Re: Safety Grounds
Hi Bob,
I'm not really the one to comment on safety grounding since I've never used one in any of my personal projects, so I've never given it much thought. I would agree with the need in any tube gear, but my passion is primarily the execution of solid state circuitry (which I'm quite proud of the results of my efforts over the years).
In my defense though all of my transformers end up on isolation mounts of some sort and are well fused.
What you designed sounds fine as long as it will actually support the current needed to blow the fuse. I appreciate the question though.
Regards, Mike.
Bob Cordell said:
Hi Bob,
I'm not really the one to comment on safety grounding since I've never used one in any of my personal projects, so I've never given it much thought. I would agree with the need in any tube gear, but my passion is primarily the execution of solid state circuitry (which I'm quite proud of the results of my efforts over the years).
In my defense though all of my transformers end up on isolation mounts of some sort and are well fused.
What you designed sounds fine as long as it will actually support the current needed to blow the fuse. I appreciate the question though.
Regards, Mike.
Re: Re: "Naked base-emitter junctions"?
Hi:
Professor Leach doesn't seem to agree with you.
http://users.ece.gatech.edu/~mleach/lowtim/output.html
Regards,
Milan
mikeks said:
Hi:
Professor Leach doesn't seem to agree with you.
http://users.ece.gatech.edu/~mleach/lowtim/output.html
Regards,
Milan
Re: Safety Grounds
Bob,
The practice I usually see is to connect the line cord safety ground directly to chassis and then tie this point to signal ground through a network such as you describe. Seems to me this gives about the same noise isolation, but provides a more direct path for fault current due to HV on the chassis. Your approach does have the advantage of not having to isolate the input jacks from chassis, and maybe this provides some further protection or noise isolation. Any thoughts on this?
Joe
Bob Cordell said:
Bob,
The practice I usually see is to connect the line cord safety ground directly to chassis and then tie this point to signal ground through a network such as you describe. Seems to me this gives about the same noise isolation, but provides a more direct path for fault current due to HV on the chassis. Your approach does have the advantage of not having to isolate the input jacks from chassis, and maybe this provides some further protection or noise isolation. Any thoughts on this?
Joe
Re: Re: Re: "Naked base-emitter junctions"?
If you have already a good driver working in class A you don't need to bias output stage, use it on higher currents that your driver can't supply to the load, if you can't live without emitter followers. Professor Leach analyzes fashion designs, it is his job. No need to follow them if you develop something new for your own purposes.
http://wavebourn.com/images/audio/swinik-III.gif
I've presented already in this thread an example of symmetrical opamp with 100% NFB, with OE outputs (4 transistors and 4 diodes only). It does not have symmetrical emitter followers where emitters fight against each other producing hardly controlled heat and wide spector of harmonic distortions. Also, no need to overload input in case of output overcurrent, it protects itself gracefully limiting output current by slowly switching from mode with 100% global feedback by voltage to 100% local feedback in driver transistors by current, if overloaded. http://www.diyaudio.com/forums/showthread.php?postid=1044880#post1044880
Try to simulate it and compare with what professors teach about (I personnally don't like simulators, they don't teach to feel, see, and hear schematics, as well I don't like when they teach children to use calculator when they can do the same things in own imagination developing own gray substance).
moamps said:
If you have already a good driver working in class A you don't need to bias output stage, use it on higher currents that your driver can't supply to the load, if you can't live without emitter followers. Professor Leach analyzes fashion designs, it is his job. No need to follow them if you develop something new for your own purposes.
http://wavebourn.com/images/audio/swinik-III.gif
I've presented already in this thread an example of symmetrical opamp with 100% NFB, with OE outputs (4 transistors and 4 diodes only). It does not have symmetrical emitter followers where emitters fight against each other producing hardly controlled heat and wide spector of harmonic distortions. Also, no need to overload input in case of output overcurrent, it protects itself gracefully limiting output current by slowly switching from mode with 100% global feedback by voltage to 100% local feedback in driver transistors by current, if overloaded. http://www.diyaudio.com/forums/showthread.php?postid=1044880#post1044880
Try to simulate it and compare with what professors teach about (I personnally don't like simulators, they don't teach to feel, see, and hear schematics, as well I don't like when they teach children to use calculator when they can do the same things in own imagination developing own gray substance).
I maybe making mistake back then, because I also don't believe it. But it appears different between different RCA females.
The setup is : Female RCA, the most obvious one is the comparison between plastic-cased cheap RCA and full brass expensive RCA.
RCA is connected to preamp input. Turn the volume to max, attach to amplifier, see the output of the amp in osciloscope. The female RCA is not connected to anything.
The distoriton (noise?) has different shape, only because I changed the female RCA (while nothing is attached to it).
