has anyone else found that when the tabs of two gainclone chips are conected electrically, one channel has no output? both my gainclones are mouned directly on the heat sink, but they are on seperate heatsinks. today, i tried connecting both heatsinks together with a pice of metal, and one channel stoped working! i immediatly disconnected power, and felt the chips, they were not even warm, so i tried again, with the same result. has anyone else noticed this? i do not know why this would happen, because both tabs are at -v.
Hi!
One thing that comes to my mind is that even if you connect both to the same supply, I bet you still use seperated filter caps for supply voltage.
So both ships are not "really" sharing the same supply, because of their own filters...
I will not check this out, but on my P3A I have one toroid, but apart from that totally seperated power supplies... and I bet that my P3A woult not like it very much if I connected V- from one supply with V- from the other...
They still share mass, though...
But maybe someone else can shed more light on this...
Bye,
Arndt
One thing that comes to my mind is that even if you connect both to the same supply, I bet you still use seperated filter caps for supply voltage.
So both ships are not "really" sharing the same supply, because of their own filters...
I will not check this out, but on my P3A I have one toroid, but apart from that totally seperated power supplies... and I bet that my P3A woult not like it very much if I connected V- from one supply with V- from the other...
They still share mass, though...
But maybe someone else can shed more light on this...
Bye,
Arndt
Hi folks,
I haven't built a gainclone, so I'm taking a wild guess about the typical IC amp circuits here...
Am I right in assuming that the inputs are (somewhere along the electrical path) connected at the audio source or pre-amp?
In that case the circuits have at least one common reference level.
Connecting the heat sinks (and thereby taps) you create a second common level (more or less). Since this is not at precicely the same potential, it causes a fault current, which is sensed by one of the sensing circuits on the chip. This triggers it's alarm state. This, in turn, shuts off the output to avoid self-destruction or un-intentended operation.
Try checking for multiple electrical paths for the same signals/potentials...
Jens
I haven't built a gainclone, so I'm taking a wild guess about the typical IC amp circuits here...
Am I right in assuming that the inputs are (somewhere along the electrical path) connected at the audio source or pre-amp?
In that case the circuits have at least one common reference level.
Connecting the heat sinks (and thereby taps) you create a second common level (more or less). Since this is not at precicely the same potential, it causes a fault current, which is sensed by one of the sensing circuits on the chip. This triggers it's alarm state. This, in turn, shuts off the output to avoid self-destruction or un-intentended operation.
Try checking for multiple electrical paths for the same signals/potentials...
Jens
Matttcattt,
You forgot to say what power op-amps are you talking about.
I think you use OPAs, don't you?
I remember reading on one datasheet (don't remember what) that the tabs shouldn't be used do conduct power.
That is to say they should be isolated.
But if you used a single supply (+ and ground) the tabs would be at ground potential and no problems.
You forgot to say what power op-amps are you talking about.
I think you use OPAs, don't you?
I remember reading on one datasheet (don't remember what) that the tabs shouldn't be used do conduct power.
That is to say they should be isolated.
But if you used a single supply (+ and ground) the tabs would be at ground potential and no problems.
my last kick at the cat Matt...and I may be wrong here...but some manufacturers do connect a power IC substrate to the mating surface and although it is a common connection it wont conduct enough...they refrain you from using a heatsink for a common connection because they know of possible isolation problems
until you tell us some voltage readings and what testing you have have done I`m kinda stuck about your problem as I have not read the data sheet or am familiar with the chip you are using.....but I`m sure one of the audio pro`s here will have a better clue
DIRT®
until you tell us some voltage readings and what testing you have have done I`m kinda stuck about your problem as I have not read the data sheet or am familiar with the chip you are using.....but I`m sure one of the audio pro`s here will have a better clue
DIRT®
JOE DIRT® said:my last kick at the cat Matt...and I may be wrong here...but some manufacturers do connect a power IC substrate to the mating surface and although it is a common connection it wont conduct enough...they refrain you from using a heatsink for a common connection because they know of possible isolation problems
until you tell us some voltage readings and what testing you have have done I`m kinda stuck about your problem as I have not read the data sheet or am familiar with the chip you are using.....but I`m sure one of the audio pro`s here will have a better clue
DIRT®
ok, ill read the voltages when i get a chance.
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