Details: do-it-yourself microlab h200 from a real master for the site my.housecope.com.
The entire audio complex can be conditionally divided into three parts - an active subwoofer with an amplifier for other channels, connected passive speakers and a control unit (volume, timbre, balance).
All this is somewhat confusing, but it is compensated by the ease of management and operation. On the table near the PC there is only a remote control with a preamplifier, and the speakers themselves and the subwoofer box are distributed throughout the room.
The problem manifested itself as a dropout signal. Occasionally the sound would “break through”, but most of the channels were silent. The power LED was just lit.
Sound control unit
Let's start the repair from the control unit. Here, in a small plastic case, we see a power transformer and a pallet with details. The signal taken from the line-out of the computer is mixed, amplified and frequency corrected.
LF component is also extracted from the stereo signal for the subwoofer. With the help of sufficiently thick and high-quality cables, the sound is fed to an active subwoofer, in which there are power amplifiers (UMZCH).
By connecting a high-impedance headphone (or any simple amplifier) to the outputs of the preamplifier unit, you can determine the presence of sound. If it is not there, the problem is inside the control unit.
In my case, everything sounded and was regulated - that means we go to the next module.
Active subwoofer Microlab H-200
We unscrew the back cover and remove the transformer with the UMZCH board. First of all, we measure the supply voltages on the board near the microcircuits. Unfortunately, they are normal. That excludes freebies, such as a blown fuse or a rectifier diode :)
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Video (click to play). |
This very norm is easy to calculate by the brand of installed amplifier microcircuits. In this case, it was not the familiar TDA2030 that pleased us, but the more advanced LM3886. It is very rare to find such an UMZCH in inexpensive active speakers.
Having downloaded the datasheet for these LM3886, we immediately see the value of the supply voltage - two channels of 25 volts each. Which is fully consistent with the measurements (26B). By the way, if the voltage was skewed or significantly underestimated, you can sin on the failure of one of the electrolytic capacitors of the power filter.
The next step is to determine the reason for the silence of the microcircuits. Since there are three of them, the simultaneous combustion of all of them is excluded. Most likely a problem with the strapping or lack of signal at the inputs.
We again use a high-impedance earpiece - there is a signal even at the input pins of the microcircuits. It remains to check the harness, in particular the elements responsible for the electronic inclusion (mute mode).
In the process of measurements, while touching the probes to the board, a sound appeared. Most likely, the internal resistance of the multimeter affected. Since there was no desire to re-solder every detail from the mute module, I simply remembered this place on the board and soldered a resistor there for a couple of hundred kilo-ohms.
The sound appeared immediately, and the clicks when turning on and off were almost imperceptible. Perhaps you should have looked more closely for the problematic part, but not this time. When they bring it back, then I'll look :)
A test run of the home theater showed no problems, and after a couple of hours I screwed the subwoofer box back. Repairs to Microlab columns can be considered successful!
We process with a brush two or three times with a thin layer with a break of a couple of hours all speaker mounts with the proven Doctor Wax DW5343 solution - this improves microdynamics and protects the mounts. If you have a paper diffuser, it can be treated with Diffusor CHITIN
The cheap acoustic aluminum cable from the kit is immediately replaced with an oxygen-free copper tinned non-oxidizing cable with many small cores SCT-25-2.50, an acoustic cable 2x2.50mm sq. With a base, puddles, yellow-transparent .. From 15 m rubles per meter.The black stripe on it is a minus, and on the adjacent conductor the direction of the inscription and the arrows -> -> -> indicate the direction from the amplifier to the speakers and is connected to the plus.
A high-quality cable is necessary, since with a high damping factor (low output impedance of the amplifier), the resistance of the cable and connectors begins to play a significant role. For a 2 m cable, a resistance of 0.05 ohms is quite a decent indicator. But for an amplifier with an output impedance of 0.01 Ohm, the dumping factor at a 4 Ohm load with such a cable will decrease from 400 to 66!
Modification of the crossover of microlab speakers
The speakers from the microlab sets A-H200, H-220, A-H500D, H-200, H-500, H-510 are the same in terms of filling - they are not bad, but small and with a curved crossover inside, due to which a large dip is formed at the middle frequencies and the sound is squeezed and dull.
But tweeters ML-010610G-01 The 6 ohm 60mm outer diameter and 25mm dome in these speakers turned out to be surprisingly very good, much better than the larger Pro 3 series. ML-010620G-03 6 Ohm 60 mm outer diameter and 30 mm dome - they generally sound dull, it is better to change them right away.
