Hi,
I just put together my LC Audio ZAPpulse 2.3SE amp and it works great from my soundcards output however when I connect it to my main system I get some nasty behaviour and I am stumped!
My main source is a Behringer DEQ2496 where I have bypassed the output stage and go direct to a pair of S&B TX102 attenuation transformers. The DAC chip had 2.6V DC on its like but when wired balanced to the transformers it becomes common mode so I wouldn't think this is the issue....
Anyway when I connected it at a low volume setting I get a fair but of hum and noise. I thought maybe it was an impedance issue as the LC Audio modules are only 17K Ohms input impedance. I switched to only a small amount of attenuation so the DAC sees nearly the full 17K but like this the modules started glowing red hot and smoking! I pulled the plug in time to save them though it did blow the tweeters on my test speakers.
It was as though the input earth was connected to the heatsink of the modules (output transistors connect to the heatsink, maybe the adjust pin? Why don't they use mica pads?)
I am lucky they still seem in perfect condition but I can't use them if I can't make it work with my set-up!
Please help!
I just put together my LC Audio ZAPpulse 2.3SE amp and it works great from my soundcards output however when I connect it to my main system I get some nasty behaviour and I am stumped!
My main source is a Behringer DEQ2496 where I have bypassed the output stage and go direct to a pair of S&B TX102 attenuation transformers. The DAC chip had 2.6V DC on its like but when wired balanced to the transformers it becomes common mode so I wouldn't think this is the issue....
Anyway when I connected it at a low volume setting I get a fair but of hum and noise. I thought maybe it was an impedance issue as the LC Audio modules are only 17K Ohms input impedance. I switched to only a small amount of attenuation so the DAC sees nearly the full 17K but like this the modules started glowing red hot and smoking! I pulled the plug in time to save them though it did blow the tweeters on my test speakers.
It was as though the input earth was connected to the heatsink of the modules (output transistors connect to the heatsink, maybe the adjust pin? Why don't they use mica pads?)
I am lucky they still seem in perfect condition but I can't use them if I can't make it work with my set-up!
Please help!
Okay well I checked to see if I had been sent a low noise version or something which has only a 2K input impedance which after the transformers my DAC wouldn't like much but I don't have that! So it has a 17K input impedance which I think should be fine... I am completely clueless why they like to smoke so much lol! They are addicted!
Tenson said:
What was the part that was smoking? I have had the 2.3SE and I got them smoking as well. The part that can easily be smoked is the resistor in the zobel network. If you get the amp to oscillate at a high frequency (which was not so tough with the 2.3SE in an experimental setup) then that resistor has to burn a lot of power, I have seen smoke from that resistor and I have also blown up one. This may also explain why your tweeters were fried (too much HF power).
I do not have a solution for you. Probably you have to look into earthing etc, to prevent that the thing oscillates. If you want an amp that behaves well, just use an Hypex UcD180 or 400 (as I do now), these amps are very low noise, do not have any HF oscillation issues and do not have a zobel filter, so one less part to blow up 🙂
Best regards
Gertjan
Thanks Gertjan!
I think the first time it smoked with this set-up was a fluke, I must have had something shorted as I have not got it to smoke that badly again (visibly glowing hot in less than 5 seconds).
However, I do still get smoking, and it is from the resistor in the zobel.
I did a bit more experimentation…
1. Using the attenuation transformers driven from my soundcard (which worked fine direct) also works fine, so it is not the transformers causing the problems.
2. I then tried the modded output from my DAC with the transformers, but I put in a pair of 2.2uF caps to block any DC. It now makes some very loud low frequency hum! Odd, as it should do the opposite! It also still gets hot so it is not DC on the line causing the problem.
3. I connected it up as I did when it went red hot last time with the modded DAC output and the transformers, no DC blocking caps as the DC should be common mode (like I said I think I had a short last time) and now, the left channel works fine (though still noisy) and the right channel gets very hot.
I looked over the right channel very carefully and I found a hair-crack in the orange cap on the input. I had bent it back a little bit to make soldering the input easier, obviously it didn't like it and cracked!
I think maybe this blocked high frequencies on the input and now its broken the right channel is oscillating.
Does this sound like the reason to you? Does anybody know the value of that cap so I can replace it?
I won't know what all the noise is until I solder up the transformers nicely instead of using crock-clips I just hope it is not an impedance issue as the noise is reduced with more attenuation (lower level) which does result in a higher input impedance and a lower output impedance on the transformer. However, I don’t see it should be an issue when the amp has a 17K input.
Cheers,
I think the first time it smoked with this set-up was a fluke, I must have had something shorted as I have not got it to smoke that badly again (visibly glowing hot in less than 5 seconds).
However, I do still get smoking, and it is from the resistor in the zobel.
I did a bit more experimentation…
1. Using the attenuation transformers driven from my soundcard (which worked fine direct) also works fine, so it is not the transformers causing the problems.
2. I then tried the modded output from my DAC with the transformers, but I put in a pair of 2.2uF caps to block any DC. It now makes some very loud low frequency hum! Odd, as it should do the opposite! It also still gets hot so it is not DC on the line causing the problem.
3. I connected it up as I did when it went red hot last time with the modded DAC output and the transformers, no DC blocking caps as the DC should be common mode (like I said I think I had a short last time) and now, the left channel works fine (though still noisy) and the right channel gets very hot.
I looked over the right channel very carefully and I found a hair-crack in the orange cap on the input. I had bent it back a little bit to make soldering the input easier, obviously it didn't like it and cracked!
I think maybe this blocked high frequencies on the input and now its broken the right channel is oscillating.
Does this sound like the reason to you? Does anybody know the value of that cap so I can replace it?
I won't know what all the noise is until I solder up the transformers nicely instead of using crock-clips I just hope it is not an impedance issue as the noise is reduced with more attenuation (lower level) which does result in a higher input impedance and a lower output impedance on the transformer. However, I don’t see it should be an issue when the amp has a 17K input.
Cheers,
Okay so I obviously need to replace that cap even if it is not the full problem.
Its a 'BC128 47uF 6V3' Google says it is a solid aluminium.
Where can I get a replacement? I looked on RS but I don't see any 'solid aluminium' section!
This is the one-
How about replacing it with a 47uF 6.3V Tantalum?
Or maybe a SMT aluminium electrolytic?
Its a 'BC128 47uF 6V3' Google says it is a solid aluminium.
Where can I get a replacement? I looked on RS but I don't see any 'solid aluminium' section!
This is the one-
An externally hosted image should be here but it was not working when we last tested it.
How about replacing it with a 47uF 6.3V Tantalum?
Or maybe a SMT aluminium electrolytic?
Hi Tenson,
Don't use Tants mate, they won't sound as good as the BC128's😉
You can get both the 6.3v and 10v 47uf BC128 from Farnell, order code is 1166620 for the 10v
Good luck with sorting out your problem, I'm afraid I've never had any experiance with the ZAP modules so can't really help
Regards,
Leo
Don't use Tants mate, they won't sound as good as the BC128's😉
You can get both the 6.3v and 10v 47uf BC128 from Farnell, order code is 1166620 for the 10v
Good luck with sorting out your problem, I'm afraid I've never had any experiance with the ZAP modules so can't really help
Regards,
Leo
Have you any possibility to check your DAC with a scope to see if any HF is getting out this way?
Rgds
Rgds
Usually the output is as clean as something very clean but I can hear noise all over it so I know there is HF noise on the line. Why, is another matter. I think it is likely to be not using any shielded cables, though it has not been a problem in the past. The amp runs fine from my soundcards output via shielded cables so I will build the transformers and DAC into a nice case with short shielded wires and see where we are then.
Thanks for the help and I will keep you updated.
Thanks for the help and I will keep you updated.
Maybe ask Lars Clausen if he know of a good replacement. He have had some problems on his new module (NCD) where a cap failed. Read here for details: http://www.diyaudio.com/forums/showthread.php?s=&threadid=80526&perpage=10&pagenumber=44
And aparently he will replace it so he might be able to sugest a new one even if he is not involved in LC Audio any more. www.newclassd.com is his new site.
Rgds.
And aparently he will replace it so he might be able to sugest a new one even if he is not involved in LC Audio any more. www.newclassd.com is his new site.
Rgds.
In the zappulse 2.2se these caps were black gate n..🙂
And the bigger caps were black gate fk I think.
I have blown a couple of 2.2ohm resistors in the zobel network all right..
And the bigger caps were black gate fk I think.
I have blown a couple of 2.2ohm resistors in the zobel network all right..
bambadoo said:
Thanks guys, I'm glad I'm not the only one!
I have just this moment started with putting the pre-amp into its case (I hate metal work!) so I can get rid of all the crock-clips and see if that sorts out the noise. This one will take a while as it is a complex build (6 channels and digital Xover in the same case with room to add further mods to the PSU later).
Crap! I just found out why only the right channel's resistor was getting hot. Its because the other one is completely blown! I didn't realise because the amp seemed to be working fine. What power rating is that resistor? Looks like 5w or so?
This means it is probably not the cracked orange cap at the input causing the problem and it just wants to oscillate away regardless.
What are the reasons the amp could act like this? Also, what is the zobel even for?
Cheers, 🙁
This means it is probably not the cracked orange cap at the input causing the problem and it just wants to oscillate away regardless.
What are the reasons the amp could act like this? Also, what is the zobel even for?
Cheers, 🙁
Tenson said:
Hi Tenson,
I think these amps are allergic to experimental setups. If you clean up the wiring, twisted powercables etc etc, it may work. Possibly, experimental setups pick up more HF noise (maybe even from the modules themselves) causing oscillations. At least that is how I got my resistors smoking🙂
I guess you really need to build them up in a nice box with correct wiring etc to get them running without isues.
