Tube Amps / Music Electronics
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|6/12/1999 9:44 PM|
|Bill S.||Tantalum VS. FILM!|
Anyone know know which is better for audio work? DO film caps have a better sound?
|6/13/1999 0:06 AM|
Tantalums are good substitutes for Electroilytics but not for mylar, polypropelyne, or polystyrene film caps, or foil caps for that matter. Tantalums are very poor capacitors in terms of Equivalent Series Resistance (ESR) and Dielectric Factor (DF) qualities. The only redeeming quality of tantalums is their low temperature coefficient. In other words, they don't change value much as they heat up.
Film caps on the other hand have lower ESR and DF values than tantalum caps making them better for audio. In general, the capacitor 'quaility' hierarchy is as follows:
1. Electrolytic *** Lowest Quality ***
3. Paper (1950- 60's. These are no longer made)
4. Paper Saturated with Oil (i.e. Vitamin Q style)
5. Mylar (i.e., Polyethylene)
8. Teflon *** Highest Quality ***
In general, you get what you pay for with higher quality caps costing more. Although some poor quality caps, like vitamin Q's, will cost you an arm and a leg because they are built to last forever rather than for sound quaility.
A quick discussion of DF is needed to fully understand why certain capacitors sound better than others. In essence, DF is a measure of a capacitors ability to discharge quickly. The faster a capacitor can discharge, the more accurately it can reproduce music. For, example, polypropylene capacitors sound alot more 'accurate' than mylar capacitors even though both are film caps. They also tend to reproduce high frequencies more accurately and therefore are sometimes perceived to sound a bit brighter.
There is one caveat to a cap having a good DF rating. Vintage guitar amps sound vintage because they used relatively poor quality paper capacitors in their manufacture. In other words, the poor DF of these caps was part of the amplifier's tone. A poor DF cap tends to smear the sound a bit making it less accurate but darker and warmer sounding which, though not desireable for audiophile applications, is a desirable quaility for some guitar amps.
This is not to say that a poor DF rated cap is what you want for your guitar amp. High end amps made today like Matchless or Trainwreck use polypropylene and polystyrene caps deliberately to take advantage of their more accurate sound. More conventional amps, like Marshall and Fender on the other hand, almost universally use electrolytics in their power supply and cheap mylar caps in their audio circuitry. There is a very good reason why a Matchless costs more than a Marshall.
Here's a few final comments on capacitor types:
1. Paper capacitors were used in the 1950-60's because they were cheap to manufacture. Unfortunately, they tend to go bad over time causing constant problems among vintage amp collectors. If you really want to retain the amp's vintage sound without going through the headache of constant repair, replace the original paper caps in a vintage amp with Paper in Oil caps which are the closet things that are still manufactured today. Paper in Oil caps such as Vitamin Q caps have an added benefit in that they are known to last forever and usually never needing replacing.
2. Different capacitor types have tremendous variations in their size for a given amount of capacitance. This is one reason why you don't see Polystyrene caps used alot even though they sound superior.
3. Internal construction of the cap also makes a big diffeence in sound. If a film cap is constructed coaxially, like MIT Multi-caps for example, the cap will have a more accurate sound then a conventionally constructed capacitor.
4. Film caps are always inferior to Foil caps in terms of sound for a given dielectric. A film cap is manufactured by spraying a very thin coating of metal such as aluminum on the dielectric material such as mylar. This technique is used because it saves on cost of materials as well as time and labor. Foil caps on the other hand use thin sheets of metal for the conductors within the capactors. Because of higher cost, you rarely see foil caps used in guitar amps eventhough they are greatly superior.
I hope this information helps somebody.
|6/13/1999 10:38 PM|
Nice write up. Just so you know that your time didn't go to waste, I printed it for my notebook. I periodically print articles from the various sites that I feel I would like as a handy reference down the road. Even though I have several books concerning amps, theory and components, etc., it's still nice to have these articles. So, I thank you! Terry
|6/14/1999 9:42 AM|
wonderful discussion of caps. i would like to add that tantalums have a very long life compared to electrolytics, although electrolytics have improved dramatically over the years. tantalums will generally fail during test burn-in if they are going to fail at all, which helps with longevity trust. we'd all like the devices we buy to last for 30 years or more so we can sell them to cover lost social security benefits. basically for high value caps, we only have tantalums and electrolytics to pick from... one is solid and epoxy-dipped, and one is an aluminum can filled with wet goo and sealed with a rubber plug. note that electrolytics traditionally have four digit date codes like potentiometers and speakers (freshness dating!) and tantalums never do.
|6/14/1999 9:50 PM|
Great writeup! I did have a question about film caps. Is this the same beast as the Sprague polyester film Orange Drop caps currently made by SBE? Here is a quote from their site:
"Type 225P capacitors are wound from PETP polyester film
and thin gauge aluminum foil under carefully controlled atmospheric conditions. They are protected by a conformal coating of orange epoxy. The pressed profile of the Type 225P also allows for optimum board space utilization."
IMHO the Orange Drop caps have their own sound, possibly due to their construction and larger size. If I replace all of the coupling caps in an amp with Orange Drops (Type SBE418P) I usually find the sound to be a bit dark so I'll put in a few regular high-quality polyester or polypropylene caps to bring back some of the high frequencies.
|6/15/1999 2:02 AM|
Are you actually able to find the 225P and 418P caps? So far I've only been able to find the PS series, 715P and 715P from places such as Antique Electronics, Angela Instruments, New Sensor, Hoffman and a couple of other places I can't think of at the moment. Someone awhile back had mentioned another electronics supplier but when I checked their site (can't remember name now) they seemed to only have a very limited quantity in stock and were out of some values. I emailed SBE to find a supplier of the 225P and 418P but have never received a reply. Terry
|6/15/1999 2:08 AM|
Are you actually able to find the 225P and 418P caps? So far I've only been able to find the PS series, 715P and 715P from places such as Antique Electronics, Angela Instruments, New Sensor, Hoffman and a couple of other places I can't think of at the moment. Someone awhile back had mentioned another electronics supplier but when I checked their site (can't remember name now) they seemed to only have a very limited quantity in stock and were out of some values. I emailed SBE to find a supplier of the 225P and 418P but have never received a reply. Terry PS that was my post earlier but forgot to put my email address.
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