I have finally got my first pair of Zappulse nicely built up and in a box. However, it makes rather a lot of noise at "idle", and since a number of other people have mentioned it, its probably worth documenting it here (Perhaps Lars will also comment and offer recommendations on minimising it?)
Pictures: http://www.wildgooses.com/downloads/amp4.jpg
There is a lot of documentation on building the Zappulse modules, and I will put it all together in a different thread later.
Subjectively the amps are pretty good. Decent midrange and bass. They don't seem to clip easily/at all. The imaging is excellent and much better than my Meridian 557. However, the treble is a different matter... It takes a good while to soften up, and subjectively to me, even after 100+ hours it is still quite harsh and has some ringing.
At idle, they make a kind of crackle which is clearly audible. It's louder than the idle hiss of my (baseline) Meridian 557 power amps, and it's got more crackle than hiss. It's not audible at the listening position with my speakers though.
However, the thing which *is* really driving me up the wall is that the right hand channel has a high pitched whine. It's completely audible at the listening position, and it's probably about a similar frequency to that noise a TV makes when operating (probably slightly different freq, a little lower I think). Perhaps many people can't even hear this high, so it wouldn't be an issue..?
I am slightly unsure as to whether the idle high pitched whine could actually be intermodulating and causing the harsh treble that I am hearing normally...?
Basically, I wired them up according to the cookbook, then also joined the audio and the power earthwires together (in an attempt to improve earthing effects, but with no improvement audible...)
The high pitched whine is only in the right hand channel and has been there since I first built them on a piece of aluminium. The problem is that I only checked it was audible at the listening position just now, and you know how it is, once you notice it you can't take you mind off it!
Any thoughts on removing the high pitched whine would be appreciated
Ed W
Pictures: http://www.wildgooses.com/downloads/amp4.jpg
There is a lot of documentation on building the Zappulse modules, and I will put it all together in a different thread later.
Subjectively the amps are pretty good. Decent midrange and bass. They don't seem to clip easily/at all. The imaging is excellent and much better than my Meridian 557. However, the treble is a different matter... It takes a good while to soften up, and subjectively to me, even after 100+ hours it is still quite harsh and has some ringing.
At idle, they make a kind of crackle which is clearly audible. It's louder than the idle hiss of my (baseline) Meridian 557 power amps, and it's got more crackle than hiss. It's not audible at the listening position with my speakers though.
However, the thing which *is* really driving me up the wall is that the right hand channel has a high pitched whine. It's completely audible at the listening position, and it's probably about a similar frequency to that noise a TV makes when operating (probably slightly different freq, a little lower I think). Perhaps many people can't even hear this high, so it wouldn't be an issue..?
I am slightly unsure as to whether the idle high pitched whine could actually be intermodulating and causing the harsh treble that I am hearing normally...?
Basically, I wired them up according to the cookbook, then also joined the audio and the power earthwires together (in an attempt to improve earthing effects, but with no improvement audible...)
The high pitched whine is only in the right hand channel and has been there since I first built them on a piece of aluminium. The problem is that I only checked it was audible at the listening position just now, and you know how it is, once you notice it you can't take you mind off it!
Any thoughts on removing the high pitched whine would be appreciated
Ed W
All the electronics are from LC Audio, and they have been very helpful in designing the amp and answering questions. (The powersupplies, etc will all work well with the UCD as well, and a few people are doing that.)
The case is from audiokit.it and is very nice looking with the front plate fitted. A bargain as well at about 40 Euros. However, make sure they ship it properly, the first two were sent wrapped in "brown paper" and came with all the corners bashed in... They did replace them free of charge though (in a box next time).
I will write up a much longer thread with more pictures and pull together all the building instructions, shortly. The whine at idle is my main concern right now.
The case is from audiokit.it and is very nice looking with the front plate fitted. A bargain as well at about 40 Euros. However, make sure they ship it properly, the first two were sent wrapped in "brown paper" and came with all the corners bashed in... They did replace them free of charge though (in a box next time).
I will write up a much longer thread with more pictures and pull together all the building instructions, shortly. The whine at idle is my main concern right now.
mattjk said:
How much closer can I get them? They are already right next to each other...?
Duck-Twacy said:
They are 200Va 2x42v torroids from LCAudio. They also have a 15V secondary which is used to power the boards themselves in order to save a small amount of power on idle.
The powersupply is wired to that there are two torroids each supplying one rectifier, and hence one rail. The secondaries are paralleled into each rectifier. So really it's one torroid per powersupply rail.
