Author Topic: Pickup amps/volts  (Read 13976 times)

0 Members and 1 Guest are viewing this topic.

Offline nigec

  • Pub Night Playa
  • ***
  • Posts: 163
  • Good Vibes 5
Pickup amps/volts
« on: December 16, 2012, 08:54:36 pm »
Just out of interest how many amps do pickups usually pull? also the working voltage?
My guitar has,  3 Custom Vintage Style Single-Coil Strat® Pickups with Staggered, AlNiCo 3

My test subjects are probably the standard ones fitted to the Standard Squier Strat, can you actually tell the difference visually?

Guitars:  Hofner Bass, Squier classic vibe Stratocaster; Fender look alike Jazz bass from a kit, Cigarbox 3 string, Uke, Mandolin and the devil loves a tryer!

Offline shadowscott007

  • Stadium Superstar
  • ******
  • Posts: 3400
  • Good Vibes 119
Re: Pickup amps/volts
« Reply #1 on: December 16, 2012, 09:24:06 pm »
Pick-ups don't pull amps, the source them; but not very many.

Pick-ups are a very high impedance voltage source (that is they can source very little current) which is why guitar amps have very high input impedances.

I've looked up the voltage output before, but wasn't able to get a very good consistent value.  From 1 to 4 volts rms depending on type, single coil, humbucker, passive, active.

Shadow
The early bird gets the worm, but the second mouse gets the cheese.

Offline jacksroadhouse

  • Stadium Superstar
  • ******
  • Posts: 1613
  • Good Vibes 48
    • Acoustic Passion Blog
Re: Pickup amps/volts
« Reply #2 on: December 16, 2012, 09:44:12 pm »
Are sure about that? Electronics isn't my strong suit, but I believe that would put a guitar pickup at up to 14 dBu.

This might help:
http://en.wikipedia.org/wiki/Pickup_%28music_technology%29#Output

EDIT: okay, just read the rest of it...  ;)
However, my strat needs about 40-50 dB amplification to get anywhere near 0. I'm confused. Is that due to impedance mismatch?
As I said, not my strong suit...

Offline nigec

  • Pub Night Playa
  • ***
  • Posts: 163
  • Good Vibes 5
Re: Pickup amps/volts
« Reply #3 on: December 16, 2012, 10:01:09 pm »
Ah right, I get what your saying guys, worse case going by the Wiki is around 5v on one run of the mill pickup, which is fine
I was looking at this the wrong way and I understand now :) I was assuming they are powered up :-[ god I have so much to learn lol
Guitars:  Hofner Bass, Squier classic vibe Stratocaster; Fender look alike Jazz bass from a kit, Cigarbox 3 string, Uke, Mandolin and the devil loves a tryer!

Offline shadowscott007

  • Stadium Superstar
  • ******
  • Posts: 3400
  • Good Vibes 119
Re: Pickup amps/volts
« Reply #4 on: December 16, 2012, 10:08:20 pm »
I have looked for decent electrical engineering specs for pick-ups and haven't found any great ones.

But pick-ups are sources not loads so they don't pull current.  And they act like voltage sources and don't drive a lot of current.  As soon as you try to make the start providing any significant current the voltage stats to collapse.

I think the input impedances of most guitar amps are in the 100's of kohms for some reason a half a megohm comes to mind.

I messed around with a scope and a guitar in the past and the issue with making measurements is coming up with a consistent string attack.  Lots of variation in the output voltage level (open) with the force and number of strings hit.  I seem to remember 4 volts peak voltage with just the 1meg scope probes attached as a typical response.

Shadow


The early bird gets the worm, but the second mouse gets the cheese.

Offline jacksroadhouse

  • Stadium Superstar
  • ******
  • Posts: 1613
  • Good Vibes 48
    • Acoustic Passion Blog
Re: Pickup amps/volts
« Reply #5 on: December 16, 2012, 10:25:14 pm »
I think, the word "peak" (as in "transient", I suppose) is very much relevant here.

Btw: the input impedance of a couple of amps I checked out was at 1 MOhms. Some of my own gear goes up to 2 MOhms - whether or not that's really necessary is another matter, I suppose.

