Agile Intrepid 828 Cepheus Pickups Mod :: split, passive mods, active buffer mods ...

[helferlain]

Hi,

it's 3 weeks now since I got my Agile Intrepid 828. I couldn't let my hands of the wiring becaus I want to see (and hear) what I can get out of the stock pickups. After a few days of trying and testing, I did my last soldering today.

Using parts for only a few cents I got some great sounds out of the stock cepheus pickups. This may be interesting for some folks here who don't want to by always new expensive pickups to get some minor changes in sound.

Here is what I did:

1 :: changing strings & tuned to EADGCFAD
2 :: trying some new pickup combination with split & coil filters
3 :: setting 4 positions for a rotary switch
4 :: build in a buffer circuit
5 :: edit the buffered pickups for pleasing sounds

I will write some detailed reports including sound samples during the next few days. Those changes are plainest with the clean and crunchy tones, therefore most of the soundsamples are recorded in clean settings.

stay tuned ...

EDIT: spelling correction

 

[helferlain]

1 :: changing strings & tuned to EADGCFAD

this is self explaining. For this tuning I'm using a GHS 10-46 set and some single strings:

D 010 - GHS-set
A 013 - GHS-set
F 017 - GHS-set
C 026 - GHS-set
G 036 - GHS-set
D 050 - GHS single string
A 070 - GHS single string
E 090 - GHS single string

I also ordered similar strings from Elexir, with the next string change I'm going to compare those. If you live around Germay I highly recommend SchneiderMusik.de for buying strings.

2 :: trying some new pickup combination with split & coil filters

I made a quick record playing some simples chord stuff to show how the stock pickups / setting sounds:

Agile Intrepid pickup mod 1 - standard pickups & positions

to be continued...

 

[Empryrean]

you sir, amaze me with your work. Please keep up the good work!

 

[helferlain]

2 :: trying some new pickup combination with split & coil filters (continuation)

... some simples chord stuff to show how the stock pickups / setting sounds:

Agile Intrepid pickup mod 1 - standard pickups & positions

You can find there samples of the tests with the concept of coil filters. This topic was brought in by SirMyghin recently:
http://www.sevenstring.org/forum/pickups-electronics-general-tech/168921-coil-filters-you.html

I also found some older detailed descriptions on a german website. If you can read german language go here: Humbucker als Pseudo-Single-Coil

The coil filter concept can be executed with a standard tone pot, but in my case I chose a fixed solution like displayed in the german article. You can do it in the same way like a standard split switch, it only has a capacitor in it's way to the ground connection.

With bigger capacitors you set the crossover frequency lower. It should be high enough to cover the low frequency noise you get from the AC hum in you area (mostly 50Hz or 60Hz). Everything above depends on your taste or the hum and noise you want to avoid.

I did some experimets with a 68nF and a 220nF capacitor. Follow the first link in this post and you can compare those settings with the standard pickup setting.

Thats all I wanted to show you about the standad passive pickup possibilities. Before I move to active buffer circuits let's play wit some ...


3 :: new pickup configuration for a 4-way rotary switch

The split and coil filter thing was a big step in the right direction, but there are still some annoying things. Like the middle position of the toggle switch, for me a quite useless sound. The limits of that toggle switch for other combinations. The influence of different cable lengths on the sound. The tone pot that I want in a fixed position ...

But this Intrepid is brand new and I want to keep the appearance. That means no additional mini switches, no blade switch for pickup selection, no drilling holes in that pure new body...

Let's just swap the tone pot with a rotary switch for pickup selection and use the toggle switch later with a buffer circuit for fixed tone selection.

to be continued ...

 

[helferlain]

3 :: new pickup configuration for a 4-way rotary switch (continuation)

If you look for rotary switches you can find some expensive ones, "made for guitars". Then there are some sealed switches, made of plastic. And I found some standard open switches, with knurled shaft to retain the original intrepids knobs. They are made with 1 - 3 layers and 1 - 3 switches per layer.

I decided for a 1-layer, 3-switch, 4-position model:
Its a MONACOR 134S MONACOR INTERNATIONAL : Produktdetailseite

I really like the part when it comes to pen, paper and sketches. There are more than 20 options for pickup configuration for a double humbucker guitar, and it took some time to find the useful ones for me.

I decided the positions out of theory and experience with other guitars before I ordered the switch, because you need more or less switches per layer, depending on you chosen configuration. But even the mighty 3-layer / 6x6 position switch should match in the Intrepids electronics cavity

I didn't buy this switch, because they have only the long shaft version...

