If you absolutely can't stand the idea, get Cornel Dubelier PP.
Mark Levinson has odd choice for cap upgrades in one of their service bulletins. Why?
Pursuant to one of the Mark Levinson service bulletins, for Model 331, 332, 333 etc, they have outlined one of many things that should be performed on any amp that comes in for service.
One of the line items has me baffled. They recommend replacing four caps on each voltage gain / input board. These eight caps are PP type of .01uF @ 160v. They recommend replacing them with Ceramic X7R .01uF @ 200v. These are axial configurations.
This is not an expensive upgrade but I thought to myself that polypropylene caps had low failure rates and good longevity compared to other types especially if they were used in a proper operating envelope.
I just finished watching and reading some information on the perils of using ceramic caps in certain applications. For one, they tend to drift heavily with temperature changes. In a monster like the Model 333 there will definitely be a large temperature swing. The ceramics also tend to exhibit piezo effects with vibration. While vibration is only inducing small voltages, I can imagine the sum of many caps being subject to vibration not being a good recipe for an audio signal.
ML has stated that the ceramic replacements should be installed with spacers to keep them lifted from the circuit board. I am guessing that this could address temperature concerns, vibration or parasitic capacitance issues. They do not provide any reason.
I would really like to learn a little more behind their reasoning as it seems this particular "upgrade" is counter-intuitive. Can anyone shed some light on this?
One of the line items has me baffled. They recommend replacing four caps on each voltage gain / input board. These eight caps are PP type of .01uF @ 160v. They recommend replacing them with Ceramic X7R .01uF @ 200v. These are axial configurations.
This is not an expensive upgrade but I thought to myself that polypropylene caps had low failure rates and good longevity compared to other types especially if they were used in a proper operating envelope.
I just finished watching and reading some information on the perils of using ceramic caps in certain applications. For one, they tend to drift heavily with temperature changes. In a monster like the Model 333 there will definitely be a large temperature swing. The ceramics also tend to exhibit piezo effects with vibration. While vibration is only inducing small voltages, I can imagine the sum of many caps being subject to vibration not being a good recipe for an audio signal.
ML has stated that the ceramic replacements should be installed with spacers to keep them lifted from the circuit board. I am guessing that this could address temperature concerns, vibration or parasitic capacitance issues. They do not provide any reason.
I would really like to learn a little more behind their reasoning as it seems this particular "upgrade" is counter-intuitive. Can anyone shed some light on this?
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- 19 posts total
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@teo_audio; Why pull your post? I get the argument from both sides and I really appreciate all input. Dialogue like this challenges my thought processes and possibly will answer some questions for others that casually read this thread. Since ML has made these particular PP caps an area of concern I am going to address it. Normally I would have skipped PP caps and focused all of my energy on electrolytics. I have seen bizarre ESR readings from the electrolytic caps in this amp. Two identical caps sitting right next to each other having starkly opposite readings is a reality. I now feel that the amp has had enough of its guts replaced to live another long life. The ML service bulletin specifically called out 6 small electrolytics, 2 op amps, and the 8 PP caps described herein, as parts that had high rates of failure. I have addressed all these items with the exception of the PP caps. I found these Philips caps which, value for value, are direct replacements. Different construction though. http://www.ebay.com/itm/New-20-Pcs-01uF-160V-Film-Foil-Axial-Capacitors-Metalized-Polypropylene-DC/131455088503?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D44758%26meid%3D877ec48210ec4acaa78afefdf7b41d42%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D140594885371 The very large main caps were Philips as well. Don’t get me started on the black ooze mess they made in this amp when they failed! They had a horrendous track record so Cornell Dubliers sit there now. So should I consider these ebay Philip PP’s? I can find a suitable replacement on Mouser or Digikey but the voltage rating is more than double. I was taught that a higher voltage cap could be used but I should not go higher than 20 percent. Any thoughts on the Philips? |
generatorlabs The XR7's are great for HF filtering, I use them on dac I/V stage voltage rail decoupling.That's why ML are recommending them. Cheers George |
- 19 posts total