This modification will suit many microlab speakers, since they have almost the same crossovers everywhere.
The Chinese have clearly saved on capacitors and calculations.
Calculations and measurements were made by Siniyyyy, personal thanks to him for the work done! It was he who prompted the revision of these speakers, and then the KEF Q1. His tweak is described on in the topic "Redesigning crossovers in the speakers", he uses my modified circuit there.
The squeezed sound of the speakers is obtained due to the midrange speakers (woofers) themselves and the failure at the midrange due to the crossover, but if you do not supply frequencies above 2 kHz to them, but give them to tweeters, then the sound becomes open!
Based on the frequency response of the speakers from the measurements of the ixbt A-H200, we select filters so as to maximize the equalization of the frequency response of each and the final frequency response.
In the native midrange filter, the coil is designed for a section with somewhere around 1.8 kHz, and a capacitor with 4.5 kHz for 6 Ohm speakers. Together it turns out 3 kHzbut fig.
The midrange should be cut no higher than 2 kHz, since there is a very strong nonlinearity in the frequency response of the midrange speaker.
We remove the midrange speaker. The crossover is glued with hot melt glue, pry it from below with a large flat screwdriver and tear it off. After revision, we glue it with double-sided tape.
In the filter on the midrange after the coil we put on the ground 12 uF (to the existing small barrel of 4.7 μF, a slightly larger 10 μF electrolyte can be soldered in parallel), thereby reducing the cutoff frequency to 1.8 kHz.
In the Zobel circuit, we put an electrolyte of 2.2 μF (enough instead of 3.3 μF in the diagram) and a 7.5 Ohm resistor (R * 1.25).
In the high-frequency filter, parallel to the existing 4R7 resistor, we solder a jumper on the back of the board, and instead of two 4.7 uF electrolytes we put polypropylene 8.2 (4.7 + 3.3) μF and 10 (4.7 + 4.7) μF, thereby reducing the cutoff frequency from 4.5 kHz to 2.6 kHz with a sharp characteristic according to Chebyshev. The quality of the first capacitor in the chain is much more important than the second, it must be installed with a film! The second can be supplied with electrolyte ELNA Silmic II 10 uF 100V, although it is polar, it allows 30% reverse voltage. And it can only be set on HF. In low frequencies, better than Nichicon KZ.
Tweeter resistors for L-pad are needed 2.2 ohm and 10 ohm, and in Zobel - 7.5 ohm
If you want a smooth characteristic, then the capacitors are 4.7 and 14 μF, respectively, but then the dip at 3-4 kHz will not be corrected, since with our approximation according to Chebyshev, the hump on the frequency response above the section straightened it.
For audiophiles, slightly better, but unreasonably expensive components:
Audiocore S-Line capacitors 8.2 and 10 uF (450 rubles / pc)
ELNA Silmic II 100V capacitors for 2.2 and 10 uF (122 rubles / piece) - are needed exactly for 100 volts, with a margin, since they are electrolytic polar, and they will work on alternating current!
MOX Jantzen 5W resistors at 2.2, 10 and 7.5 Ohm (32 rubles / piece)
Over the condensers there is the mundorf camp and there is the jantzen camp. The former give a deeper warm sound, while the latter give a more accurate and brighter sound. Audiocore - cheaper analogs of jantzen, made at the same factory.
The midrange is now cut by 1.8 kHz at the top, and the high frequency at 2.6 kHz at the bottom instead of 3 and 4.5 kHz, respectively.... In between, they still play together.
The frequency response has become clearly smoother. There used to be a strong dip at 3-4 kHz.
And we turn the coils where necessary so that the input (+) enters the inner winding, and exits from the outer one.
A single resistor in series with the 6 ohm tweeter gives attenuation
0.7 Ohm / dB, that is, every 0.7 Ohm gives a 1 dB attenuation of the head sensitivity.
Instead of a single resistor 3.9 ohm... 4.7 Ohm (-4.5 dB... -5 dB) at the input to the crossover to a 6 Ohm tweeter, put a resistive divider L-pad at the crossover output (2.2 Ohm and 10 Ohm = -4 dBu). It is better to solder the resistors to the tweeter itself.
About the hump on the frequency response and its reduction using the L-Pad is well written here: Say a word about the poor squeaker
We put a Zobel-Bushe compensator on the midrange speaker (7.5 ohms and 3.3 uF (set 2.2 uF)).
It is advisable to put a double folded fluffed sheet of 1 cm of padding polyester inside the columns on the walls, or you can glue it with bitoplast 1 cm on an adhesive base for a car (foam rubber impregnated with bitumen so as not to rot).
