Reccomend a bass compressor

[Kipper4]

Those vactrols are blooming expensive I might go take a lookie see at bits box mate and HR is

http://homerecording.com/bbs/forum.php

I tried the thumb tonight it sounds sweet but I'm not sure it's going to be what my friend wants . I will show him the thumb anyway and look into ldr led combos advice appreciated though if you have some tips .

[gritz]

Those vactrols are blooming expensive I might go take a lookie see at bits box mate and HR is
Homerecording.com/bbs/
I tried the thumb tonight it sounds sweet but I'm not sure it's going to be what my friend wants . I will show him the thumb anyway and look into ldr led combos advice appreciated though if you have some tips .

Are you sure your buddy is absolutely sure about what he's looking for? I'd be tempted to pack him off to a well stocked music shop so he can try some fx and report back - it might help to narrow down your search from "poking about in the dark" to "I need to clone a Boss Satsuma CS2000 RX+++++1" thingy.

Vactrols expensive? Yes and no. The Silonex NSL-32SR3 is £2.22 (plus the dreaded VAT) from Farnell:

http://uk.farnell.com/jsp/search/productdetail.jsp?sku=3692218&CMP=i-bf9f-00001000

I can't buy a pint of beer for that round here! It's also a drop in the bucket compared to the cost of the other stuff that makes up a pedal (enclosure, a couple of decent jacks, good quality pots, knobs, switch and all the other gubbins). It's also stupidly fast, If you don't need fast then home brew vactrols are ok.

If it's any consolation our bass player tried any number of compressor pedals and turned his nose up at all of them - they were either not transparent enough, or did nowt at all (which pretty much sums up the majoity of compressor pedals for me too).

Compressing bass is hard - the detector part of the circuit needs to smooth the signal effectively (to prevent distortion), but without slowing down the response. I think someone's already mentioned compression with a wet / dry mix. It's also called parallel or New York compression and is a good way of reclaiming transparency from a compressor.

Still, perhaps he'll be happy with the Engineer's Thumb, or he may at least be able to say "can you make it more this / less that"...

Hope it goes OK. 

[Mustachio]

The flatline I suggested is an optical comp that uses a vactrol or a roll your own ldr/led . You can actually get away with building it with a vtl5c7 instead of the 3 , change a resistor I think it was 220K to a 470K theres info on the forum about it and change the input cap to something like 1uf .

It's an easy build and really seems to be what bass players want. Its not a dyna/ross type squeeze its just more transparent gives that long sustain and a soft knee to the attack. At least with the few changes made to it I did its a wonderful comp. Bass players seem to usually want transparent sound with more thump/low-mid gut and longer sustain and I think the flatline does it well and simple. I would suggest trying one of the ldr's from tayda with a lightly sanded led. And if anything socket the limiting resistor to the led to adjust till its perfect. And of course shrink wrap it. I think when it comes to rolling your own it helps to spread the light out. If you look at the viewing angle on newer high bright leds its narrow and intense at the center point. I built a mutron 3 and used an led with a Fresnel lens that had a lower forward voltage and let me use a limiting resistor that was very close to the original and sounded great!

I don't mean to sound like I'm pushing the ticket on the flatline I'm just saying it really sounds like something to consider. 3 bass players I've given this to love em.

here's a simple vero version



I drew up a pcb for it in pcbexpress if you want that let me know ill post it. And I think there's a few pcb images in the layouts gallery . I believe madbean offers a pcb for it as well.

[pappasmurfsharem]

I built the Demeter Compulator using the layout from tagboard effects

It works great for my basses and guitars

What I really like is it limits my Rickenbacker 4003. That thing has so much output. It's twice as loud as my jazz bass. Run it through the Compulator and I get all the squish and the same volume as my jazz.  Keeps the sound guys happy

[moosapotamus]

+1 on the Demeter Compulator. Awesome compressor. I've had one on my pedalboard for years. But I don't know if it's really the best option for "thump". I think it's main strength is transparency. Even with the comp knob cranked for massive gain reduction, you can barely hear it working. Instead of "thump", I would use the words "smooth" and "transparent" to describe it's sound.

~ Charlie

[Kipper4]

I did look at the Demeter and yes it has plenty of sqaush but as Charlie said i'm not sure it has that thump thing.
The flatline looks intresting too i'm gonna go review it now.
I think i'm going to need something with either a gate or severe adjustment on the attack (lots of time) and plenty of squish too.

[pappasmurfsharem]

I did look at the Demeter and yes it has plenty of sqaush but as Charlie said i'm not sure it has that thump thing.
The flatline looks intresting too i'm gonna go review it now.
I think i'm going to need something with either a gate or severe adjustment on the attack (lots of time) and plenty of squish too.

That's why you don't use max compression. :-)

I do just because it keeps the dynamic feel but stays a constant volume.  Even during my slap parts.

[merlinb]

I would usually suggest Merlin's 'engineers thumb' but I'm not sure how well it will cope with a potentially very hot signal (OTAs don't clip very nicely).

If you use the input protection diodes then OTA clipping isn't a problem. Another advantage of the ET is that it is inherently tweakable to any threshold, ratio attack or decay that you might want, and because it is feedforward you don't get overcompression with long attack times.

The main difference between a bass and a guitar compressor is not the 'type' of compression, but that the bass compressor side chain has some form of tone control in it, so you can adjust the range of frequencies that trigger compression. The ET has a spare OTA, so if you used that to make two in the same box then you could arrange one to compress the bass, the other the treble, and mix the outputs. I could see that making an exceptional bass compressor...

