THE Crossover Thread
- Thread starter laatsch55
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I need some help filtering pops in balanced connection of the DriveRack pa2 crossover. Also happing with Rane ac23 crossover
turning on - off or disengaging components in my balanced system create pops in system. This never happed in the old unbalanced configuration. This is not limited to one unit.
I avoid pops by staging power up / off with amps on last and first off. The rub is switching sources. Bugs me to no end. I’ve tried make then break switch’s and low voltage bc relays. Both these systems work well if used in a unbalanced install. So if I tune off the power to the dolby unit I get Hugh pop. If I switch sources with relay box still lessor pop.
I thought a make then break would transfer source best and it is better than break then make.
overview
in building my crossover system I have gone full balanced by Converting the unbalanced output of my carver to balanced. This has been not as easy as I thought it would be. Trying various ways including Rane transformers, tascam electronic converter. And finally the RDL Radio Design Labs RU-LA2D IHF-PRO Interface. The last is best and silent. I use them to convert from unbalanced and back again at the amp to unbalanced. In future I’m going to build a balanced output in a carver and some Pl’s with balanced inputs built into them
what can tame these connection transfer issues, or grounding transfers?
turning on - off or disengaging components in my balanced system create pops in system. This never happed in the old unbalanced configuration. This is not limited to one unit.
I avoid pops by staging power up / off with amps on last and first off. The rub is switching sources. Bugs me to no end. I’ve tried make then break switch’s and low voltage bc relays. Both these systems work well if used in a unbalanced install. So if I tune off the power to the dolby unit I get Hugh pop. If I switch sources with relay box still lessor pop.
I thought a make then break would transfer source best and it is better than break then make.
overview
in building my crossover system I have gone full balanced by Converting the unbalanced output of my carver to balanced. This has been not as easy as I thought it would be. Trying various ways including Rane transformers, tascam electronic converter. And finally the RDL Radio Design Labs RU-LA2D IHF-PRO Interface. The last is best and silent. I use them to convert from unbalanced and back again at the amp to unbalanced. In future I’m going to build a balanced output in a carver and some Pl’s with balanced inputs built into them
what can tame these connection transfer issues, or grounding transfers?
Last edited:
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Glen, you are way further in this game than I am. And the more I read of Rane notes or other publications on balanced to unbalanced the more I figure I dony know shit.
Glen,i have the pop too. Changing sources not at all hardly, maybe the Coherence mutes the outputs for a t few ml milliseconds or something....
Glen,i have the pop too. Changing sources not at all hardly, maybe the Coherence mutes the outputs for a t few ml milliseconds or something....
- Joined
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- Halfbiass...Electron Herder and Backass Woof
Thank you Don I’ll have to check into that.
I resolved 99% of my issues yesterday by removing the cable box rca output to the preamp. I had it running through an isolation transformer pack without succes. Now I run it with optical connection only.
What remains as the biggest issue is turning on and off power to components. With stage start and stop one can avoid altogether Any piping .
when you get a of loss of main power or accidentally turning something off ends with massive bang. Don do It need ark protection on power switches-, small caps, large caps or something to soften power switching? I have a large 1500 watt power backup I could put new batteries into and run all the usual suspects off that to cove power outages , but say I do dump and turn off my Dolby unit without having the amps off then kaboom which is unnerving
I’ll wait for you comments
thanks
I resolved 99% of my issues yesterday by removing the cable box rca output to the preamp. I had it running through an isolation transformer pack without succes. Now I run it with optical connection only.
What remains as the biggest issue is turning on and off power to components. With stage start and stop one can avoid altogether Any piping .
when you get a of loss of main power or accidentally turning something off ends with massive bang. Don do It need ark protection on power switches-, small caps, large caps or something to soften power switching? I have a large 1500 watt power backup I could put new batteries into and run all the usual suspects off that to cove power outages , but say I do dump and turn off my Dolby unit without having the amps off then kaboom which is unnerving
I’ll wait for you comments
thanks
I’ve been reading up on the ways to eliminate dc
here is one interesting thought:
Lets look at stopping DC from a source component. This shows a series cap and a resistor to ground. Typical values would be a small 0.47uf film type cap and a 470k resistor. This ensures that whatever DC is present on the source does not get past the cap. The output is always 0.0000 volts DC.
