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  • Listening tests of high end capacitors...

    I've been approached by a maker of high end capacitors to try some out in passive treble cut guitar circuits. My prejudice is to believe that you cannot hear the difference between one cap of a given value and another given that they are treble bleed and are literally not in the signal path. I think that the differences that people claim to hear are because of tighter tolerances, etc.; in other words, there is another explanation for one cap sounding different from the other than the quality of the cap itself.

    But, not to be fooled by my prejudices, I'm going to set up a double or even triple blind test to see and hear what's what.

    I'll put capacitor toggle switches into a couple of guitars and even wire the switches in reverse from one another...forward or up will be cap A in one guitar, cap B in the other. Then I'll turn the guitars over to someone who has no idea of which way is which, and they will flip the switches while yet another person plays the guitars. The pots will be the same and won't switch. I'll test pots for resistance. I'll test the caps and get them within 2%. Then we'll play and test with the pots wide open, closed all the way down, and at some sort of mid positions. I could even test resistance of the mid positions by bringing a couple of test terminals up to the surface of the guitars.

    Am I missing anything here?

  • #2
    Originally posted by Rick Turner View Post
    Am I missing anything here?
    Yes, add this picture to your collection:



    You're welcome!
    Pepe aka Lt. Kojak
    Milano, Italy

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    • #3
      Well, if a statistically significant number of pussies agree on the sniff, I think it becomes scientific...

      And I'm willing to take on all the pussies who apply...

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      • #4
        subscribed..... definitely curious to know what you find

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        • #5
          Am I missing anything here?
          Yes. Just follow proper double blind test procedures. Double blind means that neither the subject nor the evaluator know where and what the DUT is; proper test means that the same stimulus (signal) must be applied to the DUT.

          All properly done DBTs have demonstrated that there is strictly *NO* perceptible subjective difference between properly built/used/chosen caps using the same technology.

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          • #6
            A key issue is getting the guitarist to play consistently. A switch has two positions and thus can act as a bias, even quite unintentionally, as the guitarist's hand returns to the strings after switching. You can use a mini-phone plug, or similar connector, instead of a switch, jumpered under the cover of the plug, and thus invisible to the guitarist, to connect either cap A or B. You wire up a set of plugs and number them, labeling them randomly before each pass. The guitarist calls out the number. Even with this, random changes in picking can hide any real differences. You need someone consistent.

            An interesting question is: can anyone hear the difference between any capacitor and a short with the tone pot at maximum resistance?

            I assume you have read Bateman's excellent work on capacitor distortion? Not necessary for this test, of course, but good general knowledge. (If not, search for capsound3.pdf.)

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            • #7
              Originally posted by Rick Turner View Post
              Am I missing anything here?
              Keep the wires from the switch to the caps the same length.

              Also if possible, test the caps to see how close they are to the rated value. If possible match up caps of each type.

              I agree that I think it's a lot of hooey. I'm partial to those little yellow plastic film caps, but I've used ceramics in some instruments and they sound fine too.
              It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. — Albert Einstein


              http://coneyislandguitars.com
              www.soundcloud.com/davidravenmoon

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              • #8
                Originally posted by Rick Turner View Post
                Well, if a statistically significant number of pussies agree on the sniff, I think it becomes scientific...

                And I'm willing to take on all the pussies who apply...
                No pussy sniffing allowed here... they have other forums for that!
                It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. — Albert Einstein


                http://coneyislandguitars.com
                www.soundcloud.com/davidravenmoon

                Comment


                • #9
                  Rick -

                  Glad you're giving this test every chance to reveal possible differences. Count me in as another one who feels that in this application the cap basically just ain't in the signal path.

                  However, this gives me the opportunity to bring up a somewhat related issue, which is where to put the cap in the RC chain. Forgive me if this has been well established before, but I've found that grounding one leg of the cap can be a helluva lot quieter than stringing the thing between the volume & tone controls, as is so often seen in guitars from some of the biggest names in the business.

                  It's especially dramatic to change this in someone's 335, where full shielding can be inconvenient, to say the least. However, I've gotten quite surprising results even in guitars that I thought were well shielded; the cap seems to serve as an antenna in some situations.

                  OK.. enough of this, now back to David's subject...

                  Bob Palmieri
                  Last edited by fieldwrangler; 08-27-2010, 03:48 PM.

