i don't think potting is necessary. i don't care which module comes out on top, as long as i can hear a difference. i may well think the cheap parts sound better, who knows. stranger things have happened. if you really insist, you could pot the switch to which things are connected. that's all that really matters.
we should use an active stage to test. let's make a simple preamp. input shunt attenuator, gain or buffer stage of your choice. i like the Borbely buffer cuz it's got high input impedance (JFET), good ouput drive capability, is simple to build, requires a capacitor (so we can test those too), and sounds transparent. i have a supply already built for it, the black box can use a standard 3-pin XLR jack for power connection. but if someone else has a better suggestion please chime in.
we should use an active stage to test. let's make a simple preamp. input shunt attenuator, gain or buffer stage of your choice. i like the Borbely buffer cuz it's got high input impedance (JFET), good ouput drive capability, is simple to build, requires a capacitor (so we can test those too), and sounds transparent. i have a supply already built for it, the black box can use a standard 3-pin XLR jack for power connection. but if someone else has a better suggestion please chime in.
Dorkus, I think you miss the point. It's not whether or or not you prefer the premium parts, it's whether or not you hear ANY difference.
The buffer is fine if you agree in advance that it is transparent and will not affect your ability to tell a filter made from grungy parts and wire (I might even use a coathanger!) from a filter made with your choice of premium parts and wire.
The buffer is fine if you agree in advance that it is transparent and will not affect your ability to tell a filter made from grungy parts and wire (I might even use a coathanger!) from a filter made with your choice of premium parts and wire.
sounds good
i agree the first step is to see if i can even hear the difference at all. again, i think potting the switch should be sufficient. make sure you document beforehand which is which though.
maybe we can use color-coded wires coming out of the potted block, and you hold the key to the color code. make sure it's six-9's copper with teflon insulation tho! j/k.
the buffer is a good circuit. it is not a filter, but it will have an output coupling cap, which is a LPF after all, and it also has a feedback cap of sorts (.22uF, value not critical). so we can test the performance of both electrolytics and films.
shall i start taking suggestions for what parts to use in the "cream of the crop" version?
below is a diagram of the circuit from the original thread (http://www.diyaudio.com/forums/showthread.php?threadid=2281). a couple resistors missing but otherwise correct.
i agree the first step is to see if i can even hear the difference at all. again, i think potting the switch should be sufficient. make sure you document beforehand which is which though.
maybe we can use color-coded wires coming out of the potted block, and you hold the key to the color code. make sure it's six-9's copper with teflon insulation tho! j/k.the buffer is a good circuit. it is not a filter, but it will have an output coupling cap, which is a LPF after all, and it also has a feedback cap of sorts (.22uF, value not critical). so we can test the performance of both electrolytics and films.
shall i start taking suggestions for what parts to use in the "cream of the crop" version?
below is a diagram of the circuit from the original thread (http://www.diyaudio.com/forums/showthread.php?threadid=2281). a couple resistors missing but otherwise correct.
Attachments
Frank: No, it shouldn't, but it would be nice to get formal agreement at the outset that the buffer is not so egregiously bad that it obscures the differences being tested for. When I tell a True Believer that I tested component XYZ in my system and couldn't hear its supposed superiority, the first thing they descend on is my lack of exotic wire or magic capacitors or somesuch. "Clearly, your system isn't high enough resolution!" If I'm going to go to the trouble here, I want to eliminate the common excuses first.
my hearing is ok
and my girlfriend has even more sensitive ears (women have better high frequency hearing). this test will be enough to convince me one way or another though.
if i fail at this test, then perhaps someone else can try it with the same black box. when the test is over, SY can report the results without giving away the switch configuration, so it can be repeated on others.
and my girlfriend has even more sensitive ears (women have better high frequency hearing). this test will be enough to convince me one way or another though.
if i fail at this test, then perhaps someone else can try it with the same black box. when the test is over, SY can report the results without giving away the switch configuration, so it can be repeated on others.
That's a seriously good point. Well-designed experiments don't "succeed" or "fail," they give information regardless of outcome.
More positions are better; 8 is a pretty minimal number, 12 would be better*. But you have no time limit. Sort them at your leisure. Take a month. Take two months. Invite your friends over to guess. Have fun with it. If electrolytics and coathanger wire sound as bad as many claim, you might be finished in an evening, n'est-ce pas?
Potting the switch alone accomplishes nothing; it would take me perhaps 3 minutes and a DVM to do the sorting without listening under a setup like that. I'd rather work out a way to seal the box securely, if you're worried about potting materials. I note, though, that electronic grade potting materials are used in all kinds of high-end gadgetry, including those speaker cables that cost as much as my Volkswagen.
*12 positions is really only 6 trial pairs. Your chances of getting a pair correct is 50% if there is no sonic difference. So the test is one that gives a chance level of (0.5**6) = 1.5%, if you score 100% correct pairing, i.e., there's only a 1.5% chance that you will guess correctly purely by chance. The 6 position switch is only three pairs, giving a chance level of (0.5**3) = 12.5%. The confidence levels drop further if we name one of the pairs so that you can have a known, fixed reference.