Jaka Racman said:
That's a good idea actually. I have tried unplugging the source connections (turning off the amp each time), and the high pitched whine jumps to the other channel then...
Right now, after fiddling with both it's a little quieter in the right, and there is some whine in the left channel as well...
With only one channel running (right), then there was only normal background hiss, hardly any high pitched whine, and a tiny bit of "AM tuning" type noise (you know the kind of wheee-awww kind of noise that you get when you tune an am radio). It was just lightly in the background and moving slightly in pitch
With both channels running and no interconnects plugged in at all, then both channels are pretty quiet. There is a tiny bit of high pitched crackle in the right channel, but basically just the normal hiss in each channel (less hiss in the left channel though..?)
Hard to interpret this and decide if I am just picking up radio interference in the amp (via the interconnects), or whether it's some kind of intermodulation between the two modules. I suspect radio interference actually, but I just don't understand why it's mainly in only one channel (and I had the interconnects the other way around earlier and I'm sure it was still in the right channel then...?)
Any interpretations on the above?
Thanks
It’s really worrying to hear (no pun intended) about “Crackles, Pops, Whines & AM tuning radio type noise”.
Your construction seems very neat, but I would have placed the modules further apart – rather then closer, but this would not explain why a single module still makes noises.
If a single module does it by itself, then it would suggest that the modulator is intermodulation with IT'S SELF! If this is in fact the case, then this is a VERY poor design.
Gut reaction says your always going to have intermodulation issues with multi channel hysteresis type modulators – but that said, UCD owners don’t seem to have an issue.
Do you still hear noises with ONLY one channel operating and its inputs shorted? If so it, really points to internal modulator noise.
I hate to think what affect the RF leakage from a CD / DVD player will have on the sound. The fact that the units have a very “harsh” treble is a SURE sign of High Frequency RF issues.
John
Hi, Indeed JohnW might be onto the right idea. But although I haven't tried the modules with the inputs shorted, the noise does go away if I simply unplug the interconnects (as I said in that earlier message).
The noise seems to shift to the other module if there is only one inteconnect on the left channel. Right left hanging
The noise seems to go away on the right channel if I turn off the left channel...
I think this points to some kind of radio RFI interference, and it could well be picking up something nearby. I have a computer, TV, mains filter, 802.11a network and all kinds of nasty stuff within a couple of meters. However, quick tests of turning off most of it and moving the amp around have not shown it to be related to that. I have noted a slight tendency for the noise to change freq if I tilt the whole amplifier at an angle though (lift up one side)
Any thoughts on tracking this down would be appreciated. What order of tests should I try now:
- grounding on the input lines?
- Adding in the LCAudio amp clock module to bring the modulator up to 1Mhz?
- different modules in the amp...
Thanks
P.S. To anyone thinking of copying the layout shown in the photo... Be careful there is not enough cooling in this case if you just strap the module to the steel cooling area at the base of the case. I guess the heat does not run far enough away from the modules and the case above and below the modules gets hot enough to burn you... I will have to add an aluminium plate to it today...
The noise seems to shift to the other module if there is only one inteconnect on the left channel. Right left hanging
The noise seems to go away on the right channel if I turn off the left channel...
I think this points to some kind of radio RFI interference, and it could well be picking up something nearby. I have a computer, TV, mains filter, 802.11a network and all kinds of nasty stuff within a couple of meters. However, quick tests of turning off most of it and moving the amp around have not shown it to be related to that. I have noted a slight tendency for the noise to change freq if I tilt the whole amplifier at an angle though (lift up one side)
Any thoughts on tracking this down would be appreciated. What order of tests should I try now:
- grounding on the input lines?
- Adding in the LCAudio amp clock module to bring the modulator up to 1Mhz?
- different modules in the amp...
Thanks
P.S. To anyone thinking of copying the layout shown in the photo... Be careful there is not enough cooling in this case if you just strap the module to the steel cooling area at the base of the case. I guess the heat does not run far enough away from the modules and the case above and below the modules gets hot enough to burn you... I will have to add an aluminium plate to it today...
Hmm, interesting discovery. When I was testing it before I had it plugged into the wall socket directly. Since building it in its box I had it plugged into one of these Kemp mains filters:
http://www.hificollective.co.uk/accessories/kemp_power_source.html
Unplugging it from the Kemp unit and plugging it back into the wall gets rid of the high pitched whine! Just the normal hiss remains and the crackle goes back to being the usual soft hiss that an amp seems to make at idle.
