Hissing sound!

[Guest warlock]

Hi guys... !

 

I made a interconnect cable for my Sonic Impact T-Amp so that it can drive my headphone Senn HD590 (120 Ohm) . The expected impedance that the T-amp drives is 6 Ohm. Hence in order to make the effective impedance of the load around 6 Ohm, I connected a 8 Ohm resistor to each channel (left and right) in parallel to the headphone.

The result is, it can drive the headphone easily, I usually use only a quarter to half of the volume max. But the bad thing is there's loud hissing noise in the background.

I've tested the t-amp with a passive speaker and there's no such hissing noise.

I dont know if the hissing sound is due to the resistors or the quality of the cable or the workmanship (soldiering and stuff).

Any pointer would be much appreciated.

Also I can see that the 2 ground point of the outputs (left and right) of the T-Amp are not connected. Is it normal? I've connected them because the minijack female has common ground point, not separate.

Thank you.

[1bit 0]

hi warlock

well the hissing noise could be caused due to a variety of reasons, but there's one apparent problem in your setup.

 

the sonic impact t-amp uses a tripath ta2024 for its amplification

a quick peek at its datasheet, in page 5 the schematic shows that the chip has a differential output

it has two active outputs: the positive (red connector at your t-amp), and negative

tripath has an explanation of differential output here

 

so basically in the t-amp case you cannot connect the 'ground' terminal from left and right channel

[1bit 0]

you need to do this kind of modification to your headphone to use it with the t-amp.

 

[Guest warlock]

thank you very much...

Probably I will go for a normal headphone amp then. Mine is not the type with the Y cord so I have to rewire the whole headphone to use with the t-amp. Not worth it in my opinion.

 

[Guest warlock]

1bit, you are right.. just tried 1 side only.. no hissing sound. :-)

[jasonhanjk 0]

There is only one headphone that I know uses speaker amp. Other headphone should definately try to use headphone amp.

 

A very good reason is speaker amp have higher noise level than headphone amp.

[Guest warlock]

thanks for the info. is the headphone u mention K1000?

 

[neutralzz 0]

yup akg1000, else if i m not wrong one of the grado H-series can be driven by a speaker amp too..

[huangyong 0]

i think the problem lies in that 8ohm resistor in parallel. i tried using tube intergrated amp driving headphone before, but resistor should be in series. if in parallel, you calculate the current flow over your headphone.. 120/8 current divider rule..wah

 

of coz in this case is digital amp, and i have no experience in it.. just my 2cent.

 

i tried akgK1000 direct driven by power amp before, no problem at all.. sounds exellent.

[huangyong 0]

http://www6.head-fi.org/forums/showthread....ht=sonic+impact

 

try this.. that guy use 150ohm in series. i recommend 5W resistor.

[siriuz 0]

try before oredi, the grounds on each channel cannot be connected, will hiss

[Guest warlock]

yup akg1000, else if i m not wrong one of the grado H-series can be driven by a speaker amp too..

sorry I havent heard of Grado H-series before. K1000 is way over my budget

[Guest warlock]

I dun know what happened ... but the hissing sound has miraculously diminished to a hardly audible level. I let friends try and they cant hear it at all.

Last nite I used it for a few hours continuously at loud level (so I cant hear the hissing sound). And this morning I realized that it's almost no longer there

Edited December 8, 2005 by warlock

[Guest warlock]

After I DIY the cable, because of the hissing sound, i didnt touch it until last nite... do u guys think that the "burn-in" with the cable sort of like help in this case?

[1bit 0]

wow that's rather miraculous, huh? lol

well looks like the internal components of the tripath for the two negative terminals sort of adjusted themselves

 

lol wow