[Paul - iBasso]

Got my iBasso CF-01 yesterday but only get to listen to it today. So here are a few impression:

1) The design of the case is very nice - roomy on the inside, even for a pair of CIEM. I especially like the built-in air cushion that will offer quite a lot of protection to the earpiece.

2) I COMPLETELY dislike the smooth outer finishing of the case - it is very slippy and I almost had the case flying out of my hand a few times when I tried to open the case by one hand.

3) The adapters themselves are nicely finished.with a blend of plastic and metal. The actual size is even smaller than TRN BT20s / FiiO UTWS1, but so are the overall battery life (if you don't consider the battery case). Cable isn't rigid like other but not completely soft either, which I like. Button placement on the top is acceptable, though I prefer it on the side.

3) No hissing detected with my MassDrop Plus.

4) Output impedance is a WHOOPING and very disappointing 20 ohm (measured twice to confirm, which kinda explain why it doesn't hiss at all)

I listened to CF-01 with my dual driver MassDrop Plus first, and it sounded very warm and almost slightly veil - which is not the normal MassDrop Plus's warmish neutral reference sound that I am fairly familiar to, and that made me feel suspicious. A quick measurement revealed that the CF-01 has a very much unforgivable 20 ohm output impedance and that just mess up how MassDrop Plus is supposed to sound. In contrast, OE Audio WS-1 manages just 0.5 ohm of output impedance even though it hiss very faintly with Massdrop Plus (*only on near silence passage and usually close to undetectable during music playback). With an MMCX-to-2-pins adapter, I listened to CF-01 again with MoonDrop SSR (*which is one of my recent good find) - being a single dynamic that doesn't get affected much by output impedance, SSR sounds much more 'correct' than Plus. I can tell SSR still sounds slightly warmer, richer and smoother than usual, but at least it is not offensive.

At this point I am not sure I'll recommend CF-01 - it does a lot of things right, namely the premier overall design and the finishing of the adapters; But it has its faults as well, namely the overly smooth outer finishing and that 20 ohm elephant in the room that can't be ignored by anyone who intends to use CF-01 with multi-driver IEM (*which will probably be like > 90% of people out there these days). Ouch! (and considered this is by far the most expensive TWS adapter I bought yet!!!)

The output impedance is around 1 ohm, not 20 ohms.

 

[monsieurfromag3]

Plot thickens!

 

[frix]

Thak you clieOs for pointing out the output impedance issues.

 

[ClieOS]

The output impedance is around 1 ohm, not 20 ohms.

Just measured it again
(with 1kHz pure tone and True RMS multi-meter)

Right: No load 0.169V
Left: No load 0.170V

Right: 47ohm load: 0.118V
Left: 47ohm Load: 0.118V

Output Impedance Formula: [ (VnL - VL) / VL ] x R
VL = Voltage Loaded
R = Load resistance
VnL = Voltage no load

so just taking Left
[(0.170 - 0.118)] / 0.118 x 47 = 20.7 ohm

 

[lightlight]

@ClieOS Thank you Bro! Been waiting for your review all this while.. Wondering if the impedance issue will be an issue with my earphones .. I want to pair this with my se846.. Which has an impedance of around 10 ohm if I am not mistaken.. What do you guys think?

 

[Paul - iBasso]

Just measured it again
(with 1kHz pure tone and True RMS multi-meter)

Right: No load 0.169V
Left: No load 0.170V

Right: 47ohm load: 0.118V
Left: 47ohm Load: 0.118V

Output Impedance Formula: [ (VnL - VL) / VL ] x R
VL = Voltage Loaded
R = Load resistance
VnL = Voltage no load

so just taking Left
[(0.170 - 0.118)] / 0.118 x 47 = 20.7 ohm

You have our CF01 outputting 0.17V, this needs to be increased to the output of 0.4~0.5V when doing this measurement. The output impedance of the CF01 is right around 1 ohm. We would not produce the CF01 to be 20 ohms, that would not work well with many IEMs.

 

[ClieOS]

@ClieOS Thank you Bro! Been waiting for your review all this while.. Wondering if the impedance issue will be an issue with my earphones .. I want to pair this with my se846.. Which has an impedance of around 10 ohm if I am not mistaken.. What do you guys think?

The general guideline is that the headphone used should have at least 8 times the impedance of the source's output impedance to avoid FR interference. SE846 probably best used with source of sub-1 ohm output impedance if you want to keep to its original sound signature.

