Can I make my own active pick-up?

[kindyroot]

My question is simple: I am a quite experimented do-it-yourselfer and
i wonder:
1- If I can make my own active pick-up.
2- If it is really worth the trouble.
Thank you in advance.

PS: The guitar I am designing is intended for metal and rock (hign
level of distortion, Fat sound... etc).

[tho x. bui]

kindyroot wrote:
> My question is simple: I am a quite experimented do-it-yourselfer and
> i wonder:
> 1- If I can make my own active pick-up.
> 2- If it is really worth the trouble.
> Thank you in advance.
>
> PS: The guitar I am designing is intended for metal and rock (hign
> level of distortion, Fat sound... etc).
>

1. yes. All you need is the right material. From your previous posts
on other threads, you indicated that you already made pickup with 200
turns of wire. That, in essence, is a low output "active" pickup. All
you need is hook it up to a pre-amp and you have an active pickup.

2. silly question. Nobody but you can answer that. Why do you want to
make your own active pickup? saving money? make the "perfect" pickup?
personal enjoyment? The answer tells you whether or not it's worth the
trouble.


Tho

[kindyroot]

> 1. yes. All you need is the right material. From your previous posts
> on other threads, you indicated that you already made pickup with 200
> turns of wire. That, in essence, is a low output "active" pickup. All
> you need is hook it up to a pre-amp and you have an active pickup.
>
> 2. silly question. Nobody but you can answer that. Why do you want to
> make your own active pickup? saving money? make the "perfect" pickup?
> personal enjoyment? The answer tells you whether or not it's worth the
> trouble.
>
> Tho

Hi,
Thank you very much, I was glad that you recognised me, i think i'm
really going to go into the pleasant trip of making an active guitar
pick-up, since i already built lots of pre-amps in highschool so all i
need now is to gather the to pieces.
Well the number one reason i want to make and active pick-up is that i
really can't afford buying a good one, number too is that i want to
play with all the parameters to get the particular sound i am looking
for, and i think it's worthless to tell you how much i enjoy this
work, so i think i now the answer now: it is actually worth the
trouble to try and i will.
Only a small part remains unknown to me! what kind of pick-up should i
include? a single coil? a double coil? a small pick-up of my own as
you said? does it really make a difference? what kind of difference?
if you have any information please tell me, it will help me a lot.
thx.

[tho x. bui]

kindyroot wrote:
>>1. yes. All you need is the right material. From your previous posts
>>on other threads, you indicated that you already made pickup with 200
>>turns of wire. That, in essence, is a low output "active" pickup. All
>>you need is hook it up to a pre-amp and you have an active pickup.
>>
>>2. silly question. Nobody but you can answer that. Why do you want to
>>make your own active pickup? saving money? make the "perfect" pickup?
>>personal enjoyment? The answer tells you whether or not it's worth the
>>trouble.
>
> Thank you very much, I was glad that you recognised me, i think i'm
> really going to go into the pleasant trip of making an active guitar
> pick-up, since i already built lots of pre-amps in highschool so all i
> need now is to gather the to pieces.
> Well the number one reason i want to make and active pick-up is that i
> really can't afford buying a good one, number too is that i want to
> play with all the parameters to get the particular sound i am looking
> for, and i think it's worthless to tell you how much i enjoy this
> work, so i think i now the answer now: it is actually worth the
> trouble to try and i will.
> Only a small part remains unknown to me! what kind of pick-up should i
> include? a single coil? a double coil? a small pick-up of my own as
> you said? does it really make a difference? what kind of difference?
> if you have any information please tell me, it will help me a lot.
> thx.
>

Good for you! Personally, I think you can make a better pickup than the
factory, but chances are bad that it will not be the first one you make.
Like most things, the more you build, the better you'll be at making it.

You probably will not to make a double coil, hum-bucker. The main reason
that you get hum is because of the large number of turns and the long
length of wire used in a passive pickup. An active pickup doesn't have
nearly as long, so it is less effective as an antenna; less susceptible
to hums.

There is also 'capacitance' issues, as well as resonance issue of the
pickup, all of which will be affected by the number of turns. Since you
will be making your own, it's an easy adjustment to start with a large
number of turns and then remove them as you go.

