Black Finger

[Nasse]

I think the tone control is what makes this somewhat differrent of other compressors of that time. I remeber that you could dial a deep bassy jazzy tone and a bright trebley sustaining sound too, almost normal at slight over middle position. Anyway dramatic chances possible with just that passive circuit. The hiss is there, and there is annoying distortion when the note decays and sustain is up. Always wondered if it is the 741 or 3080, or both. With fresh batteries it was little better.

I once tried the bassist´s late 70´s Fender Jazz Bass into a Black Finger, after reading that bassists use compressors and several newer amps were equipped with built in compressor. But nasty feedback and squealing resulted, and bass was weak, so quess the freq response is tailored for guitar. Or are 70´s Fender bass pickups that bad, think not???

There was a circuit many years ago in ETI with 13600 or 13700 in the neg feedback loop of 553X opamp, and it was a mic/line compressor, quite large project and pcb pattern, I have that magazine somewhere. Don´t know if the ota in the feedback loop has some benefit for less distortion.

[Nasse]

Ok, does anyone have the black finger schematic that I am looking for??

There is sometimes danger that kid goes with the washing water, everybody interested of old but not so popular and common old EH. I have no info about that early model, might be short production time and even rarer example. There was mentioned something in the owners manual of my pedal that Jimi Hendrix used early Black Fingers... thrown away that paper... Maybe that´s true, or just marketing department hype...

Maybe you could find somehow the position of the wires without the schematic, if it is impossible to find. If the wire is connected somewhere at the opposite end, what it is - is it at ground potential or supply voltage, input or output? - you can measure it without doing damage to the circuit.  What colour are the broken wires? In my EH battery wires are flexible wire, and other are stiff non-flexible one... The solder point is inside the wire lenght distance somewhere in the circuit board... Is it two battery or one battery device???

I once detected where a wire was originally connected, by carefully looking solder spots with magnifying class under bright light, the sharp short broken wires were clearly visible

[Mark Hammer]

A 13700/13600 in the feedback loop is exactly what we have in the Hot Lyx and Black Finger (IC version).  Again, I ask the question "What is the difference between directly controlling gain in an OTA for compression, and sticking an OTA in the feedback loop of an op-amp?".

The tone control works exactly the same as a Big Muff Pi, except that the component values are set at different corner frequencies for the highpass and lowpass sections that make up the control, so it will act the same but sound somewhat different.

As for hiss under no-signal conditions, well that's what most compressors DO, my friend.  That's also one more reason why limiters are sometimes preferable to compressors.  Where limiters will only reduce gain on peaks but NOT increase gain on soft passages, compressors will aim for a constant level by both decreasing peaks and boosting quieter parts.  The trouble with compressors is that when your input stage is not the quietest thing around, what you end up boosting is residual hiss.  Of course the trouble with limiters is that designing a device to only provide gain reduction above a certain threshold is harder than designing a device that simply makes gain inversely proportional to input level independent of what that level actually is.  In that sense, compressor are "dumber" than limiters.

The solution is to: a) feed them a nice hot crisp input signal so that lots of gain reduction can be produced with minimal gain added inside the compressor, b) make sure that everything leading up the the gain reduction element (whether op-amp, OTA or what not) is optimized for low noise (so, use FETs instead of bipolars, or low noise bipolars, low-value metal-film resistors, low-noise op-amps, etc.), and c) keep the compression as light as is practical so that only minimal boosting of softer passages occurs.

[toneman]

good comparason Mark!
never noticed the HLyx and BFinger similiarities.
DO know the HLyx sounds great.
Probably why Paia *still* sells the kit.

the opamp or the OTA.
which is "noiziest"??
my guess is the opamp.
increase gain & U can hear the noise increase with no signal.
OTA, OTOH(heh heh OnTheOtherHand), use a current
to control it's gain.  OTA's are used for VCAs all the
time, and operate full on/full off.
the circuit is interesting in that the OTA is in parallel with
the negative feedback  resistors.  The OTA changes
the gain by changing the apparent resistance of the
feedback.  Does the OTA give "more" gain.
Seems like it reduces gain of the opamp.
The Blackfinger also had another almost all transistor model.
It used a 748 opamp also, but it wasn't part of the gain-
controlling circuit.

so Mark,

Again, I ask the question "What is the difference between directly controlling gain in an OTA for compression, and sticking an OTA in the feedback loop of an op-amp?".

dang, can't get the quotes 2 work right!!!  

i would say it gives U "more" control than an OTA by itself.

interesting circuits, interesting folks @ this forum..
afn
tone

[puretube]

R.G.-time......  :wink:

[puretube]

The OTA changes
the gain by changing the apparent resistance of the
feedback

here`s where part of the answer lies...

the other thing to take into consideration is the noisefloor/headroom thing
with OTAs, that don`t like more than ~10mV at the input...

so in a compressor, would the OTA be used as "series-regulator",
at the lowest inputsignal moments it would have to amplify with maximum
"gain" (Gm)...
now this small signal at its input has alreadybeen attenuated a hundred times (100k/1k) beforehand (so as not to overdrive the OTA), and now wants to be beefed up to become as loud as the highest inputsignal moments - you get max. amplified noise.

whereas in the FB-loop "anti-parallell-regulator",
the OTA`s max "gain" (Gm) co-incides with the loudest inputsignal,
where the amplified (fedback) noise gets masked...

(only my explanation for personal use )

[Lonestarjohnny]

would anybody like to see a schematic of the Standard Memory Man + chorus from 1978.
Johnny

[puretube]

feel free to PM or email it to me...

[michael_krell]

Hey I have a whole bunch of pictures of the Black Finger Im working on. I posted some pics of the outside and now im giving you pics of the inside. Please let me know if theres anyhting missing and where these wires go. I cant find a schematic so maybe someone can help me.

[michael_krell]

Anyone have any idea at all? It looks like theres some open holes in the PCB. Does that necessarily mean that components were removed??

[toneman]

hard 2 tell from the pics.
open holes--could B "factory".
Looks like "triangle knob" arrangement.
L2R---Volume-sustain-tone

i count 9 transistors.
is silver "can" an opamp?
maybe a 748?
looks like not the OTA unit.
case looks like my 70s BigMuffPi.

U need to find in and out, pwr and gnd.
feed a signal thru and see where it goes/no goes.
a scope is very helpful.
afn
tone

[Nasse]

I´ll comp on that. You need to find if input and output and power leads from battery (is it two or one battery job?) and that power switch and the bypass switch arrangement, looks like no-true-bypass. I could not see any broken wires in the pics, maybe I have not looked enough...

You could quess the input and output stages and tone control might be roughly similar as later version...

:? Can you tell us, if there is a wire with one loose end, where is the opposite end of that wire connected???

[gez]

Looks like there's a wire missing on the top jack.  Is this the input or output?

[michael_krell]

I can figure out the power no problem, but the thing im most puzzled about is that the tip and sleeve of the out put jack are connected to the SPDT switch by those 2 red wires. (the signal and ground)

[hair force one]

a red black finger T-shirt that'll be cool!

[michael_krell]

anyone wanna buy this thing??? give me a price

[Nasse]

20 euros  :mrgreen:

But quess posting or shipping it would cost your arm and leg, and last time I received something from States it came in two pieces :x .

But it would have been interesting to know what makes this discrete component forerunner of the 741/3080 version tick.

I think not enough info so nobody can help or have an idea how to fix it. Have you tried to buy the schematic if it is available?