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WolfX700 Measurements of Topping Pre90/Ext90 Preamplifier/ Extender

Max

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#44
@WolfX-700 Is it possible to measure THD+N vs Volume adjustment (or vs "time" by adjusting volume manually, if more convenient) with a nominal fixed voltage at the input ?

To see the pros of [fixed DAC + Pre] versus [adjustable DAC]
 

win

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#45
Kudos to topping for the measurements, and thanks for filling in niche gaps!
 

win

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#55
Don't want to hijack this thread, but I'm sure there are plenty of us who would love an education on why low input impedance is good/bad. The Schiit Freya S looks like the most direct competitor to this preamp, at least in terms of use case, and it doesn't even list input impedance. https://www.schiit.com/products/freya-1
 

gvl

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#57
Low input impedance is particularly problematic when the source output impedance depends on the frequency, such as in case of capacitor coupled outputs which are common in older gear, and you end up with low frequency droop. There's nothing good about low input impedance, in this instance it's a side effect of omitting the input buffer with the only reason to post a good SINAD value on this forum. If you think about it, it's those with legacy gear who should be the target customers for such a preamp, yet due to its low input impedance it may not be an ideal pairing.
 
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WolfX-700

WolfX-700

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Thread Starter #58
@WolfX-700 Is it possible to measure THD+N vs Volume adjustment (or vs "time" by adjusting volume manually, if more convenient) with a nominal fixed voltage at the input ?

To see the pros of [fixed DAC + Pre] versus [adjustable DAC]
SINADvsVolumebmp.jpg

Basically the measurement result is limited by... APx555...

Dashboard 0dbrA set on 5V:
-20Dash.jpg

-30Dash.jpg
-60dash.jpg
-90Dash.jpg
 
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