There are a large number of websites out there that will teach you all
the basics in designing a magnetic pickup. Google is your friend!

Tho

[kindyroot]

Just now i removed the wire that was in and old fender pick-up (it was
no longer working) and rewired it with 250 turns of truly heavy wire
(almost 0.4 mm) i think this can be a good starting point, i will try
to build the amplifier tomorrow in the evening, i will search for
designs on google right now, thank you.
cheers.

[kindyroot]

Woooooooooow, I DID IT !! it took me two days (made lots of mistakes)
but I made my own ACTIVE PICKUP !! I am very excited. As i told you i
had made a small coil with 250 turns of heavy wire over an old strat
pickum skeleton, and now i finished making the preamplifier, i did the
design myself, and it's based on a LM741 (donknow if you have this in
america but it's popular here) operational amplifier (inversor
structure), it does'nt sound too bad, it only has too much highs and
it lacks some basse but maybe this is normal because i mounted the
pick-up in bridge position, when i make it work in the linear area the
sound quite heavy but too clean even when i do distortion in the amp !
i don't understand this, maybe you do, i also experimented clipping
and found that like it's said by everybody the integrated amplifier is
very bad in clipping, it distort the signal in a not so musical way
(its sounds really odd! believe me), so now the next step for me is to
find an effitient way to filter my sound and make it closer to the
powerful metal sound i am looking for, and after doing this i will
find a way to integrate a basic overdrive switch in my circuit
beacause i also would like to have the oppurtunity to tailor my own
disto/overdrive, if id doesn't work or it won't fit I will do this as
a separate project.
Thank you tho x.bui for having been with me.
c you later.

[tho x. bui]

Try an FET preamp to see if it works better:
http://scotthelmke.com/Mint-box-buffer.html

I've built similar ones for piezo pickups. It's an impedance matching
circuit, so it doesn't have the massive gain that you may need for the
crunchy overdrive you're wanting. It is so simple to build, and very
inexpensive.

Tho



kindyroot wrote:
> Woooooooooow, I DID IT !! it took me two days (made lots of mistakes)
> but I made my own ACTIVE PICKUP !! I am very excited. As i told you i
> had made a small coil with 250 turns of heavy wire over an old strat
> pickum skeleton, and now i finished making the preamplifier, i did the
> design myself, and it's based on a LM741 (donknow if you have this in
> america but it's popular here) operational amplifier (inversor
> structure), it does'nt sound too bad, it only has too much highs and
> it lacks some basse but maybe this is normal because i mounted the
> pick-up in bridge position, when i make it work in the linear area the
> sound quite heavy but too clean even when i do distortion in the amp !
> i don't understand this, maybe you do, i also experimented clipping
> and found that like it's said by everybody the integrated amplifier is
> very bad in clipping, it distort the signal in a not so musical way
> (its sounds really odd! believe me), so now the next step for me is to
> find an effitient way to filter my sound and make it closer to the
> powerful metal sound i am looking for, and after doing this i will
> find a way to integrate a basic overdrive switch in my circuit
> beacause i also would like to have the oppurtunity to tailor my own
> disto/overdrive, if id doesn't work or it won't fit I will do this as
> a separate project.
> Thank you tho x.bui for having been with me.
> c you later.
>

[kindyroot]

Yes i already have this idea, i think i will finnally do this, because
heavy sound and cool distortion are my number one priority, but anyway
the circuit that i already have now works pretty cool, if i do some
basic equalisation (truly basic) on it and i get close from the sound
that i seek it would be ok and i will handle the problem of distortion
at another stage (maybe another project, who knows?).
I wanted to ask you about the equalisation, i want to do something
like two variables resistances and some capacitors before the amp (or
should i place them after the amp?) anyway i hope you have the
answers, i just want to correct the drawbacks of having a single coil
and too few turns of wire, i am sure the response sould not be flat at
all (i can hear that in the speaker) so some rectification is needed,
thank you in advance.
C U.

