5 string fretless: "Ignis 3"

[Macrocosmcwh]

Great Build.... Sub'd

[Stealth]

Wow. A hybrid BJT/FET preamp. And a PNP one, too! Color me intrigued.

This V/T/buffer layout reminds me of an unusual and rare Fender - in a good way, too.

[T-34]

From the first post:

Originally Posted by T-34

...
* weirdo homebuilt electronics, more on this later
...

[T-34]

I had the idea for this buffer reading the TI's "FET Circuit Applications" document:
http://www.ti.com/lit/an/snoa620/snoa620.pdf

Page 8 refers to a "High Impedance Low Capacitance Wideband Buffer", which uses one PNP.


I've told myself "finally I will be able to use my stock of germanium pnp-s for something useful, other than ubiquitous fuzz pedals
The negative AC and DC feedback loop being very strong, one can drop pretty much any transistor here and the buffer will still work fine.

[T-34]

Some news: I've applied the second coat of oil. The roasted ash darkens dramatically once oiled!

[roberthabraken]

Love it!

[MPU]

That looks great.

[Freestyler]

It looks like your bass is made of gingerbread.
Yummy !

[T-34]

The neck looks more like smoked tuna for me

[Nomad98]

Nice build... The neck wood is fantastic!

[T-34]

I've bought more of the same wood for another project

[Insederec]

And this is all the encouragement I needed to make myself a custom bass of my own. That is just goddamn beautiful.

[Beauchene Implements]

Man, this thing is stunning. That neck back... wow. And I'm trying to get my head around what you're doing with the pnp's and the JFET. My self-taught EE skills are lacking.

[T-34]

This circuit is composed of two basic amplifiers - "common source" and "common emitter", DC coupled in a smart way with many advantages: saving on number of components, permitting very deep negative feedback and therefore stabilizing DC operating point, reducing output impedance, enlarging frequency response. I understand it is not more widely used because of pnp transistors which are PitA to manufacture in ICs (more easy to add two npn's than use fewer but difficult to implement pnp's)

[Geoff St. Germaine]

Wow, the roasted ash/maple neck looks fantastic. The rest isn't too shabby either.

[Mr_Music90]

Beautiful! That's all I can say One of a kind

The neck looks to have a thick mass, could be the camera as well, but it looks good

[T-34]

It is more on a slim side actually (I agree, it is difficult to judge from the photo)

[Beauchene Implements]

Originally Posted by T-34

This circuit is composed of two basic amplifiers - "common source" and "common emitter", DC coupled in a smart way with many advantages: saving on number of components, permitting very deep negative feedback and therefore stabilizing DC operating point, reducing output impedance, enlarging frequency response. I understand it is not more widely used because of pnp transistors which are PitA to manufacture in ICs (more easy to add two npn's than use fewer but difficult to implement pnp's)

Thanks for the explanation! I'll have to study this a bit. I have some PNPs from another audio project, and the bass I'm working on now needs a pre. Curious to see/hear how this works for you.

[T-34]

Oh that's just a simple buffer (well, two identical buffers), no gain added, flat frequency response. Supposed to be non-intrusive and transparent The only valid reason I use it is to separate two passive tone controls. In fully passive circuit there is no way to make two tone controls be independent without losing a lot of gain.

I've tested the board already, it appears to be working. If something goes wrong, I've the backup solution in case this preamp goes wrong: the same double buffer functionality but implemented on opamp chip (it is the smaller circuit):

[T-34]

Originally Posted by Insederec

And this is all the encouragement I needed to make myself a custom bass of my own. That is just goddamn beautiful.

Thank you

don't hesitate to dive in, it is a lot of fun!