The New iRiver/Astell & Kern AK100: A High-End DAP

[AnakChan]

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What they did I liken to "throwing stink bombs in an old folks home!" . Or lighting $#it on fire and leaving it on someones doorstep .

 
Oi! Who you're calling old!!?? 

 
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Well to be honest tds even if the longer cable helps it will still detract from the portability factor of it. Who wants to use a 10 foot cable on the go .
 

 
Well, I need a new belt anyway.
 
Jokes aside, that is a good find by Jan. I must say I never thought of it as way of increasing capacitance. I thought a longer cable (and interconnects or extended connectors) would increase resistance instead. But how that's different from adding a load impedance, I'm not certain. In fact I thought adding a load impedance is a lot more controllable. So much more technicalities I need to read up on.

 

[VisceriousZERO]

..before I pop on it.

............. .............

Missed an o?

 

[Vinnie R.]

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Dear headfellows,
 
As I don't own the AK100 myself I haven't read this thread, sorry. However, today I had a visit from a friend who recently bought this player and who was very unhappy with the sound in combination with his Ultrasone Signature PRO. It all sounded harsh and hollow and very clinical.
 
The strange thing was, that in combination with my T1 the player sounded much better and much warmer. Normally the Signature PRO has the deeper and stronger bass but not so on the AK100.
 
We increased the load impedance using a 120 Ohm adapter but that didn't help.
 
Next we used a cable-extension to increase the effective cable capacitance. That did help!
 
Next test: The SIGNATURE PRO comes with two cables, a short one and a long one. The long cable sounded much better.
 
So it appears that the player reacts strongly to the effective cable capacitance.
 
My suspicion is, that the output stage of the player is close to instability (or is already oscillating) when the cable capacity is very low (= the cable is short). I haven't done any measurements but members might be interested in doing some measurements and/or testing themselves.
 
Just wanted to share this idea with you!
 
Cheers
 
Jan

 
The high output impedance of the stock unit (22 ohms) combined with higher cable capacitance creates a 1st order low-pass filter (RC filter).  I'm not sure of the capacitance value of the cable is, and without that info, we won't know the cutoff frequency.  But I'm not surprised by Jan's findings based on this.
 
The stock output stage is not unstable or anywhere close to oscillating (I've measured it) with low cable capacitance (or no cable at all).  The fact of the matter is that with the stock 22-ohm output impedance, the other variables (cables, headphone specs.) will have a bigger role on the results (for better or worse) than if the output impedance was as low as possible...

 

[Achmedisdead]

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before I pop on it.

 

 

[goodvibes]

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The high output impedance of the stock unit (22 ohms) combined with higher cable capacitance creates a 1st order low-pass filter (RC filter).  I'm not sure of the capacitance value of the cable is, and without that info, we won't know the cutoff frequency.  But I'm not surprised by Jan's findings based on this.
 
The stock output stage is not unstable or anywhere close to oscillating (I've measured it) with low cable capacitance (or no cable at all).  The fact of the matter is that with the stock 22-ohm output impedance, the other variables (cables, headphone specs.) will have a bigger role on the results (for better or worse) than if the output impedance was as low as possible...

At 22 ohms the capacitance should be negligible. If it were an issue, having a headphone with a 22 ohm higher impedance would show the same effect. You'd need over 0.1uF to even consider an effect in the audio range and it's unlikely that there's even a nF in any cable. The instability he's speaking of would have to be represented by ultrasonic ringing which is likely what Jan meant and could in turn influence things lower down but I'd think you'd notice that on a scope. It could just be that decreasing the already marginal damping factor (with the 22r) is warming things up. The 2 wrongs sounding not as wrong scenario.

 

[tds101]

 :atsmile:

I guess I SHOULD poop on it instead???

 

[VisceriousZERO]

This thread goes from anger to analytical to poop quickly.

 

[Jan Meier]

Dear headfellows,
 
> Please do some tests with different hp's connected (RMAA), then post the graphs. And use the differing cable lengths to prove/disprove your results
 
I don't have an AK100 myself and my friend took his ones home. So I can't do any measurements.
 
> Otherwise opinions are opinions only.
 
No, it's just an observation that was made. And a possible way of direction that might be interested for you guys to investigate. Nothing more, nothing less.
 
> The high output impedance of the stock unit (22 ohms) combined with higher cable capacitance creates a 1st order low-pass filter (RC filter).
 
No, that's not the point here. Any high frequency signal at the electronics-site of the 22 Ohm resistor would still be seen by any feed-back circuitry, thus possibly causing oscillation.

However, be aware that at very high frequencies the electronic drivers (opamps) all have a rather high output impedance (which is lowered by the feed-back) and when the load impedance (22 Ohm + impedance of the capacity) is very low the high frequency signals are already attenuated at the output of the opamp by this internal high output impedance. This strongly reduces feed-back and thus possible oscillation. If the load impedance is higher, then such attenuation will not take place (or less strongly).
 
Be noted that, if cable capacity really does make a difference, then this effect could also be achieved by adding two small capacitors at the output (adapter or built into the cable) if you prefer to use a short cable. A typical cable capacity is 100 pF / meter so 220 pF or 330 pF capacitors may already make a difference.
 
> The stock output stage is not unstable or anywhere close to oscillating (I've measured it) with low cable capacitance (or no cable at all).
 
Be aware that measurement cables also add capacitance!!
 
Anyway, I only told you guess the observation that my friend and I made and a possible hypothesis of the cause. I have no intention proofing/solving/improving anything for myself, as I don't use the AK100 myself. That's all up to you!!
 
Have fun trying!!
 


Jan

 

[uelover]

Nice seeing you Jan popping by! =)

 

[Vinnie R.]

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Anyway, I only told you guess the observation that my friend and I made and a possible hypothesis of the cause. I have no intention proofing/solving/improving anything for myself, as I don't use the AK100 myself. That's all up to you!!
 
Have fun trying!!

 
It's already improved/solved by bypassing the 22 ohm output resistors 

 

 

[VisceriousZERO]

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It's already improved/solved by bypassing the 22 ohm output resistors 

 

 
Good one!

 

[FullCircle]

The sollution is simple:
 

 

 

[tds101]

The sollution is simple:

Right, buy your iem's to make a flawed player sound the way it's supposed to. No,...I don't think so. After investing $700 I'd rather pay for the RWA mod and be free to use ANY iem or headphone I choose.:rolleyes:

 

[ChrisSC]

The solution is simple:  how about we all agree to not buy this product until they fix it?

 

[audionewbi]

I would buy the Tzar 350 for its own sake not for the sake of AK100, having said that I am sure the match will satisfy a large portion of those who are not into upgrading.