Offline nigec

  • Pub Night Playa
  • ***
  • Posts: 163
  • Good Vibes 5
Re: Pickup amps/volts
« Reply #6 on: December 16, 2012, 10:40:13 pm »
I was a auto electrician and cars have similar things, a pickup in the  ignition system springs to mind, it just never dawned on me thats how a guitar pickup works, I'm so used to stuff spinning around and a lot easier to test, I can see a vibrating string would be a nightmare, actually to get a constant value you might be better off with something turning similar to a car's ignition



thanks guys
Guitars:  Hofner Bass, Squier classic vibe Stratocaster; Fender look alike Jazz bass from a kit, Cigarbox 3 string, Uke, Mandolin and the devil loves a tryer!

Offline shadowscott007

  • Stadium Superstar
  • ******
  • Posts: 3400
  • Good Vibes 119
Re: Pickup amps/volts
« Reply #7 on: December 16, 2012, 10:43:36 pm »
This post tickled my inner geek.

I think peak as applied here is related to someone bashing multiple strings very hard.  So yeah, a transient.

And I get about 3.8 volts for 14dbu.

I'd buy those readings for a DC input resistance, strictly speaking impedance implies a specific frequency or frequency range.  At frequency the capacitors to ground will tend to reduce the impedance.

Shadow
The early bird gets the worm, but the second mouse gets the cheese.

Offline TB-AV

  • Honorable Ex-Mod
  • All Time Legend
  • *****
  • Posts: 12698
  • Good Vibes 331
Gone

Offline shadowscott007

  • Stadium Superstar
  • ******
  • Posts: 3400
  • Good Vibes 119
Re: Pickup amps/volts
« Reply #9 on: December 16, 2012, 11:51:31 pm »
Cool chart, but as always the engineer in me needs more.   In other words I have to assume stuff.

One string (pole piece) is what I assume, and I assume rms rather than peak.  I don't know what the bass mid and treble numbers are, and I don't think the DC resistance is the output impedance when the pick-up is acting as a source.  It is a measure of the length and diameter of the wire used in the windings.

But it would be easy enough (at least conceptually) to experiment and find that all out.  Well if my curiosity would overcome my natural laziness.

But I am in way over geek mode.

Here is a a wiki page that has something more like I have been looking for.  Notice the 700k+ output impedance at the resonant frequency.

 http://en.m.wikipedia.org/wiki/P-90#section_1

Shadow
« Last Edit: December 17, 2012, 12:11:54 am by shadowscott007 »
The early bird gets the worm, but the second mouse gets the cheese.

Offline misterg

  • Stadium Superstar
  • ******
  • Posts: 2437
  • Good Vibes 125
  • Wales, UK
Re: Pickup amps/volts
« Reply #10 on: December 17, 2012, 12:21:39 am »
I work on about 100mV RMS as a 'strumming level' output (single coil or humbucker). It's a ball-park figure - digging in can generate transients of 1-2 volts, and really quiet picking gets down to <10mV. I guess 'hot' pickups could be 2 to 3 x these values (seems to be borne out by TB's chart).

You can tell *some* of the differences, such as DC resistance; the diameter and length of the magnets; the aspect ratio of the winding (tall and thin or short and fat), and maybe wire gauge. What you can't see easily is what material the magnets are made of and how strongly magnetised they are; and whether the wire is wound on the magnets, or if there is a bobbin.

There is an interplay between the pickup inductance, the cable capacitance, the volume and tone pots on the guitar and the amp input impedance.

Food for the inner geek:

http://buildyourguitar.com/resources/lemme/

I found something a while ago which attempted to explain the effects of pickup construction on performance, but I didn't book-mark it and haven't been able to find it again yet. I will post it when I do.

Offline TB-AV

  • Honorable Ex-Mod
  • All Time Legend
  • *****
  • Posts: 12698
  • Good Vibes 331
Re: Pickup amps/volts
« Reply #11 on: December 17, 2012, 12:34:35 am »
I would have expected ~1v max. Maybe 2 on some hot stufff.... that 3 to 5 volt seems really hot
Gone

Offline shadowscott007

  • Stadium Superstar
  • ******
  • Posts: 3400
  • Good Vibes 119
Re: Pickup amps/volts
« Reply #12 on: December 17, 2012, 12:17:32 pm »
The info I can find seems to be all over the map.  I assume that the higher voltage levels are peaks at the pick attack and probably multiple strings.

Shadow
The early bird gets the worm, but the second mouse gets the cheese.

