Thanks for the advise and links to those posts guy's.... I have Ordered some BAV21's
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HelloDear DIYAudio!
Im having some problems!
I finished my build after a whole year. Whew that was slow! But I checked every connection twice, so I won't have to repair my amplifier.
Yet today, on the big day of turning on the amplifier, I got sad.
I started the amplifier.
Soft start. Check.
Speaker Protection. Check.
Bias set to 30 mV at thermal stabilization. Check.
DC offset is at 0V. Check.
CCS Set to midpoint. Check.
And it starts to hum.
I am desperately searching for the problem 5 hours ago, but can't find any, so I decided I would ask for some help. My audio is coming from an unbalanced source, and my signal ground is grounded to chassis (I have tried lifting it, but it made more noise). My Toroidal is net having any DC on, I have already checked that too. Strangely, when my heatsing isn't touching the backplate/lower plate, it seems to have a bit lower noise. not any, but lower.
I have attached some pictures of my build...
Please Help me, I don't want to use my speaker with this buzzing noise!
Thanks!
Im having some problems!
I finished my build after a whole year. Whew that was slow! But I checked every connection twice, so I won't have to repair my amplifier.
Yet today, on the big day of turning on the amplifier, I got sad.
I started the amplifier.
Soft start. Check.
Speaker Protection. Check.
Bias set to 30 mV at thermal stabilization. Check.
DC offset is at 0V. Check.
CCS Set to midpoint. Check.
And it starts to hum.
I am desperately searching for the problem 5 hours ago, but can't find any, so I decided I would ask for some help. My audio is coming from an unbalanced source, and my signal ground is grounded to chassis (I have tried lifting it, but it made more noise). My Toroidal is net having any DC on, I have already checked that too. Strangely, when my heatsing isn't touching the backplate/lower plate, it seems to have a bit lower noise. not any, but lower.
I have attached some pictures of my build...
Please Help me, I don't want to use my speaker with this buzzing noise!
Thanks!
Attachments
As Smart21 suggests run one channel at a time and get them silent individually first. AndrewT will be all over you for the wiring. Either twist or bundle all you power wiring, speaker wiring, ect into pairs/triples. Rail powers and ground running together in a bundle, speaker out and return together in a bundle, ect.
Input signal ground shouldn't be chassis grounded, it should connect through a loop breaker. If you connect signal ground to chassis any noise your chassis picks up will be heard through your amplifier.
It looks like you have a control transformer right beside the input of your left amplifier channel. Those little transformers are very noisy.
You should have ground wires running from each heat sink to earth ground. If this is making a difference, this is usually a sign of instability/oscillation. Fix your wiring up first and see if this improves.
Input signal ground shouldn't be chassis grounded, it should connect through a loop breaker. If you connect signal ground to chassis any noise your chassis picks up will be heard through your amplifier.
It looks like you have a control transformer right beside the input of your left amplifier channel. Those little transformers are very noisy.
You should have ground wires running from each heat sink to earth ground. If this is making a difference, this is usually a sign of instability/oscillation. Fix your wiring up first and see if this improves.
Smartx21 has hit upon a key element of problem solving. You'll need to simplify the system to check it, bit by bit.
Don't feel bad. I have done exactly (and I'd be most of us have) what you did, build the whole amp with great care but not checking the sub systems as it goes together. After all, it is fine if it works out
So, if you can bear it, break the thing down. Photograph as you do and look for contacts that don't belong. Check/test each board. Maybe build it back up in it simplest form, no soft start etc. Mine is a straight by the book build and I've never had an issue with it. Hum is almost always a connection that didn't go right, something simple but hidden.
Cheers!
Don't feel bad. I have done exactly (and I'd be most of us have) what you did, build the whole amp with great care but not checking the sub systems as it goes together. After all, it is fine if it works out
So, if you can bear it, break the thing down. Photograph as you do and look for contacts that don't belong. Check/test each board. Maybe build it back up in it simplest form, no soft start etc. Mine is a straight by the book build and I've never had an issue with it. Hum is almost always a connection that didn't go right, something simple but hidden.
Cheers!
