tweezers an ungrounded socket for connecting a pickup or directly to the control grid of the first amplifier tube. If the amplifier is running, there will be a strong hum in the speaker. The volume control should be in the position corresponding to the maximum volume.

It is also necessary to connect the devices correctly. First of all, connect all the terminals to be grounded. The terminals of the devices located on the input side are connected to the Ground terminal of the amplifier's input, and the corresponding terminals of the output devices are connected to the Ground terminal of the amplifier's output. Then the ground terminals of the input and output of the amplifier are connected with a jumper. The sound generator is connected to the amplifier input using a shielded wire; the shield is reliably grounded.

Then the receiver is turned on to play the record, and the volume control is set to the maximum gain position. If the receiver has a tone control, then the test is carried out at different positions of this control. At any position of the tone controls and maximum volume, the amplifier should not be excited. Excitation is detected when an intermittent sound or whistles of various tones appear in the loudspeaker, as well as by readings from measuring equipment.

In addition to self-excitation, hum may appear in the amplifier alternating current. The presence of background is also checked when there is no signal at the amplifier input.

Then they begin to check the operation of the amplifier in the presence of a signal at the input. As an example, consider the procedure for checking the ULF of the Sirius-309 industrial receiver.

The output hose of a GZ-33 type sound generator or a similar device is connected to the block for connecting a tape recorder. An output meter of type VZ-2A is connected in parallel to the secondary winding of the output transformer. The radio is turned on to play a record. The volume control and tone control should be in the position of maximum gain and maximum bandwidth. The generator is set to a signal with a frequency of 1000 Hz and an output voltage level at which the voltage on the VZ-2A output meter will be 0.8V, which corresponds to the rated output power. The output voltage of the sound generator is the sensitivity of the ULF and should be no worse than 80 mV for a given radio. For receivers of other brands, with an output voltage of the sound generator of 0.2...0.25V, the amplifier must deliver power close to the rated one to the load.

After this, check the frequency response of the amplifier and the operation of the tone and volume controls. A signal equal to 0.25 V with a frequency of 1000 Hz is supplied to the ULF input from the generator. The tone control is set to the position corresponding to the cutoff of higher sound frequencies. Using the volume control on the output meter, set the voltage to 0.8 V. Then, without changing the voltage, set the frequency to 5000 Hz on the sound generator. In this case, the output voltage on the output meter should decrease to 0.4 V.

To check the operation of the volume control, it is necessary to apply to the input of the radio from a generator type G4-102 a voltage modulated in amplitude by a voltage of 1000 Hz with a modulation depth of 30%, at which the output meter will show a voltage of 2.5 V. The volume control should be in the position maximum volume. The volume control is then set to the minimum volume position and the output meter reading is noted. The ratio of the voltage (at the receiver output) corresponding to the rated output power to the voltage corresponding to the minimum volume position of the volume control (in decibels) must be at least 40 dB.

When checking the frequency response and the actions of the tone and volume controls, you must ensure that the voltage at the output of the sound generator corresponds to 250 mV. Output voltage measurement limits during testing frequency response and tone and volume adjustments in receivers of other brands should be indicated in the repair instructions in the form of a table.

The method for testing ULF with a single-cycle output stage was discussed above. In high-quality ULF receivers of the first and highest classes and transistor receivers, the final stages are assembled using push-pull circuits.

The setup of push-pull output stages begins with the phase inversion stage. When adjusting this cascade, the same output voltage values ​​are set, shifted in phase by 180°. To do this, select the resistance values ​​of the resistors in the collector and emitter circuits. Transistors used in a push-pull power amplifier circuit must have the same parameters. It’s good if the transistors’ collector currents and current gain differ by no more than ±10%. If the transistors are not identical in parameters, then the bias voltage must be adjusted using resistors connected in the base circuits. The condition for the normal operation of a push-pull final stage is the symmetry of its arms in both direct current and alternating current.

If you need to check the polarity of the connection of the feedback circuit, a signal with a frequency of 1000 Hz is supplied to the ULF input from the sound generator, such a value at which the output voltage would be approximately half the nominal one. Then short-circuit the resistor from which the feedback voltage is removed and observe the readings of the output voltage meter. If at the same time the output meter readings increase, then the polarity of the feedback is negative (correct), and if they decrease, it is positive. To change the polarity, it is necessary to swap the ends of the secondary winding of the output transformer.

The final stage of adjusting the amplifier is checking all its quality indicators: a) measuring the output power; b) taking the frequency response; c) measurement of harmonic distortion coefficient; d) checking the background level.

Other articles dedicated to the construction of this ULF.

Assembly.

Right during the installation, I made a harness or connecting cable. Call it whatever you like.