You have our CF01 outputting 0.17V, this needs to be increased to the output of 0.4~0.5V when doing this measurement. The output impedance of the CF01 is right around 1 ohm. We would not produce the CF01 to be 20 ohms, that would not work well with many IEMs.

Just doing one side to save time: Same setup as before, doing it on very low and very high voltage to cover all the bases.

No load: 0.041V
Loaded: 0.029V
[ (0.041V - 0.029V) / 0.029V ] x 47 = 19.4 ohm

No Load: 0.425V
Loaded: 0.297V
[ (0.425V - 0.297V) / 0.297V ] x 47 = 20.3 ohm

No real difference detected.

Besides, how many IEM can take 0.4V for volume?

 

[Paul - iBasso]

The general guideline is that the headphone used should have at least 8 times the impedance of the source's output impedance to avoid FR interference. SE846 probably best used with source of sub-1 ohm output impedance if you want to keep to its original sound signature.



Just doing one side to save time: Same setup as before, doing it on very low and very high voltage to cover all the bases.

No load: 0.041V
Loaded: 0.029V
[ (0.041V - 0.029V) / 0.029V ] x 47 = 19.4 ohm

No Load: 0.425V
Loaded: 0.297V
[ (0.425V - 0.297V) / 0.297V ] x 47 = 20.3 ohm

No real difference detected.

Besides, how many IEM can take 0.4V for volume?

It is the weekend. I will post some images on Monday and show you what the output impedance is. It is not 20 ohms. Many IEMs would not even sound good at a 20 ohms output impedance.

 

[ClieOS]

It is the weekend. I will post some images on Monday and show you what the output impedance is. It is not 20 ohms. Many IEMs would not even sound good at a 20 ohms output impedance.

The number of my measurement say otherwise and I am not sure how you can disprove that, but I'll entertain the idea. On other hand, it was because my Massdrop Plus doesn't sound good with CF-01 that I went to measure it in the first place.

 

[ClieOS]

Small update: over the weekend I got confirmation from another owner that his measurement also indicates CF-01 has an output impedance of 20 ohm.

 

[lightlight]

Small update: over the weekend I got confirmation from another owner that his measurement also indicates CF-01 has an output impedance of 20 ohm.

Aiyoh! iBasso why like that? Now I am looking to get the shure aonic adapter.. I do not need their SE215...just need that adapter. The reason why I still prefer that over the CF-01 is because of the convenience in charging.. charging the two sides individually seems like an major annoyance, especially in a product that was made for convenience in the first place.. I mean convenience is one of the key selling points of true wireless earphones right?

 

[ClieOS]

Aiyoh! iBasso why like that? Now I am looking to get the shure aonic adapter.. I do not need their SE215...just need that adapter. The reason why I still prefer that over the CF-01 is because of the convenience in charging.. charging the two sides individually seems like an major annoyance, especially in a product that was made for convenience in the first place.. I mean convenience is one of the key selling points of true wireless earphones right?

Isn't all TWS adapters needed to be charged separately, regardless whether it is with a cable or a battery case?

 

[Ocelitgol]

What's a cheap and easy way to measure OI? I'd love to confirm this myself

 

[ClieOS]

What's a cheap and easy way to measure OI? I'd love to confirm this myself

It isn't going to be particularly expensive but definitely not going to be easy.

The tool you need are: First, a load (basically a pair of resistors will do, but keep it to decent wattage rating as you can burn the resistor if the wattage rating is too low). Secondly, you need a volt meter or multi-meter that can measure AC down to mV. Lastly, you need a source (some kind of DAC if the thing you want to measure doesn't have its own). In case of TWS adapter, which already has a DAC inside, you need a frequency generator app that can generate a pure tone. Since my multi-meter is pretty good, I use 1kHz pure tone. For lesser multi-meter, 500Hz pure tone should be used. As it is not easy to measure TWS adapter directly on the MMCX socket or have a load attach to it while still able to measure it directly, I actually also make an custom adapter cable and load in order to make measurement easier and more repeatable (see picture below).

The measurement process is simple: First set the TWS adapter to a decent volume, measure the output without any load. Then measure again with the load, follow the formula I have given previously and you can calculate out the output impedance. Note that usually you don't want to set the volume too high in case there is clipping that will affect the result. You can repeat the measure on different volume setting to double check.

 

[shortstories]

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