The speakers began to play an order of magnitude better, as if they were taken out of the toilet.
Before that, the sound was very dull and the midrange failed. Now everything is smooth and clear. The mids have increased, the treble has become much clearer. The sound with Zobel and L-pad has improved dramatically. The sound is transparent. With a sub, they now sound almost like expensive floor-standing speakers.
Previously, there was a hump at a frequency of 1-3 kHz, but at a frequency of 3-4 there was a dip. The hump 1-3 has been straightened by the downward shift of the crossover frequency and the L-pad. And the failure of 3-4 was straightened out by Chebyshev. Then there was still a hump higher from the influence of the midrange speaker, it also straightened by shifting the frequency of the section down, plus Zobel a little.
In a microlab with closed bass reflexes, the sound is better, especially if the speakers are close to the wall. Apparently the phasics are also poorly calculated, with closed sound it is clearer on the mids and the bass is more intelligible. It is best to plug the phasics with cotton pads at the pipe outlet. Ideally, pull the tubes out and close the holes in the body with plastic plugs.
The best test for speakers is jazz. The saxophone sounds on bad speakers in general like a pipe of some kind, and if there is an uneven frequency response, then it constantly walks along the level. Plus, in jazz, there is usually female vocals, for an additional test of the average for lousy. Usually jazz sounds great only on large floor-standing speakers with a separate midrange speaker (like Celestion F30), or on acoustics more than 60 thousand +. Otherwise the saxophone is completely distorted. When compared with the tweaked microlab, it turned out in an incomprehensible way that they play the middle as well as good floor speakers. And the tops are even more pleasant at times, of course, if the volume is not too high. Shocked)
These crossovers can also be used with other 2-way speakers:
For 4 ohm speakers you need C3 18 μF, L2 0.7 mH (you can just pull out the core and measure it, it should just match), if the coil is not changed, then leave 12 μF - the weakening will start smoother, from a lower frequency, and go into a sharper decline at a higher one.
At HF for 4 Ohms: C1 10 μF (film required), C2 22 μF (electrolyte is possible) then the coil can not be changed.
With a second order filter for a 4 Ohm tweeter, a 14 μF (Chebyshev) or 12 μF (Butterworth) capacitor is needed, the cutoff frequency is 2.4 kHz.
L-Pad should be counted depending on the ratio of the sensitivity of the midrange and tweeter heads (how many dB you need to lower the treble, usually by -4-5 dB - 1.5 ohms in series and then 6.8 ohms in parallel to the tweeter)
Zobel: 5 ohm, 4.7-8.2 uF
The Microlab A-H200 multimedia top-level (entry-level Hi-Fi) speaker system is the pinnacle of Chinese compact 2.1 acoustics for a computer and other sources.
The revision concerns the crossover of the speakers and the preamplifier unit, since the ULF in the subwoofer is sufficiently well wired, except that it is possible to separate the signal and power wires in it further from each other, replace the separating capacitors with film capacitors with a margin of 1 μF, replace the diode bridge with a powerful assembly and increase the capacity in the power supply: add 2x10000 uF to the existing 2x6800 uF 35V and add film 1-4.7 uF in parallel. It is quite easy to greatly improve the sound at the HF.It is necessary to hang film capacitors on the ground 1-4.7 uF K73-17 directly on the legs of the ULF LM3886 for the plus and minus of the power supply.
A very noticeable result is provided by the refinement of the speaker crossover. The sound has become open! You can start with this to immediately get a noticeable result, and the rest of the improvements are optional.
The subwoofer contains a toroidal transformer 2x22V 4.5A (after the rectifier (* 1.3) = + -28 volts, and this already gives a good level of amplification of about 40 W), a powerful amplifier based on 3 high-quality mono-microcircuits LM3886TF with honest 40 W ( THD + N Like 55 Follow
Is your TV, radio, mobile phone or kettle broken? And you want to create a new topic about this in this forum?
First of all, think about this: imagine that your father / son / brother has an appendicitis pain and you know from the symptoms that it is just appendicitis, but there is no experience of cutting it out, as well as the tool. And you turn on your computer, access the Internet on a medical site with the question: "Help to cut out appendicitis." Do you understand the absurdity of the whole situation? Even if they answer you, it is worth considering factors such as the patient's diabetes, allergies to anesthesia and other medical nuances. I think no one does this in real life and will risk trusting the life of their loved ones with advice from the Internet.
