Thermal noise study...

[dkemppai]

Originally posted by fdegrove


When you solder carelessly and apply too much solder to make a good joint the endresult will inevitably be a noisy circuit all else being equal.

Ciao,

Do you mean cold solder joint, or a joint with excessive solder.
Just curious, do you have any data, or theories to back this up???
Without explanation of why this happens, it sounds rather subjective. (Subjective is OK, if you state that it is so)

Dan

[dkemppai]

Originally posted by SY
What is first order distortion? This is a term I'm unfamiliar with.

Second order distortion is characterisitic of any single-ended circuit, independent of the type of device used. Some will have more than others, but they'll all have it.

First order distortion is his music! It Means he really likes silence

Also, can you define for me what you mean by second order distortion, maybe mathematically? You mean frequecies double that of the fundimental?

-Dan

[fdegrove]

Hi,

Do you mean cold solder joint, or a joint with excessive solder.

I mean the excessive use of solder.
Without proof other than experience I can hardly call this scientific.

Is it the fact that when using too much solder one creates a less defined path for electrons to pass through,hence creating spurious noise?
I really wouldn't know.

Observation shows however that the less solder one uses the less noisy it becomes and the better the same circuit sounds.
I suppose this would be a measurable factor,I just never did do appropriate measurent on this.

Cheers,

[fdegrove]

Hi Dan,

Also, can you define for me what you mean by second order distortion, maybe mathematically? You mean frequecies double that of the fundimental?

Are you asking for an explanation of what harmonic distortion is?

Caio,

[dkemppai]

Hi,

Originally posted by fdegrove


Are you asking for an explanation of what harmonic distortion is?

Caio,

Nope, actually I'm asking for a definiton so that we are all on the same page. I'm just not sure what you guys refer to as first and second order harmonics. I believe you are speaking of Even and Odd harmonics, correct? First order being odd multiples of the fundimental, and Second being Even multiples... ...is this true?


Sort of off subject, and that it's on my mind, how do you feel that frequency response and it's corresponding phase shift affects the summation between harmonic multiples? Espically at the low frequency cutoff of an amplifier (if the amp is not rated for DC output, that is).


As for the large vs. small solder, there may be some merit to it, like I say I don't know. I've never heard of any differences, other than I've heard that the millitary wants a little solder as possible on solder joints. (I believe this is because they want to be able to inspect the joint properly) It is possible that too much solder prevents the rosin from completely removing the oxide layer on the metals, which could be bad.

-Dan

[fdegrove]

Hi,

Nope, actually I'm asking for a definiton so that we are all on the same page. I'm just not sure what you guys refer to as first and second order harmonics. I believe you are speaking of Even and Odd harmonics, correct? First order being odd multiples of the fundimental, and Second being Even multiples... ...is this true?

Yes.

THD.

Your second topic:

how do you feel that frequency response and it's corresponding phase shift affects the summation between harmonic multiples? Espically at the low frequency cutoff of an amplifier (if the amp is not rated for DC output, that is).

The broader the frequency response the better,provided you can maintain stabilty from the amps.
Being a vinyl person I don't feel the resonance frequency of tonearm/cartridge should be passed unimpeded.
This will often create a pumping effect on the amp, draining the PSU's energy.
In turn leading to uninvolving,lifeless soundreproduction.

As for the large vs. small solder, there may be some merit to it

I welcome other peoples' comment on this.

Ciao,

[mrfeedback]

Solder is not a very good conductor relative to copper.
(96S is better conductivity than lead/tin solder).

I have not experimented with varying the amount of solder on each joint, so I do not have a reference there, however more solder resumably means a more conductive joint.
I do however make sure that the whole joint is tinned properly (including the cut end of the component lead), and that sufficient time and tremperature is given to ensure thay the solder alloys properly into the surfaces being joined.

Eric.

[fdegrove]

Hi,

however more solder resumably means a more conductive joint.

No,not true.
When soldered correctly added solder will not increase conductivity but will add extra noise IMO.

Ciao,

[dkemppai]

Originally posted by fdegrove
Hi,

No,not true.
When soldered correctly added solder will not increase conductivity but will add extra noise IMO.

Ciao,

sorry guy, but I fail to see how a more robust connection will make noise?

Back on subject, I tried an experiment last night. I set up an op amp with a gain 100, and tied the open input to a resistor. Two 9 volt batteries were used to power the AMP. I used some heatsink compound to mount the IC to a thermoelectric cooler/heater.

I took a RMS voltage measurement of the noise (After shutting everything else off, and running a self cal on my scope). I then cooled the amp to 10F (-12C for you european types) and took a secont measurement. I then heated the amp to around 130F (around 55C) and took a third measurement.

What did I learn, well, not much.

NOT MUCH: -> The noise seemed to be slightly higher at higher temperatures, but no real changes could be detected. (the change was about .1 to .2mV RMS total from 10 to 130F. The total RMS noise voltage in all three cases was about 2.3mV RMS.

NOT MUCH MORE: -> Assuming the that the signal input was sufficient to drive the amplifier to within +-1 volts of th 9Volt rails,
that would give us a Signal to Noise Ratio of approximatley 68dB.

For what it's worth

-Dan

[halojoy]

What was the working temp specification of the OP-amp?