ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

Building an Attack Delay

5/9/2000 1:40 PM
jon	Building an Attack Delay Hi Anyone ever build one? I've found RG's schematic for the Slow Gear on GEO, looks like there's an OP amp of some sort...any suggestions of what to use here? I also remember the EH Attack Delays; any idea if there's schematics for these anywhere on the net, or where I might be able to purchase them? Any clue as to general principles that make these things work? Thanx, Jon

5/9/2000 1:40 PM

jon

Building an Attack Delay

Hi
Anyone ever build one? I've found RG's schematic for the Slow Gear on GEO, looks like there's an OP amp of some sort...any suggestions of what to use here?

I also remember the EH Attack Delays; any idea if there's schematics for these anywhere on the net, or where I might be able to purchase them?

Any clue as to general principles that make these things work?
Thanx, Jon

5/9/2000 2:20 PM
Mark Hammer	Attack delays are essentially sluggish noise gates. Noise gates work by attenuating the signal unless it detects signal over a threshold value (presumably higher than the background noise it is trying to suppress). Once detected, the audio "gate" opens up and allows the signal to pass until it decays below the threshold value again. Most decent noise gates will include controls for gate attack and decay time so that the signal can be made to sound more natural (fading out naturally, and having a less abrupt and switch-like onset). Attack delays exaggerate the attack time so that the gate turns on very gradually. The inexpensive "Gator" kit from PAiA (www.paia.com), as designed by Craig Anderton, is essentially his noise gate project from the EPFM2 book, retweaked to provide the option for very slow gate turn-on time. The key element to the Slow Gear is the FET that is used to attenuate, and fade in the guitar signal to the output. Another approach is taken with analog guitar synths. Here, there is a generic "event detector" module, for identifying new notes. This will result in a trigger/gate pulse being sent to an envelope/function generator. This latter module then generates a fixed envelope voltage (the old ADSR type or simply an AD type), which can be used to control lots of stuff. If you use it to control a voltage-controlled amplifier (VCA), it can automatically vary the volume of whatever you feed the VCA to produce slow onset sounds or whatever you set the envelope generator controls for. This is obviously more complicated. One important thing to keep in mind about both systems is that they work by identifying "new events", without discriminating between strings, and generally without discriminating between notes that came from out of silence and notes that were added on top after the first note had been plucked. This is the complicated way of saying that such an effect works best when you play monophonically (single notes) and leave a bit of space between notes. You CAN play chords on them without chaos (unlike octave-down boxes), but the chord has to feel like a single note to the unit to make it behave right. Incidentally, more effective simulation of "backwards tape" tone will generally involve some timbral adjustment too. Normally, the initial attack of a note contains more harmonics, so a decent emulation of reverse tape would include some envelope-controlled filtering as well. You could do this within the design of the effect, or simply tack on an envelope controlled filter afterwards, set for minimal to modest modulation.

5/9/2000 2:20 PM

Mark Hammer

Attack delays are essentially sluggish noise gates. Noise gates work by attenuating the signal unless it detects signal over a threshold value (presumably higher than the background noise it is trying to suppress). Once detected, the audio "gate" opens up and allows the signal to pass until it decays below the threshold value again. Most decent noise gates will include controls for gate attack and decay time so that the signal can be made to sound more natural (fading out naturally, and having a less abrupt and switch-like onset). Attack delays exaggerate the attack time so that the gate turns on very gradually. The inexpensive "Gator" kit from PAiA (www.paia.com), as designed by Craig Anderton, is essentially his noise gate project from the EPFM2 book, retweaked to provide the option for very slow gate turn-on time. The key element to the Slow Gear is the FET that is used to attenuate, and fade in the guitar signal to the output.

Another approach is taken with analog guitar synths. Here, there is a generic "event detector" module, for identifying new notes. This will result in a trigger/gate pulse being sent to an envelope/function generator. This latter module then generates a fixed envelope voltage (the old ADSR type or simply an AD type), which can be used to control lots of stuff. If you use it to control a voltage-controlled amplifier (VCA), it can automatically vary the volume of whatever you feed the VCA to produce slow onset sounds or whatever you set the envelope generator controls for. This is obviously more complicated.

One important thing to keep in mind about both systems is that they work by identifying "new events", without discriminating between strings, and generally without discriminating between notes that came from out of silence and notes that were added on top after the first note had been plucked. This is the complicated way of saying that such an effect works best when you play monophonically (single notes) and leave a bit of space between notes. You CAN play chords on them without chaos (unlike octave-down boxes), but the chord has to *feel* like a single note to the unit to make it behave right.

Incidentally, more effective simulation of "backwards tape" tone will generally involve some timbral adjustment too. Normally, the initial attack of a note contains more harmonics, so a decent emulation of reverse tape would include some envelope-controlled filtering as well. You could do this within the design of the effect, or simply tack on an envelope controlled filter afterwards, set for minimal to modest modulation.

