Electrolytic caps VS. film for timing etc.

[Mike Nichting]

Is it crucial to use elec. caps in circuits if you can use film?? I am building a Phaser and don't want to use elec. caps unl;ess I have to. I have the same value caps in film so wopuld it make a huge difference ??

Mike

[Peter Snowberg]

Unless you want the sonic signature of the electrolytics, go for film!

The only place you might want to specifically use one for sound would be in a distortion or overdrive effect where it will filter more of the highs naturally and distort the signal in its unique way.

Same goes for tantalum. Apparently they are vital to the tone of at least one OD pedal.

In a phaser (or any clean effect), the extra quality adds to the sparkle. Most of the time that's good.

Sometimes good doesn’t equal good, but most of the time it does.  :?

-Peter

[Mike Nichting]

So Peter,
you're saying that I can use the same value cap but film?? If it will sound better than I'm in. Why does Tantalum sound so bad??? I take it it's the material but is it  dull sounding or flat??
Are Tantalums OK in any circuits??

thanks
Mike

[amz-fx]

Are Tantalums OK in any circuits??

Most of the Zvex pedals that I have owned used tantalum capacitors, likely due to the small size, and I doubt that they had any adverse effect on the tone.

There is a big difference comparing capacitors in hi-fi audio equipent and in stompboxes where there is a lot of intentionally induced distortion and the amp limits the frequency response to about 4000 Hz!

Doug Self, the highly regarded amplifier designer, has much to say on the subject... especially note the section about the Limits of Perception.  To quote Doug:

Several writers have advocated passing pulse signals through two different sorts of capacitor, and subtracting the result, claiming that the non-zero residue proves that capacitors can introduce audible errors. In fact such tests expose only well-known capacitor shortcomings such as dielectric absorption and series resistance, and perhaps the vulnerability of the dielectric film in electrolytics to reverse-biasing. No-one has yet shown how these imperfections could cause capacitor audibility in properly designed equipment.

http://www.dself.dsl.pipex.com/ampins/pseudo/subjectv.htm

regards, Jack

[Mike Nichting]

Hi Jack,
so your saying that it shouldn't make any difference if I use tantalums or electrolytics or did I miss the point completely??
Or are you saying that Tantalums have their sound and elec's have their sound and I should decide which one I like??

I was just looking at your boxes that you made jack, very,very nice indeed~!!

Mike N.

[Peter Snowberg]

Tantalums will work in any circuit where they don't get reverse biased (tantalums don't like that at all), but I would say they have a "chunky" tonal character. I don't hear the highs in them like I do in ceramic, film, or silver mica. This may be an advantage in some cases.

You'll find tantalums in plenty of audio circuits, mostly in circuits that are mass-produced or have space constraints, but apparently they are also an important ingredient in the tone of at least one distortion pedal. Tantalums also have the major advantage of long life which it's chief competitor does not. That's reason enough to use them over electrolytics, which typically have a 5 to 10 year shelf life and degrade after that. I have plenty of old electrolytics that still work fine, but some from the 70s have already failed on me. Your only other choices in that capacitance range get HUGE.  

In some of the amp world there is a term called "audiophoolery" which is applied to "audiophiles" that can hear the difference between things with no difference . The outcome is usually biased by how expensive the parts are or how much of a cult following there is around a particular brand. There is much pseudoscience and hogwash in this arena. These people face serious problems in blind A/B tests.

On the other side you have people who rely on equations and a "solid" theoretical background who say there is no difference between different things. :?

That aside, capacitors are complex things with a lot of variables. You have ESL - equivalent series inductance, ESR - equivalent series resistance, temperature coefficient, resonant frequencie(s), tolerance, dielectric loss, conduction loss, EPR - equivalent parallel resistance (leakage), humidity resistance, and when you get into high power supply circuits, you also have to pay attention to dissipation factor unless you want exploding caps.

I'm sure there are some others, but beyond the rated voltage and capacitance, above I've listed ten more variables. There are also other characteristics that are not part of the regular ratings, like displaying piezoelectric effect (ceramic caps being microphonic).

Some of these variables are also frequency dependant, just to to add to things.

