HV 11 Headphone amplifier

[vale25]

Hello,

I built an HV 11 headphone amplifier starting from a chinese board (but using trusted components).
ZEROZONE HV11 Full discrete no feedback Direct coupling headphone amplifier board L6 20|Headphone Amplifier| - AliExpress
It is based on the CKII circuit from amb, except for the differential input transistor, (I've used bc550/60 instead of the discontinued toshiba 2sk170 and complementary JFETs). Moreover, the power supply is different too, with a classic 4-diodes bridge and tons of capacitance (3*470uF) after each lm7X15 regulator. I also added a protection board, wich has is proper rectifier bridge and regulators, using the same 15V-0-15 V transformer to power both the boards.
E12-I Protection circuit board support 2,3,4 channel for headphone amplifier | eBay

Now, altough the amplifier seems to work, and I have near to zero CC at the output, sometimes, for no apparent reason I have a "pop" or a "tac" noise on both channels. Moroever, when the amplifier has been turned on from a long "switch off" time, if I insert the headphones jack I can hear a really creepy shrill and strident sound on both channels (this sound ends when the jack is fully inserted), and the phenomenon disappear after some minutes.

Does anyone have some idea of what is going on? 😀

 

[adason]

Yes, none of your modifications make any sense. You should leave it as it was. It works great that way.

 

[vale25]

Of course none of them were made with the aim to improve the amp. I simply followed the chinese board for caps, and I used BJT at the input cause they are way cheaper than matched pairs of discontinued toshiba JFETs. Anyway, the original Kumisa III that inspired the AMB CKII uses BJTs as input transistor as well. The Kumisa III Headphone Amplifier. – HeadWize Memorial
Could you please clarify what are the issues with the modifications?

Do you refer to the original AMB or to the HV11 clone when you say it works great? Because the clone already uses bc547/557 as input pair (and more caps too after regulators).

Edit: I forgot to say that I have the same casual popping also bypassying and disconnecting from power the protection board

 

[adason]

first, you do not replace bjt and jfet in the circuit, without proper redesign and modifications
second, you do not put large amount of capacitance after the voltage regulator, that prevents it to work properly, you put caps before the reg
the design has servo to prevent dc on the output
no need for additional protection
third, if you would use all the supplied parts from zerozone, and followed that schematics, it would work perfectly
i have it, it works without any flaws
that's all

 

[vale25]

first, you do not replace bjt and jfet in the circuit, without proper redesign and modifications
second, you do not put large amount of capacitance after the voltage regulator, that prevents it to work properly, you put caps before the reg
the design has servo to prevent dc on the output
no need for additional protection
third, if you would use all the supplied parts from zerozone, and followed that schematics, it would work perfectly
i have it, it works without any flaws
that's all

Maybe I was not clear. I exactly followed the design from zerozone. The differences I'm referring to (bjt instead of jfet, mor caps after regulator), are already in the zerozone board, with respect to the original design from amb (surprise! your chinese ampli is not an original design). You say you have it. Did you notice that there is no JFET at the input stage of your chinese clone?

 

[adason]

Sorry, I misunderstood your post. I though you took zerozone and mod it to original with jfets.

 

[vale25]

No worries

 

[kozard]

I don't know if you got your HV11 working properly in the end. However I would like to know what Zerozone HV11 owners think of the finished kit relative to other available headphone amplifier kits.


If you have the Zerozone HV11 is it your best headphone amplifier? If not, which is your best?