Sam Ash Fuzz Boxx tone control... worth it?

[Solidhex]

Yo

  I was about to build a Sam Ash Fuzz Boxx using the fuzz central layout http://fuzzcentral.ssguitar.com/schematics.php . I've read a lot about the tone control on these being pretty useless. Is it possible just to omit the pot or are there other components that need to be taken out? Does anyone like the tone section?

--Brad

[yeeshkul]

read this http://www.diystompboxes.com/smfforum/index.php?topic=58296.0
The tone control i complete rubbish.
Actually my little evil thing (described above) sounds the same. I spent plenty of time testing it.
By the way, i just finished a circuit board design for it today and had it made. i can put it up here after testing...

[Dragonfly]

replace it with either the scooped tone control from the shin-ei fy-2, or mark hammers swtc .

[Mark Hammer]

Are we certain that the schematic is accurate?  Not to disparage Phil's skills or his diligence and generosity in providing the schematic, but just looking at the schematic, it would appear to offer so little potential for reasonable sound-shaping as to be a waste of a pot, knob, legending, and the labour to install it.  So why would Sam Ash have put it in in the first place?  This makes me think it was drawn incorrectly and simply never corrected.  For example, if that 1k8 resistor in series with the tone pot was a cap, the control would make a lot more sense and have a lot more effect.

[soulsonic]

I agree with Mark. I think it's a mistake in the schematic. There's no way anyone would ever think that is any sort of a tone control. Any change in tone would be due to changes in impedance in the circuit as the control is turned... and that's just stupid. If redone, it could be a cool circuit. Maybe mess with options for the diodes or whatever. It seems like a pretty open project.

[Dragonfly]

im telling ya...ditch the existing one and sub a swtc.

[9 volts]

I coincidently dug out mine last night and rebuilt it. I spent alot of time researching this at the time of first building. Partlicularly comparing the schematic to the pictures at the following site
http://analogman.com/graphics/astrotone/astrotone.htm
There is a 1.8k resistor in there and the cap count and resistor count is the same. (check it out). Not sure what to make of it. Last night I thought  I would test drive it for what it is (cheesy sounding but ok wit the tone pot turned down), increasing the output cap seems to make it a bit more of a player. Check out also that the two transistors look similar in the picture at the above site.....any chance of of a discrepancy here? (schematic has different transistors).
ps Also listen to the sound samples at tone frenzy, to my ears they sound kinda rude/cheesy also..
Hey I'm just throwing thoughts at the wall to see if any stick.

[Solidhex]

Yo

  So I built the pedal up. I was just too curious about the original tone pot so I included it. I used the 1n914 diodes, a 2n3565 in Q1 ( I tried a couple 2N2222's but felt the 2N3565 was a little more "open") and the nte123 in Q2. It sounds pretty damn good. Its a treble booster type tone with a great midrange crunch and slight fuzziness around the edges when playing leads. Very responsive to dynamics and volume roll-off. The volume does what it should. The attack knob works as you'd expect from looking at the schematic. Sort of a pre gain. It has decent output. Not a huge boost but enough to get the job done.
  Oddly enough I acutally like the tone control! It sort of comes across as a thick to thin knob. Subtle but still usefull. I could see turning it to the thin side when recording for overdubs etc. I sort of prefer tone shaping by guitar choice or amp settings anyways so I'm not dissapointed.
  I'll have to jam it through the Marshall Superbass to get the full effect but so far its very Tommy Bolin. It can make a strat aggressive but in a smooth way not twangy or brash.
  Thanks for the suggestions everyone.

--Brad

[soulsonic]

Hmmm... the tone control goes from thick to thin? That sounds interesting and that suggests that it works exactly how I guess it would - by changing the impedance the output cap sees, and therefore changes it's response. I thought it was a stupid way of doing it, but if it actually works decent, I guess I must have been wrong.
I will have to try it so I can get my own opinion. I'm down for trying anything different.

[Mark Hammer]

Thick to thin sounds more like the Univox Square Wave tone control.  There, the output stage has a cap going to the volume pot and a second pot in parallel with the output cap.  Increase the parallel resistance and only the top end makes it to the output.  Decrease the parallel resistance and the whole signal finds its way through that second path to the output.  here's the two schems from Phil's site for comparison.


The glaring omission, though, is that IF the ground end of that tone pot is really supposed to tie to the other side of the cap, then what is blocking DC at the output?  In the Squarewave, that task is accomplished by the 4.7uf cap, but in the Sam Ash it is accomplished by the .047uf cap and would be undone by sticking a resistance in parallel to it.  In the absence of a longer, more studious look, I'm stumped.

[MetalGod]

I'm busying etching the PCB for this thing - am I right in thinking this uses Si for Q1 and Ge for Q2

[Dragonfly]

I'm busying etching the PCB for this thing - am I right in thinking this uses Si for Q1 and Ge for Q2

DS66 cross references to a NTE123AP ...small signal NPN silicon....so anything from a 2N3904 to a 2N5088 should be fine.

http://www.rselectronics.com/Catalog/ViewPart.aspx?Part=DS66(PLASTIC)&MFG=GEQ

[MetalGod]

I'm busying etching the PCB for this thing - am I right in thinking this uses Si for Q1 and Ge for Q2

DS66 cross references to a NTE123AP ...small signal NPN silicon....so anything from a 2N3904 to a 2N5088 should be fine.

http://www.rselectronics.com/Catalog/ViewPart.aspx?Part=DS66(PLASTIC)&MFG=GEQ

cheers for that.  I actually got off my lazy arse and looked up the datasheets myself this afternoon and found that Q1 and Q2 are both NPN Si with gains in the 100-150 range.  I've had gastoenteritis for the past week so I could maybe be forgiven for slight lazyness (still fell 'rough')

[slacker]

I might be looking at this too simply but isn't the tone control a variable high pass filter?
I'm not sure how it interacts with the volume control as far as doing the maths goes but it seems to vary the rolloff from a few 100Hz up to a couple of 1000Hz, so it should vary the sound from thin to fat, providing those frequencies have made it through the rest of the pedal.

[Mark Hammer]

I might be looking at this too simply but isn't the tone control a variable high pass filter?
I'm not sure how it interacts with the volume control as far as doing the maths goes but it seems to vary the rolloff from a few 100Hz up to a couple of 1000Hz, so it should vary the sound from thin to fat, providing those frequencies have made it through the rest of the pedal.

Well that's just it.  In principle, the tone-pot path and the .047uf cap ARE a variable high pass filter.  It's just that the pot is not isolated from the volume pot and the potential for a) interaction, and b) serious volume reduction, seems quite high.

The setup in the Squarewave, is also a variable highpass filter of a different type, except that it doesn't interact with its own volume pot quite as much.

[soulsonic]

I have to admit; I'm beginning to like the idea of changing the impedance seen by the output coupling cap to change the frequency response. It could be really cool if there's a decent range to the control.

[Yun]

i built this per that  schematic, and no it doesn't work.    

Unless you want a fuzz box that you can bareley hear, that is ....

[Solidhex]

I'll try to get some audio samples going of mine with different tone control settings...

--Brad

[STOMPmole]

I just built one and to my ears the tone is useless.  It sounds MUCH better with the tone control deleted from the circuit.

[Dragonfly]

I just built one and to my ears the tone is useless.  It sounds MUCH better with the tone control deleted from the circuit.

Have I mentioned the SWTC ?