Analogguru - Pickup-probe

[analogguru]

Ok, here is a project only for the more sophisticated solder-jockey - Analogguru´s Pickup-probe.

As I could see recently on the requests in this forum, there seems to be a demand for built-in preamp for bass and guitar. But why fiddle around in your holy guitar and change always batterries ?

Therefore I will release and old design by be (only) to freestompboxes.org members for their personal use.

At first you can see in the schematic, that it is possible to construct an "phantom-powered" high-impedance preamp with only one screened cable and a low impedance output. This is important cause as lower the output impedance is, as less the cable capacitance will lead to a treble loss o other problems with non-true-bypass pedals.

The "head" could me mounted in the guitar, but what when the rest is stolen or you want to use another guitar ? This can be overcome by building the "head" into the jack which plugs into the guitar.

As you can see in the following pictures, a Neutrik jack has enough room inside for the head and the cable.

The right input cap can be recycled from old RAM-modules as shown.

The gain of the complete systems is about 10 which is approx. 20dB. As can bee seen in the oscilloscope picture, the amp starts clipping at 4,5V pp but very round and smooth as it is typical for a tube.

the complete prototype can be seen in the last picture.

enjoy improving your soldering skills and I don´t want to see any builds of this offered on evilbay or somewhere else,
analogguru

[Silent Fly]

Very interesting.

It reminds me a little bit the FET Preamp Cable by J. Donald Tillman.

I like the analogguru version more because it used a jack-jack connection instead of a jack-XLR.

[analogguru]

Thanks for that link, an interesting article I haven´t seen before. I also didn´t know that someone even has a patent on such a design. I have to read that patent.

But the informations there tell the patent uses a source follower so the gain is 0 dB. Tillman talks about 3 dB gain of his cable and the pickup-probe has 20 dB gain.

Tillman´s design has no input coupling-cap, which is not my taste. His use of a mixer´s phantom power supply appears to me a little bit "brutal", especially by grounding the second resistor. I have to try that circuit and see how it biases with 48V and a 6k8 when the shipment with my bunch of J201´s arrives. I never used that FET before.

analogguru

[Torchy]

Here you go
Vero 7x10.

[Silent Fly]

I took the liberty of designing another version of the Pickup probe. I am not 100% sure but I think D1 can be omitted.

I am sure you have seen some elements of my design before

[Silent Fly]

Sorry, I just realized that my schematic was wrong.

I removed it.

[seniorLoco]

WTF ??? AG... whats that ??

[analogguru]

WTF ??? AG... whats that ??

As I said:
A (vintage) Single Inline Memory Modul with 256kB x 16 + parity bit and an access time of 150nS...... built in 1984 by the company Pertec (Triumph-Adler):
http://en.wikipedia.org/wiki/Pertec_Com ... orporation

analogguru

[seniorLoco]

Oh ok ...thanks

Whatif those were BBD's

Btw i like your design for it's simplicity and may try using those SMT caps...that is if it doesn't keep on disappearing.

[ChristoMephisto]

What did you mean by 'mojo'?
Would you be able to wire up a 100k pot w/10k for a 'mojo knob'?

Whats going on in the top right hand corner above the +9v?

Safe to use 1/8w resistors in the cable?

Went and got a clear red cigarette case for the project at the dollar store
Was thinking if there was a way to add some kind of mod to cables,
but I was thinking something like a 'sweet switch' config, but now I see it wouldn't have worked

[analogguru]

What did you mean by 'mojo'?

The TS-9 to TS-808 conversion-saga.

Would you be able to wire up a 100k pot w/10k for a 'mojo knob'?

yes....

Whats going on in the top right hand corner above the +9v?

If you mean the schematic, than this is an (optional) DC-jack.

Safe to use 1/8w resistors in the cable?

The complete construction should only be made in a neutrik-jack because the construction requires that the cable is prohibited to move by tightening the plastic cover (screw).

analogguru

[ChristoMephisto]

From the schems I've seen, the 100 ohm res. is before the 10uf cap in TS pedals
altho have seen the resistor after in you config too

[gus]

http://www.littlelabs.com/std.html

Two batteries with a unity gain circuit for guitar?
Ground lift and not a transformer?

I think AG will understand.