Blackfire Build Pictures and Report

[Hydesg]

Hi
i just built the pedal today.

it sounded very agressive
but its really too noisy
and too loud somehow when i plug it into the amp


could this be rectified?
hmm? probably due to the 5 transistors gain stage?
or do i need to match the transistors?

[audioguy]

Shorten the leads and you'll get rid of much of your noise problems. Joes distortions are amazing- the Vulcan and the Obsidian are my 2 faves- but you really need to use the shortest leads possible. And then box it up and you should get a pretty clean pedal.

[ragtime8922]

Yeah, all Joe's stuff is awesome. I've built all of them, even the old stuff from the old site and once they are boxed up with MUCH shorter leads they sound great. My favorite is the Vulcan with the Obsidian transistor a close second.

I twaeked the Vulcan for frequency response and a few other things to get a customized metal pedal for myself.

[Hydesg]

do you mean those wires connected to the pedal itself must be as short as possible? as in the wires connecting to the jacks, battery holder, vol pots etc?

anyway would using shielded wires help ?
im thinking of shortening everything and use shielded wires


should i rebuild it in a much more compact design?

[petemoore]

I had long input/output wires from either jack to sw or switch to board, I shielded these, and noticed less noise.
 Offboard wires to pots I just plan and make them fairly short, same for the other wires, run against ground plane [box].
 I don't [try not to] run wires parallel, and try to 'X' them where they cross.

[Hydesg]

this is another version where by i shorten every wires connecting to the main board.

voltages at C are

Q1 8.7
Q2 4.45
Q3 8.7
Q4 4.55
Q5 4.28

are they biased correctly?

somehow shortening the wires made the collector voltages nearer to 4.5
before that they were at around 4.04 and 4.9

do you guys shield the enclosure box with foil inside?

i was wondering if that would be an overkill

[Hydesg]

the volume pot seems to be very loud even though i turn it a little

is that normal?
i think its about 10% on the knob

50% would make me deaf
:twisted:

100% ill turn  :evil:

so guys any solutions to make the volume pot more usable at a wider range?

the sound is quite thin and sharp
is that normal
?

any thing to make it more fat sounding
?

[markr04]

I just built the Blackfire project also and I have the same problem with R7 (1M pot). There's almost no volume until 10 degrees, then full volume the rest of the way. I can't figure out what that pot is supposed to do.

My guess is that R7 functions as a gain pot - but that's a guess only. R21's wiper goes to the output, so I'm guessing it's the output attenuator.

I built the project from a "jdavisson-pack.zip" file I downloaded a couple weeks ago. Here's temporary access to the .pdf so folks know what we're talking about: http://www.siteofmark.com/images/J%20Davisson%20-%20Blackfire-T.pdf

Hopefully someone can help us .

----
About your shielding question: if you use a metal box like the Hammond sort, it's not necessary to shield the box. It provides quite a bit of shielding from outside interference.

[Kleber AG]

the volume pot seems to be very loud even though i turn it a little

I guess you had used 100K pot "linear" instead of 100K "log".

If thats true, try a 100K log/audio there, you should have a way better response from your volume pot.

[robotboy]

I just built the Blackfire project also and I have the same problem with R7 (1M pot). There's almost no volume until 10 degrees, then full volume the rest of the way. I can't figure out what that pot is supposed to do.

My guess is that R7 functions as a gain pot - but that's a guess only. R21's wiper goes to the output, so I'm guessing it's the output attenuator.

R7 is the gain. The original schematic is here.

http://diystompboxes.com/analogalchemy/pedals/blackfire.gif

I used log pots for gain and volume as specified in the original schematic, and my blackfire has a smooth response in regard to both. It should clean up nicely when you back off on the gain. If it doesn't something might be wrong. Also, I used shielded cable for the input, and it's an amazingly quiet pedal considering the amount of gain it produces. I played it through my halfstack cranked, and no squealing. Getting it into an enclosure has a lot to do with that too...

[petemoore]

The wiring now looks much more acceptably neat/short.
 Blackfire=high gain, high gain needs more attention to layout and wiring than lower gain circuits do.

[Hydesg]

im using 100k log pots
but using linear pots for the 1meg gain pot


i cant find 1meg log pots here


its very nice sounding

the tone is aggressive which i like
and very sensitive

[MartyMart]

im using 100k log pots
but using linear pots for the 1meg gain pot


i cant find 1meg log pots here


its very nice sounding

the tone is aggressive which i like
and very sensitive

You ABSOLUTELY need the 1M log gain pot !!
Linear 100k will give you HUGE gain much too early in the travel   :shock:
A 500k log pot will help a lot though ....

Cheers,
Marty.

[Hydesg]

hi
do you mean that i can use a 500k log pot instead of the 100k log pot for volume?

[MartyMart]

hi
do you mean that i can use a 500k log pot instead of the 100k log pot for volume?

No, for your output "volume" pot a linear or log 100k will do ..........
for your "gain" pot - which should be 1M log - whatever "log" pot you have available will help, if you have a 500k log USE IT

The "gain" pot is half way through the circuit, the "Volume" pot is at the
end just before your output jack  ( just being clear about this OK? )

Cheers,
Marty.

[Hydesg]

would using a 500k log pot change the gain of the circuit?

[petemoore]

Probably not so's you'd notice, or marginal gain change, also the BF is so high gain I can't see how it would matter. Stick the 500k in there and see what you think.
 I notice huge resistors at the stage inputs, perhaps noiseless biasing could work some mileage here?...Hydesg...I'm askin' [?].

[octafish]

Can you get 2M lin pots? If so you can use the EMH at the anolog alchemy website to make a 1M log pot substitute. Aim for a taper of about 10 to20%. This won't completely fix your problem but will give you a 1M pot that is log-ish

[markr04]

I just got my Mouser order of 1M log Alpha pots in. They didn't fix the problem.

I was comparing the gain control of this to the Tube Screamer before. Maybe I can describe a bit differently, and hopefully Hydesg can confirm. It seems like "0" to "1" (1-10 scale) is almost a dead area - little to no gain at all. The slightest turn gives a heckuva lotta gain. With the log pots, I do have a more useful turn of the knob after "1", with more gain happening throughout the rotation. After the "dead area", it seems to go from very high gain to very, very high gain. Is that the jist of this project? If so, maybe we need to do something about removing the dead area rather than try to expand it.

It's unlikely that this problem is the pots themselves. I've tried other brands and values.

Those that are responding to this post, did you build this from the same layout that we did? I wonder if the layout has a problem...

Thank you all very much!

[Hydesg]

ill try the 500k log pot savaged from my old guitar electronics and let u guys know