| Author |
 Topic  |
|
zentropa
Gold Member
USA
837 Posts |
 Posted - 03/09/2008 : 16:31:09
|
Sorry if this has been discussed before, but the search function doesn't appear to be working on the forum and i didn't find anything in ~25 pages worth of this section...
I was wondering if there was any terminology to properly describe the burn in/break in of pedals due to use.
As an example, I had two 1979 CE-2 Chorus pedals both produced in the same month (according to the serial number decoder) and with the same IC chips. One of them I purchased VERY used... looks like it's been through a war, probably has over 1000 hours of use on it. its tone is very dark (bordering on too dark), very warm, very rich, very full. The other CE-2 I purchased NOS in the mid 90's (it had fallen behind a shelf in a storage room for like 15 years). The NOS was a bit thinner and substantially brighter and sounded nearly identical to a barely used Taiwan made CE-2 that i have (the serial number decoder says this was produced feb '91). All 3 of these CE-2's seem to fall on the extreme ends of the spectrum tone-wise and I'm guessing it has to do with the aging of the components due to current being run through (or not being run through) them.
I was curious if there is a set term for this phenomenon.
Thanks. |
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/09/2008 : 16:59:41
|
G'day Zentropa!
What is probably happening is that the capacitors in the unused pedal "went dry". Boss uses electrolytic capacitors in the audio signal path - while this is not good engineering practice, the electrolytic type of capacitor is small and cheap.
From Wikipedia (about electrolytic capacitors) - "maintaining the integrity of the dielectric usually requires the steady application of the correct polarity of direct current else the oxide layer will break down and rupture, causing the capacitor to fail. In addition, electrolytic capacitors generally use an internal wet chemistry and they will eventually fail if the water within the capacitor evaporates"
Another Wikipedia quote about a variation of electrolytic capacitor: "The oxide insulating layer will tend to deteriorate in the absence of a sufficient rejuvenating voltage, and eventually the capacitor will fail if voltage is not applied"
So, electrolytic capacitors are evil, and Boss pedals usually have between 2 and 6 of them in the audio signal path.
As they fail, the capacitance changes, and this changes the "knee" frequency of any circuit they are in. I can quite believe that a pedal would sound thin after 15 years behind a shelf!
I've been systematically changing all the electrolytic capacitors out of the audio path in my pedals - I bought a bag of 1�F metallised polyester film capacitors (the most common size for these in Boss pedals) and I just swap them for the electrolytics. It usually (but not always) makes the pedal a bit warmer.
Hope that helps...
Laurie. |
Edited by - Laurie on 03/09/2008 17:01:52 |
 |
|
|
jack
Platinum Member
USA
1418 Posts |
Posted - 03/09/2008 : 20:59:52
|
| Also keep in mind tolerances used for the components as well. For example, carbon resistors usually have a tolerance of 5%, so when the schematic calls for a certain value resistor, the resistor may be plus or minus 5% of the value it is denoted to be. So pots, caps, resistors, and transistors all have certain and various tolerances so the actual values of these components may vary in the same model of pedal enough to make them sound a bit different from one another. |
|
|
|
DeFrag
Moderator
USA
3409 Posts |
Posted - 03/09/2008 : 21:41:04
|
| I burn-in new pedals overnight. |
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/10/2008 : 00:00:16
|
quote:
Originally posted by DeFrag
I burn-in new pedals overnight.
What temperature do you set the oven to?  |
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/10/2008 : 00:02:18
|
quote:
Originally posted by jack
Also keep in mind tolerances used for the components as well. For example, carbon resistors usually have a tolerance of 5%, so when the schematic calls for a certain value resistor, the resistor may be plus or minus 5% of the value it is denoted to be. So pots, caps, resistors, and transistors all have certain and various tolerances so the actual values of these components may vary in the same model of pedal enough to make them sound a bit different from one another.
Uh. Yup. jack, I completely forgot to mention this is also a factor - I got on my usual rant about electrolytic capacitors (don't get me started on "expensive" cables  )
|
|
|
|
Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 03/10/2008 : 02:23:38
|
Hi lauries2
If ranting about electro's is your thing, please get yourself an ESR meter.
Then you won't have to preach, just get out the ESR meter & show them.
You'll have a Guaranteed 100% conversion to the (lauries2-Church of electo's)
I have a small collection of dead/faulty caps with MASSIVE increases in their ESR (1000uf caps with ESR's of 63 ohms) when they should be around 0.01-0.05 Ohms ESR.
