[w62820616]

With the employ of current mirror buffer, the peak current per channel can be around 200ma (15ohm load)
 
Use 1% dale resistor , the channel difference is less than 2%

 
The band with is around 1.1MHZ

 
Starting Freq. 1KHz Amplitude 1.0V pp

End cut off Freq 1.1MHz. -3 dB 1Vpp ->0.707Vpp

 
100KHz Square wave, no over shoot, no ring 15ohm load

 
Back ground noise per channel is hard to test, I turn off the machine and the scope shows 10mVpp, but when I turn on the machine the scope still shows 10mVpp, I think the scope is picking up the noise in the lab.

 

[cfcubed]

I see you've solicited the help of this DIY community in designing "your" headamp.
Do you plan to offer a low- or no-profit kit or PCB to the DIY community?
Otherwise I don't see why we'd care about your post above.

 

[w62820616]

Quote:

I see you've solicited the help of this DIY community in designing "your" headamp.
Do you plan to offer a low- or no-profit kit or PCB to the DIY community?
Otherwise I don't see why we'd care about your post above.

 
I will make a no-profit kit if I could find more of that earphone jack(I only have 4 left). Also I don't know if I should match the transistor/resistors or not. I am currently working on the 2nd edition of that board. Trying to improve wiring and add in more features. I am currently a full time student who about to graduate and going to the military. So maybe if I can't make the kit I will just mail the extra PCBs for free to the people who helped me.

 

[Avro_Arrow]

You mean this earphone jack?

 

[w62820616]

Quote:

You mean this earphone jack?

 
 
It has to be threaded otherwise the board is secured by the pot only.

 

[Avro_Arrow]

So this one...

 

[w62820616]

Quote:

So this one...

Thanks !!! There are couple things I need to decide before I finalized this project and make a kit.
1. The resistor value between the opamp and the transistor buffer (currently 1k for BJT 400ohm for FET)
2. The resistor value between the output jack and the transistor buffer(currently 15ohm)
3. Should I use inductor at the output instead of resistor (like AMB mini3)
4. Should I use large value feedback resistor to reduce the output DC offset (BJT opamps) (will induce more noise_
5. Should I use small value feedback resistor to reduce the background noise (but BJT opamp will kill the earphone easily)
6. Powersupply, should I stay with 9 V or 18V (9 V will limit the use of OPAMPs but 18V will reduce the run time)
7. Gain, I am using 7X right now, 5X is kinda weak for my k702 (40% vol from my iphone,)
......... many more
 
The most concern is the the circuit is tuned in with my perspective. My biggest fear is if I release a kit and people don't like it .
 

 

[2000impreza]

Nice work. Is this a 2 or 3 channel design? I would love to get my hand on one of these to build.

 

[Avro_Arrow]

It's an active ground design.
 
Quote:

Nice work. Is this a 2 or 3 channel design? I would love to get my hand on one of these to build.

 

 

[w62820616]

Quote:

It's an active ground design.
 


 

 
Here is another one that already sent to the factory. Simply ground + low impeadence ground buffer. PCB traceguard and improved wiring. Ground plane at back and "clear window" for all the opamps. (Due to the space limitation I remove the current mirror buffer, may consider SMD transistors for the next version)