John Curl's Blowtorch preamplifier part II - Page 3654 - diyAudio
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Old 9th March 2013, 07:58 PM   #36531
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trust good, check better.

Better to use parts only you've got long time experience with, and/or do fatigue tests yourself, instead of checking for the stamped mark.

Aka, don't trust the label before taking a shuttle for a spin, but check the gaskets.

(must be a Euro-Pee-An thinking)
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Old 9th March 2013, 07:59 PM   #36532
1audio is offline 1audio  United States
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Quote:
Originally Posted by Kindhornman View Post
Jacco,
You mean all the capacitor failures in the earlier Apple Imac that I have had to change for a friend, all the leaking cheap lowest cost caps leaking all over the place with puffy end caps giving it away! Sometimes I do wonder how they got away with some of that?
Other side of the power interface, anything goes. Many computers suffered from this problem. Partly due to an abundance of counterfeit caps in China.
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Old 9th March 2013, 08:02 PM   #36533
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Quote:
Originally Posted by simon7000 View Post
Let us assume I have a setup where two identical turntables with identical recordings, completely in sync, drive two different preamplifiers, that in turn drive identical amplifiers going to a single switch to a single loudspeaker in a well balanced room. The listener sit on axis and has an ABX switch. What does it prove if no listener can tell what x is? ES
Nothing

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Originally Posted by simon7000 View Post
What if only one of the panel can tell? ES
That there is an audible difference

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Originally Posted by simon7000 View Post
What if they all can tell?
That there is an audible difference

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Originally Posted by simon7000 View Post
Now if none of the listeners can tell, but the power amplifier is changed and the results change, what does that mean?
ES
Depends on the changed results.

Does this help you to figger out the concepts, Ed?

jan
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Old 9th March 2013, 08:05 PM   #36534
bcarso is offline bcarso  United States
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Originally Posted by 1audio View Post
Other side of the power interface, anything goes. Many computers suffered from this problem. Partly due to an abundance of counterfeit caps in China.
I think I've related my horror story with substandard ceramic discs, and in a situation where nothing else held a voltage down. And that was on the other side of an ostensibly-safe simple stepdown transformer wall-wart. Probing the circuit with even a 10M scope probe was enough to conceal the mechanism and eliminate the effect.
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Old 9th March 2013, 08:34 PM   #36535
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I would like to point out something important:
UL listing is NOT MANDATORY for making a safe piece of audio equipment.
UL listed parts are certainly recommended for ANYTHING in the high voltage above, let's say 35V, because we cannot always tell from JUST LOOKING whether a product is safe from overvoltage or overcurrent, or from some strange, unusual condition.
UL listing is EXPENSIVE, and bureaucratic, and a bit of common sense and experience keeps it from being necessary, to make a safe product. One thing that I do, is I ALWAYS attempt to cover any exposed AC with heatshrink, and not just depend on spacing to prevent arcing, etc. If you are a complete newbe, then try to get some UL regulations over the internet or even buy the appropriate UL spec manual for your product. They are expensive, but CHEAP by comparison to having your product actually LISTED by UL. Common sense, once you read the specs, will be apparent, and maybe keep you from overlooking something. You might say that UL is an accumulation of more than 100 years of experience in fire and electrical dangers, and you can learn from them.
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Old 9th March 2013, 08:35 PM   #36536
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Originally Posted by jan.didden View Post
Nothing



That there is an audible difference



That there is an audible difference



Depends on the changed results.

Does this help you to figger out the concepts, Ed?

jan

Jan,

I think you get the point. Doing an accurate listening test is extremely difficult and the results are very specific.

As an example I used to have a box that simulated the RLC of 12 gauge cable in 3/4" conduit by 100' steps to 1000' Now if one listened to the difference between 100' and 200' most could not tell the difference. But the conclusion that the cable length didn't matter would of course be wrong because between 100' and 1000' pretty much anyone could tell the difference.

ES

Last edited by simon7000; 9th March 2013 at 08:42 PM.
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Old 9th March 2013, 08:41 PM   #36537
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Attached are the FFT results for six different transformers of different construction but all about the same ratings. They are imposing a voltage on the chassis as shown in my test setup (Prior Post.) There is a duplicate of one transformer but using an aluminum chassis.

Four of the transformers (All Signal Brand) are mounted on PC cards. The R core came with a bracket and the Triad Torroid uses a single bolt. The ac cord is the same shielded 6' type with the safety ground connected to the chassis. The R core has a shield that is also grounded.

ES
Attached Images
File Type: jpg 14A-20-24.JPG (492.9 KB, 130 views)
File Type: jpg DST-6-24.JPG (500.5 KB, 127 views)
File Type: jpg LP-24-1000.JPG (542.1 KB, 110 views)
File Type: jpg LP-24-1000 Aluminum Chassis.JPG (526.2 KB, 105 views)
File Type: jpg PC-24-1000.JPG (484.9 KB, 102 views)
File Type: jpg R Core.JPG (498.8 KB, 30 views)
File Type: jpg Torroid.JPG (485.7 KB, 38 views)
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Old 9th March 2013, 09:07 PM   #36538
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by john curl View Post
I would like to point out something important:
UL listing is NOT MANDATORY for making a safe piece of audio equipment.
UL listed parts are certainly recommended for ANYTHING in the high voltage above, let's say 35V, because we cannot always tell from JUST LOOKING whether a product is safe from overvoltage or overcurrent, or from some strange, unusual condition.
UL listing is EXPENSIVE, and bureaucratic, and a bit of common sense and experience keeps it from being necessary, to make a safe product. One thing that I do, is I ALWAYS attempt to cover any exposed AC with heatshrink, and not just depend on spacing to prevent arcing, etc. If you are a complete newbe, then try to get some UL regulations over the internet or even buy the appropriate UL spec manual for your product. They are expensive, but CHEAP by comparison to having your product actually LISTED by UL. Common sense, once you read the specs, will be apparent, and maybe keep you from overlooking something. You might say that UL is an accumulation of more than 100 years of experience in fire and electrical dangers, and you can learn from them.
That used to be enough. But now Europe and even China now require such safety proof or they cannot be imported into their countries, legally. And distributors are more and more weary of holding the bag if anything they imported goes wrong. Its insurance.

But my point here is for the non-manfr'ers... the less knowledagable DIY builder. The short story to be safe with parts exposed to the ac line voltage is to use proven safe parts and the other would be to get informed... such as what JC pointed out.

Thx-RNMarsh
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Old 9th March 2013, 09:11 PM   #36539
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by simon7000 View Post
Attached are the FFT results for six different transformers of different construction but all about the same ratings. They are imposing a voltage on the chassis as shown in my test setup (Prior Post.) There is a duplicate of one transformer but using an aluminum chassis.

Four of the transformers (All Signal Brand) are mounted on PC cards. The R core came with a bracket and the Triad Torroid uses a single bolt. The ac cord is the same shielded 6' type with the safety ground connected to the chassis. The R core has a shield that is also grounded.

ES

How are you going to make them all - transformers - zero/base-line'ed?
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Old 9th March 2013, 09:17 PM   #36540
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How are you going to make them all - transformers - zero/base-line'ed?
If you have an idea how to do it I am very open for it. What I tried was to mount them all using the mounting typical for each type. All centered in the same chassis. With the exception of the R core they all have the same voltage rating and are close on current.
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