Cradle22 , if you are running your amp from the PC , then I can almost guarantee that the hiss you are hearing is originating in the PC.
Turning down the volume slider won't necessarily fix the issue because the output buffers will still be live and still be picking up crap from the PC.
Ask anyone who's ever used a PC in a recording studio and they'll tell you just how much junk noise they throw out, not just from audio out's , but onto power lines and coupled into external cables.
The SMPS in the PC is a major culprit, but running CPU's at microwave speeds creates HUGE amounts of RFI.
Try running your amp from a battery powered minidisc / CD player , then you'll see whether the noise is created by the amp itself. I suspect that you'll be surprised.
ray
Turning down the volume slider won't necessarily fix the issue because the output buffers will still be live and still be picking up crap from the PC.
Ask anyone who's ever used a PC in a recording studio and they'll tell you just how much junk noise they throw out, not just from audio out's , but onto power lines and coupled into external cables.
The SMPS in the PC is a major culprit, but running CPU's at microwave speeds creates HUGE amounts of RFI.
Try running your amp from a battery powered minidisc / CD player , then you'll see whether the noise is created by the amp itself. I suspect that you'll be surprised.
ray
Hi again!
Some things to answer...
and
Of course the whole setup gets quiet that way. If you connect a portable, you don't have a ground loop at all (and I'm pretty sure ground loops are the origin of Mattyo5 and my probs)...
I already trie connecting the case to ground with a 470nF cap several times (but without resi), didn't help at all, but I will try with resi...
Of course I meant that I omitted some stuff from the drawing, but not from the actual circuit...
And I would say that the overall agreement where to put the smoothing caps is as closely to the pins of the IC as possible - and I have 2 * 220 uF in the (outsourced) supply to provide some initial smoothing...
And all connectors are isolated from the case, all with infinite resitance to case...
And the overall agreement the connection to PC itself (or the PC itself) is the cause for noises: Apart from being different amps, I had exactly three different amps hooked up to my setup, first of all the cheapo Onkyo integrated stereo premain amplifier (no noise, only when I turn volume all the way up, that is the noise of the Onkyo), then my heavily modified Marantz amp (no noise apart from some hissing, way lower than with the GC - but I blew the STK chip on that one, see another Thread - "Heatsink Grease"), and then the GC itself (noises, distortions, hummmmming) I never changed the hookup to wall outlet, the way my input cable goes, the LS cables...
Maybe I will have to contact supplier again in order to try with LM3875... will try OPA548 (which I already have) when I have parts for that...
Thanks so far!
Arndt
Some things to answer...
Mattyo5 said:
and
Of course the whole setup gets quiet that way. If you connect a portable, you don't have a ground loop at all (and I'm pretty sure ground loops are the origin of Mattyo5 and my probs)...
I already trie connecting the case to ground with a 470nF cap several times (but without resi), didn't help at all, but I will try with resi...
Of course I meant that I omitted some stuff from the drawing, but not from the actual circuit...
And I would say that the overall agreement where to put the smoothing caps is as closely to the pins of the IC as possible - and I have 2 * 220 uF in the (outsourced) supply to provide some initial smoothing...
And all connectors are isolated from the case, all with infinite resitance to case...
And the overall agreement the connection to PC itself (or the PC itself) is the cause for noises: Apart from being different amps, I had exactly three different amps hooked up to my setup, first of all the cheapo Onkyo integrated stereo premain amplifier (no noise, only when I turn volume all the way up, that is the noise of the Onkyo), then my heavily modified Marantz amp (no noise apart from some hissing, way lower than with the GC - but I blew the STK chip on that one, see another Thread - "Heatsink Grease"), and then the GC itself (noises, distortions, hummmmming) I never changed the hookup to wall outlet, the way my input cable goes, the LS cables...
Maybe I will have to contact supplier again in order to try with LM3875... will try OPA548 (which I already have) when I have parts for that...
Thanks so far!
Arndt
another gc
I have posted a few pictures of my GC here:
http://www.diyaudio.com/forums/showthread.php?postid=143721#post143721
Sound is really good, very fast and dynamic, but since my speakers are not so good at the moment, I can't be more specific. One of these days I will test it on some high-end speakers.