However, curiously if I bring the mains cable anywhere near the mains conditioner, or inline with the middle of it's axis even quite far away, then the whine comes back. (ie the conditioner is standing upright and if the cable is on the floor it can be quite close, but as soon as I raise the cable near the center of the conditioner then it makes the whine no matter how close it is....
I had assumed that this conditioner was a decent transformer device (looking at the size of it), but clearly something is causing it to act as a radio transmitter that the Zappulse power supply is picking up. I have a Schnaffer medical mains filter fitted (on advice from Lars), but I notice that some people like Bruno Putz dont agree with these things, could there be any interaction there...?
So we seem to have cleared the Zappulse from being the culprit in this case (which is great). However, I wonder if someone can advise me how to adjust my powersupply to be immune to this kind of radiated junk? Is it going to be earth pollution causing this problem?
http://www.hificollective.co.uk/accessories/kemp_power_source.html
Unplugging it from the Kemp unit and plugging it back into the wall gets rid of the high pitched whine! Just the normal hiss remains and the crackle goes back to being the usual soft hiss that an amp seems to make at idle.
However, curiously if I bring the mains cable anywhere near the mains conditioner, or inline with the middle of it's axis even quite far away, then the whine comes back. (ie the conditioner is standing upright and if the cable is on the floor it can be quite close, but as soon as I raise the cable near the center of the conditioner then it makes the whine no matter how close it is....
I had assumed that this conditioner was a decent transformer device (looking at the size of it), but clearly something is causing it to act as a radio transmitter that the Zappulse power supply is picking up. I have a Schnaffer medical mains filter fitted (on advice from Lars), but I notice that some people like Bruno Putz dont agree with these things, could there be any interaction there...?
So we seem to have cleared the Zappulse from being the culprit in this case (which is great). However, I wonder if someone can advise me how to adjust my powersupply to be immune to this kind of radiated junk? Is it going to be earth pollution causing this problem?
As far as I understand this mains conditioner is fully passive. In this case there must be something external causing a stray-field from this mains conditioner. Is there anything else plugged into it when the whininh happens ?
BUT if this mains conditioner isn't working passively at all (i.e. like some UPS do by the use of another class-d amp !) then it's RF hash might INTERFERE with the ZAP amp's own carrier frequency.
Have you got a scope that you could use to check for any RF stray-field from the conditioner by using a pickup-coil ?
The main reason why Bruno P dislikes those RF filters is their caps connected to mains ground.
Apart from Peranders' suggestion of using shielded input cable there are other possibilities to reduce internally generated EMC problems. The modules offer the possibility of synchronisation. They also feature symmetric inputs AFAIK.
Make use of these intrinsic features !
Regards
Charles
Hi Phase_accurate. Thanks for the suggestions
As you can see from the pictures I am using a balanced input already, and although it's not clear, and they are too close to the output coil, the input cables are actually braided
The mains conditioner is an unknown, but I would have *assumed* that it was just a large 1:1 transformer? It's very heavy and quite chunky, which tends to confirm this...? I wonder if because I have tilted the thing so it stands up, the center of the transformer is now firing out into the room. Is there likely to be a ton of magnetic/rf junk on the center line of a big tranny? (going out quite far away from the tranny?)
I unplugged everything else from the conditioner during testing, except the preamp (Meridian 502, decent commercial design). Still the whine persists.
Even now with the conditioner just sitting there, bringing the mains cable for the digital amp, either inline with the middle of the conditioner, or very close at the edges, causes the whine to restart. Waving the mains cable around makes a noise like tuning an AM radio (as the cable passes near the conditioner).
Curious...
As you can see from the pictures I am using a balanced input already, and although it's not clear, and they are too close to the output coil, the input cables are actually braided
The mains conditioner is an unknown, but I would have *assumed* that it was just a large 1:1 transformer? It's very heavy and quite chunky, which tends to confirm this...? I wonder if because I have tilted the thing so it stands up, the center of the transformer is now firing out into the room. Is there likely to be a ton of magnetic/rf junk on the center line of a big tranny? (going out quite far away from the tranny?)
I unplugged everything else from the conditioner during testing, except the preamp (Meridian 502, decent commercial design). Still the whine persists.
Even now with the conditioner just sitting there, bringing the mains cable for the digital amp, either inline with the middle of the conditioner, or very close at the edges, causes the whine to restart. Waving the mains cable around makes a noise like tuning an AM radio (as the cable passes near the conditioner).
Curious...
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.