Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Datasheet Specs vs Average Conditions In DIY Use Cases
Datasheet Specs vs Average Conditions In DIY Use Cases
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 6th July 2018, 10:21 PM   #11
MarcelvdG is offline MarcelvdG  Netherlands
diyAudio Member
 
Join Date: Mar 2003
Location: Haarlem, the Netherlands
Quote:
Originally Posted by spaceistheplace View Post
Would lesser classes of ceramic capacitor have the higher losses you suggest?
No, I just looked up the dissipation factors of a couple of Z5U capacitors and they are similar to those of X5R and X7R.

Quote:
Originally Posted by spaceistheplace View Post
I take it even if they did, these are depreciating returns?

I gather from what you are saying the .1uf cap is often added in an automatic manner, but the real answers as always arenít as simple or direct.

How many ICs / parallel resonances before this begins to be problematic?
Two capacitors and one parallel resonance if the resonance happens to be at a very inconvenient frequency. I've seen a situation like that at work once, in an RF circuit.

Nonetheless, I've built digital and audio hobby circuits with dozens of ICs with no apparent problems without thinking very much about the resonances. Besides the ceramic decoupling caps, I did always include a few cheap aluminium electrolytic capacitors here and there. They are good dampers because they have quite high losses. If the power grid looked regular (similar-sized ICs placed at a fixed pitch), I usually used several different values of ceramic capacitor to spread the resonant frequencies a bit, but again without thoroughly analysing anything.

Quote:
Originally Posted by spaceistheplace View Post
I would very much appreciate if it wasnít a further burden on your time a simplified example/schematic in an audio application in which the additional resistors and capacitors you suggest would be fruitful.

My building has been mostly confined to tube circuits... almost exclusively films, electros and micas. So, as I begin to experiment in solid state thereís a whole wealth of parts and standard practices which are a bit foreign to me.
With a possible exception for oversampled data converters, I don't think it is likely to be a big problem in audio circuits. The resonances are usually way above the audio band, so as long as nothing starts to oscillate, there shouldn't be any problem in audio amplifiers. As long as you don't need to pass EMC tests and the resonance doesn't occur right at the clock frequency, digital circuits are also likely to work fine.
  Reply With Quote
Old 7th July 2018, 01:24 AM   #12
trobbins is offline trobbins  Australia
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
I would recommend you spend time and effort on specifying your operating conditions, and trying to define what if any change in a circuit's performance behaviour would occur due to different part choices.

Eg. some simplistic operating conditions would include your operating conditions, such as in the range 10C to 35C temp for the actual parts in operation. How many hours operation per day and per your diy lifetime will you be using the equipment, and an expectation that you won't stop using it next year/decade as your interests change.

At least then you would get some value from your effort, as imho if you are starting at each part's datasheet without any tangible practical goal to use as a target then your musings have no relevance.
  Reply With Quote
Old 10th July 2018, 08:32 AM   #13
davidsrsb is offline davidsrsb  Malaysia
diyAudio Member
 
Join Date: Dec 2005
Location: Kuala Lumpur
I first ran into capacitor resonance with a video amplifier I was developing for the BBC. The combination of capacitors caused an early video opamp to have an odd frequency response wobble at about 6 MHz. The root cause was a two layer pcb with through hole capacitors and long tracks. These days you would use a ground plane and smd capacitors, which shifts the problems up into the VHF/UHF
  Reply With Quote
Old 12th July 2018, 05:55 PM   #14
spaceistheplace is offline spaceistheplace
diyAudio Member
 
spaceistheplace's Avatar
 
Join Date: Jun 2012
Location: Proxima Centauri b
Datasheet Specs vs Average Conditions In DIY Use Cases
Default Datasheet Specs vs Average Conditions In DIY Use Cases

Quote:
Originally Posted by trobbins View Post
I would recommend you spend time and effort on specifying your operating conditions, and trying to define what if any change in a circuit's performance behaviour would occur due to different part choices.

Eg. some simplistic operating conditions would include your operating conditions, such as in the range 10C to 35C temp for the actual parts in operation. How many hours operation per day and per your diy lifetime will you be using the equipment, and an expectation that you won't stop using it next year/decade as your interests change.

