Srovnávací měření zesilovačů (Purifi,DPA,PMA...) sjednocenou metodikou (Stránka 3 z 3)

LOAD1 https://www.tme.eu/sk/cs/details/hs200- … s200-8r-f/ , dva paralelne

LOAD2 8x 0R5 do serie, prichytene na velky chladic cez termal pady 
https://vi.aliexpress.com/item/10050071 … ry_from%3A

toto cele este ide na chladic

Zalezi aj na spojoch/konektoroch, nemagneticke musia byt.
Este v roku 2019 som pisal s Amirmom z ASR

Laco: Hi, what dummy load do you use when measure very low thd amp ?
I use a pair of ARCOL resistors: https://eu.mouser.com/ProductDetail/Ohm … cycode=USD
The standard in the industry is the Dale version but they are more than twice the cost and they are rarely in stock. I compared them to the ones above and performance is identical. The Dales do have much beefier heatsinks on them. I have mine mounted to a chassis so that is not a big consideration.

Laco: How important is VCR in the case of dummy load ?
It depends on the damping factor of the amp. In the case of the Benchmark AHB2, it made at least a 10 dB difference in third harmonic distortion. WIth my old dummy loads which high VCR, I could not measure better than 105 dB SINAD.

I experimented with all aspects of that and was surprised that the resistor was the worst offender. After that, the speaker terminal/connection became dominant. Wiring was not an issue surprisingly (using Kelvin type connection of course) in the variations I tested.
For Benchmark, I had to get down to -130 dB which required everything lining up.

Laco: I found cheaper HS300 in TME (europe) https://www.tme.com/us/en-us/details/hs … s300-8r-f/
Unfortunately that is not the one I bought. It is missing the letter "N" from the start of the part number which indicates low inductance. They don't specify what the difference in inductance is so hard to tell whether it makes a difference. Given the critical nature of my work, I went ahead with the low-inductance version.