Quote:   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...

Quote: 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...

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

Quote:   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...

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...

Hello,          I am having trouble to set up an restriction area for OPAMP. I don't want the ground plane to cover the OPAMP socket. Should I use restrict or keepout layer ?   Best Kee

Quote: Thank you so much Fred. So I assume 100k is the input resistor (hi-pass filter). 1k3 and 10k are the feedback resistor. So if i am calculating right, the gain is around 10; The input offset current for JRC4560 is around 200na, for 100k input that will be 0.02v input offset...

I can't really tell the difference in color :( Or I am so used to multimeters :P

One directly connect to the input jack, one directly connect to the input cap, one directly connect to the ground. Do you think the cap is leaking? I am using WIMA 0.47uf

I noticed that my alps RK097 pot has a noise problem when I turn the shaft really fast. It only happen to the right channel ( where the metal shaft directly connected to). you need a low impedance ear phone to hear the problem (i am using UE ). But if you turn the pot really slow, you will not...

I have room for 2 9v batteries and I don't want put them in series ( my gain is only around 5) so 9V is enough. I was thinking maybe i can put them in parallel so that I get double the run time.

Or they will drain each other ? If it does, is there any way to save that issue ?

seems that all other opamps will have a 0.0xx mv idle voltage but only 4560 will have 70mv. the feedback resistor is 499 and 2k

Quote: Thank you. I have a question about the idle voltage on the output jack. If i use opa2017, the idle voltage will be 0.08mv per channel, but if i switch opamp to a RC4560, the idle voltage went up to 70mv. do you know why and how to fix the problem?

Finally, after 3 weeks, I got the boards.   pretty nice sound !  

Suggest use LDO voltage regulators from LT. They are great!!!

  Can't really hear the difference. It will lower the volume around 50%. Homemade PCB, fly wires, hmmmmmmmmmmm..........

Thanks for the reply. I am confused with the result from this transistoramp software: Above the the settings and below is the results:   So here is how I analyze : R1 and R2 bias the emitter so: VR2=(9/(180+56))*56 = 2.14V Therefore, The voltage across R4 should be 2.14-0.6...

Hello everyone, I've found some PNP Ge transistors and want to build an audio amplifier from it. I used to work with NPN a lot and I know the way to bias them is to use a two resistor voltage divider. However, because the PN junction in PNP is reversed, the resistor divider dose not work...

Quote:      Is the output of the transformer as 12V AC? of after the rectifier the DC voltage should be 12*1.414= 16.9V. Is that right?

Quote: So here is the specification for my transformer :   Output: 2 x12V292mA NO load:  2 x16.2V Resistance2 x7.7Ω Weight Cu = 36 g     I want to use LDO linear voltage regulators like LT3015 and LT 1963. Do you think I need a 15V output transformer and lower the...

Quote: Hmm it looks like that the voltage drop for same model LEDs are pretty much the same. I found some old LEDs and they all have a voltage drop around 1,83X V

Quote: Do you know what kind of LED I need to use? Do I need to pair it?  

Quote: Sorry for the late response, I was working on the schematic. Here is the main structure of the amplifier. It is still an OP+BUF arti. Please give me some suggestions. :D Obviously it will not run for very long on a battery so I need to make a separate linear voltage...

Quote: Thanks for the info! It looks linear is just means analog amplifier.