Filter capacitor proximity.
Bricolo,
I would have to second Tube_Dude's observations. Take a look at Peter's, BrianGT's, or JordanG's pictures or take a look at one of my experiments. Link to a gratuitous posting:
Picture of 2nd Gainclone.
Granted, this is based on the LM3875 but the same P2P principles can be applied to your project. Have a go at it. At the very least, you will sharpen your soldering skills.
Later,
Bricolo,
I would have to second Tube_Dude's observations. Take a look at Peter's, BrianGT's, or JordanG's pictures or take a look at one of my experiments. Link to a gratuitous posting:
Picture of 2nd Gainclone.
Granted, this is based on the LM3875 but the same P2P principles can be applied to your project. Have a go at it. At the very least, you will sharpen your soldering skills.
Later,
I subjected one of my GC to a torture test today. While auditionong at the friend's house, the outputs were connected by accident to a jumper (instaed of speakers input
) which created dead short. While we were wondering for approx 15 min. why there is no sound, the amp just got a bit warm, but otherwise didn't suffer any damage.
) which created dead short. While we were wondering for approx 15 min. why there is no sound, the amp just got a bit warm, but otherwise didn't suffer any damage.
It's too bad that mine isn't protected against reversed supply voltages and/or short between IC pins and/or GND
However, it's a good thing to know that we can accidently connect a jumper instead of a speaker
hehehe ! thanks Peter for the hint
BTW, which project are you working on these days Peter ? I'm curious and I guess I need so inspiration
Regards,
However, it's a good thing to know that we can accidently connect a jumper instead of a speaker
hehehe ! thanks Peter for the hint
BTW, which project are you working on these days Peter ? I'm curious and I guess I need so inspiration
Regards,
Hi again!
I, too, would like to post pics, since maybe then somebody would be able to help me, but I don not have any access at all to a digicam...
The hum I have sounds pretty much like a ground loop to me, but the only thing where I did not do a proper star-grounding would be, that I only run 3 cables from supply, thus having in fact two grounding points, one in the supply (where the central tap(s) are connected to the bridge), and one at the power connector in the amp (a short pin soldered to the connector base plate, and everything else soldered to this pin within the range of 1.5 cm).
What drives me mad is that I had one side working hum- and distortionfree, only when I hooked up the second channel, without properly connecting the non-inverting input (and therefore getting distortions), everything went downward from there on. Now I cannot get even one channel properly working without the hum.
The humming sound is actually not that big a deal, it is almost impossible to hear when more than 1.5 m away from speakers, and is not audible at even very sensible volume levels if a music is playing. But still, I would like to get rid of it.
I still did not try a zobel, but I don't think that adding it would change that annoying sound - but maybe I'm mistaken.
Frustrating that a lot of people report instant success, while I cannot get it to work properly. But I won't give up (at least not until the parts for my P3A arrive...)
If anyone still has some suggestions what I could try, please add some comments...
Bye,
Arndt
I, too, would like to post pics, since maybe then somebody would be able to help me, but I don not have any access at all to a digicam...
The hum I have sounds pretty much like a ground loop to me, but the only thing where I did not do a proper star-grounding would be, that I only run 3 cables from supply, thus having in fact two grounding points, one in the supply (where the central tap(s) are connected to the bridge), and one at the power connector in the amp (a short pin soldered to the connector base plate, and everything else soldered to this pin within the range of 1.5 cm).
What drives me mad is that I had one side working hum- and distortionfree, only when I hooked up the second channel, without properly connecting the non-inverting input (and therefore getting distortions), everything went downward from there on. Now I cannot get even one channel properly working without the hum.
The humming sound is actually not that big a deal, it is almost impossible to hear when more than 1.5 m away from speakers, and is not audible at even very sensible volume levels if a music is playing. But still, I would like to get rid of it.
I still did not try a zobel, but I don't think that adding it would change that annoying sound - but maybe I'm mistaken.
Frustrating that a lot of people report instant success, while I cannot get it to work properly. But I won't give up (at least not until the parts for my P3A arrive...)
If anyone still has some suggestions what I could try, please add some comments...
Bye,
Arndt
Cradle22 said:
Hi,
try zobel, this can cure distortion-maybe oscillation.
Minimalistic GC are technicaly speaking "on the edge" and is very sensitive how build it (without checked pcb and determined part position). GC look simple, but is not (if you have not experience, scope, etc). Dont give up.
You can draw small picture in paint or .....Can help.
Regards
Hi all,
on site http://sound.westhost.com/project74.htm I find simple RF probe, useful for detecting parasiting oscillation in GC.
C1 and C2 can be 100nF ceramic!, D1 can be AA series, BAT, or last-worst choice 1N4148. You dont need coax connection, twist wire to multimetar on DC position will be enough.
Oscillation will be apper if you detect some reading (greather then ca 1V) on output when input is grounded or simple without signal.
Regards
on site http://sound.westhost.com/project74.htm I find simple RF probe, useful for detecting parasiting oscillation in GC.
C1 and C2 can be 100nF ceramic!, D1 can be AA series, BAT, or last-worst choice 1N4148. You dont need coax connection, twist wire to multimetar on DC position will be enough.
Oscillation will be apper if you detect some reading (greather then ca 1V) on output when input is grounded or simple without signal.
Regards
Another thing I tried, with mixed success (the best so far):
I wrote that I extend the power connector "ground plate" with a pin. Normally I tried soldering all ground connections as close together as possible on that pin (like a star ground). Now I soldered all "real" power connections (the ones goind to IC) directly at the power connector, and those from signal at the other end of the pin.
Well, the hum is gone! So far, so good.
