Listening tests concerning the combining of pickups

[Mike Sulzer]

In determining whether a pickup connected to another causes changes in the tone (frequency response) of the pickups, it was agreed that a listening test comparing the sound when two pickups are buffered individually or connected together before buffering determines the answer.

Figure 1. at this link (http://www.naic.edu/~sulzer/CombiningPickups.png)
shows the circuit used in my test. There is no difference when the pickups are connected together or individually buffered. The pickups have 6.5 K and 6.6 K resistances.

Figure 2. shows a circuit where a pickup can be connected to another pickup away from the strings. The circuit is not buffered, but connected directly to the cable. The difference heard in this case shows that the effect some people attribute to frequency dependent loading effects is a cable capacitance effect. With both pickups connected, the inductance is halved, thus increasing the resonant frequency.

The cable capacitance effect is still significant when the pickups are not identical, although one expects some additional effects as well if the pickups differ enough. That is, the test described in Figure 1. would have different sounds between the two switch settings if the pickups are sufficiently different. In all but extreme cases, I would expect the cable capacitance effect to dominate in the test shown in Figure 2.

Here is a simple way to explain the results of the test described in Figure 1. Suppose the two pickups are identical; each pickup sees the other as the bottom part of a voltage divider. The impedances in the top and bottom parts are the same at all frequencies. Consider how the frequency response would be altered. Would bass be cut? Treble? There is no way to decide. Thus there is no change in the frequency response.

[David Schwab]

With both pickups connected, the inductance is halved, thus increasing the resonant frequency.

Thus there is no change in the frequency response.

So which is it? If the resonant frequency was raised, then the one pickup effected the other. That means the frequency response has changed, how can you say it hasn't? Also don't forget that the high frequency response drops off after the resonant peak, so therefore combing the two pickups increased the frequency response, since it raised the resonant peak. This is easily heard. So how has it not changed the frequency response?

Run each one though a buffer and the resonant peak will not raise in frequency when the two are combined. But combined after the buffers, not the way you have it in fig 1.

So what are you trying to prove here Mike?

Also your tests are flawed because they do not match any known instruments. So do with test first with a passive guitar with no buffer. Then passive mixing with a single buffer after the pickups. Then a separate buffer for each pickup mixed after the buffer. No connections before the buffer.

That's a realistic and reasonable test.

[Mike Sulzer]

The circuit in Figure 1. has two states.

First, when the switch is open, the pickups are buffered separately, and the outputs of the buffers are combined.

Second, when the switch is closed, the pickups are combined before buffering. The combined signal then proceeds through both buffers. The outputs of the buffers are combined, but this changes nothing since the two signals being combined are identical.

Since the signals sound the same with the switch in either position, connecting the pickups together does not alter the frequency response. Not from loading, not from anything, because there is no change.

In Figure 2, we have the cable connected directly to the pickup(s). The change when switched results from a change in the interaction with the cable, not from the pickups loading each other. We already know that there is no change in frequency response from connecting the pickups together from the results of the test described in Figure 1.

[Marko Ursin]

Could you post the samples so that we could also listen to them. Also what does mixing the signals with blend pot buffered vs nonbuffered sound?
Marko

[RedHouse]

Could you post the samples so that we could also listen to them. Also what does mixing the signals with blend pot buffered vs nonbuffered sound?
Marko

Good idea Marko.

Yeah Mike why don't ya post the sound clips _AND_ some pics of the guitar _AND_ these pickups you are testing with, in their test configuration?.
(time to show-n-tell)

[Mike Sulzer]

Could you post the samples so that we could also listen to them. Also what does mixing the signals with blend pot buffered vs nonbuffered sound?
Marko

Sorry, I did not make recordings. I have not tried this with blend pots. You could use a blend pot with a pretty high resistance on the pickups and connect its output (slider) to the input of a high impedance buffer. It would be a lot better than no buffer, but it would have some disadvantages. For example, its noise performance would probably not be as good as what you have implemented.

So there is no question IMO that buffering both pickups is the way to go when using a blend pot. I would be inclined to use another buffer at the output, but if you use something like 10K pots for blends and volumes it would be OK. IMO you want to keep impedances, and especially impedance changes with pot rotation, small, looking from the cable back into the guitar small.

My only only concern with using all these buffers on pickups is that you can lose the sound of the resonance. But that is easy to put in with C and R loading on the pickups, and in any case it is how you want the sound that counts.

Another way to put back the resonant sound is to use an active resonant low pass filter before the output.

[Mike Sulzer]

Good idea Marko.

Yeah Mike why don't ya post the sound clips _AND_ some pics of the guitar _AND_ these pickups you are testing with, in their test configuration?.
(time to show-n-tell)

Brad, you seem to doubt that I even know how to make a pickup. Here is a discussion of the kind of things that I like to do. I guess you missed it, or have forgotten.

http://music-electronics-forum.com/t13930/

[RedHouse]

Brad, you seem to doubt that I even know how to make a pickup. Here is a discussion of the kind of things that I like to do. I guess you missed it, or have forgotten.

http://music-electronics-forum.com/t13930/

No doubt here, and yep I do remember that thread, a year ago, are we still waiting on that write-up then? but never mind, it's not important. If I recall correctly that thread didn't have any pics of your work either (I'll go back and check) you did link to someone else's work though.

Mind if we see your test setup, and the pickups you're testing in this thread?
(as they say, a picture says a thousand words)

{Edit} my mistake, there is a pic to be found in that thread.
(I can see what looks like any single coil, with modified poles and custom baseplate)

Is that your testbed guitar then Mike? any chance can we see those onboard electronics the thread was talking about?

[Mike Sulzer]

Is that your testbed guitar then Mike? any chance can we see those onboard electronics the thread was talking about?

