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Old 11th January 2007, 02:58 PM   #1
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Default where is a resistor or a capacitor very important?

speaking of resistors and capacitors.

I would like to know where a resistor assumes importance, i mean, speaking of quality.
For example : is more important to have a good quality resistor on the feedback network or
on the resistor in series on the base of a transistor of an input differential stage? (just to mention something)

I don't know if i explained myself well enough!

The same question applyed for a capacitor.

Where would you say that a quality is important,meaning, where would you use an expencive oil and paper jensen
capacitor or an expencive Caddock reistor, and why?


Hope to learn something more from you guys!


Best Regards,
Stefano.
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Old 11th January 2007, 04:50 PM   #2
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Stephano,

You have to consider only resistors and capacitors used IN the signal path!
{Not saying that others don't matter...}

Then noise at the Power Supply outputs for input, driver and Final stages...

Using metal film resistors would insure lower noise and long life
and high quality teflon and quality Oil caps minimise the "capacitor" effects
{knowing that No cap is always better in the signal path}

Then you have to consider the cost for these "upgrades" and even in the DIY world
it can be huge... But first a good schematic, and very good design can provide
good sound quality, after that it's only "how big you wallet is !"

What design are you planning, schematics would help to make choices!
And Is it a "no cost object project!" ; otherwise a commercial product could
fit in your budget ; all depending on your experience and will.

Regards.

Alain
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Old 11th January 2007, 09:29 PM   #3
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Without detracting from what Alain has said, I'd like to add that different people define "in the signal path" in different ways. For instance, Nelson defines it as the shortest path between the input and output. Now, since he tends to use pretty good stuff throughout his circuits, he tends to cover the non-signal path items anyway. With that in mind, he tends to build fairly decent pieces of gear (ahem). On the other hand, I take "in the signal path" to mean any part that I can look at with a scope and see a wiggly trace...and sure enough, signal ends up in some surprising places. Sometimes I just shrug and say it's all in the signal path--sometimes I split hairs a little more finely. Others feel that everything, and I mean everything matters. Petter (a member here, see X-amp thread at top of Pass forum) feels that brass hardware is best because it's non-magnetic, hence not likely to contribute to ground eddy currents in an EM field, such as the one emanating from the power transformer. As a logical extension, the chassis then becomes part of the signal path.
As you might expect, there are also people who claim that nothing matters, but then again there are people who believe the Earth is flat. They can be entertaining or aggravating, depending on their personalities, but most people tend to feel that it's worth expending some effort and attention to detail.

Grey
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Old 11th January 2007, 11:42 PM   #4
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I feel that it depends on the circuit, and function in the circuit. In a zero feedback design, I tend to say pretty much everything in the amplifier circuit is in the path, and so is the power supply. But I'd put less emphasis on say, constant current circuit components

For speaker crossovers, the common opinion is that components in series are more important than shunt components. It has seemed that in our experiments, shunt units may be a bit less important, but not markedly so.

In a high feedback design, I'd put a lot of emphasis on any series components outside the loop (input coupling capacitor for example), and the feedback components also.
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Old 12th January 2007, 05:27 AM   #5
KBK is offline KBK  Canada
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My quick thoughts on the subject:

The higher the quality of the given component-part for the given corect application of the part or component, the more it shows up the weakness of the rest of the parts. It almost seems like a never ending battle.

One has to reach their own given level of parts quality understanding through both emperical and measurable quality, and thorough experimentation. There is no substitution for experiment, listen, experiment, listen, over and over and over.

Through this, you learn..over time..what is good and what is not. One must train the mind to 'get it' over time. We all hopefully get better at it, via this sort of methodology, or a similar kind of effort.

edit: for example, Nelson, if you dip into this here thread... check these out if you don't know about them. These caps, may, I repeat, MAY have serious potential (groaner!):

A new "King Of The Hill" electrolytic?

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Old 12th January 2007, 07:10 AM   #6
lineup is offline lineup  Sweden
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Signal path

This expression can be used in different ways.

Signal Path
In a strict limited way, it is the shortest way
through the transistors/components.
Because there is no other good expression we can use for this.
Not that I know of.

-----------------------

As told here, there are many things that will effect the signal.

Try your amplifier
1. With a good power supply - powerful and clean 'without ripple'
2. Now change to a weak transformer and without proper ripple filtering.

Did this effect the quality of signal output, in any way?
-----------------------

In a broader sense 'Signal Path' can be seen as also include
especially the power supply
and environment in which the amplifying circuit will have to work.


Regards
lineup
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