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★★ Free PCB for JLH 2005 Class-A Amplifier

Fab out!

Begin to ship today, first 25 orders will be shipped soon. Later orders will be shipped a few days later.
 

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Happy with the testing reslut!

Today I'm sooooo happy with the testing result. After the following modifications of the original first design I posted:
1. VR1 changed to 100R
2. R13 changed to 10R
3. Q3 changed to BD139

The amplifier is working great! At the beginning the THD is 1% @1KHz/1W/8Ohm, pretty high for a class-A. I realize that Q1 and Q2 should be paired matched. Then I changed them with 2 pair matched transistors, the THD drops to 0.05%!

I also tried with some other transistors such as 2N3055, 2N3773 and finally 2SC5200. In my own opinion I like the sound of 2SC3280 most, high freq is very clear.

BD139 and BD140 works great in the testing. I think it's no need to worry about the high current. The don't have a heatsink and were slightly warm during working.

Hope your guys can also build a great amplifier when you receive my free PCBs.
 

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Bug and testing report

Sorry for forgetting to mention a bug on the board. A trace is missing on the fist version, the 2 collectors of Q3 and Q8 are not connected. A flying wire can solve this easily

Tested THD with different transistors, testing condition is 1KHz, 6Ohm speaker, 1W output power
2N3055: 0.06%
MJ15003: 0.03%
2SC3280: 0.03%

MJ15003 and 2SC3280 should be better options for Q1 and Q2
 

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Hi Kp93300

the $4 is price different between 2sc3280 and 2N3055. I don't have golden ears so you can't believe my judgement. I just felt MJ15003 and 2SC3280 has more clear in high frequency. The measurement result shows that THD of MJ15003 and 2SC3280 is below 0.03% while 2N3055 is 0.05%.
 
Hi there,

I am very interested in the JLH amp kit that is being offered and have a few questions:
1) I need to buy two kits to make a stereo amp
2) how long will it take for shipping to Toronto, Canada if I choose the flat rate
3) you will take Paypal (I did not quite see it on your website) for payment
4) you will provide some support if needed (I am a newbie)

Thank you in advance for answering my questions.

Regards,

Lo_tse