Posted 9th January 2013 at 11:41 AM byrjm Updated 21st January 2013 at 08:12 AM byrjm
The $50-from-China-via-ebay NJM4556-based headphone amp, pictured below, fails the "Is thing thing on?" test. With 16 ohm, 104 dB/mW headphones there is a faint-yet-audible background hiss when the unit is powered up and the volume is turned all the way down. The hiss increases only slightly as the volume is turned up (input disconnected).
The output noise of an op amp is normally estimated from the input-referred voltage noise density multiplied by the gain, and the current noise density multiplied by the gain and the sum of the input impedances on the inverting and noninverting inputs. The NJM4556 datasheet does not give a figure for current noise, but a reasonable guess is 1 pA/sqrtHz. The voltage noise density is estimated at 8 nV/sqrtHz.
This is the continuation of my personal journey to build my first tube amp.
It was a very happy day yesterday when the first mono bloc powered up and produced music. I was pretty comfortable that I had not made mistakes that would result in smoke, but really did expect some issues with hum, grounding or tube substitution. But nothing! Hum was barely audible with my ear on the speaker or from the chassis. And music played! My first test flight was one channel only driven by a Sony Walkman on a small Totem speaker. Even under these conditions the sound was pretty good, and really started to open up after the first 60 minutes. I was like a proud father
The first picture shows the pair with a Rotel CDP in the middle for scale.
I will not be able to fully know the sound until both are wired, broken in and hooked to the good speakers and source. I think they will be amazing. Already better than the very respectable chip amp they replace. There is a switch...
Posted 6th January 2013 at 03:32 PM bysuwaned (tube audio friends suwaned)
Updated 2nd July 2013 at 12:25 AM bysuwaned
Preamp cleo4 Triodedick's
The First falling in Love with TUBE, when i had heard the preamp B406 my friend.
I have build the first Project tube , preamp B406 single stage.
Preamp with Phillips B406 and Phillips D3a with output line transformer Hasimoto HL10K_600.
rectifire Valvo AZ1.
Thank you for your Help and advised my Friend "The_Manta" and my friends_audiotube.
Posted 5th January 2013 at 06:50 AM bysuwaned (tube audio friends suwaned)
Updated 18th January 2013 at 05:49 PM bysuwaned
i have set krell CDT DM-1 , dac studio and preamp.
i cann't used my set because my dac is fail.
the problem it can't locking when i connecting with CDT. i think this must fail at board digital input and filter.
there are to old.
i can not find what wrong? i see krell's pcb is complex and closed. this is dificul.
i have tried check board pcb digital.but no have meansure intrument like digital analyser. become i not know how?
my be jitter or digital reciver or xtal or ect problem.
I think “ why I did not try to use part of the DAC Krell was still good: power supply and the overall analogues by replacing the digital part of the DAC”
When I see there is a chart on Web andrea ciuffoli DAC. with a detailed explanation of the parts that can be used. to replace the digital
board from my Krell...