Појачало 41Hz Audio AMP9 (4x50W na 4Ω при мало изобличување, 4х100W пик)

[van]

Моето прво рачно направено појачало, 41Hz Audio AMP9 kit.  

41Hz Audio AMP9 kit. 28V max, tall capacitors

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http://shop.41hz.com/shop/item.asp?itemid=35

4 channel amps for 24V and low impedance loads

    * Four channels of Tripath sound quality, based on Tripath TAA4100A
    * Output 4x50W at low distortion, 4x100W peak
    * Suitable for low impedance loads, 4 x 2 ohms 12V typical
    * Up to 27V supplies makes this model suitable for 12 or 24V systems.
    * Outputs can be paralleled for even higher outputs into very low impedance loads
    * Mostly hole mounted components. Relatively low component count.
    * 35A rectifier on board
    * Board size 50 x 160 mm
    * Height 60 mm with 3 x 15.000 uF 35V bulk capacitors for up to 27V supplies (standard model)
    * Low profile version 30 mm with 3 x 12.000 uF 16V capacitors for 12V supplies

Појачалото е сместено во адаптирана кутија од стар UPS. Најмногу работа имаше баш на кутијата, инаку треба уште неколку работи да се изведат:
- да поставам парче метален лим меѓу трансформаторот и плочката од појачалото (заради магнетот, инаки колегите ми велат дека сум параноичен во врска со ова )
- да го сместам рачно направениот GrubDAC (USB DAC)



Не сакав да ви го успорувам вчитувањето на странава па за подетални фотографии кликнете на линкот од сликиве, па на страната од Flickr кликнете на Actions (менито над сликата), па на View All Sizes (најголемата резолуција е 1024х768)


Amp9_01 by vanlok, on Flickr



Amp9_02 by vanlok, on Flickr



Amp9_03 by vanlok, on Flickr



Amp9_04 by vanlok, on Flickr



Amp9_05 by vanlok, on Flickr

[batka]

Интересен проект во Т класа,италијански ,првобитно предвиден како ауто-појачувач.Не сум го чул до сега,па *развртив* малку и еве некои прикази:

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http://translate.google.mk/translate?hl=mk&sl=en&u=http://www.diyaudio.com/forums/class-d/116262-tripath-taa4100a-issues.html&ei=3eF9TtDsFuai0QWX0qj6Dw&sa=X&oi=translate&ct=result&resnum=2&ved=0CCYQ7gEwAQ&prev=/search%3Fq%3DTripath%2BTAA4100A%26hl%3Dmk%26prmd%3Dimvnsfd

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http://www.tnt-audio.com/ampli/autocostruire_mc4x100_e.html

[van]

Дап, првобитната чивија ми влезе баш од tnt-audio.com чланакот за италијанскиот модул, уште пред неколку години.

Изведбата на 41Hz чијшто кит го купив е поекономска варијанта и целосно направи сам кит (за разлика од Италијанците кои продаваат готова плочка). 41Hz се од Шведска иначе.

[batka]

Мислам дека сепак е доста скапа варијанта.Набрзина не прочитав - какви заштити има појачувачот ? И сепак,се на едно ИК.... Јас лично не сум присталица на вакви интегрирани излези.Колку те чинеше USB DAС плочката? Јас направив една комбинација со УСБ читач на SD картици,кој има МР3 аудио излез и УСБ влез. Преку лап-топ внесувам песни на картицата, вршам измени,бришење,впишување, а репродукцијата си оди континуирано.Ме чинеше 400 ден и сеуште работи добро.Ги произведува Гембирд, а се напојува со 1,5в батерија.

[van]

Колку те чинеше USB DAС плочката?

Китот што јас го земав (без пластична кутија и други некои додатоци) беше 35$ (плус поштарина)

[batka]

Разумна цена

[van]

Јас уште не сум направил некакви озбилни мерења (проектите со звучните кутии ми се приоритет во моментов), ама еве некои мерења од форумот на сајтот.

http://www.41hz.com/forums/showthread.php?3436-AMP9-performance-measurements
http://www.41hz.com/forums/content.php?355-AMP9b-measurements

Done tests now:

• First I left it idle, unmuted (no input) at 30V overnight. No problem.