The same is in the repair of radio equipment, although of course these are all the material benefits of modern civilization and in case of unsuccessful repairs, you can always buy a new LCD TV, cell phone, iPAD or computer. And for the repair of such equipment, at least it is necessary to have the appropriate measuring (oscilloscope, multimeter, generator, etc.) and soldering equipment (hairdryer, SMD-hot tweezers, etc.), a schematic diagram, not to mention the necessary knowledge and repair experience.
Let's consider a situation if you are a beginner / advanced radio amateur soldering all sorts of electronic gizmos and having some of the necessary tools. You create an appropriate thread on the repair forum with a short description of “patient symptoms”, ie. for example “Samsung LE40R81B TV does not turn on”. So what? Yes, there can be a lot of reasons for not switching on - from malfunctions in the power system, problems with the processor or flashing firmware in the EEPROM memory.
More advanced users can find the blackened element on the board and attach a photo to the post. However, keep in mind that you are replacing this radio element with the same one - it is not yet a fact that your equipment will work. As a rule, something caused the combustion of this element and it could “pull” a couple of other elements along with it, not to mention the fact that it is quite difficult for a non-professional to find a burned-out m / s. Plus, in modern equipment, SMD radio elements are almost universally used, soldering which with an ESPN-40 soldering iron or a Chinese 60-Watt soldering iron you risk overheating the board, peeling tracks, etc. The subsequent restoration of which will be very, very problematic.
The purpose of this post is not any PR of repair shops, but I want to convey to you that sometimes self-repair can be more expensive than taking it to a professional workshop. Although, of course, this is your money and what is better or more risky is up to you.
If you nevertheless decide that you are able to independently repair the radio equipment, then when creating a post, be sure to indicate the full name of the device, modification, year of manufacture, country of origin and other detailed information. If there is a diagram, then attach it to the post or give a link to the source. Write down how long the symptoms have been manifesting, whether there were surges in the supply voltage network, whether there was a repair before that, what was done, what was checked, voltage measurements, oscillograms, etc. From a photo of a motherboard, as a rule, there is little sense, from a photo of a motherboard taken on a mobile phone there is no sense at all. Telepaths live in other forums.
Before creating a post, be sure to use the search on the forum and on the Internet. Read the relevant topics in the subsections, perhaps your problem is typical and has already been discussed. Be sure to read the article Repair strategy
The format of your post should be as follows:
Topics with the title “Help fix the Sony TV” with the content “broken” and a couple of blurred photos of the unscrewed back cover, taken with the 7th iPhone, at night, with a resolution of 8000x6000 pixels are immediately deleted. The more information you post about the breakdown, the more chances you will get a competent answer. Understand that the forum is a system of gratuitous mutual assistance in solving problems and if you are dismissive of writing your post and do not follow the above tips, then the answers to it will be appropriate, if anyone wants to answer at all. Also note that no one should answer instantly or within a day, say, no need to write after 2 hours “That no one can help”, etc. In this case, the topic will be deleted immediately.
You should make every effort to find a breakdown on your own before you get stumped and decide to go to the forum. If you outline the entire process of finding a breakdown in your topic, then the chance of getting help from a highly qualified specialist will be very great.
If you decide to take your broken equipment to the nearest workshop, but do not know where, then perhaps our online cartographic service will help you: workshops on the map (on the left, press all buttons except “Workshops”). You can leave and view user reviews for workshops.
For repairmen and workshops: you can add your services to the map. Find your object on the map from the satellite and click on it with the left mouse button. In the field “Object type:” do not forget to change to “Equipment repair”. Adding is absolutely free! All objects are checked and moderated. A discussion of the service is here.
Here they solve various problems together. Join us!
Gandi »08 May 2015, 15:40
The 5v contact coming from the subwoofer goes through (as I assume) IC the port for working with the remote control, comes out of it and goes to our 28-foot microcircuit.
Questions to specialists:
1) is my logic correct, is it possible to solve this problem with a similar approach?
2) By energizing this contact, will we energize the chip and the settings will not be reset?
3) if not, what contacts still need to be powered.
4) how safe it is.
Sent after 10 minutes 29 seconds:
The problem is that when the computer is off, it buzzes perceptibly, during the day it is not too noticeable, but at night it interferes with sleep, while even in this state, the rear radiator is warm, from which it follows that it consumes electricity for this heating and apparently not a little. I use speakers mainly with off-key basses. basically I listen to speech on YouTube, not music, with bass at the default value of “5” speech turns into “bubnezh” and it probably interferes with neighbors at night.
