Listening tests concerning the combining of pickups

[Mike Sulzer]

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.

Glad you found it.

Thanks David. (My internet is screwed up now and it takes forever to get anything through.)

No, I did not make that guitar. I bought a Warmoth body and neck unfinished and then did the rest. I chose that piece of wood for the top from their on line choices.

Brad: Rather than use a test bed guitar, I wanted a test project. It is nice to have the actual instrument as the record of what you have done.

[RedHouse]

...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....

So you do have a hearing disability and you think I'm rude for figuring that out? ok Mike, let me put on my eggshell slippers and say very softly and gently in a Cum-by-ya kind of voice ...pardon me.
(can ya feel the love?)

Moving forward, as you have affirmed yourself to be audibly able:

...but one good ear is good enough for electric guitar...

my comment in Mixing two pickups thread was regarding your arguement:

No. What I said was that the effect of one pickup loading another identical one does not change the frequency response of that pickup. ...What about you, Brad. Are you willing to disagree with Rick when he is obviously wrong?

and

...connecting two identical pickups together and buffering that combination gives the same frequency response as buffering each and then adding the results.

which is not true, everyone can hear it, but I'm sure you'll find a way to argue-on about it so never mind, it really doesn't matter.

Brad: Rather than use a test bed guitar, I wanted a test project. It is nice to have the actual instrument as the record of what you have done.

Sure, albeit impractical, better for most people to just document things (pic/clips etc) and move on.
(whatever floats your boat)


Life's too short to keep bickering over things I know better about.

[David Schwab]

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

I thought you were talking about this thread...

[RedHouse]

I thought you were talking about this thread...

So did I.

[Mike Sulzer]

The guitar from the front is shown here:
http://www.naic.edu/~sulzer/front.jpg

The steel bridge does not touch the top, but rests on a structure inside the guitar.

The open back is shown here:
http://www.naic.edu/~sulzer/openBack.jpg

The structure the bridge rests on and is fastened to is visible. There are a variety of pieces that can be put in there, mostly different kinds of hardwood, rectangular pieces 3/4" thick. So this guitar is a kind of test bed but not as you meant it. The composite spruce structure shown is intended to give a good sound for jazz.

On my mac, garageband does not see the built in (line) input that I need, only the built in mic. Electro acoustics tool box sees both, so it is working. Anyone know how to fix this?

To the left are a dummy coil that looks like a pickup and its single FET source follower buffer. The output of this buffer is low impedance. It is connected in series with the ground lead of each pickup through an individual adjustment trimpot. Normally, the pickups are used passive, but with active hum cancellation.

The test buffer is hanging in the lower right. The volume control has been pulled out, replaced with the test switch. The batteries and power switch are in the extreme lower right. The pickup wires have been disconnected from the selector switch and connected to the test switch. The wire to the output jack has been moved to the test buffer output.

On my mac, Garageband does not see the built in (line) input that I need, but only the mic. Electro acoustics toolbox sees both; so the line in is working. Does anyone know how to fix this?

[RedHouse]

The guitar from the front is shown here:
http://www.naic.edu/~sulzer/front.jpg

The open back is shown here:
http://www.naic.edu/~sulzer/openBack.jpg...

Wow.

Thanks for posting that, it brings perspective to your views.

[David Schwab]

On my mac, Garageband does not see the built in (line) input that I need, but only the mic. Electro acoustics toolbox sees both; so the line in is working. Does anyone know how to fix this?

Did you try changing the input in the Sound control panel?

[RedHouse]

Mike, what are these things inside your guitar?

[David Schwab]

To the left are a dummy coil that looks like a pickup and its single FET source follower buffer. The output of this buffer is low impedance. It is connected in series with the ground lead of each pickup through an individual adjustment trimpot. Normally, the pickups are used passive, but with active hum cancellation.

The test buffer is hanging in the lower right. The volume control has been pulled out, replaced with the test switch. The batteries and power switch are in the extreme lower right. The pickup wires have been disconnected from the selector switch and connected to the test switch. The wire to the output jack has been moved to the test buffer output.