At least then you would get some value from your effort, as imho if you are starting at each part's datasheet without any tangible practical goal to use as a target then your musings have no relevance.
This is simply not so. Iím happy to share with you some of my practical goals.

I did not share them in the interest of understanding some of the larger themes involved and for being of use for all parties, but here you go:

I always assume greater than 30C operating, 7 days a week 4 hours per day average. So letís say 30 hours / week x 10 years = 15,600 hours at 40C would be my minimum requirement.

I will avoid at all costs a capacitor rated under 20k.

For me long term reliability is a goal only secondary to its original measured performance. If I build something I want it to be rock solid for a long time to come.

I donít want to build and build cheaply, accumulating and reselling and so on. Iíd rather focus my energy on very few designs and use them indefinitely. Maybe this is uncommon, but I am the slow and intentional type.

The c0g vs x7r was really a secondary question, as I was wondering if the use of X7R was mostly based on cost considerations and if the c0g, now more reasonably priced than a decade ago, might be considered a reasonable substitution. There was an older thread on this topic which was abandoned before any consensus or recommendation was put forth.

The resistor issue was my main curiosity and is related to tube applications or other scenarios with higher heat, but required low ppm.

Iíll try to provide some specific info in relationship to my question with regards to resistor derating, temperature and tempco:

From digikey:

Resistance is usually specified at the ambient temperature of 20įC while most manufacturers specify the power rating at 70įC and free airflow conditions.

It seems to suggest the tempco is per degree Celsius over 20 degrees Celsius to their power rating temp at 70C.

They go on to say:

The temperature coefficient of resistance (TCR) is a constant that represents the resistance change per degree Celsius of temperature change over a specific temperature range; itís expressed as ppm/įC (parts per million per degree centigrade).

Where I live the temperature is frequently 30C (tropical, close ocean proximity environment). People in the middle of Canada who built the same circuit as me will likely achieve better performance over a longer lifetime.

I feel itís reasonable to compensate for my own harsh climate.

So, a 50ppm 1/4W resistor operating at 30C baseline would have 500ppm, a 100ppm resistor would have 1000ppm.

Letís say the resistor is dissipating 3/16th of a watt.

The more power dissipating, the warmer the resistor. At 75% of rated power with 30C ambient Iím unsure of the change in tempco but I imagine that a 50% stress factor or less would be much wiser for a more reliable environment.

Stress Ratio = Operating Power / Rated power

To use an example of a Dale PTF series with 5ppm vs a CMF55 with 50ppm, the PTF at 30C has the same exact ppm as the CMF55 at 20C if I understand correctly.

The cost differential is 10-30 cents vs $5 USD. For a quantity of 50 resistors this becomes a dramatic cost differential which may be mitigated simply through some sensible practices which are available to the diyer but maybe not so much a commercial enterprise.

Itís my understanding that reducing tempco by means of derating, improved heat dissipation, cooling methods, fans etc can provide large cost benefits in diy applications.

Also larger resistors can dissipate heat more effectively and thus reduce collective ambient temperature rises from letís say a whole board of components.

Tightly coupling all resistors to a PCB seems to be a recipe for higher tempcos across all components.

That seems to mean: derate and provide airflow between component and pcb for min. Ppm.

My assumption would be given the above is that a larger 50ppm CMF60 (1/2W) or 65 (3/4W) resistor with a small board clearance for airflow would provide improved tempco, increased reliability and greater precision over a 1/4W PTF 5ppm resistor given that both begin with the same precision (1% or .1%) at less cost.

This is especially so in tube amplifiers where ambient temperatures are much higher.

At other temperatures the calculation goes:

R= Rref[1+α(T -Tref)]
Where
R = resistance at temperature, T
Rref = resistance at reference temperature Tref
α = temperature coefficient of resistance
T = material temperature in įC
Tref = reference temperature at which the temperature coefficient is specified


A lot of ink gets spilled on costly ultra precision foil resistors.

At $25 each or more for those Texas components, I wonder if a much more cost effective behavior in more critical locations for the audio hobbyist is to heavily derate precision low ppm .1% resistors that can be had for around 25 cents.... especially when they need not be retrofitted to an existing design but simply altering the through hole spacing in an eagle file or mounting them in a ďtombstoneĒ configuration.