And in order to get up in the morning and watch YouTube, for example, I need to: 1) turn on the switch on the subwoofer under the table 2) press the exit button from the stand buy on the panel 3) press the “treb / bass” button 2 times to get into the bass settings submenu 4 ) Press the down arrow 5 times to lower the default value of 5 to 0
Dispatched after 1 minute 59 seconds:
buzzing regardless of the stand buy mode or just on.
I bought myself a Microlab Pro 3 speaker system. Inexpensively. Excellent preservation, everything is in order, except for the volume control on the amplifier. When the handle was turned, she lived her life, the volume readings jumped in different directions, regardless of the direction of rotation. From the remote control, the volume was adjusted normally, so the previous owner did not bother with repairs. For me, disassembling the device to study the device, with the possibility of repair, is a habit of many years of life, plus a reason to save money. The study of forums and other googling did not give any results. There are requests of this kind (“the volume control does not work”), but I did not find any sensible solutions, and went my own way.
I disassembled the case, removed the front panel, it is mounted on 6 self-tapping screws (I saw comments on the forums that someone could not crawl to these screws. It surprised me - the access is very simple).The knob of the regulator is removed from the splines very tightly, it is glued, you need to be careful. Under it is the usual variable resistor mounting nut, which also needs to be unscrewed.
Then, on the back of the front panel, unscrew the 6 self-tapping screws for fastening the board, and it is separated from the case.
We see the body of the volume control. We carefully unbend the metal legs that hold the upper part of the body.
And we see the following picture. The contacts of the controller are erased to black. We take a cotton swab, moisten it in alcohol, and wipe it. But this turned out to be not enough, then we take a thin sandpaper (I had 400 grids at my fingertips) and use tweezers to put things in order and shine on the contacts with small pieces of sandpaper.
In this article we will repair the speaker system type subwoofer or in Russian subwoofer, which is called microlab.
The principle of repairing the buffer we are considering can be applied to other brands, since the structural scheme of such acoustic systems is quite similar and such subwoofers for computer have different versions.
After turning on this device, a background hum in the speakers was detected, a hoarseness of sound when the volume was increased, and one of the outputs did not work.
After analysis, we see two power amplifiers, which are assembled on four TDA7265 microcircuits (two microcircuits on each amplifier).
During a visual examination of these amplifiers, with the naked eye, faulty circuit elements were identified.
The capacitors that power the power amplifiers were "swollen", and one of the microcircuits was blown up.
Well, well, the faulty elements have been identified and now all that remains is to produce amplifier repair, by replacing the failed radio components.
Since the capacitors on the power supply were out of order, other elements in this unit were also checked, which turned out to be in good condition.
So, the faulty capacitors, rated 25V 4700μF, as well as the exploded TDA7265 microcircuit were replaced with new ones.
Everything, subwoofer repair, or rather amplifier repair of this subwoofer has been successfully completed.
I also invite you to my YouTube channel , which has a lot of videos on the repair of various equipment.
Victor, you, as always, are on top. Thanks for the great article.
Hello Victor!
Can I voice here my (similar) problem with the sub, hoping for your (feasible) help? Thank you.
Subwoofer Polk Audio PSW12. Buzzing when plugged into a power outlet (both through the "pilot" and directly ...), in
independence from the position of the toggle switch (on / off).
Also, whether the amplifier and speakers are connected or not, the volume level and cutoff frequency ...
(the sound is well transmitted if you listen through (decent) acoustics or headphones).
I have already changed the capacitors (63v 4700mf) -
worked for some time (1-2 months) and buzzed again :(.
Most likely there is more
"Something" before (or after) them, but what exactly I do not know
(transistors, resistors ... - where and what ...?).
I don't have a lot of knowledge, but I want to do it myself ..., + save money (a separate topic).
I am friends with a soldering iron, but not more ...)).
P.S.
Yesterday I changed the con-ry again, but not my relatives, but those that were (with a friend) (63v, 15000mf). The hum has become much quieter (15-20% of the initial).
Thank you.
I don’t know ... by all indications - capacitors. In general, these buffers are nasty things ... I stopped taking them for repairs altogether.
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We process with a brush two or three times with a thin layer with a break of a couple of hours all speaker mounts with the proven Doctor Wax DW5343 solution - this improves microdynamics and protects the mounts. If you have a paper diffuser, it can be treated with Diffusor CHITIN
The cheap acoustic aluminum cable from the kit is immediately replaced with an oxygen-free copper tinned non-oxidizing cable with many small cores SCT-25-2.50, an acoustic cable 2x2.50mm sq. With a base, puddles, yellow-transparent .. From 15 m rubles per meter.The black stripe on it is a minus, and on the adjacent conductor the direction of the inscription and the arrows -> -> -> indicate the direction from the amplifier to the speakers and is connected to the plus.