[Steve]

tho x. bui wrote:
> Try an FET preamp to see if it works better:
> http://scotthelmke.com/Mint-box-buffer.html
>
> I've built similar ones for piezo pickups. It's an impedance matching
> circuit, so it doesn't have the massive gain that you may need for the
> crunchy overdrive you're wanting. It is so simple to build, and very
> inexpensive.
>
> Tho
>
>
>
> kindyroot wrote:
>> Woooooooooow, I DID IT !! it took me two days (made lots of mistakes)
>> but I made my own ACTIVE PICKUP !! I am very excited. As i told you i
>> had made a small coil with 250 turns of heavy wire over an old strat
>> pickum skeleton, and now i finished making the preamplifier, i did the
>> design myself, and it's based on a LM741 (donknow if you have this in
>> america but it's popular here) operational amplifier (inversor
>> structure), it does'nt sound too bad, it only has too much highs and
>> it lacks some basse but maybe this is normal because i mounted the
>> pick-up in bridge position, when i make it work in the linear area the
>> sound quite heavy but too clean even when i do distortion in the amp !
>> i don't understand this, maybe you do, i also experimented clipping
>> and found that like it's said by everybody the integrated amplifier is
>> very bad in clipping, it distort the signal in a not so musical way
>> (its sounds really odd! believe me), so now the next step for me is to
>> find an effitient way to filter my sound and make it closer to the
>> powerful metal sound i am looking for, and after doing this i will
>> find a way to integrate a basic overdrive switch in my circuit
>> beacause i also would like to have the oppurtunity to tailor my own
>> disto/overdrive, if id doesn't work or it won't fit I will do this as
>> a separate project.
>> Thank you tho x.bui for having been with me.
>> c you later.
>>
>

I would expect the pickup to be rather bright. The small number of
turns in the coil will result in a very high frequency for the resonant
peak, and I would expect the frequency response curve to be fairly flat
in range of frequencies that would be generated by your instrument. A
typical passive guitar pickup has maybe 8 to 10 times the number
windings yours has, with a resonant peak in the 3KHZ to 5KHZ range. A
hot pickup with even more turns in the coil will have an even lower
resonant peak, with a frequency response that will accentuate midrange
and cut off the higher frequencies (which is what happens above the
resonant peak).

What you've done is similar to what EMG does with some of their active
pickups - fewer windings, with the signal level brought up by the
internal preamp. But there's tone-shaping circuitry in there to cut
back some of the brightness too. I had a set of EMG actives on my Jazz
Bass for several years, but traded them for a set of Bartoninis because
I found the EMG's to be too bright.

If you have access to a graphic equalizer, try cutting back frequencies
above maybe 4 or 5KHZ, and see what the guitar sounds like that way.

--Steve

[Clifford Heath]

Steve wrote:
> I would expect the pickup to be rather bright. The small number of
> turns in the coil will result in a very high frequency for the resonant
> peak

Somewhere around the ten MHz range. The self-resonant freq of a coil
of a given copper mass varies as the 4th power of the wire diameter.
0.4mm is 400um, compared to 63um for a "normal" p/u, gives a resonant
freq range of 6.5MHz compared to say 4KHz.

> , and I would expect the frequency response curve to be fairly flat

Yes, exactly.

The traditional LM741 has atrocious noise and cross-over performance, and
cannot swing anywhere near the rail on either side. With a 9V battery, you
have a maximum swing of about 3V. Almost any other opamp will perform
better in this application, the LM741 is unsuitable for quality audio.

The electrical output impedance will be very low - a FET input is the
opposite of what's needed, contrary to what Tho recommended (his advice is
good for a piezo). Your simplest low-noise amplifier for this application
will probably be a common-base arrangement with a low-noise transistor (a
BJT). That means that you include the coil in the emitter circuit, with
appropriate feedback. Or just use a better opamp.

Clifford Heath.