Offline TB-AV

  • Honorable Ex-Mod
  • All Time Legend
  • *****
  • Posts: 12698
  • Good Vibes 331
Re: Pickup amps/volts
« Reply #13 on: December 17, 2012, 02:05:48 pm »
Possible. It sure isn't the strings at rest  ;)

http://www.guitarsite.com/news/features/Basic-Electric-Guitar-Circuits-Pickups/

Most people don't measure these high voltages you mention. Most are way down below a volt with an E chord maybe going near 1v


1volt RMS ( Average Signal ) = 1.414 volt Peak ( 1/2 of Full sine Wave ) = 2.82 Peak to Peak ( Full Sine Wave )

http://www.bcae1.com/voltages.htm


« Last Edit: December 17, 2012, 02:28:03 pm by TB-AV »
Gone

Offline shadowscott007

  • Stadium Superstar
  • ******
  • Posts: 3400
  • Good Vibes 119
Re: Pickup amps/volts
« Reply #14 on: December 17, 2012, 03:10:49 pm »
Yeah, I think those higher levels are peak or peak to peak values.  As I recall my experiment, the 4 volts I measured was the first positive peak of the wave form and started collapsing almost immediately.  That is the subsequent negative half was already somewhat lower than the initial peak I captured on the scope.

Like I said, I find values all over the map when I scour the internet with no references as to how the measurements were made.

Another thing that impacts the rms value is because the waveform is decaying the longer the time base the more the rms value 'ignores' the peak.  The math model assumes a periodic waveform so you get to use the short cut when you integrate of only calculating over one period.  When you add a decay (i would assume exponential decay) you have to integrate over multiple cycles. 

Been reading more and it sounds like the test the manufacturer's use utilizes an external coil to induce a magnetic field and measure the output response.

Another reason I may have seen such a high number (and see them floating around on the web) may be because I was measuring the output unloaded; well as much I could.  I had a 1/4 in jack, no cable, and hooked the scope probes across it.  Being a high impedance source the loading can drag the ouput voltage lower pretty easily.

I think it may be time to borrow a scope from work, or take a guitar in and start banging, triggering, and measuring.

I started thinking about this as I was looking at the rails at the input of an effect or an amp for that matter and tba absolute highest peak value it could see.  With a 9 volt battery and margin say +/- 4 volts max, but then you could also reduce the input impedance of the input which would tend to reduce the output capability of the pick-up.

Ya know I should just really go play....   :D

Shadow
The early bird gets the worm, but the second mouse gets the cheese.

Offline nigec

  • Pub Night Playa
  • ***
  • Posts: 163
  • Good Vibes 5
Re: Pickup amps/volts
« Reply #15 on: December 18, 2012, 12:11:27 pm »
Thanks for all the replies, I've learnt a lot from it ;D
Guitars:  Hofner Bass, Squier classic vibe Stratocaster; Fender look alike Jazz bass from a kit, Cigarbox 3 string, Uke, Mandolin and the devil loves a tryer!

Offline TB-AV

  • Honorable Ex-Mod
  • All Time Legend
  • *****
  • Posts: 12698
  • Good Vibes 331
Re: Pickup amps/volts
« Reply #16 on: December 18, 2012, 01:58:38 pm »
Another thing that impacts the rms value is because the waveform is decaying the longer the time base the more the rms value 'ignores' the peak.

The way I would explain that is not one of ignoring peaks but simply measuring new peak values that become increasingly less as the waveform decays. Nothing ignored. Values simply change.
Gone

Offline shadowscott007

  • Stadium Superstar
  • ******
  • Posts: 3400
  • Good Vibes 119
Re: Pickup amps/volts
« Reply #17 on: December 18, 2012, 02:12:22 pm »
Yeah.  That's why I put 'ignored' in quotes, averaged out might be closer. 

RMS is a convenient parameter, but it can be misleading.  The RMS is fundamentally a calculation that equates a (constant) sinusoidal source to a DC level in terms of the power delivered to a resistive load.  Well it doesn't HAVE to be sinusoidal, and you can do the calculus even if it isn't constant, but once you boil it down to a single number you loose the ability to.go.back and understand the peak and decay shapes.

But the instantaneous peak is what matters to prevent clipping on the input circuits.  And that is what lead me down this particular 'I wonder...' path.