Different construction methods will influence these variables greatly. In some applications, you can't even use some construction techniques (pulse power for instance) because they just result in a cap that won't fit the bill. Actual performance in a circuit is influenced by these variables. If this were not true, there would many fewer capacitor selections out there. There are all kinds of specialized caps made to address one or more of the variables in a constant way.

In (pedal) audio, these parts are rarely getting pushed their limits and to a degree they will ALL work and give you signal out just fine. LV circuits are using them in a way where they generally act very similarly, but by my ears, not the same. As Jack points out, guitar pedal audio is quite band limited.

For bypass caps there won't be much coloration of anything, but as coupling caps, I can plainly hear the difference between different caps in some cases and my hearing has been damaged by working too many concert venues & nightclubs. I do *not* have golden ears. Still, the closer you get to the rated voltage, the more it stands out to me.

If anybody tells me I'm dreaming this up, all I can do is chuckle, regardless of their credentials. I wonder what Self means by properly designed equipment? :?   I doubt most guitar gear is "properly designed" if his statement is 100% true. Amps just sound so good when you push them past red-line, something you would NEVER see in HiFi. In that world things are closer to idleing than red-line.

I modded a Fender Super for a friend and tested it during his band's rehearsals. This involved several hours of listening tests by 5 people plus myself. As they played, I flipped an A/B switch to test out many of the mods I made versus the original parts. I didn't tell him which part was in use (he doesn't know any electronics anyway), I just asked which he liked better. I got input from everybody.

Anybody who questions this can wire up an SPDT switch and try it for themselves. Draw your own conclusions. Don’t believe anything I say. The laws of physics are immutable.

Take care,
-Peter

[Paul Marossy]

Is Doug Self's site still up? I tried to visit it a while back, and it was apparently not up anymore...  

[Mike Nichting]

Thank you Peter.

Mike N.

[Peter Snowberg]

You are quite welcome Mike.

Paul, I can get to his site now without problem . I was really bummed out when it went down a few weeks back. I found the balanced I/O page in the google cache and then grabbed the thumbnails from the google image search, but now the real deal is back.

http://www.dself.dsl.pipex.com/ampins/ampins.htm

He does have a lot of great info there. IMHO, EVERYBODY should check out his Balanced Line Technology page:

http://www.dself.dsl.pipex.com/ampins/balanced/balanced.htm

That is what brought me to his site the first time.

-Peter

[Paul Marossy]

Thanks Peter.

[rocket]

Which oe is the pedal that relies on tantalum capacitors?

[Peter Snowberg]

Which oe is the pedal that relies on tantalum capacitors?

The TS series.  I've never built a direct TS clone and I don't have an original, but I can point you to this thread:

http://www.diystompboxes.com/sboxforum/viewtopic.php?t=1055&highlight=tantalum

I've used them in the cathode bypasses of tube amps while testing and I didn't hear any breakup from them (wrong application for that), but the tone was "sharper" for lack of a better term.  :?

I did try a breakup experiment on them once for tone testing. I took a Fender Twin, cut the lead from the 1st pre to the tone stack, added a big film cap to the previous stage for coupling, added tantalum cap after that, and connected the other tantalum lead to the tone stack. The tantalum got a switch across it to bypass, the junction between the new film and tantalum cap was biased by a 9V battery and big resistor, and another big resistor on the other side of the cap going to the 9V's other terminal.

Turn the master all the way down unless you want to hear a DC pop from hell when you switch the bypass switch.  :shock:

-Peter

[Doug B.]

No-one has yet shown how these imperfections could cause capacitor audibility in properly designed equipment.

I like these two articles, both fairly technical (including measurements, graphs, and even 'scope traces):

 http://www.capacitors.com/picking_capacitors/pickcap.htm

 http://members.aol.com/sbench102/caps.html

Caution:  They're both audio-related (not musical instrument).  

My feeling is that the various film types (and different brands, etc) don't sound much different with signals as simple as an electric guitar.  They might with complex audio signals (cymbal crashes on top of bass with lots of other stuff mixed in between).  Electrolytics are a different story....

A while back, i upgraded a nasty-sounding (not in a good way) solid-state practice amp (Fender Sidekick 15) by substituting films for all the electrolytics in the signal path (there were 7 or 8 IIRC, all aluminum not tantalum).  Yes, it made a difference in something i was specifically listening for.  

- Doug B.