Author Topic: ROSS / DYNA compressor (AURORA Compressor) Attack pot change sound  (Read 554 times)


Hi Guys!
I have finished a new Project. It’s a Ross / Dyna compressor: Aurora compressor by Aion. This is the layout I have two problems: The Attack pot and the Treble switch . I tested the Attack pot before mounting it and it worked properly and it's an alpha pt 150kC, but when I turn up-down this pot at PBC, the sound is the same when I play the guitar, does not vary. The level and Sustain pots work perfect. The other Little problema is the Treble switch. I mounted in the PCB a SPDT center off and CX2 360pF; C9 180pF and CX3 821pF capacitors. When I turn down the switch the sound is little dark/normal, in the middle position bright sound and in the upper position darkest sound, is it correct?? I dobble check the PCB components and I don´t found any problem. Could you help me. Thank you for your time!

1.What does it do, not do, and sound like? – The attack pot does not modify sound when turned up-down.
2.Name of the circuit = Aurora dyna comp by Aion
3.Source of the circuit (URL of schematic or project) =

4.Any modifications to the circuit? Dyna comp version as documented. Trimmer 250k,  Attack pot 150kC, Treble switch

5.Any parts substitutions? No.

6.Positive ground to negative ground conversion? No.

8. Voltage at the circuit board end of the red battery lead = 9.06
    Voltage at the circuit board end of the black battery lead = 0

See confirmed/remeasured values below

C = 7.28
B = 2.21
E = 1.78

C= 6.84
B= 2.78
E= 22.2

C = 8.89
B = 0
E = 0

C= 8.89
B= 0
E= 0

C= 9.06
B= 8.89
E= 8.31

P1= 0
P2= 4.41
P3= 4.41
P4= 0
P5= 0.71
P6= 2.74
P7= 9.06
P8= 0




« Last Edit: January 14, 2018, 12:00:04 PM by Pringles1 »

Mark Hammer

Re: ROSS / DYNA compressor (AURORA Compressor) Problems
« Reply #1 on: January 13, 2018, 11:36:48 AM »
So-called Attack controls on compressors rarely, if ever, produce an audible change in sound, since the impact will always depend on how fast one is picking.  The control alters how quickly gain gets brought back up to maximum.  If gain-recovery is slow, any note picked shortly after the first one will not be as loud, because the gain is still on its way to coming back up.  f course, the benefit of a slow gain-recovery is that notes seem to sustain longer, in a manner analogous to slowly bringing up the mixer volume control as a song starts to fade out.

The control gets called "Attack", because when the gain is recovered quickly, the next note, and ones after that, are heard at normal volume when you pick them, such that the initial pick attack is more audible.

So, unless you have done something particularly wrong, your Attack control is behaving normally.  You're just expecting too much.
« Last Edit: January 13, 2018, 06:26:17 PM by Mark Hammer »


Re: ROSS / DYNA compressor (AURORA Compressor) Problems
« Reply #2 on: January 13, 2018, 05:37:37 PM »
Nice looking build.  And good to see a Comp thread that isn't about a fake 3080.  Inspired by Dr. Hammer above, I added an "Attack" (Release) 3-way switch to my Dynacomp.  I do notice a slight boost in treble and volume when I switch to one of the faster-than-stock settings.  I guess that's just the nature of a signal that is, on average, less attenuated.  But that's with a switch, where the change is immediate, I might not notice it when turning a pot.  But if you can sweep your pot from one extreme to the other quickly, or have someone do that for you while you play, you might be able to detect that subtle difference.

Mark Hammer

Re: ROSS / DYNA compressor (AURORA Compressor) Problems
« Reply #3 on: January 13, 2018, 06:29:51 PM »
That's why I thought EHX took the sensible approach by including a simple 3-position switch in their Soul Preacher.  My sense is that most folks who own a compressor with a continuous rotary control will generally set it to either the 7:00 or 5:00 positions, simply because they have a hard time hearing any difference between those two extremes.


Re: ROSS / DYNA compressor (AURORA Compressor) Attacks pot sound changes!
« Reply #4 on: January 14, 2018, 11:59:05 AM »
Thank you for yours comments, time and help. I have tested again the pedal with fast changes of the Attack pot between 7 and 5 and I feel a beautiful discrete change in the definition of the notes, subtle, but it exists. I'm going to change the title of the topic to guide other colleagues.

Mark Hammer

Re: ROSS / DYNA compressor (AURORA Compressor) Attack pot change sound
« Reply #5 on: January 14, 2018, 01:15:36 PM »
My pleasure.  When more complex rackmount compressors include attack and release controls, the assumption underneath that is that they will be necessary for processing, and adjusting to, sound sources which are VERY different in their envelope characteristics (e.g., flute vs snare drum, crash cymbal vs. piano).  That does not mean that a guitar cannot be different enough at times to justify an Attack (gain recovery) control.  But I think one has to understand what the control is doing to be able to know what potential impact such adjustments may have.  The expectations have to be realistic.  Unfortunately, most of our experience with control knobs on pedals has to do with VERY obvious changes: speed, volume, distortion, tone, etc.  Some controls have an effect, but one so subtle and situationally-dependent, that players will often ask "Is this thing on?  Is it broken".  :icon_lol:


Re: ROSS / DYNA compressor (AURORA Compressor) Attack pot change sound
« Reply #6 on: January 14, 2018, 01:25:47 PM »
Most noticeable attack control is when playing bass with different techniques - slap, pick or fingered. Not so obvious with guitar.
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Re: ROSS / DYNA compressor (AURORA Compressor) Attack pot change sound
« Reply #7 on: January 16, 2018, 10:29:29 PM »
The "attack" pot is really only a recovery time adjustment. Set up your rig so there is a little background noise and adjust the "attack" pot fully either way. Now strike a hard and quickly mute the note. Then listen how long it takes for the hiss or background noise to rise back up after being compressed.  Now adjust the "attack" pot the opposite way and notice how the rise time is either slower or faster. I think attack pot is a misnomer.
« Last Edit: January 16, 2018, 10:32:52 PM by rosssurf »


Re: ROSS / DYNA compressor (AURORA Compressor) Attack pot change sound
« Reply #8 on: January 16, 2018, 11:15:04 PM »
> I think attack pot is a misnomer.

If anybody reads the linked documentation, they will find:

"Attack is technically a “Release” control, but it’s called Attack in both the Boss CS-2 and Keeley Compressor so the name stuck. It sets the amount of time after the input signal falls below the threshold before the compressor “resets” and is ready to compress again."