af Tube mania » fre 28. mar 2014 11:25
Joo...det er fint og jeg er enig med dem i det meste...har nu ikke læst alt. Men jeg faldt over dette under'powe ratings'...ser ud som om de måler udgangsspænding UDEN belastning. Jeg er selvfølgelig enig med dem i at der ikke findes højtalere på bare 8ohm, men nogen belastning må man have for at få en ide om forstærkerens egenskaber. Man kan ikke afgøre noget ud fra en spændingsmåling og man kan i det hele taget ikke vide om forstærkeren fungerer som den skal. Jeg håber det er mig der ikke kan læse engelsk. Udover det mener jeg at en måling med 8ohms modstand kun er et hint om forstærkeres egenskaber.
Edit<; Hvis man gør som dem behøver man ikke måle pp med osc....man kan bare måle den samlede +- spænding over hoved elektrolytterne. Den vil være meget tæt på pp out....og ikke særlig interessant udover man så ved hvad udgangs transistorernes CE spænding bør være...gerne 50-100% mere.
WATTAGE vs VOLTAGE
Some examples we've found using 1kHz test tone, Peak Oscilloscope voltages read just before clipping of the wavetop.
Watts are RMS rated into 8 ohms from the manufacturer. We don't care about testing watts ratings as watts can be read high into distortion. We test using 1kHz sine wave at 0db playing both channels together & read off the voltages on one channel at the speaker connections with an oscilloscope (peak to peak, not RMS) to see the point of clipping. Read about RMS, Peak & Music power elsewhere. We don't use any loading as no speaker is an flat 8 ohm resistor in it's response, so only this gives a reliable comparision. With loading, the readings would differ & amps have different Damping NFB & Impedance, so we simplify it in our own way with just what clean sine wave maximum is available at the outputs. Amps differ in frequency responses as some are heavily rolled off after 50Hz & some can't make the full 20kHz. To do these extremes in testing would give very different values & some specs are rated eg 50w RMS at 1kHz but only 40w RMS at 20Hz to 20kHz. Some amps quote a Peak Power, this will not be a clean Sinewave & having pushed one amp that had a relay to protect it & it could read 25% higher before the relay clicked in, ie at 'destruction' & at almost the full HT voltage. Not one to want to test for either. Our tests appear to be reliable though some amps clearly use extra current capabilities to boost wattage as the list shows, if at the expense of clean AC output.
Luxman SQ38-DUAL CS5000-McIntosh- AMT1 -Altec Lansing model 19- Rectiliniar High Boy-Arena HT25
If your amp not damp turn the volume up a bit more..
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