[poseidonsvoice]

The Coilcrafts are in my dac and buzz a tiny bit. Only if I put my ear to the enclosure, or else, no issues. The JW Miller's in my amp don't buzz at all.

FWIW,

Anand.

[wushuliu]

Thanks for the parts list jt, it's inspired me to take a similar but cheaper approach using monoprice extension cords and radio shack project boxes. Much easier than my original plan to build a single large enclosure with lots of duplexes... the strain relief connector can be found pretty cheap on amazon as well in 10-packs...

[jtwrace]

I spoke with Coilcraft today about my noisey choke.  They're working on it....I will pass the news when they send me the test report.

[mjosef]

Strange, I have never had that 'noise' problem.
Or maybe my ears are not resolving enuff to hear any buzzing.

[jtwrace]

Strange, I have never had that 'noise' problem.
Or maybe my ears are not resolving enuff to hear any buzzing.

The buzzing isn't through the audio system...it's just a mechanical noise with no load needed on the Felix.

[mjosef]

The buzzing isn't through the audio system...it's just a mechanical noise with no load needed on the Felix.

  Yes, my comprehension scanner caught that, hence my use of the word "ears" en lieu de "system".
It was all tongue in cheek anyway...I forgot to spell out the emotion with the appropriate smiley. 
 

[jtwrace]

Here is the Q.C. report from Coilcraft.  Occam what are your thoughts since this is your world?

Quality Analysis Report   QAR No. :   CO-XXXXXX

To:   XXXXX   Date Revised:   25 February 2011
Email:   XXXXXXXX

Customer :   XXXXX   Part No.:   P3717-AL   Qty: 1
PO :   XXXXX   Order No :   XXXXXX   Lot Code: 08XXXXXXXXX


1.  TEAM: Assemble several people with the process/product knowledge allocated time and authority to solve the problem and implement corrective actions.   
      Quality Engineer

2. PROBLEM DESCRIPTION: Specify the internal/external customer problem by identifying,  `What is wrong with what and describing the problem in quantifiable terms which will answer the questions:  `What?  Where?  When?  How Big?  How Many? etc.
Buzzing noise coming from some P3717-AL parts when 120V applied with no load
The part as a low pass filter at 120V with x rated capacitors before and after the choke.
The audible noise was not immediate but set in after about 10 minutes of power application.


3. INTERIM CONTAINMENT ACTION: Define and implement containment actions to isolate the effects from any internal/external customer until permanent corrective action is implemented. Verify the effectiveness of the containment action.
      N/A

Date Implemented: February 28, 2011
4. DEFINE ROOT CAUSE(S):  Identify all possible causes(s) which could explain why the problem occurred.  Isolate and verify the root causes(s) by testing each possible cause against the problem description and test data.  List possible corrective actions to eliminate root causes(s).
The part was inspected under microscope and no damage was found: the bobbin is glued to the core and
the lamination spacer was glued to the bobbin. The wire was not burnt.
Also, the part was testing per drawing for Inductance, DCR, Turns Ratio and polarity.
INDUCTANCE                              
   L 1-4=33.2 m H      LSL=   18.9   Nom=   43.9   USL=   68.9   m H   P      
   L 5-8=33.3 mH      LSL=   18.9   Nom=   43.9   USL=   68.9   m H   PASS   

TURNS RATIO                              
   Turns ratio based on Inductance is SQRT (L5-8/L1-4).                      
   TR=   1.005   LSL=   0.97      USL=   1.03      PASS      

POLARITY                              
In order to check polarity the inductance of both windings were tested when connected in series inPhase (Finish 1-4 to START 5-8) and in series in opposition (START 1-4 to START 5-8).      
   In phase Connect 4 (Finish 1-4) to 8 (Start 5-8):         
   LPhase=   130.5 mH   LSL=   75.8   USL=   275.6mH   PASS
   In opposition:                              
   Connect 4 (Finish 1-4) to 5 (Finish 5-8):   
      LOpposition=   0.943 mH      LSL=   0.700   USL=1.200   mH   PASS
      DCR   
   DCR1-4=.231 Ohms   DCR5-8=.237 Ohms   USL=   0.300   Ohms   PASS
   High Pot   The part was tested at 1500 Vac for 60 seconds between pins 1 an 4:   PASS   


The part was built per specification and no damaged component parts were found.
Based on customer description and based on the above evaluation, it is considered that the part is not defective but there is a problem with the matching of the part with the circuit.   

