Project Big Marf

[Quackzed]

don't people usually 'scale' down the 'amp' tonestacks when used with trannys?

yeah, really if the tone stack sounds good, i'd just leave it.

if the circuit isn't noisy, which it seems it isn't with pinkjimi's diode mod, thats 1 less reason to need to scale the ts.
and if you have enough output and enough low end theres no real need..
if you do find it lacks low end, scaling would probably help with that.
just thought i'd mention it, i wasn't exactly sure why it was done, but after a bit of reading up i understand the reasons a bit better.

anotherjim hit the nail on the head, and explained it alot better than i could. so yeah, if the tonestack works, i'd agree with leaving it alone.

[pinkjimiphoton]

ben, don't @#$% with it. the thing sounds killer!!

reducing the pots will reduce what they do. it doesn't matter if it's in a stompbox or an amp. the same values work for caps and pots.
why? cuz that sets the frequencies they work on.

if anything, try a 100k mid pot. if ya go lower than 50 k it won't sound as good, and you will lose a bit more signal.

you have to scale parts in the power amp if building one, yes. but in the preamp, nope. not necessary. there is no diff between any circuits in that respect. you are right, this DOES sound better than the tone wicker one.

[digi2t]

Jim- a while back I remember I couldn't do the Duncan TS calculator because I have a MAC 

"Gee Mom, can we rent this movie tonight?"

"Sorry son, it's not available in Beta."

"Awwwwwww! Why'd we have to get a stupid Beta anyway! Dumb Beta!"




Sorry.... I couldn't help myself.

[pinkjimiphoton]

hey, man, so real.... so real.

i tried macs and didn't like 'em at all. too much bullshit to go thru. windows is easier. push a button and let te machine do all the work.

and all the updates and crap that make it so the OS is unusable and then ya gotta update everything... yikes. that was 20 years ago probably , i hope they're better than that now

that said, a lot of folks swear by them for audio and graphics, so wtf do i know?? naaaada!

the thing was, was there stuff for beta only? that's what i wanna know

[Ben Lyman]

Ha! Dino- LOL. Ya, my wife had a PC when I met her in 1999. I've never owned a computer or a wristwatch... why? I dunno. Anyway, this MAC was a gift from her parents and even though I've never been a "computer guy" I must say I appreciate the ability to gather info from around the world and learn stuff from you guys. I've learned a lot from this forum in particular but guess where I learned 90% of this stuff, what caps do, what resistors do, what's a breadboard, how to solder, what's a potentiometer, how to read a schematic, or at least my limited ability to do so... I bet anyone under the age of 30 will not be able to guess where...
the local library! I just went to their catalog and reserved every single book on electronics in the Sacramento Public Library system (including all the "...For Dummies" series) and had all the books trucked in from around the county to the library around the corner from me.
Of course, I still owe an enormous debt of gratitude to all you guys for speeding me along the learning process, Thanks!

[robthequiet]

Ben, in the vid when you got to the bass adjustment I swear you were going into Highway Star. What you have there is a tone factory. There is BMP in there but it barks in other languages too. Box it!

re: the noise/diode thing, could it be the reverse of what the diode decoder detector is in an old AM radio? Just guessing. Also, the silicon in parallel might kick on if you put a booster in front of the box, so you clear like +1 volt across the clippers. Another guess, I guess. Might be a good project for an oscilloscope to poke around on.

[pinkjimiphoton]

no idea how THAT works, either, rob lol

i'd love to see someone scope it

[anotherjim]

Just punched values into the TSC. Not a huge overall difference to the contour. General cut of 6db due to output load. Mid scoop a couple hundred hz lower with everything at 12 o'clock.
In a rush so could have made an error, but what I got doesn't surprise me. My BMP I made ages ago out of junk, so I'll try the Ge diode when I get the chance - so behind with a lot of things at the moment.

[Ben Lyman]

I'll just put this here for you guys to mull over...

[robthequiet]

Thanks Ben, I actually had that question about reversing polarity on the detective diode. I'm leaning in a bit more on the fact that you have essentially an AM radio that picks up ambient noise, cranks them up in the amp stages, and the diode does carrier removal. Or maybe not. It could be just a reduction in gain from the lower forward voltage in combo with the feedback network. Fascinating stuff, thx Ben & Pink Jimmy.

Can this trick work in other gain devices? Would be gold.

[Ben Lyman]

Cool Rob, you might be onto something there but I really wouldn't know.