Yet these caps measure 100% of their stated value on a standard Capacitance merer.
I purchase all the tooling & test equipment for the company I work for.
We are one of the few companies that use ESR meters, I have about 15 in the building that we share.
A lot of the Tech's turn their noses up at them when they first start with us, but are quickly self converted, once they see how technically useful they can be.
We even measure the ESR of small rechargeable batteries, ear-pieces in headsets, & the Old Video tape heads.
They will also measure the very low value emitter resistors in power amps.
PM if you want to carry on a longer conversation about the Pro's & pro's of ESR meters.
Apologies for the slight hijack, of the thread, but I felt it was relevant to the topic.
Regards Dr. Bob |
|
|
|
zentropa
Gold Member
USA
837 Posts |
Posted - 03/10/2008 : 05:22:34
|
thanks Laurie and the others who have replied.
i didn't check the caps on the CE-2 i had but i guess i should have rephrased... the NOS CE-2's sound wasn't thin in general, just thin compared to the well-used CE-2 that i kept. the NOS still sounded better than every other compact boss chorus i've played, but it may have been a cap problem.
now that i think about it, a lot of things may have been cap problems :) now i'm kind of paranoid but i may check out my pedals...
i will revise and make a new example based upon some conversations i've had with players...
if someone were to take a NOS JRC4558D and pop it into an OD-1 that had a JRC4558D with 500+ hours on it, would they in fact sound different? and if so, what would be the term describing the difference in the chip wear? |
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/10/2008 : 05:47:23
|
quote:
Originally posted by zentropa
if someone were to take a NOS JRC4558D and pop it into an OD-1 that had a JRC4558D with 500+ hours on it, would they in fact sound different? and if so, what would be the term describing the difference in the chip wear?
Dr. Bob help me out here... but I'd think that a non-faulty 4558 with 500 hours on it would not sound any different to a new one?
What tends to happen with opamps is that over time either the gain drops off or the noise increases (or both). But that normally takes thousands of hours. I need to be clear here - "gain" in an opamp is not how loud/driven it sounds (don't think of the "gain" knob on a pedal - the technical parameter is "large signal amplification").
Loudness/drive/amplification in a given opamp circuit is almost entirely determined by the components surrounding the opamp. Indeed, most audio level opamp circuits assume the opamp is "perfect" - infinite gan. Anyway... even if the gain dropped off, I'd think you'd be hard pressed to hear it where the opamp is being used as an amplifier in a pedal.
"burn in" is an interesting subject. In solid state electronics, "burn in" is not used to "run in" the components like a car engine. Burn-in is to "detect those particular components that would fail as a result of infant mortality" (Wikipedia again). What it does is exercise the circuit to ensure nothing is going to break as soon as the consumer turns it on. "If the burn-in period is made sufficiently long (and, perhaps, artificially stressful), the system can then be trusted to be mostly free of further early failures once the burn-in process is complete".
Yeah. OK. So I'd think a pedal wouldn't sound different after 500 hours as a result of the opamp.
Regards,
Laurie |
Edited by - Laurie on 03/10/2008 05:51:32 |
|
|
|
zentropa
Gold Member
USA
837 Posts |
Posted - 03/10/2008 : 06:14:47
|
thanks again Laurie. that seems to have cleared up a lot of rumor/hearsay that was going through my mind.
btw, the 500 hours was just an arbitrary figure. any time you buy a pedal used you never really know :)
the aging of the op amp was based on an interview i'd read with a prominent pedal mod person. |
|
|
|
Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 03/10/2008 : 09:01:33
|
Hi lauries2 & guys
I'm still thinking about you lengthy post.
Just something else to think about,
There were still a lot of impurities, in the silicon wafers of the late 70's and 80'
These impurities can & will, contribute to the slow deterioration of the silicon substrate in the IC.
I have a heap of IC design Books from Motorola circa 70's , which I worked for for about 15 years.
It's really scary stuff reading these.. & all the trials & tribulations that they were suffering in the design labs.
One of these, has information about the very first batch of commercial IC's & all 3 to 5 of the integrated parts that it contained.
Basically I think what I'm trying to say, is,
In the old days there were lots of impurities in the early silicon wafers.
Lauries2 mentions this in a different way, when he says that overall gain diminishes & the noise floor increase.
Life expectancy of a working electro, is about 8000 working hours.
