WolfX700 Measurements of Topping Pre90/Ext90 Preamplifier/ Extender

[Michal]

Bravo Topping, but if they could offer multi-channel D90 + digital crossover + Pre 90 in one box (my little dream) they would probably break the bank.

 

[MusicNBeer]

Can you use XLR and RCA as two separate inputs?

 

[777]

What's the value of the input impedance ?

 

[Max]

@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]

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

 

[raif71]

I suppose I can just get the ext90 only and use with existing amp?

 

[gvl]

What's the value of the input impedance ?

That is the question. John likes it low, which would be a flaw for a preamp.

 

[JohnYang1997]

That is the question. John likes it low, which would be a flaw for a preamp.

It's the same low impedance. If anyone what it high, don't buy.

 

[gvl]

It's the same low impedance. If anyone what it high, don't buy.

OK, I won't. I was looking forward to it but IMO this is unacceptable for a pre as it should be properly buffered to work with a variety of sources, DC coupled or not.

 

[seashell]

How low is low? An actual value would be more useful.

 

[gvl]

Sounds like it's 2kohm, give or take.

 

[ririt]

That should work for HT Bypass, setting the gain to 0db.

Lack of a 12v trigger hurts the functionality

Right a trigger will be the cherry on the cake!

 

[seashell]

Sounds like it's 2kohm, give or take.

Thanks. I gather this is typical for all topping devices with analog inputs?

 

[gvl]

Thanks. I gather this is typical for all topping devices with analog inputs?

Not sure about all, but A90, L30, A50s, and this, thanks to John's obsession to lead the SINAD chart.

 

[win]

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

 

[seashell]

Not sure about all, but A90, L30, A50s, and this, thanks to John's obsession to lead the SINAD chart.

Heh. I was thinking that was probably the reason for the choice after you posted the value.

 

[gvl]

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.

 

[WolfX-700]

@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]

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

Dashboard 0dbrA set on 5V:

 

[WolfX-700]

That should work for HT Bypass, setting the gain to 0db.

Lack of a 12v trigger hurts the functionality

My goodness...I also suggested adding a trigger function... But it was rejected by Topping...

 

[Max]

View attachment 94446
Basically the measurement result is limited by... APX-555

Thanks Wolf !
The effect of the internally gain switching is well shown. And indeed, the APX's noise floor seems dominating the measurement.