2019/01/24

New updated - "Audio Frequency Analyzer" ver 5.0

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"Audio Frequency Analyzer" has updated to ver 5.0 today.

"Audio Frequency Analyzer" is a powerful Real-Time Audio Analyzer (RTA) app for iPhone.

It is available in a variety of applications, such as sound room tuning, speaker settings, audio equipment testing, stage setting measurement, evaluation of sound mixing environment and Investigation of noise environment.

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"Audio Frequency Analyzer" can measure the frequency response in 30 split band scale of 1/3 octave in realtime. Also it can be displayed the FFT analysis result.

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Please to click the following link to see the app information. It will be open the product page on AppStore.

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posted by toons at 17:38 | News

2019/01/10

SANSUI AU-5500 repair - 10

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Repair of the Sansui AU-5500 Integrated Amplifier has been completed.

The sound reproduced from the AU-5500 has become a sound quality that I can not believe to be an amplifier manufactured 43 years ago.

As a result of sound tuning, while keeping sufficient resolution and playback frequency range, it sounds a pretty dark sound. It is a very realistic sound such as jazz of 1950 - 60's.

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The front panel became beautiful, but the rust is floating on the rear panel, and it makes me feel old indeed as expected.

Also, as I was checking the sound after final assembly, I heard it as cloudy as the sound quality during muting (-20 dB) operation changed, so I replaced parts for metal film resistance from carbon resistance. Even at low volume it became pretty clear.

The replacement parts in this repair are as shown in the following picture. The total number of parts has now reached 64 pieces. Many parts deteriorated in nearly half a century, it was a timing just before a fatal failure occurred.

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I wanted to replace all the switches and the volume. But there is no compatible parts, so it became only life prolonging measures such as ultrasonic cleaning and contact revival.

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I hope that AU-5500 plays good music sound for a long time under the owner again.
posted by toons at 02:12 | Sound

2019/01/09

SANSUI AU-5500 repair - 9

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I'm running test running, but it is stable now.

It was clearer and more prospective sound than before it was repaired. Sound tuning to raise the resolution a little more and repair of the anxious place was done.

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Part 1: Change coupling capacitor
The coupling capacitor of the input signal of the power driver section was originally a standard electrolytic capacitor (ELNA 2.2 uF 50 V) was used.

I tried replacing it with an electrolytic capacitor for audio (TOSHIN UTSJ 2.2 uF 50 V) at this repair, but it was not feeling fit to this amp. For this reason, the coupling capacitor was replaced with a metallized polyester film capacitor (WIMA MKS 2 2.2 uF 50 V). I think that the resolution improved with this change and the sound quality was also improved considerably.

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Part 2: Capacitor change of high impedance compensation circuit
The Mylar capacitor (0.068 uF 50 V) that was connected to the final output stage was replaced with a film capacitor (WIMA MKS 2 0.068 uF 100 V).

Since all capacitors of the power driver section are supposed to be replaced, I think that it will lead to higher reliability of the amplifier.

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Part 3: Change of time constant of low cut filter
It has a function to cut low frequency with Low Filter switch. Original is a cutoff frequency of 70 Hz (-3 dB) which is a considerably higher frequency and is used to prevent low frequency resonance of analog records. Since it is not practical in modern times, I changed the filter time constant and set the cutoff frequency below 10 Hz.

Just at hand, there was a film capacitor (ROEDERSTEIN MKT 1818 0.33 uF 63 V) that sounds pretty good, so I adopted it.
If pop noise is mixed in from an external connection device, I think that it will be a countermeasure against it.

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Part 4: Replace the power cable
The original power cable was torn and the copper wire was exposed.
I decided to replace it with the 125V 15A cabtire cable on hand, but I had a hard time implementing it because it is a fairly thick cable. After all, it was able to attach to the cable gland part and pulled out to the tight.

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Part 5: Partial disabling of service outlet
The internal wiring of the service outlet was poor and I was concerned. Leaving only one outlet, we removed the wiring of the other two lines. Factors of power noise incorporation will also be reduced, and electrical security risks will also be reduced.

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Part 6: Change insulators
The original parts had hard plastic legs, but they were considerably deteriorated. I replaced it with an insulator with a metal cover. I had a solid foot around and it felt very good from a design point of view.