I wanted to get a tiny bit more volume out of this for when the mids and treble are reduced. The volume wasn't dropping so much as to be a problem but I still wanted that little extra reserve.
I replaced R27 with a 2K and it did the trick. Would any of you recommend a different approach?
Thanks

[robthequiet]

Question for the panel: Would a bypass cap on the Q4 emitter give Ben more oomph?

[thermionix]

Actually, disregard.

Shit! I missed it... I wanna know what you said 

Aw man it wasn't much.  I was telling of my experiments adding a 3rd diode in parallel with standard clippers in a TS.  But all Si, and the more I thought about it, I figured it probably didn't relate too much to your Si/Ge combo.

[pinkjimiphoton]

Thanks Ben, I actually had that question about reversing polarity on the detective diode. I'm leaning in a bit more on the fact that you have essentially an AM radio that picks up ambient noise, cranks them up in the amp stages, and the diode does carrier removal. Or maybe not. It could be just a reduction in gain from the lower forward voltage in combo with the feedback network. Fascinating stuff, thx Ben & Pink Jimmy.

Can this trick work in other gain devices? Would be gold.

yes it will work in other gain devices as thermoniox << sorry can't spell...>> just posted.

the basic concept will work in a couple different applications

you can do it in the bc feedback loop of a noisy GE with led's and substantially eliminate a lot of the frying bacon. add about a 470p cap or so in there to mellow it out some and it will work well with some q's, not so well with others

i have tried it with single clipper applications, and it's less noticeable audibly than in the big muff circuit. to me, the reduction in the noise was a tradeoff i decided to go with. the thing is, if ya didn't know the mod was there, you'd still think it's a big muff.
but it definitely audibly reduces noise in this circuit, and a similar use in my monkey balls really helped with the shit ac12 whatever it was i stuffed in for q1

[pinkjimiphoton]

Question for the panel: Would a bypass cap on the Q4 emitter give Ben more oomph?

yeah it would. i bet somewhere between 470n and 4.7u would be perfect. give it a bit more thump and definitely more of a bite to it

[Ben Lyman]

Haven't tried the extra bypass cap yet, I'll try it later tonight.
Check the new scheme, presence knob added between output cap and master volume.
Is it just my stupid brain telling me this is a good idea?
Is it redundant because I already have 3 other EQ knobs?


edit: just tried it for the first time with humbuckers and I don't like it, mushy and constipated.
Maybe it needs a high pass filter on the input with a switch?

[anotherjim]

Ben's diode swap video...
Amazing what a difference it makes & so totally obvious.
Voltage at the cap end of the diode needs thinking about - the meter impedance is the only thing making DC across the diode because of the blocking cap. If you have the diode cathode toward the cap, the meter is putting it into forward bias (giving it a DC ground path) & you would expect a lower reading than at the collector. If the diode anode is facing the cap, the meter is putting a reverse bias on the diode and any lower voltage compared to the collector end is due to reverse leakage.

Another thought. Leakage is something like having a high value resistor across the diode. There is already 470k NFB resistor between collector & base. To be noticeably increasing NFB, the leakage resistor must be equivalent to something not more than x5 the 470k. So if Ben has some >1M resistors handy (2.2M, 2.7M), try some instead of a Ge diode.

Maybe easy way to compare those 2 Ge diodes for leakage.
Put the diode anode in 0v socket. Meter on volts between +9v and diode cathode. Note voltage & repeat for other diodes.
This is using the meter internal resistance to feed reverse current into the diode. More leakage should mean higher voltage reading.
Maybe compare with other diode types including LED's.

[bool]

Buckers are good with a 100n or a 68n input cap. Maybe up to 150n.

[Frank_NH]

Thanks for those videos Ben.  Cool Muff variant.

Like anotherjim and others I've been puzzling over the noise clamping properties of the germanium diode.  My theory is that this effect is due to the leakage properties of the germanium diode when reversed biased.  The leakage clamps low amplitude noise while having a minimal effect on the large amplitude guitar signal.  This probably introduces crossover distortion too, but it's inconsequential given the massive clipping occurring in the gain stage.

I'd try using two germanium diodes in series.  It will provide for the same clipping threshhold as one silicon diode, but may also do a good job clamping the the white noise.

[Digital Larry]

I don't quite grasp why the Ge diode does that either other than it is reducing gain in one direction after the voltage from C to B goes over the threshold, and maybe in the other direction because of leakage.  I'd try taking out all diodes in that stage and just use a resistor of varying value to see what happens.