It is possible the  noise or buzzing is associated with a resonant condition in the circuit between Coilcraft part and the X Rated capacitors before and after the choke. 
If L and C are in series, the impedance of (L,C) combination could drop toward zero at resonance. As a result, the AC current through choke could increase and cause buzzing.  The noise could be produced by a part of the choke (wire, lamination, etc.) that resonates with the electrodynamics’ forces created by the AC component of the current through the choke.
Both inductor and capacitor could be within the limits, but a combination of L, C and frequency could lead to resonance.
The fact that the part buzzes with NO LOAD and after 10 minutes from power connection could be an explanation for resonance.
At no load, the DC bias is lower and the inductance has higher values. May be these values would meet the resonant conditions.
Since the buzzing starts after 10 minutes it is assume that heat could be involved. Inductance and Capacitance could slightly vary with the heat. This slight variation of either one or both of them could lead to resonant conditions.   It is also possible that the frequency content of the current could change from NO LOAD to LOAD conditions. This could be also a factor for resonance.
The part was inspected and tested. It meets Coilcraft workmanship requirements and parameters.  Since the part is not   defective, the cause for buzzing could be a matching issue between the part and the circuit.  The noise could be generated by a resonant condition between choke and capacitors before and after the part.  More information is needed from customer.  In order to increase the resistance to noise and vibrations, the part could be impregnated but this has to be discussed with Design Engineer and could lead to a more expensive custom part.

5. DEFINE PERMANENT CORRECTIVE ACTION(S):  Through pre-production test programs quantitatively confirm the selected corrective actions will resolve the problem for the customer and will not cause undesirable effects.  Define contingency actions, if necessary based on risk assessment.
      ---------N/A------------

6. IMPLEMENT PERMANENT CORRECTIVE ACTIONS: Establish a plan to implement Permanent Corrective Actions, and define ongoing controls to ensure the root cause is eliminated.  Monitor the long-term effects and implement contingency actions if necessary.
      ---------N/A-------------

Date Implemented:
7. PREVENTION: Consider other areas that may be susceptible to this problem and apply the appropriate preventive action.
      -------N/A----------




Prepared by:   name withheld
Date Open   February 11, 2011
Date Closed   February 28, 2011
Distribution   xxxxxxx
   

[sts9fan]

Its pretty clear.  It part is up to spec and they say its the circuit.  Anywhoo like I said before mine does the exact same thing and also took time to start.  Maybe I will insulate the box or not...

[jtwrace]

Here is the new and improved version of the Coilcraft Choke.  How does it work?  I still have to install it and try. 

[TomS]

Interesting. Some of mine buzz like bees and I assumed it was a wierd resonance with the particular caps and the choke. Do tell.

[sts9fan]

Where is the smart money?  Team buss?

[mjosef]

Here is the new and improved version of the Coilcraft Choke.

Looks like they really lathered it up with more lacquer, it's very shiny. 

I do have one that is somewhat 'loose' on the core, but it does not hum or buzz.

[Occam]

Interesting. Some of mine buzz like bees and I assumed it was a wierd resonance with the particular caps and the choke. Do tell.

Magnetostriction
http://en.wikipedia.org/wiki/Magnetostriction

[dBe]

Magnetostriction
http://en.wikipedia.org/wiki/Magnetostriction

Paul, it can be quite a thrill with very high power and it doesn't even have to be a coil.

There was a club here in Albuquerque years ago that had a huge amp rack with a bunch of the old Crown DC300 amps all on a 100A non-sequential switched service.  When the disconnect was closed the conduits would slam together and make a helluva a noise.  Same on turn-off.  The noise always freaked out the new sound guy 

Dave

[Occam]

Paul, it can be quite a thrill with very high power and it doesn't even have to be a coil.

There was a club here in Albuquerque years ago that had a huge amp rack with a bunch of the old Crown DC300 amps all on a 100A non-sequential switched service.  When the disconnect was closed the conduits would slam together and make a helluva a noise.  Same on turn-off.  The noise always freaked out the new sound guy 

Dave

Dave,

Dang, it took me some time to figure how that could actually happen. Cool!
Back our youth (40+ years ago  ) we'd just take that cmc to the transformer winder in most cities, and have it vacuum varnish impregnated. Actually, until 7 years ago, there was still a winder in Brooklyn who'd do it on spec.

For those of you who don't get the concept of magnetostriction, remember those spooky movie scenes where the helpless character is on a windswept street, the streetlight casting ominous shadows, and that transformer mounted on the creosoted pole is eerily humming and buzzing.

-Paul