That cable will work. On your amp you also need to provide a load similar to what the amp will see. An easy way to do this is if you have a 4pin XLR out as well as the 1/4" out on your amp, then you can buy a male 4pin XLR connector and solder in some 300 ohm resistors for each channel (to mimic a 300 ohm Sennheiser or ZMF load). Plug that 4pin XLR connector with resistors in at the same time as you are running the 1/4" out to the Motu.
On your amp you also need to provide a load similar to what the amp will see. An easy way to do this is if you have a 4pin XLR out as well as the 1/4" out on your amp, then you can buy a male 4pin XLR connector and solder in some 300 ohm resistors for each channel (to mimic a 300 ohm Sennheiser or ZMF load). Plug that 4pin XLR connector with resistors in at the same time as you are running the 1/4" out to the Motu.
You can definitely do that as well if you are only testing each tube or amplifier swap at a specific frequency. That would give you the particular distortion measurement at that specific frequency for that specific headphone. But as jonathan says, the impedance of a headphone will vary with frequency, so a frequency sweep (for measuring frequency response and distortion measurement across frequencies) would be affected by the headphone plugged in.
You can definitely do that as well if you are only testing each tube or amplifier swap at a specific frequency. That would give you the particular distortion measurement at that specific frequency for that specific headphone. But as jonathan says, the impedance of a headphone will vary with frequency, so a frequency sweep (for measuring frequency response and distortion measurement across frequencies) would be affected by the headphone plugged in.
I found those meters We had a bit of "trial and error" getting them to work properly, but I'm glad Mischa did as they do look nice. You are teasing us tho..... by only showing one...
I rather like the decibel meter implementation on my Luxman amp. I feel as far as meters go this is one of the more practical ones to have as it shows you visually how much headroom you have left at the volume level you are currently playing at.
You can definitely do that as well if you are only testing each tube or amplifier swap at a specific frequency. That would give you the particular distortion measurement at that specific frequency for that specific headphone. But as jonathan says, the impedance of a headphone will vary with frequency, so a frequency sweep (for measuring frequency response and distortion measurement across frequencies) would be affected by the headphone plugged in.
Keep thinking about this... So, any advantage or disadvantage of using such box as a dummy load on the 2nd headphone jack vs. being a pass-through between the headphone amp and the Motu M4?
Keep thinking about this... So, any advantage or disadvantage of using such box as a dummy load on the 2nd headphone jack vs. being a pass-through between the headphone amp and the Motu M4?
As long as the 4pin XLR and the 1/4" outputs are the same (i.e. you aren't trying to measure an amplifier that has separate balanced and summed single ended outputs), then either of these will be equivalent. If you plan to measure solid state amps that are inherently balanced but have summed single ended, then go with scenario 2. If just using for single ended tube amps, then you can go with either
As long as the 4pin XLR and the 1/4" outputs are the same (i.e. you aren't trying to measure an amplifier that has separate balanced and summed single ended outputs), then either of these will be equivalent. If you plan to measure solid state amps that are inherently balanced but have summed single ended, then go with scenario 2. If just using for single ended tube amps, then you can go with either
Thanks Mischa. For the dummy load resistors - would 5W resistors be enough? I know @L0rdGwyn used much more substantial resistors, but then again he plugs it to the speaker taps. Not headphone out...
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We had a bit of "trial and error" getting them to work properly, but I'm glad Mischa did as they do look nice.