Time will tell if this amp is so good that I will extend it into a five-channel version to be used as my main amp...
/Jan
I have posted a few pictures of my GC here:
http://www.diyaudio.com/forums/showthread.php?postid=143721#post143721
Sound is really good, very fast and dynamic, but since my speakers are not so good at the moment, I can't be more specific. One of these days I will test it on some high-end speakers.
Time will tell if this amp is so good that I will extend it into a five-channel version to be used as my main amp...
/Jan
Last weekend I hooked up my first (non-inverting) GC at the home of Jerry, with whom I'm making a new (inverted) clone.
We definately had a ground-loop there, something I did not have at home in several different setup's. It appeared that Jerry had used a power extension cord that was plugged in a different wall outplet from the CD player(only 2 meters away). After using the same power outlet everything was dead-silent again.
Anyway, here is a picture of the new amp housing made by Jerry:
The story of this "gainverter" amp is found on the >>homepage<<
Maarten
PS. Looking for fair-priced 12-/24- step mono attenuator switches
We definately had a ground-loop there, something I did not have at home in several different setup's. It appeared that Jerry had used a power extension cord that was plugged in a different wall outplet from the CD player(only 2 meters away). After using the same power outlet everything was dead-silent again.
Anyway, here is a picture of the new amp housing made by Jerry:
An externally hosted image should be here but it was not working when we last tested it.
The story of this "gainverter" amp is found on the >>homepage<<
Maarten
PS. Looking for fair-priced 12-/24- step mono attenuator switches
Question to P. Daniel
Hi!
I have one quetsion: In your commercial GC, how do you ground the chassis of the amp and the supply? Via a resistor (bypassed?), simply to ground, or current breaker, etc.?
Of course I ask this because of my oscillation probs as soon as I close the lid of my case...
Thanks,
Arndt
Hi!
I have one quetsion: In your commercial GC, how do you ground the chassis of the amp and the supply? Via a resistor (bypassed?), simply to ground, or current breaker, etc.?
Of course I ask this because of my oscillation probs as soon as I close the lid of my case...
Thanks,
Arndt
Cradle22, I do not use chassis grounding, and no AC grounding either, and I still have a hum-free amp. I used Feddes recommendations on ground wiring, see his Thor amp page
2Bak,
What circuit are you using?
As soon as I connected In+ directly to ground I started to have interference problems, I was picking some radio frequencies. The circuit was OK when using Thorsten schematic with resistor and capacitor to ground on positive input. On my first amp I grounded the chassiss by connecting it to mains ground with an extra wire from PS. On my later amps I connected the chassiss to the signal ground by not isolating one of the negative binding posts (in one channel only)
Yesterday, a friend of mine who's using very efficient Altecs, noticed that when using his cordless phone near the amp, the channel which negative output was not connected to the chassiss was picking up hum. So I advised him to connect both channels negative posts together and it solved the problem. Still, it makes me wonder why?
What circuit are you using?
As soon as I connected In+ directly to ground I started to have interference problems, I was picking some radio frequencies. The circuit was OK when using Thorsten schematic with resistor and capacitor to ground on positive input. On my first amp I grounded the chassiss by connecting it to mains ground with an extra wire from PS. On my later amps I connected the chassiss to the signal ground by not isolating one of the negative binding posts (in one channel only)
Yesterday, a friend of mine who's using very efficient Altecs, noticed that when using his cordless phone near the amp, the channel which negative output was not connected to the chassiss was picking up hum. So I advised him to connect both channels negative posts together and it solved the problem. Still, it makes me wonder why?
Hi!
I have to tell you all what caused my problems...!!!
I use the small heatsink cases from Conrad, and drilled holes for all my (insulated) connectors into one of the frontplates of this casing...
Of course I checked that the LS-connectors, cinch connectors... had no connection to chassis... or so I though...
The smooth finish of the aluminium casings is not conductive
! So, measuring resistance or (what do you call the small diode-test on multimeters) showed no connections... 
But all the time the LS connectors which directly connect to (both) ICs had connections to chassis, and so also connections to each other... I think that could have caused a lot of the problems I described in all my numerous (often annoying, I would think) postings...
