Feedback Request on Bass Compression

[coldcraft]

Hey Y'all,

I'm working on a new multi-purpose compression/limiter design and I'm trying to narrow down the most useful features for a bassist. I'll try to list all the options here, please chime in with your thoughts.

First off, my design is based on an FET attenuator. It features full-wave rectification of the audio signal for the control signal, and it is completely separate (parallel) from the audio path.

The design can be feed-forward or feedback-based. Feedforward is sometimes considered more of a limiter, affecting the initial attack more, whereas feedback-based compression lends its self to a more squeezed/funky sound with a clear attack. Preferences? Both?

Other than the standard Sustain/Threshold & Volume controls, I have the additional options of,

Attack
Release
Ratio
Clean Blend

My design also features a frequency response control that shapes how the low end triggers the compression. At higher compression settings, this can help to even out the response across the instrument range, between high and low. It filters out some bass just before the rectifier, and does not affect the bandwidth of the audio path.

My last question is regarding EQ. I've design this to be pretty flat, but I'm wondering if a 2-band HiFi EQ should be included to make this a full-fledged compression/limiter preamp.

Thanks in advance for your thoughts and comments.

[colcifer]

A passive lpf might be something to include. Maybe 500/22 for use with stiffer settings.

[bongomania]

Here's my take on the order of importance of features:

1) Wide range of input/threshold response. I.e. every instrument, from the lowest-output to the highest, has equal access to the full range of threshold response. A high-output instrument should be able to get minimal/gentle compression, and a low-output instrument should be able to get maximal/heavy compression. High-output instruments should not clip any part of the circuit, and low-output ones should not suffer a noise penalty from a hissy gain stage.

2) An LED meter to indicate when the signal is over the threshold.

If a comp just has those two features/qualities, I'm generally happy. The rest is gravy.

3) Ratio
4) Attack

Way, way, way distant tie for 5th place: make-up gain, blend, release, tone/EQ, overdrive, and everything else.

If you're going to add an EQ, to make it a "preamp", there are some extra considerations:
--What if a user wants it to be able to drive a power amp with a high (like 1.5V) input sensitivity?
--What if a user wants it to have a DI output?
--What if a user wants to be able to boost the mids?
--What if a user wants to have any/all of those features while bypassing the compressor function?
I'm not saying you should go whole-hog with all of those things, I'm just saying these are common user expectations for a "preamp" that makers often don't take into account.

Thanks for asking us! I look forward to seeing what you come up with.

[ninepoundjammer]

Ratio for sure.

Attack and release I don't need. Certainly don't need a clean blend.

Frequency response control sounds interesting. If that works well enough, then the eq probably isn't needed. I've never used a two band eq that I can say I'd want on a compressor for any reason (might be different if you had more than 2 bands). I use a dual band comp with a variable crossover, and that is very nice. Not quite sure how your freq response control would compare to that.

[coldcraft]

thanks for the great responses so far guys.

the frequency response control doesn't affect the EQ of the audio signal at all. What it does is control the bass driving the rectifier and control signal. At least on guitar, the low strings have a ton more power than the higher strings and so this really evens out the compression across the range of the guitar. I'm not yet sure how well it will work with a bass.

[bongomania]

I can tell you about that. It's a mixed bag, really. A common feature of rack comps is a setting that makes the gain controller react less to the bass frequencies; this means the bass gets less squashed, for a fuller, deeper sound--but if those big low notes are causing unwanted clipping later in the chain, then compressing them less doesn't help. OTOH, when the low end gets compressed more than the highs, you get a bright chimey/sustainy sound that's cool, but it loses a lot of the "heft" in the lows.

Basically it's a neat feature to have, but you want to be able to switch it off.

I use a dual-band comp too, and the "magic formula" for me is a high ratio and high threshold on the lows, and a low ratio and medium-low threshold on the mids and highs.

[coldcraft]

thanks for those insights. I have it set up as a knob actually, so you can get varying degrees of sensitivity. I found it useful for electric and acoustic guitar so far.

[cavemanbass]

my top five:

1. multi-segment gain reduction meter (even better if it can be switched to show I / O levels)

2. threshold and output levels to get the desired amount of compression and be able to match levels with my other gear

3. setting for slow attack and fast release - could be switches, pots, or the only settings for the pedal - I like to keep the initial transient (thus the slow attack setting)

4. getting more esoteric, I've found hard knee / soft knee options to be useful but not essential - either one can work for me

5. I always use a moderate ratio, between 2:1 and 5:1 and don't ever change once it's set; so for me as long as the ratio is in that range I wouldn't need a ratio setting

Someone recently pointed out that while there are many optical compressor stomp boxes , nobody has made a stompbox version of the 1176. Might be a way to make your new product stand out.

[ryansalmond]

Originally Posted by coldcraft

Hey Y'all,

I'm working on a new multi-purpose compression/limiter design and I'm trying to narrow down the most useful features for a bassist. I'll try to list all the options here, please chime in with your thoughts.

Awesome. This kind of approach is great to see. I applaud you!

Originally Posted by coldcraft

The design can be feed-forward or feedback-based. Feedforward is sometimes considered more of a limiter, affecting the initial attack more, whereas feedback-based compression lends its self to a more squeezed/funky sound with a clear attack. Preferences? Both?

Both!

Originally Posted by coldcraft

Other than the standard Sustain/Threshold & Volume controls, I have the additional options of,

Attack
Release
Ratio
Clean Blend

Ratio is a necessity, I think. I personally find no use for a clean blend and prefer a compressor without one.