Re: Re: Safety Grounds
Joe,
You don't mention where the power transformer ground is connected relative to the both the chassis/safety ground connection and the input jack and circuitry; input side or chassis? You mention the resistive isolation of the input circuit (as does Chris in the second quote).
As I said earlier I haven't used safety grounds but I do know that there should be no resistance inserted between the input circuit and the main power supply ground. This is a place where a noise voltage can develop across, with the noise becoming part of or riding on the circuitry ground. Bad for the noise floor, bad for any part of the circuit that uses it as a 0-reference.
If I was to add a safety ground to my system I would attach it to the chassis right where the power cord enters; I would mount any component (transformers, ac wiring terminal blocks, surge supressors, etc.) to the chassis; giving them a straight shot current wise back to the power cord. I would then create one star ground as physically close to the transformer ground wiring as practical, which acts as the 0 volt reference point for the audio circuitry. The star branches would include a separate connection to the speaker ground (or output and high level connections jack grounds in a preamp) including any output network returns; separate returns from the filter caps to the star, and a low impedance(at high freq) return to the input circuit.
The connection between the two grounds would be at the star, either directly or through the networks being discussed. I'll try this but my money is on a direct connection being fine.
I have alot of experience with this approach to internal grounding and after thinking about it, by connecting the safety ground in this manner the effect of noise on the safety ground would be relatively lower than any other approach since it creates a solid path that bypasses the noise around the input gain stages.
This of course all goes into the trash can when more than one component includes a safety ground. There is no way to avoid a ground loop once another is added (in any approach).
I think this response is more in line with Bob's earlier question, and I'm sure it will not be agreed with, due to the many different views of the proper way to ground equipment. But it does work. Well.
Regards, Mike.
Joe Berry said:
Joe,
You don't mention where the power transformer ground is connected relative to the both the chassis/safety ground connection and the input jack and circuitry; input side or chassis? You mention the resistive isolation of the input circuit (as does Chris in the second quote).
As I said earlier I haven't used safety grounds but I do know that there should be no resistance inserted between the input circuit and the main power supply ground. This is a place where a noise voltage can develop across, with the noise becoming part of or riding on the circuitry ground. Bad for the noise floor, bad for any part of the circuit that uses it as a 0-reference.
If I was to add a safety ground to my system I would attach it to the chassis right where the power cord enters; I would mount any component (transformers, ac wiring terminal blocks, surge supressors, etc.) to the chassis; giving them a straight shot current wise back to the power cord. I would then create one star ground as physically close to the transformer ground wiring as practical, which acts as the 0 volt reference point for the audio circuitry. The star branches would include a separate connection to the speaker ground (or output and high level connections jack grounds in a preamp) including any output network returns; separate returns from the filter caps to the star, and a low impedance(at high freq) return to the input circuit.
The connection between the two grounds would be at the star, either directly or through the networks being discussed. I'll try this but my money is on a direct connection being fine.
I have alot of experience with this approach to internal grounding and after thinking about it, by connecting the safety ground in this manner the effect of noise on the safety ground would be relatively lower than any other approach since it creates a solid path that bypasses the noise around the input gain stages.
This of course all goes into the trash can when more than one component includes a safety ground. There is no way to avoid a ground loop once another is added (in any approach).
I think this response is more in line with Bob's earlier question, and I'm sure it will not be agreed with, due to the many different views of the proper way to ground equipment. But it does work. Well.
anatech said:
Regards, Mike.
The amplifier is global feedback type, without output inductor.
It seems speaker cables are picking noise, and it gets into the feedback system from the power amp's binding post. There are spikes appear on the distoriton artifact when the speaker cables are attached to the amp's output, whether the load is dummy load or speaker.
It seems speaker cables are picking noise, and it gets into the feedback system from the power amp's binding post. There are spikes appear on the distoriton artifact when the speaker cables are attached to the amp's output, whether the load is dummy load or speaker.
lumanauw said:Those spikes are >20khz. I think this is the one who makes the reproduction becomes "harsh". It will not change guitar sound to piano sound but guitar sound to "harsh" guitar sound
For piano sound distortions must be asymmetrical and their spectral distribution should depend on force of impact. Harsh distortions are symmetrical distortions of high order that are brighter on lower volumes.
Hi, PMA,
I just know a difference between connecting/not connecting speaker wire (+load) to amplifier output binding post.
The output itself shows no difference at all (between connecting/not connecting), even if we magnifies the output trace alot.
But after nulling, there is the difference. It is not proportional between upper and lower screen, the lower has much bigger magnification than the upper.
What is that?
I just know a difference between connecting/not connecting speaker wire (+load) to amplifier output binding post.
The output itself shows no difference at all (between connecting/not connecting), even if we magnifies the output trace alot.
But after nulling, there is the difference. It is not proportional between upper and lower screen, the lower has much bigger magnification than the upper.