A high-quality cable is necessary, since with a high damping factor (low output impedance of the amplifier), the resistance of the cable and connectors begins to play a significant role. For a 2 m cable, a resistance of 0.05 ohms is quite a decent indicator. But for an amplifier with an output impedance of 0.01 Ohm, the dumping factor at a 4 Ohm load with such a cable will decrease from 400 to 66!
Modification of the crossover of microlab speakers
The speakers from the microlab sets A-H200, H-220, A-H500D, H-200, H-500, H-510 are the same in terms of filling - they are not bad, but small and with a curved crossover inside, due to which a large dip is formed at the middle frequencies and the sound is squeezed and dull.
But tweeters ML-010610G-01 The 6 ohm 60mm outer diameter and 25mm dome in these speakers turned out to be surprisingly very good, much better than the larger Pro 3 series. ML-010620G-03 6 Ohm 60 mm outer diameter and 30 mm dome - they generally sound dull, it is better to change them right away.
This modification will suit many microlab speakers, since they have almost the same crossovers everywhere.
The Chinese have clearly saved on capacitors and calculations.
Calculations and measurements were made by Siniyyyy, personal thanks to him for the work done! It was he who prompted the revision of these speakers, and then the KEF Q1. His tweak is described on in the topic "Redesigning crossovers in the speakers", he uses my modified circuit there.
The squeezed sound of the speakers is obtained due to the midrange speakers (woofers) themselves and the failure at the midrange due to the crossover, but if you do not supply frequencies above 2 kHz to them, but give them to tweeters, then the sound becomes open!
Based on the frequency response of the speakers from the measurements of the ixbt A-H200, we select filters so as to maximize the equalization of the frequency response of each and the final frequency response.
In the native midrange filter, the coil is designed for a section with somewhere around 1.8 kHz, and a capacitor with 4.5 kHz for 6 Ohm speakers. Together it turns out 3 kHzbut fig.
The midrange should be cut no higher than 2 kHz, since there is a very strong nonlinearity in the frequency response of the midrange speaker.
We remove the midrange speaker. The crossover is glued with hot melt glue, pry it from below with a large flat screwdriver and tear it off. After revision, we glue it with double-sided tape.
In the filter on the midrange after the coil we put on the ground 12 uF (to the existing small barrel of 4.7 μF, a slightly larger 10 μF electrolyte can be soldered in parallel), thereby reducing the cutoff frequency to 1.8 kHz.
In the Zobel circuit, we put an electrolyte of 2.2 μF (enough instead of 3.3 μF in the diagram) and a 7.5 Ohm resistor (R * 1.25).
In the high-frequency filter, parallel to the existing 4R7 resistor, we solder a jumper on the back of the board, and instead of two 4.7 uF electrolytes we put polypropylene 8.2 (4.7 + 3.3) μF and 10 (4.7 + 4.7) μF, thereby reducing the cutoff frequency from 4.5 kHz to 2.6 kHz with a sharp characteristic according to Chebyshev. The quality of the first capacitor in the chain is much more important than the second, it must be installed with a film! The second can be supplied with electrolyte ELNA Silmic II 10 uF 100V, although it is polar, it allows 30% reverse voltage. And it can only be set on HF. In low frequencies, better than Nichicon KZ.
Tweeter resistors for L-pad are needed 2.2 ohm and 10 ohm, and in Zobel - 7.5 ohm
If you want a smooth characteristic, then the capacitors are 4.7 and 14 μF, respectively, but then the dip at 3-4 kHz will not be corrected, since with our approximation according to Chebyshev, the hump on the frequency response above the section straightened it.
For audiophiles, slightly better, but unreasonably expensive components:
Audiocore S-Line capacitors 8.2 and 10 uF (450 rubles / pc)
ELNA Silmic II 100V capacitors for 2.2 and 10 uF (122 rubles / piece) - are needed exactly for 100 volts, with a margin, since they are electrolytic polar, and they will work on alternating current!
MOX Jantzen 5W resistors at 2.2, 10 and 7.5 Ohm (32 rubles / piece)
Over the condensers there is the mundorf camp and there is the jantzen camp. The former give a deeper warm sound, while the latter give a more accurate and brighter sound. Audiocore - cheaper analogs of jantzen, made at the same factory.
