envelope filter nightmares...arghhhhhhhhhhh...

[R O Tiree]

> all that's left is a bit of dip and the pieces of cauliflower nobody else wanted.

I just snorted tea all over my keyboard.  Thanks, Mark

[Mark Hammer]

I've often wondered why envelope based pedals dont provide a Sidechain Thru or something for this reason. What if I want to run my Bluebox into an autowah, f'chrissakes!

The Bass Balls sort of does that by using the rectifier gain stage as a sort of fuzz.  It will provide a distorted signal, without impacting on the dynamics too much.

The format you want, though, is the Q-Tron+, which has a send-receive loop that's tapped at the same point where the envelope folower is tapped from.  You can stick whatever you want in the loop, and as much of it as will fit, and the filer will be swept by the dynamics at the input to the pedal.

[Mark Hammer]

> all that's left is a bit of dip and the pieces of cauliflower nobody else wanted.

I just snorted tea all over my keyboard.  Thanks, Mark

I do my best to help people keep their nasal passages clean.

[R O Tiree]

>I do my best to help people keep their nasal passages clean.


AGGGGHHHHHHH - you just did it again!

[rutabaga bob]

Mark - I see a whole new career opening up for you!

[StephenGiles]

It,s also why, over the years, I've found that I get more return for my effort on variable decay than variable attack.  Some variable Attack functions work well - the MXR Envelope Filter comes to mind immediately - but in many implementations they just eat up too much drive current.  Moreover, one needs to eat up a LOT of drive current to yield audibly different attack times.  With variable decay, you can easily obtain a 20:1 or higher ratio of decay times without significant impact on the sweep width of the filter.  That's much harder to do with attack in simple circuits.

I think the HSR Fader/Panner/Gate used a trick to minimise current draw during the attack section of the envelope. I have to haul our suitcases containing summer clothes into the attic later today, so I'll try to locate the relevant issue of the mag - from 1988 or so.

We had first frost of the winter overnight!

[pinkjimiphoton]

i kinda prefer a fuzz before envelope followers, seems to track better to me, and sound more...fuzzular. i like fuzz before wahs, too...but like wahs pre distortion, or overdrive.

the colorsound diphonizer i think has the fuzz first, at least it seems like it does.. but again, i prefer that pedal to have a fuzz before, and an overdrive after it. really seems to bring it to life.

if you still play dynamically, you can get a *LOT* of sounds out of them... i often use envelope filters live so i don't need to be tied to my wah, and people don't seem to notice the difference.

[deadastronaut]

Hmmmm....

@mark: i noticed you built the Q-tripper..

i can't find any clips of it though...is it a straight autowah?....does it have good response on all strings?

can it make a cup of tea?...

[Mark Hammer]

The Q-Tripper is a bit of an oddball.  Instead of selecting filter mode via a switch, as the Dr. Q does, it uses a blend/bleed pot to emphasize which filter mode dominates.  The sound is akin to a well-behaved Dr. Q/Quack.

[deadastronaut]

cheers

ive been tinkering with the bassballs, and i have it quite sensitive now, i love the filter sound, very synthy

but i just can't get rid of the 'filter breakup jumping' (not distortion) when letting a chord ring out...rather than a smooth filter fade trail off......

thats got to be the envelope detect part i guess, any thoughts/suggestions mods on that?..

[Mark Hammer]

Half-wave rectification is usually more than enough when the event to be followed is fast.  When the event to be followed has a protracted fade-out, full-wave rectification may be a smarter path to pursue.

Alternatively, or in conjunction with, it may be wise to have a toggle-selectable time-constant/averaging-cap range switch.  So, 10uf when you want things to move along quickly, and 33uf when you want the filter to take a leisurely stroll.  The thing with half-wave rectifiers and single averaging caps is that things you do to have a slow decay get in the way of fast attack, and vice versa.

You can also try two-pole averaging - resistor/cap->resistor/cap - for more averaging/filtering of the envelope during the decay phase.  I can't speak to how one ought to optimize that, though.

It also bears noting that some of the ripple can addressed at source.  For example, older strings, worn a bit at the frets, are more likely to produce "beats" that show up in the envelope, and result in audible ripple.

[deadastronaut]

hmmmm...cheers  mark.  (i wouldn't have a clue as to a full wave rect version)..(though i think gurner was pointing me in that direction....i think!)

as of now ive ripped the BB off the breadboard, i just couldn't get a nice trail out of it clean...(shame as i liked the filters sound but hey ho..)

so now my lengthy quest for a good EF has left me with the Q-TRIPPER..

http://www8.plala.or.jp/KandR/cir_q-triper.html

ive breaded it, but alas no quack ..i tried 2n5457's/ j201's.  with a 4558 ic. ...been over the connections from in to out and all looks ok...all bias points  etc..

if i turn the depth trim/pot i can manually sweep the filter, but not auto/quackyness...

note: if i remove Q2 and put it back in i get a hint of quack for a split second...hmmmm...


edit: breaded it twice now...is the above schematic correct?..hmmm..


ok i have j201's/2n5457's...this calls for 2sk30a's..which have a different 'fet' symbol to others going by this strange datasheet pdf.
http://www.on-ele.org/up/2SK30A.pdf

so in the schematic is the input going to the 'source' of Q1.....not gate?....seems weird to me!!!..

[Mark Hammer]

This might help you:

http://www.aronnelson.com/gallery/main.php/v/MarkMs-Gallery/album15/album76/Q_Triper_LAYOUT.jpg.html
http://www.aronnelson.com/gallery/main.php/v/MarkMs-Gallery/album15/album76/Q_Triper_TRANSFER.gif.html

[Gurner]

so in the schematic is the input going to the 'source' of Q1.....not gate?....seems weird to me!!!..

I'm not familiar with that particular circuit, but I can say with a fair degree of certainty that the output of the circuit's envelope follower (the wiper of the depth pot)  should go to the fet gate (ignore the circuit symbol if this is confusing)...the source goes to bias & the drain goes to junction of c5 & c6.

If as you're saying the filter works when you adjust the depth, then that suggests there's a problem with the envelope detect aspect of the circuit......put your meter across  C10 & give your guitar a 'full on' power chord whack.....you should see the DC level across C10 move up a fair bit

[deadastronaut]

@mark, cheers yeah i saw that.

@G: yep thought so, thats how i have it setup...(that datasheet should be banned.. )

D
S
G

on the recommended schemo it calls for 2sk30a's...

however in marks Q tripper build report he mentions considering  using  2n5457's ...so i'm trying those....or j201's..maybe.
http://www.diystompboxes.com/smfforum/index.php?topic=83116.0

i gave that C10 / 10uf reading a go...

correct, no change on DMM with a whack...hmmmm...so it is the EF....i'll poke around it..

[Gurner]

i gave that C10 / 10uf reading a go...

correct, no change on DMM with a whack...hmmmm...so it is the EF....i'll poke around it..

DC voltages for U1 would be useful. (as would squirting in a sine wave from a sig gen app outta your soundcard)

[deadastronaut]

okey dokey.....4558

1   4.35
2   4.36
3   4.36
4   0.00
5   9.11
6   8.96
7   9.01
8   9.11

[Gurner]

okey dokey.....4558

1   4.35
2   4.36
3   4.36
4   0.00
5   9.11
6   8.96
7   9.01
8   9.11

Pin 5 is wrong - it should be sitting at near 'bias' (4.5V) ....put a meter on these ....VR1, R9, R15   ...& post the results

[deadastronaut]

i thought pin 5 looked moody..

ahhh i just found a dodgy connection.  the R15 wasn't going to the R9  (covered by a bent lead..) no quack though,

4558

1  4.34
2  4.36
3  4.36
4  0.00
5  4.31
6  6.02
7  6.06
8  9.09

Q1

D   9.09
S   4.86
G   3.97

Q2

D  4.30
S  4.36
G  1.83

[Gurner]

i thought pin 5 looked moody..

ahhh i just found a dodgy connection.  the R15 wasn't going to the R9  (covered by a bent lead..) no quack though,

What's the  voltage across C10 with no signal & also when a full power chord is whacked out on your guitar?