Obsidian! YEAH!

[aron]

:twisted:

Alright!!!!

http://sounds.ampage.org/files/obsidian.mp3

[Joep]

Hi Aron,

Which version of the obsidian is this (transistor, fet)

Nice sample!

Joep

[aron]

I think it's version 1 MOSFET, I mean, it's perfect  

I never felt the urge to build another!

[Marcos - Munky]

I'm almost sure that is the 2N7000 version. Sounds very cool, Aron.

[Paul Marossy]

The Obsidian Overdrive Rev. 4 (2N7000) is a great sounding circuit, except for the hiss. I basically can't use mine when playing live, but it does sounds great. I remember reading someone's post saying they used a noise gate with it. That could maybe work...

[rx5]

that was me who posted (adding noise gate afte it)..... it really helps KILL the noise when not playing.....


OBSIDIAN MOSFET REALLY ROCKS!?!?!?!

im gonna try the BS250(if part is available locally)... and the tranny version......
 

[Paul Marossy]

Not knockin' Joe's design.  :wink:
I know that he knows that it had that tendency for hiss.
The Hellfire looks interesting, doesn't it?

[rx5]

yup it is...if  i could only find those BS250....

meanwhile, gotta do the tranny version first.... just gonna use MPSA18 > hfe: 500-1500  ...WOW

dunno what to construct....I wanna try the blackfire too....

[Gringo]

What can i use just in case i can't find 2n5089's nor MPSA18's ? I replaced 2n5088's with bc549c's once and it worked ok.

Any suggestions?

[Marcos - Munky]

I think the BC549C will do the job. They have Hfe between 420 and 800.

[Gringo]

Do i have to change the biasing in any way when using the 549's? It's just that i make enough mistakes by myself so i try to play safe with the scematics/materials i use  :oops:

Thanks for your help

[aron]

I believe I built version 1 of the Obsidian. If it was noisy, it was just like any other ultra-hi-gain pedal.

[Kilby]

yup it is...if  i could only find those BS250....

Ig you are still lookubg BS250s then try www.farnell.co.uk as their parent company are distributing in the US.

[Joe Davisson]

Mouser also has the BS250 transistors...

Latest schemo:
http://www.joefus.com/pedals/images/obsidian.gif

Mods I'm working on:
-Change bias resistors to 3.3M/1.5M (puts input impedance closer to 1M)
-Raise (or remove) 100k fixed resistor on the tone control
Seems to sound slightly better that way. (Not that big a deal, but...)

Something I don't get about the MOSFET's is that they sound the best with low resistor (10k) values between stages. Compared to the JFET-based pedals or Blackfire gain stages this seems strange, where 470k or so is normal.

I can understand this on lower-impedance bipolar stages (like transistor Obsidian stages), but why is this true of MOSFET's >?<

-Joe

[brett]

Re: transistor substitutes fot the BlackFire

The BC549C will do a fine job, except it will be noisier (NF=4dB) than the 2N5088 (3dB, but too low gain except for the emitter followers and the output buffer) and the 2N5089 and MPSA18 (2dB).  
But a BC549C will still be heaps quieter than regular trannies, like the 2N3904 (10dB).

If, like me, you don't have enough 2N5089s, use the BC549s from the output buffer first, then progressively back thru the circuit.  

Must go finish that BlackFire...

[analogguru]

BC 550 C is even more noiseless

analogguru

[Ansil]

does anyone have a sampe soundclip of the Pmos obsidian or any of the pmos stuff of joes.?