The midrange is now cut by 1.8 kHz at the top, and the high frequency at 2.6 kHz at the bottom instead of 3 and 4.5 kHz, respectively.... In between, they still play together.
The frequency response has become clearly smoother. There used to be a strong dip at 3-4 kHz.
And we turn the coils where necessary so that the input (+) enters the inner winding, and exits from the outer one.
A single resistor in series with the 6 ohm tweeter gives attenuation
0.7 Ohm / dB, that is, every 0.7 Ohm gives a 1 dB attenuation of the head sensitivity.
Instead of a single resistor 3.9 ohm... 4.7 Ohm (-4.5 dB... -5 dB) at the input to the crossover to a 6 Ohm tweeter, put a resistive divider L-pad at the crossover output (2.2 Ohm and 10 Ohm = -4 dBu). It is better to solder the resistors to the tweeter itself.
About the hump on the frequency response and its reduction using the L-Pad is well written here: Say a word about the poor squeaker
We put a Zobel-Bushe compensator on the midrange speaker (7.5 ohms and 3.3 uF (set 2.2 uF)).
It is advisable to put a double folded fluffed sheet of 1 cm of padding polyester inside the columns on the walls, or you can glue it with bitoplast 1 cm on an adhesive base for a car (foam rubber impregnated with bitumen so as not to rot).
The speakers began to play an order of magnitude better, as if they were taken out of the toilet.
Before that, the sound was very dull and the midrange failed. Now everything is smooth and clear. The mids have increased, the treble has become much clearer. The sound with Zobel and L-pad has improved dramatically. The sound is transparent. With a sub, they now sound almost like expensive floor-standing speakers.
Previously, there was a hump at a frequency of 1-3 kHz, but at a frequency of 3-4 there was a dip. The hump 1-3 has been straightened by the downward shift of the crossover frequency and the L-pad. And the failure of 3-4 was straightened out by Chebyshev. Then there was still a hump higher from the influence of the midrange speaker, it also straightened by shifting the frequency of the section down, plus Zobel a little.
In a microlab with closed bass reflexes, the sound is better, especially if the speakers are close to the wall. Apparently the phasics are also poorly calculated, with closed sound it is clearer on the mids and the bass is more intelligible. It is best to plug the phasics with cotton pads at the pipe outlet. Ideally, pull the tubes out and close the holes in the body with plastic plugs.
The best test for speakers is jazz. The saxophone sounds on bad speakers in general like a pipe of some kind, and if there is an uneven frequency response, then it constantly walks along the level. Plus, in jazz, there is usually female vocals, for an additional test of the average for lousy. Usually jazz sounds great only on large floor-standing speakers with a separate midrange speaker (like Celestion F30), or on acoustics more than 60 thousand +. Otherwise the saxophone is completely distorted. When compared with the tweaked microlab, it turned out in an incomprehensible way that they play the middle as well as good floor speakers. And the tops are even more pleasant at times, of course, if the volume is not too high. Shocked)
These crossovers can also be used with other 2-way speakers:
For 4 ohm speakers you need C3 18 μF, L2 0.7 mH (you can just pull out the core and measure it, it should just match), if the coil is not changed, then leave 12 μF - the weakening will start smoother, from a lower frequency, and go into a sharper decline at a higher one.
At HF for 4 Ohms: C1 10 μF (film required), C2 22 μF (electrolyte is possible) then the coil can not be changed.
With a second order filter for a 4 Ohm tweeter, a 14 μF (Chebyshev) or 12 μF (Butterworth) capacitor is needed, the cutoff frequency is 2.4 kHz.
L-Pad should be counted depending on the ratio of the sensitivity of the midrange and tweeter heads (how many dB you need to lower the treble, usually by -4-5 dB - 1.5 ohms in series and then 6.8 ohms in parallel to the tweeter)
Zobel: 5 ohm, 4.7-8.2 uF
The Microlab A-H200 multimedia top-level (entry-level Hi-Fi) speaker system is the pinnacle of Chinese compact 2.1 acoustics for a computer and other sources.
The revision concerns the crossover of the speakers and the preamplifier unit, since the ULF in the subwoofer is sufficiently well wired, except that it is possible to separate the signal and power wires in it further from each other, replace the separating capacitors with film capacitors with a margin of 1 μF, replace the diode bridge with a powerful assembly and increase the capacity in the power supply: add 2x10000 uF to the existing 2x6800 uF 35V and add film 1-4.7 uF in parallel. It is quite easy to greatly improve the sound at the HF. It is necessary to hang film capacitors on the ground 1-4.7 uF K73-17 directly on the legs of the ULF LM3886 for the plus and minus of the power supply.
