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List of DIY headphone amplifiers - Page 5

post #61 of 64
Quote:
Originally Posted by tomb View Post

No tweaks* - the E90CC/5920 is a drop-in replacement for the 6J6, but it is quite a bit superior - less noise floor, less distortion.  An additional benefit is that they are tall enough that you can swap them out without taking the case lid off.


* Just to be sure, you need to implement both the zener diode tweak and the heater rectifier snubber caps.  Those are the primary differences from the early Torpedo prototypes and kits versus now.  Both make a huge difference.

I can't quite remember when I built my torpedo. I believe it has the Zener diode tweak. But regarding the heater rectifier snubber caps. I don't believe I've done that.

I think I built mine when you first released black cases.
post #62 of 64
Quote:
Originally Posted by koike View Post
 
Quote:
Originally Posted by tomb View Post

No tweaks* - the E90CC/5920 is a drop-in replacement for the 6J6, but it is quite a bit superior - less noise floor, less distortion.  An additional benefit is that they are tall enough that you can swap them out without taking the case lid off.


* Just to be sure, you need to implement both the zener diode tweak and the heater rectifier snubber caps.  Those are the primary differences from the early Torpedo prototypes and kits versus now.  Both make a huge difference.

I can't quite remember when I built my torpedo. I believe it has the Zener diode tweak. But regarding the heater rectifier snubber caps. I don't believe I've done that.

I think I built mine when you first released black cases.

 

You should do the snubber cap tweak.  It finally removes all noise.  The noise we thought was power supply ripple was actually around ~160 Hz.  It was caused by the power transformer picking up the switching noise from the rectifiers and injecting it through the rest of the amplifier circuit.  It's also very simple to fix - you just solder some small ceramic axial caps across the leads of each heater rectifier (D5, D6, D7, D8) on the bottom of the PCB.  It helps to replace the rectifiers, too, to ones that were not so super-fast in their switching cycle (BY228GP).  I thought that I had this detailed on the website, but I'll fix that today.

 

PM me your address and I'll send you the caps and the rectifiers for free.


Edited by tomb - 11/20/15 at 7:52pm
post #63 of 64

New topic:  I just published a modified version of the Stax SRX DIY electrostatic headphone amplifier in the November and December 2015 issues of AudioXpress.  The improvements consist of adding constant current sinks on the the input and output differential amp tails and constant current loads on the output stage, plus a simple shunt regulated power supply.  Dr. Kevin Gilmore kindly designed a circuit board for the amplifier.  There is no circuit board yet for the power supply but it is simple enough to be built point-to-point.

post #64 of 64

My best friend and I designed a combined DAC/headphone amp a few months back.

https://github.com/NiHaoMike/OpenDAC-HD

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