But now I notice a hissing sound in the tweeter, and somewhat louder than with my cheap Onkyo Amplfier put at 3/4 volume, GC should be nearly quiet...
So, like always, I'm trading off one improvement for another degraduation of sound quality...
Still wondering and looking...
Bye,
Arndt
I wrote that I extend the power connector "ground plate" with a pin. Normally I tried soldering all ground connections as close together as possible on that pin (like a star ground). Now I soldered all "real" power connections (the ones goind to IC) directly at the power connector, and those from signal at the other end of the pin.
Well, the hum is gone! So far, so good.
But now I notice a hissing sound in the tweeter, and somewhat louder than with my cheap Onkyo Amplfier put at 3/4 volume, GC should be nearly quiet...
So, like always, I'm trading off one improvement for another degraduation of sound quality...
Still wondering and looking...
Bye,
Arndt
Btw, here is a rough picture of what the current situation is (I have omitted some parts, like feedback resistors, muting resistor (the small cap actually is for muting). All connections start and end at parts, so red lines overlapping do not mean physical connection).
Maybe it helps... Otherwise I may be able to live with the "hissing" sound (like white noise at low volume). That noise totally disappears when I disconnect the line cable, but is not originating from my computer (since it also is volume independent, moving the slider up and down or actually turning output off does not change the noise at all).
Here is the pic (sorry for quality):
Maybe it helps... Otherwise I may be able to live with the "hissing" sound (like white noise at low volume). That noise totally disappears when I disconnect the line cable, but is not originating from my computer (since it also is volume independent, moving the slider up and down or actually turning output off does not change the noise at all).
Here is the pic (sorry for quality):
An externally hosted image should be here but it was not working when we last tested it.
MAGIC!! Well...I just finished my gainclone...sorta. Its w/ the Rod Elliots project 88..and its a special order for a friend. Anyway, I was having hum trouble...so I was fiddling w/ things and decided to put a resistor between speaker + and ground. The gainclone is an inverting amp, so the speaker out from the chip goes to the speaker - terminal. But the speaker+ terminal normally goes right to ground. I just put a 10 ohm resistor between both the r and l speaker+ terminals going to ground. The hum went away....ALSO!!.....the image came right into 3 dimensions. WOW!! I have never heard Holly Cole sound that ambient and smooth. There's so much ambient stuff coming from behind me! Anyway, try putting a 10 ohm resistor (5w...I hope thats enough) between speaker + terminal and ground. Maybe this does the same thing as a 1.5k "class a biasing" resistor. If someone else can try a 10 ohm between speaker + and ground and let me know what they think that'd be great. It think it rocks!
-Matthew K. Olson
-Matthew K. Olson
Arndt,
I suspect your hissing noise is being caused by spurious RFI in your cable if the hiss goes away when your disconnect the line cable. How long is your line cable? Is it shielded? I mean not like cheapo "off the shelf" stuff where the return signal comes back on the braided shield but a separate supply and return covered by a shield connected to the return at one end only. Try a few other cables your have lying around perhaps out of your current system.
I suspect your hissing noise is being caused by spurious RFI in your cable if the hiss goes away when your disconnect the line cable. How long is your line cable? Is it shielded? I mean not like cheapo "off the shelf" stuff where the return signal comes back on the braided shield but a separate supply and return covered by a shield connected to the return at one end only. Try a few other cables your have lying around perhaps out of your current system.
Hi!
Actually with line cable I meant the signal cinch cable. This cable is DIY. It uses a cable called "BKL Studio Line", which is a stereo microphone cable made for studios, with two layers of shielding woven against each other, connected both sides to ground of the input connectors (cinch on the amp side, 3.5 mm stereo on the other side), all connectors are gold plated.
The power cord is a simple, not shielded monitor power extension cable, 50 cm long.
I plan to build (actually just waiting for the connectors to arrive) a cable myself with a shielded 3 * 1.5 cable (Conrad).
But I will try the resistor Mattyo5 mentioned, but later, have to catch some sleep (although it is just noon...)
Bye,
Arndt
Philo said:
Actually with line cable I meant the signal cinch cable. This cable is DIY. It uses a cable called "BKL Studio Line", which is a stereo microphone cable made for studios, with two layers of shielding woven against each other, connected both sides to ground of the input connectors (cinch on the amp side, 3.5 mm stereo on the other side), all connectors are gold plated.
The power cord is a simple, not shielded monitor power extension cable, 50 cm long.
I plan to build (actually just waiting for the connectors to arrive) a cable myself with a shielded 3 * 1.5 cable (Conrad).
But I will try the resistor Mattyo5 mentioned, but later, have to catch some sleep
(although it is just noon...)Bye,
Arndt
Well...the hum was coming in on my CD player...I hooked up a discman and now the thing is SILENT. I worked hours getting the hum down to minimal...then...big doh...didn't check to see if it was coming from the source! I had to remove that 10 ohm resistor b/c the bass got killed. I think it did image better with it though. hmm...any ideas? I don't have a 1.5k 5 watt to play with...but I'll try to get one soon. Later all!
-Matthew K. Olson
-Matthew K. Olson
Cradle22 said:Hi!
But I will try the resistor Mattyo5 mentioned, but later, have to catch some sleep
I would definitely not advise that. That means you put a 10 ohm series resistor with the speaker. This will reduce the damping factor, the resistor will eat half of the amplifier power and ...
These two reasons are already enough ;-)
How did you connect the case ? Connect the case to the ground with a 100 ohm or so resistor and you could try 220 nF parallel. This will reduce the noise and hummm...
Watch out that the input connectors and speaker connector do not touch the case ! (electrically of course ;-) )
Fedde
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