So, is this another case of hype where people donít understand the real nature of behavior at the level of the resistor?

Or is there something Iím missing? If so, what is it?

Of course the foil resistor is a sound engineering achievement, but we arenít going to space here where every kilo or square inch is precious and incredibly expensive to launch and opportunities for service are nil. Their image is one of undeniable superiority where the best is required but I wonder in our applications by how much in practice.

In addition:

Itís clear large component manufacturers have caught on to the financial benefits of catering to the audio community. Their accounting departments have wet dreams about their components getting labeled as the new best sound. While itís certainly not ďsnake oilĒ I wonder if there is something missing from the picture.

For example it seems at point since NP gave some love to Elna Silmic II in a thread here quite a while back theyíre now labeled as audio caps in the mouser catalogue.

Anyhow, here are some datasheets for comparison;

TE YR1 and YR2 15ppm .1%, ~30cents:
https://www.mouser.com/datasheet/2/4...5_A-732410.pdf

Dale RN/CMF 25-100ppm, 1-0.1%, ~10c-$1
https://www.mouser.com/datasheet/2/4...mil-223788.pdf

Dale PTF 1-0.1%, 15ppm ~$5
https://www.mouser.com/datasheet/2/427/ptf-239718.pdf

Vishay S102 1-.01%, 2ppm, ~$10-$40:
https://www.mouser.com/datasheet/2/428/63001-4478.pdf

TX2575/2352 .1%, 1-2ppm, ~$10-$55:
http://umwxd.xdqqt.servertrust.com/v...Data_Sheet.pdf

http://www.texascomponents.com/pdf/tx2575.pdf

Iíll do some more research on the topic of drift and see if the tempco relationship can be extended there as well.
__________________
The real aim of music is to co-ordinate the minds of the people into an intelligent reach for a better world and an intelligent approach to the living future.

Last edited by spaceistheplace; 12th July 2018 at 06:20 PM.
  Reply With Quote
Old 12th July 2018, 06:34 PM   #15
spaceistheplace is offline spaceistheplace
diyAudio Member
 
spaceistheplace's Avatar
 
Join Date: Jun 2012
Location: Proxima Centauri b
Datasheet Specs vs Average Conditions In DIY Use Cases
Default Datasheet Specs vs Average Conditions In DIY Use Cases

On the topic of stability/ drift, since it is detailed as a function of hours at its rated power at 70C, one could assume the derating practice would also effect drift.

Cracking of the coated body and subsequent moisture entry leading to drift is likely a function of thermal conditions in the resistor, if not in unusual non-audio applications like a military radio in a helicopter. So, less heat, less power = less drift, at least hypothetically.

See ďCharacteristics in FiguresĒ on page 5/8 in Vishays resistor basics application note:

https://escies.org/download/webDocumentFile?id=62214

Another interesting finding in this document is that Wirewound resistors show the worst stability at rated power per 1000hrs, ranging from 1% to 10%, alongside that of carbon comp being +4 to -6 with -3% being typical.

In addition, in a high humidity ocean environment, resistor drift seems to be more of an issue.

From the military derating practices (55% rated power) on through hole metal film resistors:

Construction: This resistor is constructed by vaporizing a carbon, metal, or thick cermet film onto a ceramic or glass substrate. The element is spiraled to increase available resistance. Resistance is calibrated through trimming of a helical grove in the resistive layer. Terminations are usually a tinned copper wire welded to nickel-plated steel end caps. **The body is coated to prevent moisture and contaminate penetration, but coating varies with manufacturer and quality level.**

Reliability: The reliability of this style is
considered better than that of other
resistor styles. **The primary failure mode is resistance drift, which is often caused by cracking of the external coating layer and moisture permeation into the resistive element.** This resistor is ESD sensitive. **Heat dissipation is accomplished through the leads.**

Full info here: http://www.navsea.navy.mil/Portals/1...rsDerating.pdf

This would seem to me to indicate that larger sized resistors, which have a larger coating area and thickness would be less susceptible to drift given that they were operated beneath their power ratings.

The heat dissipation through the leads is interesting as it was my understanding it was done via the resistor body.

