kvant
Member
- Joined
- Apr 2, 2009
- Messages
- 6
I have built a headphone amp according to the schematic in the attachment (C5s are common to both channels). It is based on a PRR's drawing from headwize (the site is now down, sorry). All seems quite well and working. There is just one small issue: with sensitive ear buds there is a noticeable hiss. Practically, it is not a problem, it is inaudible with Grado and I have no plans nor needs to use the amp with those buds. On the other hand, it is sometimes mentioned that hiss could be a sign of oscillations. Unfortunately, the only tool I have is a voltmeter, which does not seem to indicate any misbehavior of the circuit. The level of my experience is not nearly good enough to make an educated guess for the origin of the hiss. I would say it does not come from the power supply, I tried several and the hiss is unchanged (CRC filtered as one, linear regulated walwart as another, even just a bridge rectifier directly into those 2350uF C5s on amp PCB - surprisingly no hum).
Finally, I am getting to my question: Is it likely that the higher level of hiss is inherent to this type of circuit (too high resistor values, noisy constant current source or what not), or should any hiss be inaudible in well functioning circuit, meaning that the observed hiss hints to some kind of misbehavior? I guess that clear answer is impossible with the little information provided from my side, but it is pretty much all I have at the moment.
Thank you very much for opinions.
Finally, I am getting to my question: Is it likely that the higher level of hiss is inherent to this type of circuit (too high resistor values, noisy constant current source or what not), or should any hiss be inaudible in well functioning circuit, meaning that the observed hiss hints to some kind of misbehavior? I guess that clear answer is impossible with the little information provided from my side, but it is pretty much all I have at the moment.
Thank you very much for opinions.