Back to my 3x4 switch. Those are the positions i set with the rotary switch:

1 - bridge humbucker (standard)
2 - inner coils of both pickups, serial configuration
3 - neck pickup, split with a 220nF capacitor (as described in my prevoius post)
4 - north coils of both pickups joined in parallel mode, then linked together in serial mode to the bridge south coil

Now I had the problem that the mounting thread of the rotary switch was to short for the thickness of the intrepid's top. A bit of woodworking was necessary to fit in the switch ( and later the new volume pot fot the active buffer circuit ).

My dremel tool was very usefull at this moment, I had to remove 2 -3 mm of the thickness of the top from inside the cavity.

I did no sound samples at this stage, they will follow after part 5 :: edit the buffered pickups for pleasing sounds.

to be continued...

 

[JamesM]

Oh yes.

 

[Kahless]

I can't wait to hear the results with the buffered circuit (and learn about it).
Thank you for making this topic

 

[helferlain]

4 :: build in a buffer circuit

Before we install the buffer circuit, let's answer the question:

Why do I need a buffer? What is its function?

I will try a very simplyfied answer without any circuit diagrams:
The sound of a standard passive electric guitar is a product of at least 3 components in a closed electric circuit, including everthing in the signal path up to the amp input:

the pickup (physically simply, but complex from physics; works as a generator, creates a signal = AC voltage from swinging strings)
capacities (found as capacitors on your tone pot, but also the capacity of the guitar cable)
resistance (found inside the volume pot but also inside the tone pot)


Every change of one of those components has an influence on the sound of the guitar. You know how your sound changes from using the tone pot (changing capacity and resistance), using the volume pot (wich does not only change the volume), or from a pickup swap (self explaining).

But the possibilities for changes inside a pure passive guitar are limited, and there are some of those components outside of the guitar: the guitar cable, stomp boxes etc.

The problem: every passive tone shaping device can only cut an original signal. There is no way to add something to that signal. For pure passive electric guitars this means, a lot of the original signal from the pickup is cut away to get the sound we all know and like.

Sometimes there is cut away pretty much and we know this as a muddy, undefined sound, no brightness etc. That does not mean that the pickup itself doesn't deliver enough signal. Just a major part of the signal is cut away.

Ask yourself: why are so many people changing their pickups (for a lot of money) and don't try to change their volume or tone pots (would be much cheaper)? Most of the passive guitars have eihter 500kOhm or 250kOhm pots, most have the same tone capacitor ...


I have shown you some of the possibilities for changes inside a pure passive guitar at part :: 2, but they are limited. And here we come to active buffers. The buffer circuit basically separates the pickup signal from the unwanted influences of resistance and capacities.

Depending on the position of the buffer in the signal path you can have the pure pickups sound withoud the influence (technically: load) of other resistance or capacities. This sounds ... strange, with high resonance frequecies and peaks, not very usefull.


But now you have the chance to find a sound you like, without cutting away to much from the original pickups signal. It's, again, just a matter of resistance and capacities.

Whatever sound you create, it will not be influenced in an unwanted way from cables, and other stuff. And wanted influences like guitar effects will work in the same way like a pure passive guitar.

In my case, the buffer circuit has the size of a thumbnail, works with a 9V battery wich should last several hundred hours. I bought it from a german guitar tech because I was to lazy to build my own from scratch.



5 :: edit the buffered pickups for pleasing sounds

As I said, the pure buffered pickup needs some adjustments for a suitable sound. I am using the following signal chain in my guitar:


[pickup] - [pickup switch] - [load resistor and capacitor] - [buffer] - [volume pot] - [guitar out]


This is not a schematic. The load resistor and capacitor are NOT in a SERIAL way, the are parallel to the pickup, connectet to ground. But they are placed before the buffer and have an influence of the sound.

The volume pot after the buffer has no influence of the sound, it just changes the volume.


This are the dimensions I'm using:

load resisor: 100kOhm
load capacitor for bright tone: 100pF = 0.1nF
load capacitor for warm tone: 1000pf = 1.0nF

If the volume pot is set after the buffer, it should be around 25kOhm (common standard for active guitar electronics). I had a 20kOhm pot here and it works fine. Using the standard 250/500k pots would bring you in the range of "wanted influence".


Here you can find soma sound sample with the buffer circuit:
agile-intrepid-pickup-mod-2-new-pickup-settings


and compare them with the passive stock setting of the guitar:
agile-intrepid-pickup-mod-1-standard-pickups


Thats it. This is the concept of active buffers in electric guitars. If you want to try, search the web. There are plenty of schematics and it's easy to make. Or look for someone with the soldering skills to creat one for you ...

Ahhh, I almost forgot: This is how the electronic cavity of my Agile Intrepid now looks. And some distorted sounds with the buffer...
agile-intrepid-pickup-mod-bonus-picture-distorted



good night!

 

[Kruxx]

Thanks for taking the time to write this up helferlain.

 

[MrGignac]

great post!! if you get some good tones from this mod, i might wire my agile similar. My stock cephius's sound good but are a little bland.