Regards Dr. Bob
|
|
|
|
ChristoMephisto
Platinum Member
Canada
1288 Posts |
Posted - 03/10/2008 : 11:11:58
|
Thats a popular thing to change out electro caps for NP types.
When the caps go bad, the sound becomes dirty, and yeah changes the knee (frequency corner) and a another reason why some people sell a pedal thats been on the shelf for a few years. |
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 05/01/2009 : 14:50:19
|
Resurrecting this thread and continuing on...
=============================================================
From Right Foot Boss: Here is a link describing the life of electrolytes. http://www.premierguitar.com/Magazine/Issue/2008/Jun/The_Life_and_Death_of_an_Electrolytic_Cap.aspx
I've been contemplating the whole electrolytic cap thing in pedals for a while (for at least as long as this thread has been alive).
I think an important build on the article above is to contemplate the difference in use of electrolytics in pedals vs amps. In amplifiers, electrolytics are used as bulk charge reservoirs, and are worked very hard mechanically (the charge/discharge cycle 100/120 times a second flexes the plates and dielectric material). In a pedal, the caps are only passing "signal" - they aren't worked very hard (compared to filter caps in an amp).
I'm leaning more towards thinking that the reason to replace the electrolytics in a pedal is purely for the sound, rather than for the age. And I'm also thinking that having to play a pedal every few months to keep the electrolytics "wet" isn't necessary. Many fantastic MIJ pedals have been sitting cupboards for 10 years without being touched.
So, if changing the caps is purely for the sound, we usually change them to good metalized polyester caps because they sound different to cheap electrolytic caps (most say "better"). And let's be clear - the electrolytics used in the signal path in a pedal are there because they are cheap - pennies instead of tens-of-pennies for metalized poly.
I'm starting to believe that electrolytic "aging" is much less of a factor in pedals. Here is my theory:
1) The "better" sound in older pedals that can be attributed to the electrolytic caps is due to those electrolytic caps simply being higher quality (made well in Japan/Europe/USA).
2) The "nastier" sound in newer pedals that can be attributed to the electrolytic caps is due to those electrolytic caps simply being crap quality (made cheap in China).
tunghaichuan added: I bought a used OS-2. When used with batteries it was dead quiet. When plugged into a PSA-120S power supply, it would make this high pitched whine. I traced it to the the two 100uF caps that filter the DC voltage coming into the pedal from the power supply. I replaced them with two 220uF caps that were slightly larger but still fit in the case. Problem solved, the pedal is now dead quiet. So apparently either the caps had dried up or had failed.
tunghaichuan's experience starts to add credence to the thought that the failure of electrolytics (when it comes to pedals) may only apply to those electrolytic caps that are used for power filtering.
I'm really starting to believe that electrolytics in the audio path will happily withstand months/years of being unused.
Righ Foot Boss summed it up I think with the comment: "Otherwise there would be tons of 'broken' pedals from the eighties floating around ebay that just need cap replacements".
|
Edited by - Laurie on 05/01/2009 14:50:53 |
|
|
|
Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 05/01/2009 : 19:54:49
|
Hi Laurie & guys
I have been read & thinking about how to answer this all day
- in fact from when the thread was first posted.
And those that know Laurie & me.
We have been discussing the merits of this problem for a long time.
So please bear with me, it's a very long winded answer,
& you will probably have to re-read this a few times,
if you want to understand the life of an electrolytic Capacitor.
While a lot of what has been posted - is very true & correct, no-one seems to have gone to the crux of the real situation.
So put on your Tech safety belts & propeller hats, it's a big roller coaster.
---
Until you start to measure capacitors with an ESR meter,
you will never see the underlying, changes in a cap - especially electrolytic caps, over time.
The ESR meter measure the the internal - Equivalent Series Resistance (ESR) of capacitors.
All caps age - how hard you push them, & how high an AC ripple component they have to deal with adds to the aging process.
And when caps age :
- Their ESR Resistance goes higher.
- Heating the cap even more.
- The heat dries out the electrolyte even more.
- Raising the ESR resistance more.
- heating the cap more.
- Drying out the electrolyte more.
- Raising the ESR resistance more
- Heating the cap more.
- Drying out the electrolyte more.
- Raising the heat & ESR resistance more.
Are you staring t to see a pattern?
That's why caps in SMPS Switch Mode Power supplies - age very quickly.
