Hmm - yep the thing is - at one channel around 1mV and at the other almost 40mV ... But also another strange thing - also those 40mV can "drop" to few mV - if I fiddle around a bit with my DMV - different angle and pressing to measuring point and voltage drops significantely ... But always on same channel??!?
@susha - no my DC offset is at speakers outputs ...
The thing that bothers me is the difference between channels ... And also this strange thing of depending how "good" contact I get ....
Btw - I still don't understand this relationship Carlos is telling about?!? I always thought that DC component is DC component ... So to stop it - you just use a capacitor ...
@susha - no my DC offset is at speakers outputs ...
The thing that bothers me is the difference between channels ... And also this strange thing of depending how "good" contact I get ....
Btw - I still don't understand this relationship Carlos is telling about?!? I always thought that DC component is DC component ... So to stop it - you just use a capacitor ...
I know that your offset is at sp. output. It certainly is. I was just reffering to your method of measurement. If input is connected to the ground you are measuring DC offset of the chip itself and nothing else. If you have some source connected it is possible that you get some DC from the source which will be amplified by the chip. Just that. This is why we are talking here about input (de)coupling cap.
Why am I telling you this? You certainly know more about electronics than I do.
And don't bother about differences between chip offsets. It has been said many times that this is production drift.
Why am I telling you this? You certainly know more about electronics than I do.
And don't bother about differences between chip offsets. It has been said many times that this is production drift.
That's another strange thing - 2 different DMMs and two different pairs of wires - always same ...
If measuring at speaker bindings on the outside - always aroun 40mV ... When measuring inside - but still on speaker bindings - with "right press and angle" - only 2-3mV ... Again - same story if using as ground the star ground ... Etc etc ... ?!?!?!
Maybe I have some bad joint somewhere?? But then again - why the other channel ain't problematic at all ...
If measuring at speaker bindings on the outside - always aroun 40mV ... When measuring inside - but still on speaker bindings - with "right press and angle" - only 2-3mV ... Again - same story if using as ground the star ground ... Etc etc ... ?!?!?!
Maybe I have some bad joint somewhere?? But then again - why the other channel ain't problematic at all ...
cjd said:Not much higher though! 15Hz is into music territory (though uncommon) - 16Hz is quite common though.
It does depend on what you listen to though.
C
And what speakers do you have that reproduce that?
This is not a (big) subwoofer amp.
Your speakers can't reproduce that, and your room may not even be big enough to have clean bass at as low as that.
And the recordings...
I do prefer quality to quantity, I love tight, fast, detailed bass.
Trying to put a big speaker into a normal room can sound very bad.
The amp for your main speakers doesn't really need to reproduce at lower than around 10Hz (first order filter).
carlosfm said:
And what speakers do you have that reproduce that?
This is not a (big) subwoofer amp.
Your speakers can't reproduce that, and your room may not even be big enough to have clean bass at as low as that.
And the recordings...
I do prefer quality to quantity, I love tight, fast, detailed bass.
Trying to put a big speaker into a normal room can sound very bad.
The amp for your main speakers doesn't really need to reproduce at lower than around 10Hz (first order filter).
Good point, that.
I have an IB sub that's clean to 10Hz but then, it has its own little amp. And that's also in my theater, not my music rig (which is not really more than a glimmer on the horizon at this point beyond some early components that are mostly testbeds, but will have its own sub of some kind that'll get that low while still being clean and fast). Some of the bigger 3-way speakers I've been designing will reach to 20Hz or a bit below still. On the other hand, I was just commenting that 10-15Hz was an ideal range, and I think we agree on that. I was more addressing my comments to the "there's no music below 40Hz" folks.Plus, I've been working with active filters (where I *do* want those frequencies if they exist) so it just kind-of popped into my head.
Of course, a chip-amp may not be out of the question for an IB given their low power requirements at 10Hz.
C
i usually try to use about a 2hz cutoff on my inputs for the following reasons:
1.) there have been or will be other 1st order fitlers in the signal path, and 2hz should not affect any of them.
2.) 2hz is low enough that phase at 20hz is not affected signifigantly. if you have a cutoff at 20hz, then you can affect the phase up to 200hz. if the tolarces are off a bit you might get some differences in phase for the low freqeuncies where phase is more important to localizing sound. granted i've never quantified any of this, but of the things that could go wrong in an amp, this seem more likely then a lot of the cable-voodoo stuff.
my choice is for 1uf mylar (i got them cheap) and 100k input impedance.
also, for measureing with the DMM, make sure your hands don't touch either lead or you will induce hum onto the leads. while this is AC, you can get some aliasing on the readout and get erroneous results.
1.) there have been or will be other 1st order fitlers in the signal path, and 2hz should not affect any of them.
2.) 2hz is low enough that phase at 20hz is not affected signifigantly. if you have a cutoff at 20hz, then you can affect the phase up to 200hz. if the tolarces are off a bit you might get some differences in phase for the low freqeuncies where phase is more important to localizing sound. granted i've never quantified any of this, but of the things that could go wrong in an amp, this seem more likely then a lot of the cable-voodoo stuff.
my choice is for 1uf mylar (i got them cheap) and 100k input impedance.
also, for measureing with the DMM, make sure your hands don't touch either lead or you will induce hum onto the leads. while this is AC, you can get some aliasing on the readout and get erroneous results.
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