Transistor Obsidian Perfected(close anyway)

[rx5]

YESSSS!!?!?!!!!!!! lucky for me.... there was 1 store selling 2N7000 ....... ....guess Ill have to build the MOSFET obsidian..

[RDV]

I don't think that version of the Blackfire even works, all I get is oscillation and bizzare quivery low octave madness and hum. All my voltages look right till I get to that fifth transistor. I've rebuilt twice. It's a joke that Joe put out as a parting shot obviously before he took down his site. It doesn't work.

Bumming

RDV

[Alex C]

Hey, I just got done tweaking my Obsidian build a little more.  It sounds good, except it's a little muddy on power chords below the A on the low E string.  Palm muting sounds muddy too below C on the A string.  Can anyone suggest a fix for this?   I'd like to box it (make it a "keeper") but it's just not usable the way it is right now.

Also, I get that crazy oscillation too, and i have to shift the board and mess of wires around to find a "sweet spot" where it doesn't happen.  I've wiggled all the wires and can't seem to narrow it down to which one is the fix.  Any hints on this?

Alex

[RDV]

Hey, I just got done tweaking my Obsidian build a little more.  It sounds good, except it's a little muddy on power chords below the A on the low E string.  Palm muting sounds muddy too below C on the A string.  Can anyone suggest a fix for this?   I'd like to box it (make it a "keeper") but it's just not usable the way it is right now.

Also, I get that crazy oscillation too, and i have to shift the board and mess of wires around to find a "sweet spot" where it doesn't happen.  I've wiggled all the wires and can't seem to narrow it down to which one is the fix.  Any hints on this?

Alex

Trim your wires down to minimum length. Be neat and take your time. Changing the first cap value made a big difference on mine. I also added a 3PDT switch with an LED, which seems to help oscillation also.

Good Luck

RDV

[troubledtom]

the mosfet 2n7000 ver. is totally rock'n but noisy as hell itself . joe was never 100% happy w/ it. i never use mine anymore . i never tried a noisegate after it , because i not like them . but someone else might.
          peace,
             - tom

[rx5]

My obsidian 2N7000 works.... yup it sounds good (distortion) but noisy.....
what do you mean by noisy?? the oscillation???


got 2 MOSFET obsidian diagrams here... Im reffering to the 2000 version...
here are my mods...... changed the 3rd stage 2.2uF to 10uF to add some BASS .... changed the LEDs to 12v Zeners..(i dunno if this makes a diff, just wanna make it compact).... changed the 47k middle leg GAIn pot to 470K...so that it will minimize signal and OSCILLATION to the succiding stages.... changed the .01uF in the tone control to .02uF and had to change the 5.6K drain resistors coz mine didnt read 4.5V ...... had to use a pot to get the value... w/c was 2.3K for the 1st stage and 3K for the 2nd and 3rd stage.... wierd....how come the 2nd and 3rd stage hav different bias voltage? anyway, the DRAINs ae in 4.5V bias... no other mods for this..... BTW you can even change the 470K (middle leg GAIN pot) to a max of 1M just to tone down the oscillation.... noise can be minimzed by short wires and METAL enclosure.... even did mine using electronic bypass...got my switching scheme from boss super OD .... really works.... now I wont have to bother buying carling switches, cant get them anyway.....no one sellls it it my hometown

really important: keep wires short as possible (shielded is best) and use metal casing for it.......

I can even compare it to BOSS dual OD....my obsidian has lesser noise than the boss pedal...even at full gain.... (I refer to the sound heard even when your not playing the guitar, sounds like AC HUM???)

HAPPy modding....

OBSIDIAN MOSFET ROCKS!!!!!!!!!!!!!!!! :wink:

Regards


-Ralph

[rx5]

ooopss.... I was a bit wrong bout the NOISE level.....

here it is:

BOSS dual overdrive settings : LEAD : GAIN=full ; TONE=high (distortion sound & noise level)

is equivalent to

Obsidian Mosfet : GAIN = 1/4 from minimum ; TONE = mid only (distortion sound & noise level)

both of the above setting sound alike......
---------------------------------------------------------------------------------------------------------------

if I crank up the TONE to full(obsidian) , It adds more treble......If I add more GAIN, then I also get more NOISE...

conclusion: obsidian has MORE gain and more treble "boosting" than my Boss dual OD.... I think thats what you get (NOISE) because of it being a HIGH GAIN overdrive..... but you could adjust the gain to minimize noise....

Hope this clears up the troubles.....

--------------------------
btw, I highly recomend JFET bypassing (from boss super OD) than using 4016/4066/4053 switching.......
just "delete" the op-amp section and replace with your OWN overdrive/dist effects.....
remember: op-amp section only......

Regards

-Ralph

[WGTP]

My experience is with the Black Fire, but you can tweak the hi's with the 470pf cap in parallel with the 470K resistor.  You can go from 0 to 10uf if you like.  Good place for a socket.

[RDV]

My experience is with the Black Fire, but you can tweak the hi's with the 470pf cap in parallel with the 470K resistor.  You can go from 0 to 10uf if you like.  Good place for a socket.

Which Blackfire, might I ask? I just tried the 5 transistor one from earlier in this thread, and it didn't work.

Regards

RDV

[WGTP]

I built the first version which didn't have the 5th inverting stage trasistor.  I don't have oscillation problems with it, I presume because I didn't use a switch.  It rocks big time.  It is one of my top 3 favorites.  It has a different sort of sound, I can't really pinpoint.  Seems to blend well with my tube amp i.e. it doesn't sound like a seperate pedal overdriving the amp.  Sort of edgy with a big bottom.  Compression.  Maybe the least troublesome build I've done.  I used 2N5089's and it fired right up.  Cool.   I'd give it another try.  

[RDV]

I built the first version which didn't have the 5th inverting stage trasistor.  I don't have oscillation problems with it, I presume because I didn't use a switch.  It rocks big time.  It is one of my top 3 favorites.  It has a different sort of sound, I can't really pinpoint.  Seems to blend well with my tube amp i.e. it doesn't sound like a seperate pedal overdriving the amp.  Sort of edgy with a big bottom.  Compression.  Maybe the least troublesome build I've done.  I used 2N5089's and it fired right up.  Cool.   I'd give it another try.  

I've got a schem drawn with a tonestack, does yours have this?

RDV

[WGTP]

No tone stack on mine.  When it came out, people were adding stacks, the Marshal stack seemed to be mentioned a lot.

Mine is the beta version, there was a latter beta2 version.  The first had a 3.3 meg resistor that the later version used a 4.7 meg.  Also the 2.2K was replaced with a 1K and the .002uf cap was replaced with a 470pf cap.  Joe said it increased the gain and reduced the highs slightly.  

[petemoore]

And mosfets [where the signal's coming off the enitter[source]/and collector]drain] goes to Pos rail.
 Oh that's a Blackfire, but NTE47 is the dross ref for 5089.
 Also I had just fine results with mpsa18's.
 Low noise high gain Q's make these ckts work...great !
 I think the BlackFire is just a little too good!

[rx5]

guys,

I keep hearing MArshall tone stacks...are they tone controls?? any links or diagrams??

thanks..


-Ralph

[WGTP]

Da a search for the Duncan Tone Stack site.  It has several variations to play with.  It is a passive 3 pot tone control, with the values of a marshal amp.  

[Peter Snowberg]

I think Tone Stack Calculator is one of the coolest pieces of freeware ever written:

http://www.duncanamps.com/tsc/

Also get his Tube Data Sheet Locator. Neat stuff!

-Peter