Originally Posted by coldcraft

My design also features a frequency response control that shapes how the low end triggers the compression. At higher compression settings, this can help to even out the response across the instrument range, between high and low. It filters out some bass just before the rectifier, and does not affect the bandwidth of the audio path.

Sounds cool.

Originally Posted by coldcraft

My last question is regarding EQ. I've design this to be pretty flat, but I'm wondering if a 2-band HiFi EQ should be included to make this a full-fledged compression/limiter preamp.

I can only speak for myself of course, but I don't like the pre-packaged combo approach, and I think a lot of pedal people will agree with me. The appeal of pedals, to me, is the modularity. I like that I can get a pedal to perform each function to my sound, and if something better comes along, replace just that one while keeping all the others the same. Many pedal companies take a 'swiss army knife' approach however, aiming to please the more novice pedal crowd (not that it only pleases them) whose main concern is not having 'too many pedals.' EQ is the most often added-on secondary feature of pedals I think it's safe to say, and so it's easy to end up with a rig that has EQ on the bass, EQ on one pedal or more, and EQ on the amp. In fact, come to think of it, many amps have EQ happen twice- once in a 3 or 4 band style, and then again with 5-10 bands of graphic EQ. Trying to adjust such a rig can be a real pain.

Personally I'd rather have EQ (as well as every other function in my signal chain) happen once. Thanks for bearing with me as I got a little long winded there!

By the way, I've checked out your website before. You make GORGEOUS looking enclosures. My oh my.

[coldcraft]

thank you everyone for your comments! and thanks for the compliments ryansalmond.

I think I failed to mention, this is going to be a medium-sized stomp box, so a big gauge or VU meter is out of the scope of this, but I think I could manage having an LED where the brightness corresponds to the gain reduction.

I agree with you guys about dropping the EQ. I don't really want this to be an all in one solution, I just wasn't sure if that was desired or not. What I really want is a super tweakable, but still simple compressor in a compact package.

A new question, and mostly because I haven't yet had time to experiment. When there's controls for attack, release and threshold... can people notice the different in a ratio control, or is it more of a subtle thing?

[bongomania]

??? Ratio is a totally different thing.

[coldcraft]

I'm very aware that it is different. I'm wondering if many everyday users get much use out of a fully variable ratio or if it's a more subtle control.

[bongomania]

Most pedals just have a knob for "more" or "less" compression. Most users have no idea what this knob actually does on any given pedal. It could be ratio, it could be threshold, it could be gain boost into a fixed threshold...

IMO ratio is not subtle at all. But again, most pedal users would not have any way to know one way or the other.

[coldcraft]

My current design controls the amount of compression by attenuating a signal just before the rectifier/threshold. I need to experiment with a ratio control to see how they interact.

[walker rosewood]

Most pedals just have a knob for "more" or "less" compression. Most users have no idea what this knob actually does on any given pedal. It could be ratio, it could be threshold, it could be gain boost into a fixed threshold...

with that in mind... I would appreciate a pedal that had better labeling, or at least a manual that gives such details. I'd love to know if the ratio went from 1:1 to infinity:1, etc. Or how many db is the make up gain, or exactly how many milliseconds is the attack, hold, release.

[wiseguyst]

I really love the simplicity of my BBE Optostomp, but am intrigued by the new MXR just because of the LED meter and size of footprint. I prefer compression on the attack of the note especially when switching to a pick. The less knobs the better in my opinion. Not all of us are like Bongo and understand all of the ins and outs of compressors.

[Swift713]

I like the ratio knob on my Maxon CP-9 pro + as well as the threshold. I can see where a meter might be preferable but the single LED works fine for me. I know when the threshold is crossed and I can adjust by ear from there. It's very easy to set up for different instruments or qualities of compression. I have 0 experience with adjustable attack and release times.

[coldcraft]

Thanks for all your feedback friends.

Through your comments and some experimenting, I've settled on a couple ideas. First off, I'm dropping the EQ. I want this to be simply a full-featured compressor. It sounds as if bassists don't really need/want clean blend, and I'm still evaluating if that is something acoustic guitarists might want in their signal chain.

Controls,
Threshold
Ratio
Attack
Release
Volume

Features,
LED Threshold Indicator
Limiter/Compressor Toggle (Feedforward/Feedback)
18v Internally Doubled Power Supply and/or Rail-to-Rail OpAmps for clean headroom.

[ninepoundjammer]

Originally Posted by coldcraft

the frequency response control doesn't affect the EQ of the audio signal at all. What it does is control the bass driving the rectifier and control signal. At least on guitar, the low strings have a ton more power than the higher strings and so this really evens out the compression across the range of the guitar. I'm not yet sure how well it will work with a bass.

Ok, but if you get less compression in the low end, then you get more perceived loudness or whatever in the bass, so close enough to an eq from a practical perspective.

I find dual band to be pretty critical for me, but it sounds like your frequency response control might give me the results I'm looking for in a single band, which is cool.

I agree with the consensus that a proper eq is not the way to go.

My current thinking is the fewer knobs the better for a pedal, as long as I can get the results I'm looking for. Visual indicators like LED's however are great. I think ratio is important, but on the comps I've tried I haven't been able to discern much difference with them. I suppose their range just wasn't big enough because I know what to listen for. Knobs bad LED's good

[ninepoundjammer]

Originally Posted by bongomania

I use a dual-band comp too, and the "magic formula" for me is a high ratio and high threshold on the lows, and a low ratio and medium-low threshold on the mids and highs.

I run a higher ratio on my highs to keep things a bit tamed, but otherwise I'm right there with you.