It's an eye opener to watch a capacitors ESR, rise over a few weeks
of use in SMPS & a lot of older CRT - Monitors & TV's.
I have seen large value electro caps, go from bout 0.01 ohms ESR to
1.x ohms ESR in a matter of a week of ordinary use.
0.01 to 1.0 - is an amazing 100 time increase in ESR resistance
And then these will onto larger values of change, 10 to 60 to 90 ohms ESR.
I consider caps that have reached 3 ohms ESR, to be cactus & replace them.
Dr. Bob's ESR rule "If it's (3)ohms throw it".
With really expensive high quality, high ripple caps, this process can take 12 months or more.
Yeap that's why a lot of old PC power supplies seem to just magically die.
The culprit most times, is a small value cap 10uf to 100uf, known as the startup cap,
that now measure 3 to 99 or more ohms ESR.
You can't see the with a standard capacitance reading,
in most case the cap will look 100% fine on a Cap meter or RCL bridge.
I show this to all my new staff & apprentices, & at first the go Yeah - yeah yeah, & look skyward with boredom. 
But once they have had time to familiarize themselves with using ESR meters, to analyze faulty circuits - they never look back.
As far as I am aware, we are one of the very few large companies that use ESR meter to analyze faulty gear.
Our tooling & supply rep, has told me that he only sells them to us, & an odd TV - monitor Tech that might clued up on their benifits.
Or has once worked for us...
All this is on top of the fact, that about 2-3 years ago, someone stole the formula/process for making newer higher density caps & more cost effectively, it was a case of industrial espionage.
We unfortunately , they only got about 1/2 the formula & process.
but it was enough to make caps that worked - we they worked but only for a very short time.
All the Asian cap makers jumped on this cheaper faster process & formula, and made billions of VERY SOON TO FAIL CAPS.
Some Techs & companies, are very aware of this problem.
And it's near impossible to tell if you have these faulty caps in your stock.
As they will work of some period of time, & they fail dramatically - or just leak & vent all over the PCB.
We are still finding caps in our bulk store that are from the batches of Billions of CRAPPY Caps. from 2-3 years ago
Many mother board manufactures are all to aware of the problem.
---
Now getting back to ESR & low voltage - signal caps, yes you are also correct Laurie & guys.
They are less critical in these situations.
But also be aware, that interstate coupling caps on older gear can measure as high as 10 or more Ohms ESR, & still function fairly well.
But if you change them out - after measuring the High ESR value ones.
You will find a marked improvement in the tone.
I keep hearing the words MORE CLARITY & BRIGHTER - LESS NOISE.
Of course replacing a cap that measures 10 Ohms ESR, with one that is about 0.01 ohms or 0.1ohms or even 1 ohm ESR, is going to make a dramatic difference.
Tantalum's also have very low ESR -
When new, and seem to age more graciously over time, compared with standard run of the mill Electrolytic's.
But overall, today's capacitors are a work or science & voodoo & art. Small per value density & very consistent in vale, even cheap Electro's, have lower ESR & leakage than caps from 10-20 years ago.
I'm guessing that most people stopped reading this after the first few lines?
The Old Doc Ranting Once again.
But please remember I see this Everyday of my working life,
In a very large workshop-Lab with heaps of Techs & Engineers working on hundreds of different and varied products, & Technologies.
And most times it - BLOODY CAPS.
I spend many thousands of Dollars on Tooling & Analytical equipment,
You don't want to see my monthly budget for this gear & parts.
But if you were to look at what is getting used the most, on an hourly - daily basis.
It's our humble ESR Meters & our humble Digital Multimeters.
Understandably - I guess it's really difficult for many people to understand & grasp - but simply:
An ESR Meter shows you how much a capacitor has deteriorated with time in use.
This is the device that will really make you understand the life of a capacitor.
Regards Dr Bob
How may of you are still awake....  
|
|
|
|
verivorax
Platinum Member
Canada
1185 Posts |
Posted - 05/01/2009 : 21:56:40
|
I read the whole thing and found it very interesting Doc!! 
Also to Laurie!
I'm still a layman in terms of electronics but I feel decidedly more edumacated from you guys!!  |
|
|
|
nathanscribe
Silver Member
United Kingdom
376 Posts |
Posted - 05/01/2009 : 22:13:31
|
...sounds like it's time to find an ESR meter.
Interesting read. Thanks for that. |
|
|
|
Topic |
|
|
|
Pedal "Burn In"