Oh, another bit of free advice worth more than you pay for it...you don't need 12ga wire, anywhere! I started out doing as you have with the heavy stuff but have dropped back to 18ga, even 20. It is far easier to manage and sounds fine. Double it up if it makes you feel better but I have not found it makes a audible difference. I buy military surplus, silver plated wire, in bulk. It is cheap and solders like a dream. jwilhelm above is right. You'll need to be more tidy with your wires and thus, you'll be rewiring as you put it through testing and the final re-assembly. Make that process easier 
and drop down a few gages.
Cheers!
and drop down a few gages.Cheers!
Oh, another bit of free advice worth more than you pay for it...you don't need 12ga wire, anywhere! I started out doing as you have with the heavy stuff but have dropped back to 18ga, even 20. It is far easier to manage and sounds fine. Double it up if it makes you feel better but I have not found it makes a audible difference. I buy military surplus, silver plated wire, in bulk. It is cheap and solders like a dream. jwilhelm above is right. You'll need to be more tidy with your wires and thus, you'll be rewiring as you put it through testing and the final re-assembly. Make that process easier
Cheers!
It's always best to follow CSA/UL ratings for wire sizing. If you are running 15 amps ( not hard to do in rail feed wiring) through a wire minimum size should be 14AWG. If you want to be able to wire neatly look for a good quality annealed wire like TEW. Many industrial electricians buy this on 300m spools and will sell short pieces cheap( amplifier lengths are usually shorter than the cut off scraps from a job). Good wire won't spool itself back up into a coil when you unroll it. This makes for much neater/easier wiring.
Okay, I have disconnected everything from everything, and powered it up!
Poof there goes the 2 V- fuses!
I have disconnected the "control transformer, since I won't need the line driver anymore.
I am trying to bundle the wires together, but it is hard to do.
Disconnected the chassis from signal ground too, let's hope for the best.
Until some day, I have to pause this project, I have got no more fuses, and it is easter: the shops are closed...
Thanks for the advices!
Poof there goes the 2 V- fuses!
I have disconnected the "control transformer, since I won't need the line driver anymore.
I am trying to bundle the wires together, but it is hard to do.
Disconnected the chassis from signal ground too, let's hope for the best.
Until some day, I have to pause this project, I have got no more fuses, and it is easter: the shops are closed...
Thanks for the advices!
Inputs shortened? Open inputs may cause hum pickup.
Check for ground loops. Use ground loop breakers to avoid ground loops in stereo amps. The speaker protection units may introduce undesired connections between the left/right audio GND, or possibly even between the audio GND and the chassis safety GND.
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Check for ground loops. Use ground loop breakers to avoid ground loops in stereo amps. The speaker protection units may introduce undesired connections between the left/right audio GND, or possibly even between the audio GND and the chassis safety GND.
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Hi to all, can anyone who build the HB amp help me with some advice:
1. The 47pf Silver Mica caps next to power resistors, how did you guys soldered these because these are quite big and do touch the resistors that might get quite hot during use and I don't really want that, I want to solder these flat to the PCB but that will make the legs a big longer, does it matter if the leads a longer and by that I mean like 3-5 mm long.
2. The input pairs of transistors how recomended is to match gaine these? i don't really own a measuring instrument to do that at the moment, I am aware that it might cause some bigger offset if these are not well matched, but is that a big concern?
The parts were bought from RS Components in a larger "" lot"" (200 pieces) so I think might be from the same batch.
I have attached a picture to see :
Thanks.
1. The 47pf Silver Mica caps next to power resistors, how did you guys soldered these because these are quite big and do touch the resistors that might get quite hot during use and I don't really want that, I want to solder these flat to the PCB but that will make the legs a big longer, does it matter if the leads a longer and by that I mean like 3-5 mm long.
2. The input pairs of transistors how recomended is to match gaine these? i don't really own a measuring instrument to do that at the moment, I am aware that it might cause some bigger offset if these are not well matched, but is that a big concern?
The parts were bought from RS Components in a larger "" lot"" (200 pieces) so I think might be from the same batch.
I have attached a picture to see :
An externally hosted image should be here but it was not working when we last tested it.
.
Thanks.
When I get lucky one day and get a pair of these pcb's, then I will create 2 monoblocks and build aluminium walls in each cabinet between the transformer and everything else in the complete power amplifier.
The transformer radiate some magnetic field that can turn into hum.
Maybe you have to look at this thing too ?
The transformer radiate some magnetic field that can turn into hum.
Maybe you have to look at this thing too ?