5/9/2000 4:26 PM
Mark Hammer	Interesting followup If you go to http://www.tonefrenzy.com/2/boss_dd5_reverse_mod.htm, you'll be able to hear a backwards tape simulation that is stunning. It involves a modded BOSS DD-5 (done by the designer at Way Huge). If you like backwards, you'll love this. I wish I knew how they did it. What this also means is that there is a third way to get bowed attack backwards tones: via digital delays.

5/9/2000 4:26 PM

Mark Hammer

Interesting followup

If you go to http://www.tonefrenzy.com/2/boss_dd5_reverse_mod.htm, you'll be able to hear a backwards tape simulation that is stunning. It involves a modded BOSS DD-5 (done by the designer at Way Huge). If you like backwards, you'll love this. I wish I knew how they did it. What this also means is that there is a third way to get bowed attack backwards tones: via digital delays.

5/9/2000 6:45 PM
Ry	I can't speak for the modded DD-5 you mentioned, but the theory for the Lexicon PCM-41 reverse tape simulation was to read the RAM addresses that contained the guitar signal out in a reverse order compared to how were written in. I designed a horribly complicated delay unit based on this theory for my EE senior design project 3 years ago. It almost worked, too...after some re-thinking in the last few months, I (along with my partner in crime) have deivsed a way to make it work very well (when we get back to working on it)... so many things to build, so many songs to record, so very little time. Ry

5/9/2000 6:45 PM

I can't speak for the modded DD-5 you mentioned,
but the theory for the Lexicon PCM-41 reverse
tape simulation was to read the RAM addresses
that contained the guitar signal out in a reverse
order compared to how were written in. I designed
a horribly complicated delay unit based on this
theory for my EE senior design project 3 years ago. It almost worked, too...after some re-thinking in the last few months, I (along with my partner in crime) have deivsed a way to make it work very well (when we get back to working on it)...

so many things to build, so many songs to record,
so very little time.

Ry

5/10/2000 3:54 AM
Mark Hammer	I have a schematic for a project in Practical Electronics from 15 years ago or so (called the "Poly-Whatsit") that could do exactly that. The notes at Tone Frenzy are a little too deliberately "hip" to be completely coherent or transparent (and this may be a function of the restricted information they were supplied with by the designer). My sense from reading it is that the effect involves an internal mod, and the use of an external feedback loop, from the physical output of the pedal (perhaps just the delay portion) to the physical input of the pedal. You really ought to give it a listen if you can. It's quite remarkable. I'm sure George Martin would have kept more hair over the years if this had been available in 1966.

5/10/2000 3:54 AM

Mark Hammer

I have a schematic for a project in Practical Electronics from 15 years ago or so (called the "Poly-Whatsit") that could do exactly that.

The notes at Tone Frenzy are a little too deliberately "hip" to be completely coherent or transparent (and this may be a function of the restricted information they were supplied with by the designer). My sense from reading it is that the effect involves an internal mod, and the use of an external feedback loop, from the physical output of the pedal (perhaps just the delay portion) to the physical input of the pedal. You really ought to give it a listen if you can. It's quite remarkable. I'm sure George Martin would have kept more hair over the years if this had been available in 1966.

5/10/2000 1:32 PM
Ry	That's amazing! I'm certain that he rewired the switch on the DD5 to start a counter that reverses the 'write' address to create the 'read' address. There would have to be, at minimum, a new counter that counts down from the address coming out of the 'write' counter. Nice! I'm interested in this "Poly-Whatsit" schematic. Is it scanned on the web anywhere? Ry

5/10/2000 4:02 PM
jon	Hi Guys, Thanx for the input. You're way over the top for me with this stuff. I recently built Kevin O' Connor's Wide Range Tremelo circuit from the Tonnes of Tone. While I prefer tube tremelos, this one is OK. What got me to thinking was: if I time the notes right to the trem rate, I can get a reasonable form of attack delay. I was thinking maybe there's a simple way to get rid of the continuous oscillation after the first pick attack, thereby getting the attack delay using a simple oscillator/modulator circuit? Jon

5/10/2000 4:02 PM

jon

Hi Guys,
Thanx for the input. You're way over the top for me with this stuff. I recently built Kevin O' Connor's Wide Range Tremelo circuit from the Tonnes of Tone. While I prefer tube tremelos, this one is OK. What got me to thinking was: if I time the notes right to the trem rate, I can get a reasonable form of attack delay. I was thinking maybe there's a simple way to get rid of the continuous oscillation after the first pick attack, thereby getting the attack delay using a simple oscillator/modulator circuit?
Jon

Page 1 of 2

Next>

Last Page>>