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I am concerned that there may be some confusion over the term "bypass" as used in this thread. I use the term (in this context) to refer to multiple capacitors wired in parallel in the same physical location, or nearly so. The purpose of this (at least within the realm of high-end audio) is to create a single, conjugate capacitor that outperforms ("sounds better than") any single cap in the same application. The mix of caps is usually arrived at through a series of listening evaluations, so the process is mainly subjective.On the other hand, stable circuit design often demands the use of "decoupling" caps located as close as possible to the circuit elements they are helping to stabilize. These caps are often referred to as "local bypass" caps, and they are electrically in parallel with the main power supply caps. While these may be considered "bypass" caps, they do not really fall into the category being discussed in this thread. Of course, these local bypass caps may themselves be bypassed, but I digress.... I design fairly wideband preamps and amps, and they are stable without the need for zobel loading networks. I could remove all of the bypass caps in any of my designs and they would continue to operate perfectly. I would not, however, consider removing the local decoupling caps.Steve McCormackdesigner, SMc Audio, McCormack Audiowww.SMcAudio.com
To Imperial: I'm sorry, but I don't understand your question about "nodes." Were you asking about my "DNA" technique for distributing the larger electrolytic capacitors in a solid-state output stage? Or something else? I do use bypass caps in my designs in the sense that I use multiple types of caps grouped together for improved performance. Exactly which caps I use and how they are employed varies depending on the product, but beyond that information, sorry - I'm not giving away the farm Happily, most of my designs are direct-coupled, so I rarely have to concern myself with the quality of a coupling cap.Best regards,Steve McCormackdesigner, SMc Audio, McCormack Audiowww.SMcAudio.com
Hi Guys!To Pat: Please read previous posts before you reply. I have clearly stated that bypass capacitors need to be placed as close to the circuitry as possible. I even gave an example: "For example, if it's a mosfet output stage amplifier, the bypass caps need to be located as close to the mosfets as possible." I NEVER said that the bypass cap was located at the main electrolytic capacitor. Please do not falsely accuse me of making such statements. Trust me Pat, I know physics. To Mr. McCormack:I have listened to your amplifiers and preamps and they are FANTASTIC! Rough specs of some of the amps I worked on are +/- 1dB 0-500kHz, I cannot get away without a zobel.I think that a lot of the readers here do not understand what bypass capacitors (or decoupling - local bypass as you have called them) do. Truth is, is that they're all over the circuit board. Without them, solid state amplifiers would NOT operate properly. They would generate, oscillate, transistors could overheat and fail, etc. I have never ever seen any design without them!To Readers:The capacitor is a bypass capacitor regardless if it's sitting somewhere on the circuit board miles away from the power electrolytic or if it's directly soldered to the electrolytic cap's leads. If you don't understand that, there are many great Electronics 101 books on www.amazon.com Now this all started because I was answering a question for Mr. Bronk, so let me elaborate a little further. I believe that you were talking about a tube amp? Your power supply capacitors are 4700uF, so realistically speaking you have to use electrolytic capacitors. In the schematic, are there any smaller value capacitors connected in parallel to the larger caps? If yes, than pretty much all you can do is plug and listen to different caps to see which ones you like best. My personal favorite are the Vishay BC Components for large values and Vishay MKT 1822 for smaller values. If there are no smaller value capacitors connected in parallel, than you can try adding some yourself. Remember, electrolytic capacitors do not operate well with high frequencies, so adding smaller value film capacitors will make the now new capacitor as a whole much better. And it doesn't matter if they are Black Gates, or Elna's, or Jensens, etc. Bypassing electrolytic capacitors with smaller film caps will ALWAYS make the power supply better electrically speaking. Weather you will hear a difference in your tube amp or not is an objective opinion.Thanks!Norbert
Thanks John! I have revised my signature per your guidelines.Steve McCormackdesigner, SMc Audio, McCormack Audiowww.SMcAudio.com
For the purposes of high-end audio, bypass caps are almost exclusively film types (polyester, polypropylene, polystyrene, Teflon, etc.) Generally speaking, electrolytic caps are only useful because of their high energy density - otherwise we would much rather use nothing but film caps.
I've been into audio for 11 plus years and I have heard dozens of capacitors. Everything from military specd, to audiophile grade. Ranging in price from just a few pennies to hundreds of dollars. And the best capacitors that I have ever heard are Vishay. These are made in Germany by Vishay Roederstein to be exact, model number MKT 1822. They were previously know as the ERO capacitors. The MKT1822 is a box style timing capacitor, made out of metalized polyester. They range from 1000pF - 15.0uF and have voltages from 63vdc - 250vdc. Most audiophiles will disagree because it goes against all audiophile grade logic. They don't have Teflon, copper foil, silver foil, polypropylene/foil design, silver leads, oil, etc. But what they have is what counts, absolutely stunning sound.It is virtually vale free and grain free. I have never heard any other capacitor come close! They have incredible resolution and sparkle to the high frequency. The term "liquid" should have been invented for these caps. Plus they have to most un-electric midrange I have ever heard. The best part is that they are dirt cheap, a few bucks max for the larger values. And they work as well in speaker crossovers as they do as coupling or bypass capacitors in amplifiers, preamps, dacs, etc. Here's a list of some capacitors which I compared the MKT 1822's to.AuriCapHovlandSCR SolenJensenRelCap Audio Cap ThetaMultiCap RTXMultiCap PPMFXRussian Military Teflon High Voltage Types
You can order them from www.mouser.com