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Part 7: Nameplate of back panel
The nameplate of the back panel was in a beautiful state without miraculous scratches because the protective vinyl was affixed to the surface. Peel off old protective plastic and paste the liquid crystal protective film.

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In addition, I performed electrical checks at once and readjusted the offset voltage and bias current as the final adjustment of the power driver section.

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For this time, the bias current was set to 30 mA slightly deeper (setting standard: 25 mA } 10 mA). The distortion factor in the high range at the time of the small signal should be lower than the previous setting.

I will do continuous operation for a while, and will make the final assembly.

posted by toons at 06:28 | Sound

2019/01/07

SANSUI AU-5500 repair - 8

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In the power amplifier section, I adjusted the DC offset voltage and the bias current.

It seems that the original semi-fixed resistance seems to be considerably deteriorated, and it turned out that it shifts slightly every time it adjusts each time.

It is a carbon-coated type semi-fixed resistor that was used frequently in the past, but now it is a discontinuous component. As it is still an electrical part with moving parts, the resistance value seems to fluctuate considerably due to contamination of the internal electrode.

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I decided to replace it with a cermet type sealed semi-fixed resistor. It is some parts of Marine Blue which is very conspicuous on the board of the main amplifier part. Cermet has advantages such as good temperature characteristics and less noise generation due to sliding.

DC offset adjustment is like this, it was set to almost 0V. The recommended value is 0 V } 10 mV.

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In addition, I adjusted bias current and was adjustment while checking the sound quality with some current values.

The recommended value of the bias current is 25 mA } 10 mA, but I tried it with a slightly deeper 28 mA. In truth, I want to pass more bias current, but this is a balance with reliability.

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I tried to raise the bias current to 100 mA and listened to the playback sound in class A operation area, and it was confirmed that it reproduced with very good sound quality.

However, it is not likely to withstand practical use in this heat dissipation structure of this amplifier because the calorific value is too much. So it should set the bias current near the recommended value.
posted by toons at 08:34 | Sound

2019/01/06

SANSUI AU-5500 repair - 7

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The block capacitor in the main power supply was replaced.

The original block capacitor was ELNA 4700uF 50V (size: 35 x 70 mm).

Because the layout of the main power supply part of this amplifier was good, the temperature rise of the block capacitor was suppressed to the minimum and it seemed that it was not exposed to the thermal stress so much.

Apparently there is no abnormality such as expansion and leakage of electrolyte in particular, but electrolytic capacitor is an electronic part which easily deteriorates over time, so decided to replace it.

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The original two block capacitors slightly differed in feeling in hand. So, I measured each weight.

Then, it had a weight difference of about 10%. It seems that the internal electrolyte is getting dry up in 43 years. There is a high possibility that the electrostatic capacity is also decreasing. I think that I tried to replace it just in case.

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The block capacitor replaced this time is "Super Through" 4700 uF 63 V (size: 35 x 50 mm) of Nichicon's audio electrolytic capacitor KG series. It is a gold and black sleeve and a fearless appearance.

Electrolytic capacitors are now extremely miniaturized, and the size is not suitable for mounting in this amp, so it was very difficult to select parts.

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# NICHICON KG "Super Through" 4700F 63V
- Rated voltage: 63 V
- Rated capacitance: 4700 F (tolerance } 20%)
- Case size: 35 × 50 mm
- Loss angle tangent (tan ): 0.22
- Rated ripple current: 4.5 Arms
- Category temperature range: -40 C to + 85 C
- High temperature no-load characteristic: 85 C. 1000 hours

Even though it may be much bigger, the problem of rush current and the possibility of collapsing the sound balance are also high, so I kept it the same capacity.

This block capacitor adopts low resistance electrode foil for audio, and it can be expected quite a bit because tan is very small even at large capacity.

As soon as I switched on the power and tried to make a sound, I thought that the frequency range was narrow and I failed with a dull sound, but it gradually became clear in about 3 hours, the low frequency also steadily emerged It was.

Since new electrolytic capacitors also have thermal stress due to soldering, it is necessary to conduct electricity for several tens of hours until the internal anodized film self-recovers.

I think this capacitor is the most expensive among the parts that I exchanged, so I'd like it to work for improving sound quality.

posted by toons at 23:57 | Sound