But I am on vacation and this is treading close to work stuff.

Shadow
The early bird gets the worm, but the second mouse gets the cheese.

Offline Scooter Trash

  • Stadium Superstar
  • ******
  • Posts: 3033
  • Good Vibes 83
Re: Pickup amps/volts
« Reply #18 on: December 18, 2012, 02:36:21 pm »

But the instantaneous peak is what matters to prevent clipping on the input circuits. 

Why would you want to do that on a tube amp?  ;)
I dream of a better tomorrow where chickens can cross roads without their motives being questioned.

Offline TB-AV

  • Honorable Ex-Mod
  • All Time Legend
  • *****
  • Posts: 12698
  • Good Vibes 331
Re: Pickup amps/volts
« Reply #19 on: December 18, 2012, 02:40:20 pm »
Yeah, my only point earlier was that people are probably using different measurements for the same thing. .... and not everyone wants to prevent clipping.... so... those high numbers could be a problem. You could design to accept them but what if you were designing for clipping... If you desire clipping you don't want to design for 4 volts when your typical signal will only be 200mV.
Gone

Offline shadowscott007

  • Stadium Superstar
  • ******
  • Posts: 3400
  • Good Vibes 119
Re: Pickup amps/volts
« Reply #20 on: December 18, 2012, 02:57:36 pm »
Here is the particular specification I saw that started my most recent wondering along these lines:

Ch 1 Sensitivity: 1mV for clipping
Ch 2 Sensitivity: 1mV for clipping
Ch 3 Sensitivity: 16mV for full output

I thought holy xx--xx - how do you get anything clean; what does this mean; what kind of levels do pick-ups deliver; and just generally WTF!?!?!

I have come to the conclusion that this means if you crank the gain knob up to 10, a signal as low as 1mV can be made to clip.  So then because I and the musician voices in my head can't make the little engineer voices in my head STFU and just play the damned thing, I wondered - well what is the hottest signal I can shove in the front end that WILL NOT clip (i.e., gain on 0).

Shadow

P.S.  Specs are from my Carvin V3M tube amp.
The early bird gets the worm, but the second mouse gets the cheese.

Offline Scooter Trash

  • Stadium Superstar
  • ******
  • Posts: 3033
  • Good Vibes 83
Re: Pickup amps/volts
« Reply #21 on: December 18, 2012, 03:08:08 pm »
Here is the particular specification I saw that started my most recent wondering along these lines:

Ch 1 Sensitivity: 1mV for clipping
Ch 2 Sensitivity: 1mV for clipping
Ch 3 Sensitivity: 16mV for full output

I thought holy xx--xx - how do you get anything clean; what does this mean; what kind of levels do pick-ups deliver; and just generally WTF!?!?!


Are those specs at unity? Isn't the input pot usually a 100k attenuator?
I dream of a better tomorrow where chickens can cross roads without their motives being questioned.

Offline shadowscott007

  • Stadium Superstar
  • ******
  • Posts: 3400
  • Good Vibes 119
Re: Pickup amps/volts
« Reply #22 on: December 18, 2012, 03:12:57 pm »
@scooter: dunno

In my minds eye the VERY first thing in an amp or effect would be a unity gain buffer.  Prevents loading the source, replicates the signal with no clipping, and protects the amp/effect from the outside world.

Then AFTER you get past that - all the other stuff you want done gets done...

Mebbe my mind's eye is blind...

Shadow
The early bird gets the worm, but the second mouse gets the cheese.

Offline Scooter Trash

  • Stadium Superstar
  • ******
  • Posts: 3033
  • Good Vibes 83
Re: Pickup amps/volts
« Reply #23 on: December 18, 2012, 03:38:03 pm »
I couldn't find a schematic for your amp, but this is the input section of my Blues JuniorIII



It looks like the input is padded
I dream of a better tomorrow where chickens can cross roads without their motives being questioned.

Offline TB-AV

  • Honorable Ex-Mod
  • All Time Legend
  • *****
  • Posts: 12698
  • Good Vibes 331
Re: Pickup amps/volts
« Reply #24 on: December 18, 2012, 04:04:20 pm »
Send them an email and ask. I would like to hear the answer myself.

amps with that many knobs are bad for your mental health.
Gone

 

Get The Forum As A Mobile App