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                  • #10
                    Originally posted by Rick Turner View Post
                    I've been approached by a maker of high end capacitors to try some out in passive treble cut guitar circuits. My prejudice is to believe that you cannot hear the difference between one cap of a given value and another given that they are treble bleed and are literally not in the signal path.
                    {snip}
                    Am I missing anything here?
                    1. It's not a prejudice, merely sound (cough!) reasoning on your part.
                    For identical capacitances, the only time you'll hear a difference is if the cap has pathological traits like excessive microphonics or loss.

                    2. The only thing you are missing is a client with a clue.

                    The question becomes one of business ethics (i.e., money), whether or not you're getting paid to investigate something that is obvious upon momentary reflection, and whether or not you want to establish a business relationship with a client you will need to educate.

                    In any case, be gentle.
                    "Det var helt Texas" is written Nowegian meaning "that's totally Texas." When spoken, it means "that's crazy."

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                    • #11
                      I see a common problem: if you find no difference with their nano PTFE /superconducting buckyball foil wondercaps they will cease their affiliation with you and look for another "expert" with more sensitive ears.

                      Happens all the time in FDA trials, oil spill studies and smoking research

                      One shortcut: since correctly done double blind comparisons should show no perceivable differences between similarly specified capacitors, any finding to the contrary is necessarily an experimental artifact, thus report the negative result now without wasting time on the exp.

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                      • #12
                        Originally posted by tedmich View Post
                        I see a common problem: if you find no difference with their nano PTFE /superconducting buckyball foil wondercaps they will cease their affiliation with you and look for another "expert" with more sensitive ears.
                        I think the caps that are being sold as special are old style paper and oil, etc.

                        One shortcut: since correctly done double blind comparisons should show no perceivable differences between similarly specified capacitors, any finding to the contrary is necessarily an experimental artifact, thus report the negative result now without wasting time on the exp.
                        Here's a good example of one of these listening tests:

                        A Listening Evaluation of Discrete vs Integrated Circuit Audio Preamplifiers in Stringed Musical Instruments


                        Abstract
                        Audio preamplifier circuitry is increasingly used in electric guitars and electric bass guitars. A general preference for circuits built using discrete solid state components vs integrated circuit operational amplifiers appears to be building within the user community for these instruments. A double blind experiment was conducted to determine if users showed a preference between a JFET discrete component preamp and an opamp preamp following a listening evaluation. Results indicate no clear preference for either type.
                        Results
                        The experiment was unblinded and the questionnaires tabulated with the following results. Two (2) subjects found the tone of the discrete FET preamp preferable. Two (2) subjects found the tone of the opamp preamp preferable. Five (5) subjects found the sound identical in both preamps. Five (5) subjects found the two preamps sounded different but that neither one was superior in tone. As the data are so obviously distributed normally about the mean no additional statistical evaluations were performed. Subjects that indicated a preference also indicated that perceived differences were very subtle.

                        Conclusions
                        The majority of subjects (8) found no preference between the two circuits and preference was evenly divided among the remainder...
                        So people might hear a difference, but wont be able to express what it is, or if it's better or worse, just different and probably negligible.
                        It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. — Albert Einstein


                        http://coneyislandguitars.com
                        www.soundcloud.com/davidravenmoon

                        Comment


                        • #13
                          I did that test with a rotary switch out of an old conn organ so it held something like 6 different caps. i used various manufactureres caps- all the same type- polypropolene- orange drops, mallory, zicon- sprauge from cheapo to really expensive and I matched them all with a capacitance meter. the physical size of the capacitors varied alot. I also made sure they were oriented the same way- outside lead towards ground.
                          No discernable difference in tone using a standard guitar tone circuit and it was done with 8 people listening. I never got around to mixing types of caps partly because of the problem of matching them with a meter- you have to have alot of caps to match them.
                          We were straining to hear any difference- if you pick slightly differently that can be mistaken for a toneal difference so it takes quite a bit of effort to equalize everything. If there was a difference in tone it was beyond what most people could hear.

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                          • #14
                            Practically everything being said here is spot on with my own beliefs. I just said I'd do this test for my client Graham Henman whose guitars and basses we are starting to build. His former builder had been using $7.00 exotic caps, and when I went over the bill of materials, that jumped out like a cougar on a deer as being wrong, wrong, wrong. And given that I'm the OEM builder, the effect of a $7.00 part looks more like $21.00 or more when the retail price of the instrument is calculated. I'd rather put more money into pots and less into caps for a more reasonable trade-off.

                            BTW, I am going to put an "all controls" bypass switch on these instruments that will hardwire past the pots and tone cap. It's a cheap trick that really makes a difference.

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                            • #15
                              Would putting in a dummy switch test scenario, one with nothing connected to it, aid in offsetting any bias?
                              -Mike

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