UPDATE:
I've changed the resistor (R10) for the correct theoretical value, but in practise I still think the tweeter is way too loud (2-3db).
I was thinking rather than swapping out the resistor again, I'd put a stepped attenuator on the tweeter (after active crossover but before tweeter amp) and play with the tweeter level until it's right - at least until I am completely happy and ready to commit the new value to the amp 🙂
I've changed the resistor (R10) for the correct theoretical value, but in practise I still think the tweeter is way too loud (2-3db).
I was thinking rather than swapping out the resistor again, I'd put a stepped attenuator on the tweeter (after active crossover but before tweeter amp) and play with the tweeter level until it's right - at least until I am completely happy and ready to commit the new value to the amp 🙂
Thanks Julf.
My only problem is that I've only got 100k log attenuators, which is probably way too high, and may be too insensitive because of the taper.
My only problem is that I've only got 100k log attenuators, which is probably way too high, and may be too insensitive because of the taper.
It is approximately the same as the nc400 input impedance, so they would still work OK. The adjustment range will become a bit non-linear, but that is no problem for something you don't keep adjusting all the time.
On the other hand, any 5 quid generic double-gang potentiometer would work as a temporary measure to find the right value.
Hi guys.
Just hooked up a UCD180Hg to a 98db/W SPL speaker and a RME Fireface UCX - differential !
As soon as I turn the chain on I get heavy base noise (clearly audible) on the tweeters. I do not hope that the amp is that noisy!?!?
I suspect two sources:
Much too high gain and/or much too high input voltage.
I contacted Hypex about gain settings a while back. I was informed
that
I figured RG would be R14 on the UCD180HG.
So far so good. I left it alone for while. Now I'm on it again.
I think 13db would be more then sufficient.
What do you think? Will the gain change have an impact on the tweeter noise - which is my main concern for the time being??
Do I face any other disadvantages by dropping the gain to lowest value?
Thx for your advise.
Just hooked up a UCD180Hg to a 98db/W SPL speaker and a RME Fireface UCX - differential !
As soon as I turn the chain on I get heavy base noise (clearly audible) on the tweeters. I do not hope that the amp is that noisy!?!?
I suspect two sources:
Much too high gain and/or much too high input voltage.
I contacted Hypex about gain settings a while back. I was informed
that
I figured RG would be R14 on the UCD180HG.
So far so good. I left it alone for while. Now I'm on it again.
I think 13db would be more then sufficient.
What do you think? Will the gain change have an impact on the tweeter noise - which is my main concern for the time being??
Do I face any other disadvantages by dropping the gain to lowest value?
Thx for your advise.
Even with an incorrect gain structure the noise floor should still be decent - wonder if there is something else going on. Do you have any noise with the amp module inputs shorted?
Dropping the gain by 10 dB will of course drop the noise floor with 10 dB too - that might or might not be enough.
Dropping the gain is by increasing the feedback, so the modules should become even more linear. I don't see any disadvantages.
No -- dead quiet.
If I leave the inputs open, I do have a pretty loud hum.
Something wrong with the amp grounding? (It actually doesn't exist 😉 )
My amp installation:
I do not have any mains ground connected.
And the SMPS and the amp modules are
mounted on a piece of wood.
Thx for any advise.
Either that, or interference from electrical or magnetic fields. Any transformers nearby?
Wood is of course not very good at shielding.
Is it possible to move stuff around just to see if it affects the hum?
Similar situation here.
I have always had some noise on my tweeters as well - although not really very loud. It is slightly distracting when no music is playing though.
I have 2 UCD180ST's and a SMPS180 in each speaker.
Perhaps mine is interference though, as I only have unbalanced going into my UCD180's because my active crossovers are unbalanced. I have the everything normal on the UCD180 end but the cold signal and ground tied on the output of the crossover.
No noise when inputs are shorted either. Mine are all mounted on an aluminium plate.
I have always had some noise on my tweeters as well - although not really very loud. It is slightly distracting when no music is playing though.
I have 2 UCD180ST's and a SMPS180 in each speaker.
Perhaps mine is interference though, as I only have unbalanced going into my UCD180's because my active crossovers are unbalanced. I have the everything normal on the UCD180 end but the cold signal and ground tied on the output of the crossover.
No noise when inputs are shorted either. Mine are all mounted on an aluminium plate.
I agree. The input is differential in any case, so unless the cables are really long I don't think balanced vs. unbalanced makes a huge difference. The biggest benefit of fully balanced is that it makes earth/ground issues easier, but earth/ground issues can be resolved even with unbalanced connections.
Ok my bad - thanks for clearing that up. Could it be the fact that we're both using switch mode supplies, rather than linear supplies?
That would explain high-frequency, wide-band noise, but hum would actually be worse with a linear supply.
There are also a lot of hypex modules out there working just fine with SMPSs, without noise issues.
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