Since the top and bottom covers cannot be pulled through the pipe, the cable length had to be made redundant. This should allow you to easily reach any element of the circuit without having to unsolder any ends.


The tourniquet was tied with a harsh waxed thread. If there is no such neti, then you can make it from an ordinary one by simply pulling a thread through a candle.


Led indicator I glued the inclusions with hot glue.

Between the microcircuits and the radiator of the final amplifier I placed a gasket made of one layer of medical bandage, generously lubricated with KPT-8 thermal paste. The thickness of the compressed bandage is about 0.1 mm. This gap is quite sufficient even for a voltage of 100 Volts.



Since the entire structure is assembled using one single pin, in order for the pipe to be well fixed in the plugs, I put a rubber ring on the protrusion of each plug (the rings are marked with arrows).


Final assembly of the transformer.

I glued the halves of the magnetic circuit together with epoxy resin and finally assembled the transformer only after the ULF was completely assembled and tested.

If you do not glue the halves of the magnetic circuit together, the transformer will most likely hum. It may hum quieter or louder, but it will be audible.

If you have to break the gluing area, for example, in order to lengthen or shorten the winding, then some plates of the armor core may peel off from the impact. If this happens, it will be very difficult to completely get rid of the buzzing. Therefore, it is better to do gluing at the very end.


To complete the assembly of the transformer, you can wind a layer of electrical cardboard or paper 0.1 mm thick over the coil. It is useful to put data on the windings on paper. If you also wrap a layer of glass or varnish fabric over the paper, the transformer will take on an industrial look.

Setup.

During commissioning, only one error had to be corrected. This error manifested itself in the form of a small hum in the speakers and was caused by incorrect ground wiring on the power supply board.


The hum appeared due to the fact that a tiny ripple voltage penetrated the input of the voltage stabilizer, and from there into the pre-amplifier.

On the original version printed circuit board conclusions secondary windings The transformers going to the case were connected together, which is not correct, since all the power grounds should be connected at one point, and not at two.


Initial version of the printed circuit board.


And this is already a modified version. During modification, we had to cut one track, item 1, and add one contact, item 2, to connect the transformer winding that powers the voltage stabilizer.


In addition, another defect has surfaced in the ULF, which has not yet been eliminated. These are clicks when the ULF is turned on and off. The source of the clicks is the volume and tone control unit.

The picture shows a diagram taken at the output of the tone control block. The startup and shutdown of the microcircuit itself occurs very smoothly. Both voltage and sound volume increase within a couple of seconds. But there is a small step in the voltage rise and fall curve, which seems to be caused by some transient processes in the microcircuit. This difference hits the input of the terminals and causes clicks.

I still doubt that Philips has developed such a crooked chip and I blame the specific manufacturer NXP Semiconductors or the batch of chips. First, I’ll try to look for a similar microcircuit from another manufacturer on our radio market.

As I already wrote, an amplifier powered by a bipolar source does not create clicks when turned on and off.

I wouldn’t want to install a loudspeaker shutdown circuit for an amplifier that doesn’t need it.

So, if someone is going to use the TDA1524A, they should pay attention to this circumstance.

Otherwise, the assembly went without any complications.

Ready amplifier.

The pictures show the finished amplifier.

  1. Cooling gap between the top cover and the radiator.
  2. Power indicator.
  3. Network switch.
  4. Volume.
  5. Stereo balance.
  6. HF timbre.
  7. Bass timbre.
  8. Phone connection socket.
  9. Speaker switch.

  1. Fuse holder.
  2. Network cable socket.
  3. Right channel output.
  4. Line input.
  5. Left channel output.

  1. Radiator.
  2. The only nut that needs to be unscrewed to disassemble the ULF.

  1. Cooling holes.
  2. Legs (stoppers from some pharmaceutical bottles).

Measurements.

Ambient temperature – 20ºС.

Mains voltage – 220V.

Sine wave signal – hardware low-frequency generator.

Music cue – Carlos Santana “Jingo: The Santana Collection”.

An oscillogram taken on a ULF load when connected to the input of a low-frequency generator.

Effective power limited by supply voltage ripples – 2x9 Watts.


An oscillogram taken at a load when a music signal is connected to the input.

Peak musical power – 2x18 watts.


Radiator temperature during continuous operation at maximum power, at a frequency of 1 kHz, in power limit mode – 75ºС

The radiator temperature during prolonged music playback at maximum volume limited by supply voltage ripples is 65ºС.

Small details.

The amplifier case turned out to be quite stable. Stability is provided by weight power transformer and high friction coefficient of rubber feet. When switching the toggle switches, the body does not come off the ground, although it slightly changes position due to the elasticity of the legs.