Good luck
Gertjan
Well... the pre-amp is on its way! Just the digital Xover to add in now 🙂
This is what I call a 'serious' pre-amp 😀 Believe it or not I just soldered 150 wires on to that little switch! My fingers hurt lol!
This is what I call a 'serious' pre-amp 😀 Believe it or not I just soldered 150 wires on to that little switch! My fingers hurt lol!
An externally hosted image should be here but it was not working when we last tested it.
Hello again!
I got the bits to fix my ZAP amps today. I replaced the orange cap at the input of one of them and the 2R2 resistors at the output with 5watt types (is that enough? Looked about right).
Now I plugged them in to the output from my soundcard which had been working okay before, and while it does seem to work alright I notice that the resistors still get very hot. How do other peoples 2.3SE's run? Do the resistors get hot anyway or is something not right?
I tried disconnecting one of the modules electrically from the cassis earth in case the source used the mains earth as a signal ground and that was what the problem was, but it doesn't make a difference, the resistors still get slowly hotter.
It may have done this before but I did not notice as the music was coming out just fine! Do other peoples amps do this too?
Thanks!
Now I'm not sure if they get hotter when I push the amp harder or not... they get to a point where I can not keep my finger on them and seem to stay there. I suspect the 5watt resistor would fail after a while, maybe I just need a 10watt jobbie on there.
I got the bits to fix my ZAP amps today. I replaced the orange cap at the input of one of them and the 2R2 resistors at the output with 5watt types (is that enough? Looked about right).
Now I plugged them in to the output from my soundcard which had been working okay before, and while it does seem to work alright I notice that the resistors still get very hot. How do other peoples 2.3SE's run? Do the resistors get hot anyway or is something not right?
I tried disconnecting one of the modules electrically from the cassis earth in case the source used the mains earth as a signal ground and that was what the problem was, but it doesn't make a difference, the resistors still get slowly hotter.
It may have done this before but I did not notice as the music was coming out just fine! Do other peoples amps do this too?
Thanks!
Now I'm not sure if they get hotter when I push the amp harder or not... they get to a point where I can not keep my finger on them and seem to stay there. I suspect the 5watt resistor would fail after a while, maybe I just need a 10watt jobbie on there.
I built a ZAPpulse 2.3SE and had no problems, worked first time and nothing even gets warm, even when shaking the house! I can only think that there is a grounding issue which is causing oscillation which is causing the zobel to fry.
How have you wired the input? I shorted the cold input to ground right at the PCB using the input lead screen.
How have you wired the input? I shorted the cold input to ground right at the PCB using the input lead screen.
Hi,
I just tried jumpering the negative line to ground on the PCB but it makes no difference 🙁
I also tried yet another source and it made no difference.
I'm stumped! Do you think that maybe when it blew the first time something else has gone as well? Any ideas what it might be?
I wish I never bought this damn thing! >.< What a waste of £300.
I just tried jumpering the negative line to ground on the PCB but it makes no difference 🙁
I also tried yet another source and it made no difference.
I'm stumped! Do you think that maybe when it blew the first time something else has gone as well? Any ideas what it might be?
I wish I never bought this damn thing! >.< What a waste of £300.
Tenson said:
Don't say that, it could have happened with whatever module you bought. They are good modules. It's possible something else got damaged, but the chance is not that great IMO. Shame you aren't a bit nearer or I could have a look over it.
Can you draw out how it's all wired. Include every connection.
Do the transformers just have two input and two output leads? Are they encased in a shielded can?
Hi,
I have drawn a picture of the way the amp is wired up.
I have tried disconnecting the heatsink from the case so it is not grounded and I have tried jumpering the negative input to ground. I also have the standby feature enabled which is a bit much to draw in, but it worked just the same before. I have the external gate drive enabled being driven from a separate transformer. It has two secondaries so I used both to get the full 15VA of the transformer. It measures 17V AC, do you think that might be too high?
The amps resistors get hot even when I don't drive it via the transformer inputs. I have tried driving it from the headphone socket on my Edirol soundcard and the aux out from my DEQ2496. Both make the resistors get slowly hot (no that slowly).
I just tried disabling the external gate dive on one of them and it made no difference. I think these are broken!
I have drawn a picture of the way the amp is wired up.
I have tried disconnecting the heatsink from the case so it is not grounded and I have tried jumpering the negative input to ground. I also have the standby feature enabled which is a bit much to draw in, but it worked just the same before. I have the external gate drive enabled being driven from a separate transformer. It has two secondaries so I used both to get the full 15VA of the transformer. It measures 17V AC, do you think that might be too high?
The amps resistors get hot even when I don't drive it via the transformer inputs. I have tried driving it from the headphone socket on my Edirol soundcard and the aux out from my DEQ2496. Both make the resistors get slowly hot (no that slowly).
I just tried disabling the external gate dive on one of them and it made no difference. I think these are broken!
An externally hosted image should be here but it was not working when we last tested it.
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