JLH Headphone Amp - Page 34

sgrossklass · 25th November 2012, 07:32 PM

Well actually, you only want as much DC across a 'lytic as is necessary to keep it in good working order. At higher voltages, distortion actually increases, as Cyril Bateman found. Introducing some DC offset should be easy in the JLH, as it requires some offset trimming anyway.

Basically the largest disadvantage of using coupling caps is their size. Ideally you're looking at something like 1000µF per channel.

blackdod · 30th November 2012, 05:29 PM

I have the blue PCB and has nothing to do with the green. The blue remains perfectly the offset about 10 mvolt or so.

blackdod · 1st December 2012, 12:30 PM

Blue PCB:

On a hour, the offset is constant, around 15 mVolt more less. The sound is good. I think that the board desing (the path of the track and its travel is totally different) and the quality component is the differece.

I think that the green board "JHL" it´s a c***p...

bkercso · 1st December 2012, 07:13 PM

I built 2 blue ones and during warm up the offset changed ~100mV at both amp.

blackdod · 2nd December 2012, 11:02 AM

On Max´s unit, when start, the offset is ~180 mVolt and down to 10~30 Volt after 1 hour.

bkercso · 2nd December 2012, 06:55 PM

I used 4x1N4148 per channel as recommended in this topic, and trimpot.

oz7aff · 4th December 2012, 08:06 PM

Is that instead of the 2V7 Zenerdiode ?

bkercso · 4th December 2012, 10:41 PM

Yes.
Oh, sorry! Only 3x1N4148 per channel.

oz7aff · 5th December 2012, 07:39 AM

Ok, I think one could also try to use a LED instead.

bkercso · 5th December 2012, 08:18 AM

LED has more noise than 4148. Red LEDs are less noisy than others.

4th December 2012, 08:06 PM	#337
oz7aff diyAudio Member Join Date: May 2012 Location: Denmark	Is that instead of the 2V7 Zenerdiode ? __________________ Regards Max

5th December 2012, 07:39 AM	#339
oz7aff diyAudio Member Join Date: May 2012 Location: Denmark	Ok, I think one could also try to use a LED instead. __________________ Regards Max

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25th November 2012, 07:32 PM	#331
sgrossklass diyAudio Member Join Date: Nov 2004 Location: Germany	Well actually, you only want as much DC across a 'lytic as is necessary to keep it in good working order. At higher voltages, distortion actually increases, as Cyril Bateman found. Introducing some DC offset should be easy in the JLH, as it requires some offset trimming anyway. Basically the largest disadvantage of using coupling caps is their size. Ideally you're looking at something like 1000µF per channel.

30th November 2012, 05:29 PM	#332
blackdod diyAudio Member Join Date: Jun 2011 Location: Canarias	I have the blue PCB and has nothing to do with the green. The blue remains perfectly the offset about 10 mvolt or so.

1st December 2012, 12:30 PM	#333
blackdod diyAudio Member Join Date: Jun 2011 Location: Canarias	Blue PCB: On a hour, the offset is constant, around 15 mVolt more less. The sound is good. I think that the board desing (the path of the track and its travel is totally different) and the quality component is the differece. I think that the green board "JHL" it´s a c***p...

1st December 2012, 07:13 PM	#334
bkercso diyAudio Member Join Date: Nov 2009 Location: Hungary	I built 2 blue ones and during warm up the offset changed ~100mV at both amp.

2nd December 2012, 11:02 AM	#335
blackdod diyAudio Member Join Date: Jun 2011 Location: Canarias	On Max´s unit, when start, the offset is ~180 mVolt and down to 10~30 Volt after 1 hour.

2nd December 2012, 06:55 PM	#336
bkercso diyAudio Member Join Date: Nov 2009 Location: Hungary	I used 4x1N4148 per channel as recommended in this topic, and trimpot.

4th December 2012, 10:41 PM	#338
bkercso diyAudio Member Join Date: Nov 2009 Location: Hungary	Yes. Oh, sorry! Only 3x1N4148 per channel.

5th December 2012, 08:18 AM	#340
bkercso diyAudio Member Join Date: Nov 2009 Location: Hungary	LED has more noise than 4148. Red LEDs are less noisy than others.