[kindyroot]

Thank you very much for the explanations it has been extremely helpful
to me to understand a lot of things, and in fact all you said is
right! the sound is too bright and resonance peak must be somewhere
too far in a diagram, but what i absolutely need to know more about
now is the tone shaping you spoke about, because this is my next goal
now that i've got the sound out of the instrument via the tiny pick-up
(thanks to tho x. bui for the ideas) now i need to shape the sound to
ma taste, so o need to know wich frequencies to cut and wich
frequencies to boost, ...etc.
I unfortunately don't have a graphic equaliser but i will try to put a
small RC type low pass flilter before the preamp to cut above 5Khz and
i will see what's going to happen.
see you soon.
bye.

[kindyroot]

Sorry Cliff i sent my last post before to read yours, can you please
explaine a bit why the fet is not suitable here? i recognise that i'm
seeking a way to avoid the common-base option because i never got to
make a common-base work in my whole life, i get always lost in the
calculus ... maybe if i find some good schematics, if i don't i think
i will replace the 741 with something better, let's say an opamp with
fets in the input for example, is that ok? i found these in a
catalogue: LM387 and LF351, what do you think about them?
and finally if you have an idea about the tone shaping that i want to
do and if you know how it's done please let me know.
thank you.

[Clifford Heath]

kindyroot wrote:
> Sorry Cliff i sent my last post before to read yours, can you please
> explaine a bit why the fet is not suitable here? i recognise that i'm
> seeking a way to avoid the common-base option because i never got to
> make a common-base work in my whole life, i get always lost in the
> calculus ... maybe if i find some good schematics, if i don't i think
> i will replace the 741 with something better, let's say an opamp with
> fets in the input for example, is that ok? i found these in a
> catalogue: LM387 and LF351, what do you think about them?
> and finally if you have an idea about the tone shaping that i want to
> do and if you know how it's done please let me know.

First I'll deal with the pickup itself, so you understand what you're working
with and trying to mimic.

0.4mm wire is about 24AWG, which has a DC resistance of about 0.16 ohms/meter.
You've used 250 turns of about .2m each, so you have a DC resistance of around
*8 ohms* - one thousandth of what a typical p/u will have.

In addition, the inductance of a coil rises with the square of the number of
turns - because every turn couples with all previous turns to increase the
inductance. The same thing happens with capacitance, each turn introduces some
self-capacitance with every other turn. The use of scramble-winding vs tight
winding affects this also. Anyhow, when you get 5000-10,000 turns as in a
normal p/u, the inductance and self-capacitance produce a resonant peak that's
proportional to 1/sqrt(L*C), which means the frequency drops with the square
of the number of turns. For the same copper mass, the number of turns drops
as the square of the wire diameter, so you have a resonant freq that changes as
the 4th power of the wire diameter. With a low resistance, the peak will be quite
sharp, but at 8KOhms, the peak is very broad (low Q factor). This explains the
behaviour of normal pickups.

Check out <http://en.wikipedia.org/wiki/RLC_circuit> for more info.

Now, for the pre-amp...

A common audio preamp might have an input impedance of 50Kohm, but a piezo is an
extremely high impedance output - 1Mohm input impedance is more suitable. More
actually, but them you run into other noise problems (Johnson noise), because
you have so few electrons flowing you start to "hear" them individually.

For minimum noise, you need an amplifier that has an impedance somewhere near
your pickup's output impedance. That's why I mentioned a common-base circuit.
If you employ 20-1 emitter degeneration (use a 150 ohm resister in series with
the p/u), and feed negative feedback from the collector to the base as normal
to set the desired gain, you should get a very linear low-noise circuit.
Best to avoid capacitive coupling on the pickup at these impedances, they'd
need to be big electrolytics. I'm not a purist that avoids electros in all
audio - they can be quite acceptable - but since you have a preamp circuit
that's so closely coupled to the P/U there's no reason to avoid it. If you want
DC isolation with a response down to say 20 Hz, into a CB setup with an input
impedance of 75 ohms, you need a C around 100uF (hence electro - but don't use
a tantalum).

You probably only need a gain of 20-50 before you feed the signal into tone/volume
and further amplification. You can massage your signal any way you like from there.

It probably doesn't make sense to try to reproduce the resonance at the pickup
by adding parallel capacitance with a series resister... but that's something you
might try anyhow, if you can rig up some way to measure the response curve.

Clifford Heath.

