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Discussion in 'Effects [BG]' started by Smokeyharrisun, Jul 25, 2019.
Yep, power is a different equation. Thanks... I'll correct my post.
I feel like this is appropriate
It's a shame that the original Mythbusters are no longer on the air to test this for sure
Nope. Not possible. All the aliens are in Area 51 and trolling Talkbass and Facebook inbetween their "tests".
I know!! That was an awesome show.
Most pedal compressors use circuits that vary their ratio depending on the input signal strength. It's also relative to where we're momentarily at in the attack-release cycle. For those, when a ratio is published, it's often an averaged number based on a set test tone level. Using steady test tones can give stable results, but they don't reflect the time-based wide peak swings of our instrument. Because the ratio is such a moving target, most of those manufacturers (including me) don't bother to nail down that spec.
It gets further complicated by the fact that those circuits vary their threshold with an input gain control, and the threshold is soft, so that some compression is being applied well before the maximum ratio is reached. So "what is the threshold?" well it may start at a certain dBu level, but you may not hear it working until the signal is well over the threshold. And "what is the ratio?" well it depends on where we're at re the threshold, which changes constantly during play.
I have the equipment to test for the range of threshold response and the range of ratios, but there's not much reward for doing that work. Like Frank said, it can cause as much harm as good, because customers often make up their minds (and declare an opinion) based on specs alone. But I can tell you that for all the pedals that claim e.g. 20:1 or infinity:1 ratio, many are not effective as peak limiters, due to slow transient response. And a pedal with a low ratio can still be a moderately effective limiter if the attack is fast and the threshold is low (input is high). So a ratio number would not be as useful to me as knowing the general behavior of the specific comp, and adjusting it to the specific context.
I wonder if he's asking about a Cali76 Compact Bass?
You forgot to mention that multi-band compression can have different ratio slopes within the different freq bands and that where the freq bands crossover the ratios are a mix of ratios dependent upon the signals with the largest amplitude of the signals within those freq bands of compression if there is any soft-knee with the ratio vs threshold... but that all depends on whether it is RMS or Peak detection in the threshold detector ckt or a combo of both and whether those detectors are full-wave or half-wave... which can be hit or miss on capturing a spike if half-wave detection is used. j/k
Cyrus you do have a talent for explaining the un-explainable! Good job...
Alternatively, this could be a new Talkbass game. Points for correctly guessing the pedal with the least clues!
If it’s the BOSS BC-1x, just buy it. It’s great.
@bongomania , @boomertech
Somewhat OT, but tangentially related:
How do you in general communicate to the consumer how and possibly why your compressors (or other pedals) do what they do? @scubaduba 's work provides an incredible resource in this regard. And your commenting on this forum is invaluable, too. Sound seems such an ineffable thing. Is it just buy and try?
Whatever do you like and want, check it out before.
I usually suggest to people that are new with compression to research what they might be looking for in a compressor and then ask any questions they might have. It is always better if someone has tried our pedals and then asks questions, otherwise describing features or parameters sometimes doesn't translate well with what the person is after.
You put it on the bench with test equipment hooked to it. I did the same with the Diamond comp a while back and posted the results on TB.
I knew if anyone would have the answer, you would, Frank! Well maybe this maker isn't as good as you
Thanks Jimmy, but you are giving me too much credit. I am obsessed with numbers, especially when you have many musicians playing a comp that have wildly opposing views on how the comp performs. Then the numbers make more sense to me for understanding "why" they have the opinions that they have.
There are builders that will calculate every circuit parameter and there are others that will tweak an existing design by just swapping parts until they are happy. Both methods work well, but the person that swaps parts until they found something they are after isn't usually the person that is interested in making data measurements.
My point is measuring criteria can vary, measuring devices have variances but the real differences are the input material tested will give varying results and manufacturers do wanky stuff when nobody is watching to load their results, I know as a witness. A pure sine 1K +3db will hit one way, switch it to square another, but a plucked guitar, strummed guitar chord, plucked bass string, slapped bass string or playback music will all hit the compressor differently because of the signal content even with the same db level.
One of the weirder threads in TalkBass history of late, and that's saying something.
The two main measurements used will be peak or RMS for AC signals. Most DVM's use RMS measurements when measuring AC signals. Very expensive DVM's will have a very wide freq bandwidth, where a Walmart DVM is only fairly accurate for a narrower (general purpose) bandwidth. So the test equipment should be properly selected for the particular task.
What you are describing with measurements varying with the signal shape is because a peak detector is used. A sine wave with the same RMS dB value of a square wave, will have a larger peak amplitude. A compressors peak detector will see the two signals as different levels... even tho their RMS values are exactly the same. A RMS detector is awful at detecting impulse spikes, but it does very well at keeping the average sound levels in check. Peak detectors will be much better at capturing signal spikes, but they can cause the comp to over compensate/compress the signal level because of those quick spikes. Some comps use a blend of both types of detection to cover dynamic signal changes better, so you get the benefits of both.
If you use a RMS type of dB meter then it will accurately measure the output to the input gain reduction in RMS terms. A -6dB measurement with an RMS meter is still 1/2 of the input signal, whereas a -6dB measurement with a peak meter is still 1/2 of the input signal level in peak terms.