I would try something like this first just for the DAC feed and see how you get on. Also, for interest you could try and measure any DC voltage present. It may only be a millivolt or two but you might see something and be able to compare channels.
Its also important that the power amp input doesn't see any large change in DC resistance to ground as the input is switched as that can also cause a pop.
Edit... the cap value also depends on what impedance the power amp presents and so 0.47uf may be a bit small. Used correctly, and a small and cheap electrolytic can be very suitable if you need larger values.
And another approach
A line level output coupling cap needs to be terminated with a resistor to ground, like Mooly's drawing. Otherwise, there will be a DC voltage on the output until it is connected to a resistive load (like the input of a preamp or power amp). Then the DC voltage will drop to zero, and you will hear a pop or thump.
Try a 100K resistor in parallel with that input on your preamp switch. If your problem is what I described, then this will cure it.
and this
both preamp and the power amp should each be AC coupled at their inputs. If you use a switching arrangement as you describe (not the grounds bit though) then each input should be treated separately and each have its own cap (and resistor to ground) rather than just one cap at the preamp input. Why so. Because one cap would still cause pops if there were DC present on any input, and it would do that because the cap would see a sudden step change in voltage as the switch operated. Defining each input from the start ensures they are all at zero volts and so that is what the switch and preamp input see.
2/ Its not common practice to switch grounds. If it were not done correctly then there is a possibility of a ground floating momentarily as the switch operates causing more than just a small pop.
here is one interesting thought:
Lets look at stopping DC from a source component. This shows a series cap and a resistor to ground. Typical values would be a small 0.47uf film type cap and a 470k resistor. This ensures that whatever DC is present on the source does not get past the cap. The output is always 0.0000 volts DC.
I would try something like this first just for the DAC feed and see how you get on. Also, for interest you could try and measure any DC voltage present. It may only be a millivolt or two but you might see something and be able to compare channels.
Its also important that the power amp input doesn't see any large change in DC resistance to ground as the input is switched as that can also cause a pop.
Edit... the cap value also depends on what impedance the power amp presents and so 0.47uf may be a bit small. Used correctly, and a small and cheap electrolytic can be very suitable if you need larger values.
And another approach
A line level output coupling cap needs to be terminated with a resistor to ground, like Mooly's drawing. Otherwise, there will be a DC voltage on the output until it is connected to a resistive load (like the input of a preamp or power amp). Then the DC voltage will drop to zero, and you will hear a pop or thump.
Try a 100K resistor in parallel with that input on your preamp switch. If your problem is what I described, then this will cure it.
and this
both preamp and the power amp should each be AC coupled at their inputs. If you use a switching arrangement as you describe (not the grounds bit though) then each input should be treated separately and each have its own cap (and resistor to ground) rather than just one cap at the preamp input. Why so. Because one cap would still cause pops if there were DC present on any input, and it would do that because the cap would see a sudden step change in voltage as the switch operated. Defining each input from the start ensures they are all at zero volts and so that is what the switch and preamp input see.
2/ Its not common practice to switch grounds. If it were not done correctly then there is a possibility of a ground floating momentarily as the switch operates causing more than just a small pop.
and to add to that.
now to determine what combo of cap values and resistors up to 20k to try
the pops are a grounding issue. I suggest 2 things:
1. Assuming you used shielded cable (and you should have), connect all the shields together where the cables connect to the switch. This will provide a more stable ground reference for all the amp inputs.
2. Connect 1.2k termination resistors to EACH of the amp inputs. The resistors should be added at the amp input connectors or in the switch area, but they must be connected to all amp inputs at all times, regardless of how the switch is set. The resistors stop the deselected inputs from going high impedance when de-selected and thus picking up noise.
now to determine what combo of cap values and resistors up to 20k to try
the pops are a grounding issue. I suggest 2 things:
1. Assuming you used shielded cable (and you should have), connect all the shields together where the cables connect to the switch. This will provide a more stable ground reference for all the amp inputs.
2. Connect 1.2k termination resistors to EACH of the amp inputs. The resistors should be added at the amp input connectors or in the switch area, but they must be connected to all amp inputs at all times, regardless of how the switch is set. The resistors stop the deselected inputs from going high impedance when de-selected and thus picking up noise.
MiniDsp has a new 8X8 unit coming out soon.
https://www.minidsp.com/products/ht-series/flex-htx
https://www.minidsp.com/products/ht-series/flex-htx