But I can't widen those holes enough in order to ensure non-conductive connector mounting since it is to late and I do not want to wake my neighbours with my dremel rotating at 25000 rpm...
But at least now I can sleep soundly , with great expectations for my GC tests, and hey! it even made me test my OPA548... 
So, thanks to all, sometimes dumbness is intelligence's worst enemy...
Arndt
I have to tell you all what caused my problems...!!!
I use the small heatsink cases from Conrad, and drilled holes for all my (insulated) connectors into one of the frontplates of this casing...
Of course I checked that the LS-connectors, cinch connectors... had no connection to chassis... or so I though...
The smooth finish of the aluminium casings is not conductive
! So, measuring resistance or (what do you call the small diode-test on multimeters) showed no connections... But all the time the LS connectors which directly connect to (both) ICs had connections to chassis, and so also connections to each other... I think that could have caused a lot of the problems I described in all my numerous (often annoying, I would think) postings...
But I can't widen those holes enough in order to ensure non-conductive connector mounting since it is to late and I do not want to wake my neighbours with my dremel rotating at 25000 rpm...
But at least now I can sleep soundly
, with great expectations for my GC tests, and hey! it even made me test my OPA548... So, thanks to all, sometimes dumbness is intelligence's worst enemy...
Arndt
from Peter D.
I just finished mine based on the LM3875 and it's almost perfect to my taste. No noise even at full volume, no ground loops... well you get the point.
However I found out that my Gainclone is a little "shy" on bass reproduction. What could be the factor causing this lack of bass ?
I'm using a 1uF input cap. 10K & 220K resistor and finally 2 X 1000uF caps.
Thanks !
I just finished mine based on the LM3875 and it's almost perfect to my taste. No noise even at full volume, no ground loops... well you get the point.
However I found out that my Gainclone is a little "shy" on bass reproduction. What could be the factor causing this lack of bass ?
I'm using a 1uF input cap. 10K & 220K resistor and finally 2 X 1000uF caps.
Thanks !
The only plausible explanation I ever read about 1000uF being enough (apart from caps sitting directly at IC, thus leading to short paths and faster recovery), is that BECAUSE 1000uF are not enough capacitance to totally control the bass on strong bass impulses, the amp SOUNDS better. Better in the ways of less defined, warmer, louder.
Of course if you like razor sharp bass impulses, dry enough to punch the dust out of your couch, that will not suffice...
But over all people like to compare the GCs with tube amplifiers, having a warm, not too anaylticals sound (although without breaking in time I found the GC pretty analytical...)
So, just try it out... But when you add a lot of capacitance to the main supply, reduce the cap directly at the IC (no need for big caps, smaller and faster ones are better, maybe 220uF bypassed...).
I will definitely try this with some SlitFoils lying around
And report the differences, please!
G' Night,
Arndt
Of course if you like razor sharp bass impulses, dry enough to punch the dust out of your couch, that will not suffice...
But over all people like to compare the GCs with tube amplifiers, having a warm, not too anaylticals sound (although without breaking in time I found the GC pretty analytical...)
So, just try it out... But when you add a lot of capacitance to the main supply, reduce the cap directly at the IC (no need for big caps, smaller and faster ones are better, maybe 220uF bypassed...).
I will definitely try this with some SlitFoils lying around
And report the differences, please!
G' Night,
Arndt
Thank you very much
I added 20 000uF per rail and the bass came back
However, i used 4 X 10000uF 'cause I had only that on hand but it's still pretty good ! (You suggested more caps with smaller value)
I'm still curious about the impact of the 4.7uF input cap suggested by Equilibrium. This will be my next experience !
After that, the only thing left will be to add some windings around my transformer to light up a blue led perhaps
Regards,
I added 20 000uF per rail and the bass came back
However, i used 4 X 10000uF 'cause I had only that on hand but it's still pretty good ! (You suggested more caps with smaller value)
I'm still curious about the impact of the 4.7uF input cap suggested by Equilibrium. This will be my next experience !
After that, the only thing left will be to add some windings around my transformer to light up a blue led perhaps
Regards,
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