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Author Topic: Bakoon HPA-01  (Read 8932 times)

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ultrabike

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Bakoon HPA-01
« on: October 12, 2014, 08:11:17 PM »
This is a fairly interesting amp. This amp seems to be able to behave as a voltage source or current source depending on headphone out. I used my HD600s to check out both ports.

Out of the voltage out it sounds pretty pleasant. More lower end impact and fun factor. Still, I wouldn't call this as overtly colored sound at all. In fact I like what I heard quite a bit. Good amounts of power reserves (though they seem to get consumed rather fast... this is sort of a rechargeable amp which adds to it's uniqueness)

Anyhow, using the current out definitively adds quite a bit of hump. It's a completely different story now. Hell of a lot more gain too. This is not subtle.

Here are some frequency response plots of my HD600s out of the 2i2, Bakoon voltage out and Bakoon current out:



Out of the voltage out I measured somewhere between 1.5 to 1.76 ohms output impedance. In current out all bets are off. There is a low and high gain switch which seems to do a whole lot of nothing when using the voltage outy. However, it does control gain of the current outy.

So from the voltage output I was able to get 3.39 Vrms into an open, 3.37 Vrm into a 300 ohm load, and 3.24 Vrms into 33 ohms.

From the current output in high gain mode I was able to get 9.78 Vrms into a 300 ohm load, and 3.3 Vrms into 33 ohms. In low gian mode I was able to get 5.57 Vrms into a 300 ohm load, and 0.626 Vrms into 33 ohms. Into an open I got all kinds of weirdness.

As far as THD, different results depending on the output port. All of the following were taken @ around 400mVrms and -6dBFS from the Focusrite DAC line out. Current output was in high gain:

THD 1 kHz 300 ohm (voltage out)



THD 1 kHz 33 ohm (voltage out)



THD 1 kHz 300 ohm (current out)



THD 1 kHz 33 ohm (current out)

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ultrabike

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Re: Bakoon
« Reply #1 on: October 12, 2014, 08:12:17 PM »
IMD (similar THD measurement conditions)

SMPTE 60Hz 7kHz 4:1 300 ohm voltage out



SMPTE 60Hz 7kHz 4:1 33 ohm voltage out



SMPTE 60Hz 7kHz 4:1 300 ohm curorent out



SMPTE 60Hz 7kHz 4:1 33 ohm current out

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ultrabike

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Re: Bakoon
« Reply #2 on: October 12, 2014, 08:18:29 PM »
If I was to nitpick Mr Bakoon HPA-01 it would be on the need to charge it before using it... There is IMO a high WTF factor with that. But then again, there is some uniqueness to it as well given it's current output port and IMO sounds pretty darn decent.
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OJneg

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Re: Bakoon HPA-01
« Reply #3 on: October 12, 2014, 10:10:53 PM »
Wow, that's a major difference in THD performance with current out. I wonder what's going on inside...

This is also one of those cases that if you were to look at static RMAA read-out, you wouldn't say there's much of a difference between .0181% and .0159%. Looking at the spectrum plot tells a whole different story.
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Marvey

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Re: Bakoon HPA-01
« Reply #4 on: October 12, 2014, 10:20:42 PM »
Current Out distortion measurements look amazing?
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Anaxilus

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Re: Bakoon HPA-01
« Reply #5 on: October 12, 2014, 10:35:28 PM »
Quote from: marvey on October 12, 2014, 10:20:42 PM
Current Out distortion measurements look amazing?

Sadly, apart from the HD600, I didn't notice any other phones benefiting.  Quite the opposite in fact.  So something else is going on too.  Looking at the distortion you'd expect a sea of clouds to part and let the rays of sunshine  illuminate your recordings.  Doesn't really happen.
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ultrabike

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Re: Bakoon HPA-01
« Reply #6 on: October 12, 2014, 10:42:26 PM »
Well... Higher order harmonics perhaps look relatively clean from current out. However, for 300 ohms, IMD second order harmonics seems close. For 33 ohms it seems IMD second order harmonics are better on the current out though. Note something is up with noise floor with 300 ohms from the current out.

THD second order harmonics also look kind of close for 300 ohms. Again, noise floor seems higher with 300 ohms for current out. I dunno if current out likes highish impedance. Things got weird into an open.

(EDIT: yup, current out looks pretty clean compared to voltage out)

All that said coloration will happen with current out, and bass may get bloated too. I think there was a paper by Nelson Pass about current out stuff amps for speakers (which tend to be low impedance loads). He seemed to have built quite a bit of analog equalization stuff into them (perhaps due to similar coloration issues or to fine tune things). Maybe with certain loads there are some distortion gains to be had. Dunno, pure speculation on my part there.
« Last Edit: August 07, 2015, 10:19:32 PM by ultrabike »
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Armaegis

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Re: Bakoon HPA-01
« Reply #7 on: October 13, 2014, 12:42:16 AM »
I'd be curious to see the behaviour with something like the Senn HD595/598 which has a much larger impedance spike. Or perhaps a multi-driver iem with wonky curves.
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Anaxilus

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Re: Bakoon HPA-01
« Reply #8 on: October 13, 2014, 01:05:59 AM »
Quote from: Armaegis on October 13, 2014, 12:42:16 AM
Or perhaps a multi-driver iem with wonky curves.

I've done it with the UERM, it's awful.  I'll have a review up next week.  Just busy with other stuff atm.
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Marvey

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Re: Bakoon HPA-01
« Reply #9 on: October 13, 2014, 01:47:07 AM »
Quote from: ultrabike on October 12, 2014, 10:42:26 PM
Well... Higher order harmonics perhaps look relatively clean from current out...

All that said coloration will happen with current out, and bass may get bloated too.

Wonder how figures would be with headphones with flatter imp. curves? Still have the PM-2?
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