Would this imply better heat dissipation not only from being raised from the board for airflow but also due to the increased lead length from resistor to through hole?


I hope Iíve made some more practical and concrete suggestions for informed discussion. Looking forward to your thoughts and insights.
__________________
The real aim of music is to co-ordinate the minds of the people into an intelligent reach for a better world and an intelligent approach to the living future.

Last edited by spaceistheplace; 12th July 2018 at 07:03 PM.
  Reply With Quote
Old 12th July 2018, 07:47 PM   #16
MarcelvdG is offline MarcelvdG  Netherlands
diyAudio Member
 
Join Date: Mar 2003
Location: Haarlem, the Netherlands
Regarding the effect of self-heating on resistance: you usually can assume a linear relation between self-heating and power dissipation. Often you see a derating curve indicating the maximum power as a function of ambient temperature. The temperature at which the maximum power becomes zero is the temperature that the resistor element reaches when it dissipates its maximum power.

For example, a typical 1 % through-hole metal film resistor usually has a derating curve that crosses 0 at 155 degrees C and a temperature coefficient between -50 ppm/K and +50 ppm/K. Suppose the resistor is rated 0.6 W at 70 degrees C ambient. That means that 0.6 W causes a temperature increase of 155 degrees C - 70 degrees C = 85 K. The change in resistance due to self-heating is then 85 K * (+/-50 ppm/K) = +/-0.425 %.

When you only let it dissipate half its rated power, the resistance change due to self-heating also halves: +/-0.2125 %.

(On top of that you have the long-term drift, which also gets worse at higher temperatures.)

Last edited by MarcelvdG; 12th July 2018 at 07:57 PM.
  Reply With Quote
Old 14th July 2018, 12:51 AM   #17
trobbins is offline trobbins  Australia
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
Some comments would be:

Equipment may be in a 30degC ambient, but certain parts can easily be much higher depending on the equipment cooling design - the part temperature is where a good appreciation is needed.

Very few people would look beyond electrolytics for part life, perhaps as they are the 'low hanging fruit' with respect to the temperature and time service life.

Most of the other topics raised, such as resistance and capacitance variation, with temp or voltage or time, are nebulous without a close connection to a particular circuits operational performance. The better commercial designs know very well which parts are of any influence at all, and quite happily pull every other part down to a simple QC level for the lowest cost, most basic spec.
  Reply With Quote
Old 16th July 2018, 08:40 AM   #18
spaceistheplace is offline spaceistheplace
diyAudio Member
 
spaceistheplace's Avatar
 
Join Date: Jun 2012
Location: Proxima Centauri b
Datasheet Specs vs Average Conditions In DIY Use Cases
My observations re: diyaudio is that aside from power amplifier heat sinks there doesn't seem to be much regarding "cooling design"...

Although I will run a temp probe over some of my equipment when I get a moment on some key parts out of curiosity.

While I genuinely appreciate your time and wisdom, you don't seem to understand that my preference is to be nebulous. A cursory look at my username should've been an a-ha moment for that one.

My line of thought was going toward feedback resistors, loading and riaa resistors and so on in tube designs. So, I would imagine they have relevance. My goal was to explore how one could optimize lifetime, stability and performance for various key areas of interest by derating, lead handling (not damaging coating), placement, airflow, etc. rather than let's say spend $$$ on a Vishay S102... in areas where one might be warranted.
__________________
The real aim of music is to co-ordinate the minds of the people into an intelligent reach for a better world and an intelligent approach to the living future.
  Reply With Quote

Reply


Datasheet Specs vs Average Conditions In DIY Use CasesHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Peerless XLS 830533 Datasheet/TS Specs dreadnoughtstrength Subwoofers 8 8th April 2016 01:20 PM
which FET for these operating conditions ? Bigun Pass Labs 22 20th December 2011 04:17 PM
Moist conditions.....? 503Timber Chip Amps 3 15th December 2011 09:29 PM
Vas DC Bias conditions? BunyipElectronics Solid State 12 28th July 2010 01:03 AM
Specs / datasheet for PCM 1603 eplpwr Digital Source 1 25th July 2005 05:37 PM


New To Site? Need Help?

All times are GMT. The time now is 11:47 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki