I'm having a little problem with my ucd700 amps. Well this is the last of many main problems I will not bother you with. It's build dual mono in one case and both channels have a very ignorant high frequency noise, it sounds a bit like a jet engine motor and is allready noticable at the listening position with my small bandor 81db/w/m loudspeakers and is simply unbearable to the ears with my 118db/w/m BMS loudspeakers. This noise started after some 20 to 40 hours of play in time, before they where almost completely quiet, strange
the amps are all made of hypex components, two ucd700hg modules, two hg power supplies one soft starter and two 800VA hypex trannies. everything is connected togeter according to the hypex manual, including earthing layout etc etc.
does anyone else have the same experience with the ucd modules ? and if so what was the cure for it ?
I guess it must have something to do with earthing or Hypex has again delivered a mallfunctioning product
the amps are all made of hypex components, two ucd700hg modules, two hg power supplies one soft starter and two 800VA hypex trannies. everything is connected togeter according to the hypex manual, including earthing layout etc etc.
does anyone else have the same experience with the ucd modules ? and if so what was the cure for it ?
I guess it must have something to do with earthing or Hypex has again delivered a mallfunctioning product
Can you post a picture of the physical layout of parts and wiring inside the chassis? Have you taken standard precautions such as twisting wiring together and keeping power and signal wires as far apart as possible? How close are the modules to each other? It could be that the switching frequencies of each modules are close to each other and are producing a beat frequency. Can you test the amp with only one module powered at a time and see if the noise is still present?
The ucd700's are eventually ment for my open baffle woofers, the 118db sensitivity is from my BMS tweeters wich I tried just to hear what the noise sounded like. The noise is also audible on my woofers though, that's why I want to get rid of it. I'm not gonna use them with these tweeters, these are powered by a 300B set amp in a three way active setup. The tube amps are much more quiet than the ucd's, who ever could imagine that.
I have tried hard to spit trough the various UCD topics but it's becoming very hard because they are very large and diverse.
what I was trying to find is a correct earth connection schematics for the modules, power supply, casing, mains input, loudspeaker output etc etc. when using unbalanced inputs.
It seems that the UCD's are very sensitive to this and I can't find anything practical on the Hypex site either.
So in summary, (wich might also be of great help for anyone who want's to build a ucd amp)
what the best place of connection the case to earth ? at the input ? at one or at both? at the output ? at the power transformer ?
What about the mains earth connection when my home doesn't have an earth connection ? It still will be connected to the other equipment via the earth wire (by the way, the noise from the amp is also present when only the mains is connected with shorted inputs)
For the rest everything is allready connected the right way together via the Hypex power supply modules and the amplifier modules.
I have build many amps from scratch in my life and all of them are completely dead quiet as far as my scope can measure but now I'm having troubles with a preassembled kit, that's weird
what I was trying to find is a correct earth connection schematics for the modules, power supply, casing, mains input, loudspeaker output etc etc. when using unbalanced inputs.
It seems that the UCD's are very sensitive to this and I can't find anything practical on the Hypex site either.
So in summary, (wich might also be of great help for anyone who want's to build a ucd amp)
what the best place of connection the case to earth ? at the input ? at one or at both? at the output ? at the power transformer ?
What about the mains earth connection when my home doesn't have an earth connection ? It still will be connected to the other equipment via the earth wire (by the way, the noise from the amp is also present when only the mains is connected with shorted inputs)
For the rest everything is allready connected the right way together via the Hypex power supply modules and the amplifier modules.
I have build many amps from scratch in my life and all of them are completely dead quiet as far as my scope can measure but now I'm having troubles with a preassembled kit, that's weird
Have you tried powering only one channel at a time and seeing if the noise is still there (as I suggested yesterday)? How about that picture of your setup too?
You have mentioned that changing the grounding has not changed the noise at all. That could point to a problem that is not related to the power supply, hence my suggestion of powering one channel at a time. If you have a scope, you can measure the switching frequency of the two modules. Do that and subtract the two frequencies. If the sound you're hearing is about that frequency (or some multiple of it) your modules are interacting. Powering down one module will easily tell you if the modules are interacting in some way.
You have mentioned that changing the grounding has not changed the noise at all. That could point to a problem that is not related to the power supply, hence my suggestion of powering one channel at a time. If you have a scope, you can measure the switching frequency of the two modules. Do that and subtract the two frequencies. If the sound you're hearing is about that frequency (or some multiple of it) your modules are interacting. Powering down one module will easily tell you if the modules are interacting in some way.
Hi Brian,
I think you have misread my post. I didn't say that changing the goriunding did not make a difference, I asked for the best grounding scheme for the ucd's. I want to know first before doing any changes over and over again.
I'm gonna try the power down of one channel this weekend, I'm a bit busey at the moment. picture is coming too.
I really have to find some time for it this weekend because it's getting worse every day now.
I think you have misread my post. I didn't say that changing the goriunding did not make a difference, I asked for the best grounding scheme for the ucd's. I want to know first before doing any changes over and over again.
I'm gonna try the power down of one channel this weekend, I'm a bit busey at the moment. picture is coming too.
I really have to find some time for it this weekend because it's getting worse every day now.
Sjef said:
Hi Sjef,
Very strange that you have these issues, the issues suddenly started?
I have been using UcD180 and UcD400 modules for years now, and no issues at all, super silent, they are as silent now as they were right from the start. In fact they are the most silent amps in my house, they easily beat my Tripath based Marantz that produces lots more noise. The ZAPpulses were way more noisier. My Accuphase Class AB amp came close in (low) noise level.
There must be something wrong but can not believe that it is due to some UcD issue.
About earthing. I`m using balanced XLR input with the DEQX PDC as the source. I use UcD180s to drive tweeters and mids directly. No problems related to earthing, I use no safety earth as I do not have that available. XLR pin 1 goes to the UcD modules and to the chassis, power supply is floating from the chassis. I think this is the Hypex recommended setup.
Maybe some of the other Dutch UcD users that are bit closer to you than I am can help you out?
Best regards
Gertjan
Well I finally had the time to open the amp and disable one channel and yep, the noise is almost completely gone now so it must be interference between the two channels. The noise varies a lot over time sometimes it's almost gone and at other times it's pretty loud and very very anoying. I'm still very busy at the moment so it will have to wait for another couple of days before I can do something about it.
Generally your description would fit to some unreliable GND connection. I mean not necessarily a wrong connection, just simply one connection which does not have proper contact.
Or...may be some beating due to the two independent but similar frequencies of the wo modules? ( Ucd is self resonant & not synchronized. )
Do you hear it only if you connect both speakers, or is it also existing if you disconnect one speaker?
Or...may be some beating due to the two independent but similar frequencies of the wo modules? ( Ucd is self resonant & not synchronized. )
Do you hear it only if you connect both speakers, or is it also existing if you disconnect one speaker?
My guess is also that is has something to do with the grounding layout. As mentioned the noise dissapeared almost completely when I had one channel disconnected from mains power.
The grounding of the chassis is connected to the RCA inputs, as recommended by Hypex. The mains earth is only connected to both the static screens of the two power transformers, mains earth is NOT connected to the chassis and in fact it is not connected to earth either because my mains outlet don't provide any earth connection.
Could it be some feedback between the two static screens of the power transformers ? don't know, gonna try to disconnect them from the earth lead and see what happes. , this way they are also not connected to each other any more.
The grounding of the chassis is connected to the RCA inputs, as recommended by Hypex. The mains earth is only connected to both the static screens of the two power transformers, mains earth is NOT connected to the chassis and in fact it is not connected to earth either because my mains outlet don't provide any earth connection.
Could it be some feedback between the two static screens of the power transformers ? don't know, gonna try to disconnect them from the earth lead and see what happes. , this way they are also not connected to each other any more.
Hi Stef,
I have tried connected between power supply ground to the chassis. Try make it as short as possible. It could help reducing noise from the system. You can connect the screen from transformer to this ground too. By doing this, pls remove the input ground to the chassis, if you have it connected.
Kittikun
I have tried connected between power supply ground to the chassis. Try make it as short as possible. It could help reducing noise from the system. You can connect the screen from transformer to this ground too. By doing this, pls remove the input ground to the chassis, if you have it connected.
Kittikun
I have finally fixed the problem by rerouting all the wiring inside the amp. All the power wires where twisted together as one bundle (as per recommendation from Hypex site) wich was a bad thing. I untwisted them and made seperate twisted groups of the power lines for the input buffer, the gate driver and the powerfets. This helped but did not cure it all, the withle was still very audible.
After that I disconnected the wires from the internal shield of the power transformers, as mentioned before they where connected together to the mains earth but since I do not have any mains earth it just does more harm than it cures. Don't know what to do with the earth shield now, for this moment I just leave them unconnected.
This also helped it a bit further but still not the cure for all. Next thing I rerouted the connection from input connector to the chassis to a point at the chassis as close to the modules themselves as possible, this cured the last bit of wisthle at least. Everything is almost dead quiet now, ther is still a very small wisthle but now it only audible with my ear directly in front of the loudspeakers so I can live with that. I have put my scope on the outputs and the only thing I see now is a 250 kHz sinus wave with an amplitude of about 0,2Vpp but that seems to the normal case for the UCD's so nothing to worry about.
Since the UCD's seem to be so very sensitive to wiring layout and grounding I will experiment what some pieces of ERS sheets will do in the amp. I have had very good results when I was modifying some Trends TA10 amps with it.
After that I disconnected the wires from the internal shield of the power transformers, as mentioned before they where connected together to the mains earth but since I do not have any mains earth it just does more harm than it cures. Don't know what to do with the earth shield now, for this moment I just leave them unconnected.
This also helped it a bit further but still not the cure for all. Next thing I rerouted the connection from input connector to the chassis to a point at the chassis as close to the modules themselves as possible, this cured the last bit of wisthle at least. Everything is almost dead quiet now, ther is still a very small wisthle but now it only audible with my ear directly in front of the loudspeakers so I can live with that. I have put my scope on the outputs and the only thing I see now is a 250 kHz sinus wave with an amplitude of about 0,2Vpp but that seems to the normal case for the UCD's so nothing to worry about.
Since the UCD's seem to be so very sensitive to wiring layout and grounding I will experiment what some pieces of ERS sheets will do in the amp. I have had very good results when I was modifying some Trends TA10 amps with it.
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