[tho x. bui]

Clifford Heath wrote:
> kindyroot wrote:
>> [snip]
> Best to avoid capacitive coupling on the pickup at these impedances, they'd
> need to be big electrolytics. I'm not a purist that avoids electros in all
> audio - they can be quite acceptable - but since you have a preamp circuit
> that's so closely coupled to the P/U there's no reason to avoid it.
> [snip]

Superb post!
What is the reason people give for avoiding electrolytic capacitors?

Tho

[Clifford Heath]

tho x. bui wrote:
> Superb post!

Thanks Tho. I reasoned most of p/u behaviour myself during the
last few years, during which I've also designed and built both
some serious electronic devices, some guitars, and a number of
pickups including my winding machine. So I've had the time to
learn to explain it succinctly :-).

I have a sense that my re-invention of a new pickup like Gibson/
Bill Lawrence's Sidewinders are truly something special, but I
haven't done enough A/B tests to prove it. I just know that the
guitars I've put them on have sounded awesome. The Sidewinder
arrangement is a radically different (humbucking) magnetic circuit
than traditional pickups. Gibson's were big and ugly, and I've made
them small and more effective. If anyone credible wants a business
making special pickups unlike anything else in the market, contact
me off-list. I'm not really interested in making one-offs, but I
might help someone get started in manufacture for a share of the
return.

> What is the reason people give for avoiding electrolytic capacitors?

Here's a better answer than I could give (they're selling chips
of course): <http://www.maxim-ic.com/appnotes.cfm/an_pk/3171>.

Note that the distortion is only noticeable towards the cut-off
frequency when combined with large voltage swings. The former can
be fixed by using a larger capacitor and a lower cut-off frequency,
and the latter simply doesn't apply to the small signals we're
talking about here.

Clifford.

[kindyroot]

> tho x. bui wrote:
> > Superb post!

I agree 100%.


> Thanks Tho. I reasoned most of p/u behaviour myself during the
> last few years, during which I've also designed and built both
> some serious electronic devices, some guitars, and a number of
> pickups including my winding machine. So I've had the time to
> learn to explain it succinctly :-).

that's interesting, do you have a website with some pictures and more
details? we never know where inspiration comes from!

> If anyone credible wants a business
> making special pickups unlike anything else in the market, contact
> me off-list. I'm not really interested in making one-offs, but I
> might help someone get started in manufacture for a share of the
> return.

I am myself interested in doing this business, maybe we should do
something together, we will design the pick-ups together via internet
then i will manifacture them here in morocco (lower production cost)
and i will send them to you wherever you are (i don't know haha) and
you will find markets for us (luthiers, guitar shops, guitar
manifacturers, ...etc), we can even make active pick-ups at lower cost
and kick EMG out of the market (*joking*).
Maybe you should add me on msn here's my adress (tho x. bui this is
for you too): kindyroot(NOSPAM)@hotmail.com // without (NOSPAM).

Lets talk now a bit about sound shaping since this is what will
actually make our happy pick-up sound like hell, like heaven, or just
like earth (hell is best for metal!!), so since my pick-up produces a
flat response this means i should remove myself frequencies above 5khz
(but waaaait !! what about my artificial harmonics?) so maybe i should
only smouthly cut above 8 or 10 Khz, i forgot to tell you!! my pick-up
with its actual preamp and without filtration gives INCREDIBLE
artificial harmonics and a GREAT sustain !! even in a poor guitar! i
will try to make this not disapear.
what i want to experiment next sounds weird but seems necessary, and
that's to simulate the peak of a normal pick-up, since all guitar amps
are designed to deal with this state of nature and are equiped with
proper corrections so i think i absolutely need to do that, note that
even devices like distortion pedals and effects processors have
outputs that simulate the respone of normal pick-up (because the
designers know that the amps are designed to flatten back the
spectrum) to see a proof of this you can plug a pedal into your pc and
listen to the metallic sound that it gives and see that it's not the
same that you get out of an amp.
The question now is wether i should do these corrections before or
after the preamp! and if there are any other ways to enhance the
tonality and the sounding of the pick-up others than these two
filters.
Cheers.