Mike, were you doing that test with the pickup with the active dummy coils? You really need to get a couple of passive pickups in there and test it. Also when you are combining both pickups you still have each one into a separate buffer.

None of that matches what is being described in a standard situation.

The test should be:

• Passive pickups mixed passively, no active stages
• Passive pickups mixed passively, single channel buffer after controls
• Passive pickups, each into a buffer before any controls, outputs from buffers mixed

With its current wiring in my bass, I can do test 1 and 2. I'll have to rewire the bass for test 3.

A few of my basses have had separately buffered pickup precisely because I didn't like the way the pickups blended the other way. So I heard an issue and I also heard an improvement. It didn't sound the same.

[Mike Sulzer]

Did you try changing the input in the Sound control panel?

That does it. Thanks. I have not used the SCP in years; forgot all about. Any application should have full access to all inputs from within it. As the manual for GB says it does.

[Mike Sulzer]

Mike, what are these things inside your guitar?

The thing the black arrow points to is the mounting plate for the bridge pickup. The pickup comes out the back. No mounting screws on the front.

The right hand white arrow points to the neck tenon which is rosewood with steel sides. This is a 24 fret guitar, and there is no central extension of the body back from the cutouts. That is, it goes directly across from one cutout to the other, and the neck continues right up to the body. Thus, you need a very strong neck tenon under the neck pickup. The left arrow points to a steel plate. It and the aluminum plate to the right hold the neck in place. The fiber piece in between holds the neck pickup in place.

[Mike Sulzer]

Mike, were you doing that test with the pickup with the active dummy coils? You really need to get a couple of passive pickups in there and test it.

Those are passive pickups. I have tried the test with the hum cancellation in place and with the pickup ground leads going straight to ground (hum cancellation removed). It makes no difference and it should not; the hum cancellation circuit just puts a couple hundred ohms in series with each pickup at the ground lead.

Also when you are combining both pickups you still have each one into a separate buffer.

None of that matches what is being described in a standard situation.

When the switch is closed, the pickups are connected together. Both pickups feed both buffers. Even though the buffer input impedance is about a gazillion ohms, this assures that the impedance each pickup sees changes as little as possible when the switch is thrown.

The test should be:

• Passive pickups mixed passively, no active stages
• Passive pickups mixed passively, single channel buffer after controls
• Passive pickups, each into a buffer before any controls, outputs from buffers mixed

With its current wiring in my bass, I can do test 1 and 2. I'll have to rewire the bass for test 3.

A few of my basses have had separately buffered pickup precisely because I didn't like the way the pickups blended the other way. So I heard an issue and I also heard an improvement. It didn't sound the same.

This test is to determine if connecting two pickups in parallel causes a loading effect that alters the frequency response. It does that and nothing more. Other tests are good, too, but it is most useful to take one step at a time.

[CRU JONES]

Mike,
I tried test model 1. ( in my test guitar).
When combining identical coils passively in parallel, the inductive parts are reduced and the capacitive parts are increased. I was expecting the resonant frequency to stay the same, but I expected the Q to increase.
So why doesn't the Q change?
I would expect as the ratio of L to C changes the Q would change. What do you think?
Cru

[Mike Sulzer]

Mike,
I tried test model 1. ( in my test guitar).
When combining identical coils passively in parallel, the inductive parts are reduced and the capacitive parts are increased. I was expecting the resonant frequency to stay the same, but I expected the Q to increase.
So why doesn't the Q change?
I would expect as the ratio of L to C changes the Q would change. What do you think?
Cru

Cru,

It involves the fact that the resistance has changed also. If all the losses are associated with the inductor, then we look at the Q of the inductor, 2*pi*f*L/R. L/R has not changed because both L and R have effectively gone down a factor of two.

[CRU JONES]

Mike,
O.k. That makes sense to what I observe...
I apologize for not having reference books near me but, isn't the Q = 2*pi*f*L/R equation for resistances in parallel with inductance?
And in this case the resistance would be in series.
Cru