A very noticeable result is provided by the refinement of the speaker crossover. The sound has become open! You can start with this to immediately get a noticeable result, and the rest of the improvements are optional.
The subwoofer contains a toroidal transformer 2x22V 4.5A (after the rectifier (* 1.3) = + -28 volts, and this already gives a good level of amplification of about 40 W), a powerful amplifier on 3 high-quality mono-microcircuits LM3886TF with honest 40 W ( THD + N Like 55 Follow
8 years on the site
user # 266326
her bass is normal or not very
9 years on the site
user # 177563
Maybe someone knows why in one of the speakers the sound is louder than in the other, slightly but louder. ...
6 years on the site
user # 571300
From multimedia speakers, this is a good choice! But now they are clearly overpriced.
10 years on the site
user # 141444
people, tell me! such a story: speakers a-h200, those without a remote control. There are two inputs on the preamp: jack and tulips. So should they work at the same time? if I cut the computer and telly, then the volume sags at the second input (tulips)! Quiet generally.
* Naturally I listen not from two sources at the same time, but both are cleanly connected.
10 years on the site
user # 120079
if the jack is connected, then the left channel on the tulips “dies down”
10 years on the site
user # 141444
masterby, I have a general volume level .. Ie. and both satellites and sub .. Che for garbage ..
6 years on the site
user # 568371
If the sensitivity (volume) of the acoustics sits down when connecting different sources, it means that the inputs are simply paralleled. And due to the fact that the sound sources have different resistance (very roughly speaking), then this garbage happens. The manufacturer did not install an electronic switch. Most likely this is the problem.
12 years on the site
user # 59558
As I understand it, h200 was revived, and a remote control was added? How has the sound changed? The owner of the old ones without a remote control
6 years on the site
user # 571300
7 years on the site
user # 453679
hello! prompt plz what sound card to buy on the H200 I would be very grateful
11 years on the site
user # 79526
11 years on the site
user # 93053
Acoustics full awl:
1.the amplifier circuit is calculated incorrectly - the radiator heats up even in stand-by mode
2. Sound settings are not saved when power off.
3. (well, it's like someone) Vasya's body made of ordinary fiberboard (pressed cardboard).
I don’t understand why people give that kind of money, just for the sake of appearance? They have a red price - no more than $ 100. And they do. I don’t know, I didn’t have other awesome Chinese speakers, so I can’t compare with them. I have a blocky German telefunken of the 90s and Soviet AC-30s - the sound is much better.
Fortunately, I got these microlabs new for 60 bucks, I'll put them in the garage, let the garage workers envy, and I'll leave my telefunken at home.
Time zone: UTC + 5 hours
Hey, don't forget ^ _ ^:
"Even endless resistance"
Nice break) already blows amplifiers)
I will measure the voltage, only the battery has run out in the shop, tomorrow I will buy = (
_________________
What a blue sky. (c) fox Alice
The earth is whole.
Replaced the amplifier, turned it on without load.
The voltage after the diode bridge is 36.4 V.
Question: how to correctly measure the voltage across the trimming resistors?
Where should the shupas be leaned against?
In the photo, the place where the voltage was measured and the amplifier are marked in red.
Here they solve various problems together. Join us!
Gandi »08 May 2015, 15:40
The 5v contact coming from the subwoofer goes through (as I assume) IC the port for working with the remote control, comes out of it and goes to our 28-foot microcircuit.
Questions to specialists:
1) is my logic correct, is it possible to solve this problem with a similar approach?
2) By energizing this contact, will we energize the chip and the settings will not be reset?
3) if not, what contacts still need to be powered.
4) how safe it is.
Sent after 10 minutes 29 seconds:
The problem is that when the computer is off, it buzzes perceptibly, during the day it is not too noticeable, but at night it interferes with sleep, while even in this state, the rear radiator is warm, from which it follows that it consumes electricity for this heating and apparently not a little. I use speakers mainly with off-key basses. basically I listen to speech on YouTube, not music, with bass at the default value of “5” speech turns into “bubnezh” and it probably interferes with neighbors at night.
And in order to get up in the morning and watch YouTube, for example, I need to: 1) turn on the switch on the subwoofer under the table 2) press the exit button from the stand buy on the panel 3) press the “treb / bass” button 2 times to get into the bass settings submenu 4 ) Press the down arrow 5 times to lower the default value of 5 to 0
Dispatched after 1 minute 59 seconds:
buzzing regardless of the stand buy mode or just on.
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