Then for the real test:

• My voltage adjustable PS can deliver 6A / 32V
• So I obviously could not test more than one channel at high power
• With a 4 ohm load the 6A would be reached at around +/-24V minus voltage drops.
• So I hooked up a 4.7 / 50W resistor. and power up. It reached a frying 200 deg C in about 10 minutes so I had to hook up my big 4 ohm 600W load. I will post pictures later today.
• The PS / amp combination typically wobbled a bit so the highest nominal voltage I could use was 28.5V. Above that the amp would trip for overvoltage.
• I used a pink noise generator as signal source and tested with up to 4V ptp signal however, the current protection of the amp or PS (TBD) kicked in at those levels, making it run ntermittently. If I limited the output to a bit above +/-22V, (probably limited by the power supply overcurrent setpoint) it was all running smoothly. This would be equivalent to is around 60WRMS
• My TRMS meter is limited to 2A so I had to rely on eyesite and estimate an average of around 2-2.5A average, with peaks up to 6A (power supply current limit LED blinkig)
• The setup has been running for a couple of hours like this now with no problems.

I will add a large cap to see if I can increase the average load without trigging peak load problems.

• Summary so far: 30V at idle no problem
• 28.5V average at high power is also OK
• Overvoltage kicks in at around 30.5V and restarts again at around 25V
• I have not managed to do damage dispite moving up to the voltage limit under high output power a large number of times

Important The overvoltage limit is not a true protection. It shuts of the amp at too high voltage but does NOT protect from excessiv overvoltage. It simlpy shuts down the amp and this has two advantages:[LIST=1]

• You get a warning that something is wrong
• The shutdown stops any power supply instability that may have caused the overvoltage (peaks).

But again, the amp may / will probably be damaged by voltages above 30V, it should survive 33V and 60V spikes for 8 milliseconds according to chip specs. I have tried up to 32V without damage.
 
Note that the tests where with a single channel used only. The other channels had no input signal and a 10R resistor over the speaker conns. Tests where done with the new smaller output protection diodes but that should not make any difference.

ere are some more measurement results for AMP9
 

1) Power supply = 24VDC, input signal sinusidoal 0.41VRMS, 1KHz. Load 4 ohm resistive. The average current was about 2.7A RMS

Here we see a nice clean output signal, at a bit above 20VRMS. There is a small distortion at 2KHz but I am not sure if it's in the input signal or not.
 

2) Same as above but now 0.47VRMS input. Signal is now clipping which is clearly visible by all the additional spikes. If we had a normal scope type graph, we would see that the signal is no more nicely sinusidoal but the tops are flat because the output can not be any higher than the supply voltage. The level where the output clips is SUPPLY VOLTAGE dependent. The average current was a bit above 3A RMS in this case.

 
 
3) Pink noise signal, 28.5V supply, 4 ohm load. The input signal was turned up until the amp overcurrent protection turns it of in the peaks. The gap you see is about 0.55 seconds long. The peaks are nicely at around +/-23V peak to peak, indicating that the signal is clipping more or less all the time. The average current was somewhere between 1.5Amp. (pink noise has an average frequency distribution that similar to the average frequency distribution of music)

With a 4 ohm load and 24V supply, I could not reach the overcurrent limit, even with considerable clipping. This is the way we want it. The amp should not reach the overcurrent limit even under high power. It should only happen for example if outputs are shorted.
 
A PS on merasurements: amps with bridged outputs can not be measured ground referenced. The measurements must be floating, using a floating, non-grounded instrunment or an isolation transformer or other differential, non-ground referenced measurement. Most measurements showne here where done with an instrument with fully differential inputs.



More AMP9-BASIC measurement results.
 
First a case with 24V supply, 1KHz signal, 4 ohm load and varying the output level. We can
see a sweet spot at around 10VRMS output and when output reaches 11VRMS, the output starts clipping and the THD goes up. This is at about 30WRMS and the suppy current is then about 2.8A per channel. At 1% THD, the current is around 3.4A and output around 13.7VRMS or 50WRMS

 

Same but 12V supply, 4 ohm load



And here 12V supply case with 2 ohm load.

 

Finally a measurement at 28V supply, 13VRMS into 8 ohm, equivalent to 20W utput, while varying the frequency. Over a wide area the THD+N is in the 0.01% region, 0.007% at the best, 0.07% at worst.