There is a picture of the on board electronics module in that discussion.

No, the guitar in the current discussion is not the same one. It cannot be; the guitar in that discussion has only one pickup that has six coils and is intimately tied up with the electronics. (I have just about finished another project; this guitar has two pickups with individual string distortion. I will post something here about eventually; certainly it will not be a write up, since you hate that.)

The guitar in this discussion is not a test bed guitar; it just happens to be easy for this test because it has two pickups and the back comes off. You will see why when I get some pictures, which I can do tonight. I will haywire the little buffer card back in.

I am no musician, but could record something later in the week, after locating microphone and preamp.

You sure do expect a lot considering how rude you are!

[David Schwab]

I don't see where Brad is being rude. He wanted some info on the test setup, and that seems perfectly reasonable. people are not agreeing with the outcome of your tests, so if you say you don't hear a difference they want to hear it too. After all your setup is nothing like what you might find in guitars with or without preamps.

Also you don't need a mic to do sound clips. The guitar already has a buffer, just plug it into the Mac and use Quicktime Player to record the audio. You also don't need to be able to play to be striking a note while switching the pickups.

Also the other post was discussing mixing the pickups. This is where passive systems don't work well. It's hard to actually vary the blend.

When I get caught up I'll also do a recorded test on my bass that has a volume per pickup and master tone followed by a JFET buffer. I'll use another identical buffer for the two buffer test. Part of the test needs to include blending the pickups, because with each pickup buffered you can really add the sound of one to the other without the loading affecting the first pickup. That makes them blend unevenly.

[RedHouse]

There is a picture of the on board electronics module in that discussion..!

I must have missed it, I'll go back for a look later

It cannot be; the guitar in that discussion has only one pickup that has six coils and is intimately tied up with the electronics.

And therin lies the beauity of a "testbed" guitar, after you're finished with one project, you remove the test gear and go on to the next.

...I will post something here about eventually; certainly it will not be a write up, since you hate that.

I don't hate that, you said in that thread you were going to write up something on it, never did as far as I can tell, but never mind it doesn't matter.

You will see why when I get some pictures, which I can do tonight. I will haywire the little buffer card back in.

That's great Mike, that's what I asked in my post.

I am no musician, but could record something later in the week, after locating microphone and preamp.

I thought you said you had an on-board buffer system, is there some reason you can't go direct?

You sure do expect a lot considering how rude you are!

I'm rude? well pardon me Mike, didn't mean to be.

I don't expect anything from ya Mike, just would like to see some pic's and/or maybe hear some clips so I can verify (or dismiss) your results on my own. Talk is cheap on the internet so it's kind of nice to actually see what someone is talking about (or hear it) specially when they're using their tests as a point of reference to their debate (ie; last thread).

[RedHouse]

There is a picture of the on board electronics module in that discussion....

Ok, I went back over the thread, still can't see a picture or link to a picture, I must be blind today.

I see a pic of a schematic, a pic of the pickup, a pic of a single coil, but no pic of the electronics, can you give me a link?

[David Schwab]

Ok, I went back over the thread, still can't see a picture or link to a picture, I must be blind today.

I see a pic of a schematic, a pic of the pickup, a pic of a single coil, but no pic of the electronics, can you give me a link?

I had a hard time finding it also.

http://www.naic.edu/~sulzer/sixCoilEmod.jpg

Mike, that's a nice looking guitar. Did you make that? The bridge is very cool... is that one of those Gotoh 510s?

[RedHouse]

I had a hard time finding it also.

http://www.naic.edu/~sulzer/sixCoilEmod.jpg

Mike, that's a nice looking guitar. Did you make that? The bridge is very cool... is that one of those Gotoh 510s?

Ah, yes, see it now thanks David.

I'm blind today. Hey that reminds me I need to dig out my Jeff Healy stuff, havent been into that for a while.

[Mike Sulzer]

I don't see where Brad is being rude. He wanted some info on the test setup, and that seems perfectly reasonable. people are not agreeing with the outcome of your tests, so if you say you don't hear a difference they want to hear it too. After all your setup is nothing like what you might find in guitars with or without preamps.

Also you don't need a mic to do sound clips. The guitar already has a buffer, just plug it into the Mac and use Quicktime Player to record the audio. You also don't need to be able to play to be striking a note while switching the pickups.

Also the other post was discussing mixing the pickups. This is where passive systems don't work well. It's hard to actually vary the blend.

When I get caught up I'll also do a recorded test on my bass that has a volume per pickup and master tone followed by a JFET buffer. I'll use another identical buffer for the two buffer test. Part of the test needs to include blending the pickups, because with each pickup buffered you can really add the sound of one to the other without the loading affecting the first pickup. That makes them blend unevenly.

Brad wrote a couple of days ago:

The only explanation I can figure is you must have hearing disability, I mean litterally everyone else can hear these things ...except you ...on your guitar.

That was rude, considering I had just done a listening test and did hear the difference. It is also nonsense. Plenty of other people do not hear the differences between capacitor A and capacitor B when they set the test up right, such as, match the values. Such as you, David.

Furthermore, as I have described in one discussion, I have lost almost all hearing in one ear in the last couple of years. My life-long "stereophile" hobby is gone, but one good ear is good enough for electric guitar, but not as good as two.

I do not think Brad is a bad guy, but he does not need your help when I tell him he is rude.

I do not like the sound of electric guitar without the amp and speaker. For me, electric guitars put "low fidelity" to good use. They make "low fidelity" into a whole experience that never could happen if guitar electronics started out as high fidelity.

But it will do for a test, perhaps. Throwing a switch in the middle of a note is not a complete test, but it could do. Response to picking is very important.