[P_1]

Hi, I just built 5 cmoy amps over the weekend and I just noticed that the chip said OPA227P instead of PA is that normal? I ordered these chips from digikey.

 

[DaKi][er]

http://focus.ti.com/lit/ds/symlink/opa227.pdf
Their both exactly the same exept that the A version has more Input voltage offset than the non A

 

[steinchen]

Quote:

Originally Posted by P_1 Hi, I just built 5 cmoy amps over the weekend and I just noticed that the chip said OPA227P instead of PA is that normal? I ordered these chips from digikey.

no problem, they are fine for your application. Some of the specs of the P version are slightly better than those of the PA version, but that does not make a difference for a headamp.

 

[P_1]

wow, thanks guys. Is it normal to have sort of a hiss when nothing is playing?

 

[PinkFloyd]

Quote:

Originally Posted by P_1 wow, thanks guys. Is it normal to have sort of a hiss when nothing is playing?

Not really, no.

 

[P_1]

I've noticed this with some speaker setups as well, when nothing is going through them they would have a low hiss as long as power is going through them. Is there anyway to fix this ? The amp sounds great when music is playing but when there isnt theres a hiss.

 

[diredesire]

Quote:

Originally Posted by P_1 wow, thanks guys. Is it normal to have sort of a hiss when nothing is playing?

In my experience, the 227 series (i used the 2227) is dead quiet when not playing anything, unless you're playing them at EXTREMELY LOUD LEVELS.

There may be a few things causing this, i'd consult tangent's guide and his troubleshooting section.

 

[Pars]

You can try inserting R5 resistors (see Tangent's guide). Also, if you have these configured at the stock gain of 11, that is normally too much for many applications. See if you can cut it down to 5 or less and this should take care of the hiss.

 

[The Monkey]

Quote:

Originally Posted by Pars You can try inserting R5 resistors (see Tangent's guide). Also, if you have these configured at the stock gain of 11, that is normally too much for many applications. See if you can cut it down to 5 or less and this should take care of the hiss.

+1 on this suggestion by Pars. Try lowering the gain first, then add R5 if you still have hiss.

 

[P_1]

can someone explain to me what gain is in terms of electronics(i know how to tweak the gain from tangents guide but I do not know what it really means.)

 

[ATAT]

http://ourworld.compuserve.com/homep...wden/opamp.htm

Very informative IMO...

 

[peranders]

... but even better....
http://www.analog.com/library/analog..._handbook.html
http://www-s.ti.com/sc/psheets/slod006b/slod006b.pdf

 

[RobDD]

My OPA2227 amp (10x) driving HA3-5003 buffers is dead quiet at any volume. I built a PCB board.
Check grounding and circuit layout.
Rob