More positions are better; 8 is a pretty minimal number, 12 would be better*. But you have no time limit. Sort them at your leisure. Take a month. Take two months. Invite your friends over to guess. Have fun with it. If electrolytics and coathanger wire sound as bad as many claim, you might be finished in an evening, n'est-ce pas?
Potting the switch alone accomplishes nothing; it would take me perhaps 3 minutes and a DVM to do the sorting without listening under a setup like that. I'd rather work out a way to seal the box securely, if you're worried about potting materials. I note, though, that electronic grade potting materials are used in all kinds of high-end gadgetry, including those speaker cables that cost as much as my Volkswagen.
*12 positions is really only 6 trial pairs. Your chances of getting a pair correct is 50% if there is no sonic difference. So the test is one that gives a chance level of (0.5**6) = 1.5%, if you score 100% correct pairing, i.e., there's only a 1.5% chance that you will guess correctly purely by chance. The 6 position switch is only three pairs, giving a chance level of (0.5**3) = 12.5%. The confidence levels drop further if we name one of the pairs so that you can have a known, fixed reference.
If you indeed hear no difference, that is the result. After all that is also a valid answer and the core of our question. Can we hear a difference?
The next step is; if we hear a difference, why? That's where the measurements come in.
I have no problem with a buffer stage. Perhaps Nelson could suggest one, I would go along whith that. I seem to remember seeing somewhere that Nelson didn't think caps had much of a role in the sound of an amp, but I could be wrong.
As for a volume control we should stay with the KISS principal here. Unity gain or minimum loss so that the test box can be inserted into an existing system with out major change to system gain.
Does that seem reasonable?
Later
Bruce
The next step is; if we hear a difference, why? That's where the measurements come in.
I have no problem with a buffer stage. Perhaps Nelson could suggest one, I would go along whith that. I seem to remember seeing somewhere that Nelson didn't think caps had much of a role in the sound of an amp, but I could be wrong.
As for a volume control we should stay with the KISS principal here. Unity gain or minimum loss so that the test box can be inserted into an existing system with out major change to system gain.
Does that seem reasonable?
Later
Bruce
oh yeah, duh. continuity meter to sort out which is which. duh.
i would like to have an input shunt attenuator, so that i can use this as my primary preamp. otherwise it is a step in a c
testing 10 positions can be very time consuming because i like to listen for an extended period of time before coming to a conclusion about sound quality. this means an entire symphony, or at least an entire movement, and maybe a few different pieces. if you keep switching back and forth every few minutes you start to lose interest in the music and nothing really matters anymore. also, high quality 6 position switches are cheaper than 12 positions. i think it is enough permutations. if you want, you do not even have to split the two circuits 50/50.
again, i am not going to cheat, so just seal the box somehow. i really do not know how these circuits will react to potting and that's another variable (or excuse) that could be thrown in there.
i would like to have an input shunt attenuator, so that i can use this as my primary preamp. otherwise it is a step in a c
testing 10 positions can be very time consuming because i like to listen for an extended period of time before coming to a conclusion about sound quality. this means an entire symphony, or at least an entire movement, and maybe a few different pieces. if you keep switching back and forth every few minutes you start to lose interest in the music and nothing really matters anymore. also, high quality 6 position switches are cheaper than 12 positions. i think it is enough permutations. if you want, you do not even have to split the two circuits 50/50.
again, i am not going to cheat, so just seal the box somehow. i really do not know how these circuits will react to potting and that's another variable (or excuse) that could be thrown in there.
Frank, your reaction is more typical. The existing literature shows that detection thresholds for distortion, level, and frequency response are lowest (i.e., highest sensitivity) with rapid switching schemes.
But the switcheroo idea I'm proposing will give Dorkus the best of both worlds. He can do it fast, he can do it slow, he can do one or the other depending on the phase of the moon. Two or three months is not at all outrageous- I'm cool with that.
But the switcheroo idea I'm proposing will give Dorkus the best of both worlds. He can do it fast, he can do it slow, he can do one or the other depending on the phase of the moon. Two or three months is not at all outrageous- I'm cool with that.
A 12 position Radio Shack switch is fine if it controls relays which do the swithcing in the circuit. Shorter signal path that way too.
By the way every time the switch pos is changed the relays should drop out and reengage so a break before make switch should be used.
Back to work now (for me)
Bruce
By the way every time the switch pos is changed the relays should drop out and reengage so a break before make switch should be used.
Back to work now (for me)
Bruce
joel,
that's what the redundant switch positions are for. it is even better than having 2 identical modules, because it is guaranteed to be exactly the same. you never know if another module may be a little different due to component tolerances, differences in soldering, etc.
i thought about the relay thing, except for a problem. i'll be able to know when it's switching modules because i can hear the clicking or lack thereof. i don't think a break before make will give a long enough break to ensure a switching "click" every time, as the relay has some switching delay. so i think a high-quality coin silver switch is better.
that's what the redundant switch positions are for. it is even better than having 2 identical modules, because it is guaranteed to be exactly the same. you never know if another module may be a little different due to component tolerances, differences in soldering, etc.
i thought about the relay thing, except for a problem. i'll be able to know when it's switching modules because i can hear the clicking or lack thereof. i don't think a break before make will give a long enough break to ensure a switching "click" every time, as the relay has some switching delay. so i think a high-quality coin silver switch is better.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.