[Kipper4]

Whhoooaaa
OTA's?
ET? isnt he the little green fella with the big finger who say Phone home or something.
Please explain this jargon so as i might follow.

I love the fact that Merlin B has answered a post of mine. Drops to knees and worships you Waynes world style.

Great compressor Merlin. Thanks for sharing it.

Can i ask how it would be modded in a fashion to make the kind of thump i think my friend wants described above.

Rich

[pappasmurfsharem]

Whhoooaaa
OTA's?
ET? isnt he the little green fella with the big finger who say Phone home or something.
Please explain this jargon so as i might follow.

I love the fact that Merlin B has answered a post of mine. Drops to knees and worships you Waynes world style.

Great compressor Merlin. Thanks for sharing it.

Can i ask how it would be modded in a fashion to make the kind of thump i think my friend wants described above.

Rich

I'm not sure really what he means by thump.

What he describes sound like just an attack then mute and that you just do with your hands. Most compressors with a quick attack with hit hard fast then he just should me with his hand per the norm.

Is there a recording that he associates this "thump"  to?

[merlinb]

Whhoooaaa
OTA's?
ET?
Please explain this jargon so as i might follow.

OTA = operational transconductance amplifier. The LM13700 has two of them, but only one is used in the engineer's thumb. Therefore, you could build two ETs around one 13700, each voiced differently.
ET = Engineer's Thumb!  

Can i ask how it would be modded in a fashion to make the kind of thump i think my friend wants described above.

I don't really know what he means by thump, either. Could be separate bass and treble compression like I mentioned, could be something else. Could be almost anything...

[deadastronaut]

^ that would be nice for bass and guitar....just what i need as i play both..

but not at the same time..

[samhay]

I would usually suggest Merlin's 'engineers thumb' but I'm not sure how well it will cope with a potentially very hot signal (OTAs don't clip very nicely).

If you use the input protection diodes then OTA clipping isn't a problem. Another advantage of the ET is that it is inherently tweakable to any threshold, ratio attack or decay that you might want, and because it is feedforward you don't get overcompression with long attack times.

Fair point about the clipping diodes. However, to play devil's advocate: aren't you just trading objectionable (OTA) clipping for less objectionable (diode) clipping?
This problem is not limited to the ET, but in this case the LM13700 can cope with a +/-18V supply, so perhaps a better solution would be more headroom using a charge pump to create a bipolar supply of perhaps +/-9V.

The main difference between a bass and a guitar compressor is not the 'type' of compression, but that the bass compressor side chain has some form of tone control in it, so you can adjust the range of frequencies that trigger compression. The ET has a spare OTA, so if you used that to make two in the same box then you could arrange one to compress the bass, the other the treble, and mix the outputs. I could see that making an exceptional bass compressor...

I've been meaning to build an ET for a while. The main thing that has stopped me from doing so is the dissatisfaction of leaving half the LM13700 unused. I was thinking of doing a two-stage feed-forward/feed-back compressor, but I like this idea a lot. It might work nicely on guitar too if you set the cut-off frequency quite high to treat the trebles differently.

[merlinb]

Fair point about the clipping diodes. However, to play devil's advocate: aren't you just trading objectionable (OTA) clipping for less objectionable (diode) clipping?

Well, yes. You sound like you disapprove of this, for some reason? If you choose the diodes correctly then you can get it to clip just before the OTA would have, so you needn't lose any significant headroom.

perhaps a better solution would be more headroom using a charge pump to create a bipolar supply of perhaps +/-9V.

Unfortunately that won't help in this case because the OTA is in a feedback loop, so when it clips the gain reverts to max and everything goes ape. Hence the clipping diodes.

Not all problems can be solved with a charge pump...

[moosapotamus]

The main difference between a bass and a guitar compressor is not the 'type' of compression, but that the bass compressor side chain has some form of tone control in it, so you can adjust the range of frequencies that trigger compression. The ET has a spare OTA, so if you used that to make two in the same box then you could arrange one to compress the bass, the other the treble, and mix the outputs. I could see that making an exceptional bass compressor...

Me too! Awesome idea!

So, would you simply add the treble boost mod to one of them, or would you filter somehow closer to the input of one?

~ Charlie

[samhay]

Fair point about the clipping diodes. However, to play devil's advocate: aren't you just trading objectionable (OTA) clipping for less objectionable (diode) clipping?

Well, yes. You sound like you disapprove of this, for some reason? If you choose the diodes correctly then you can get it to clip just before the OTA would have, so you needn't lose any significant headroom.

perhaps a better solution would be more headroom using a charge pump to create a bipolar supply of perhaps +/-9V.

Unfortunately that won't help in this case because the OTA is in a feedback loop, so when it clips the gain reverts to max and everything goes ape. Hence the clipping diodes.

Not all problems can be solved with a charge pump...

Don't get me wrong, I like your ET and I think the clipping diodes are a good choice in this application. However, IF one wanted to get max headroom with a stompbox compressor, then this might not be the way to go.

I might be missing someting about the supply voltage/cliiping issue, but isn't that getting quite unlikely if both the op-amps and OTA are running at +/- 9V?
Anyway, if you can hit the rails of the OTA on a +/-9V supply then I don't see why you couldn't use a pair of 6 or 7V Zeners in place of the LEDs. I guess either way, we may need to scale down the current going into the OTA from the precision current source?

Edit - or at least the current per V out of the envelope detector.

[samhay]

The main difference between a bass and a guitar compressor is not the 'type' of compression, but that the bass compressor side chain has some form of tone control in it, so you can adjust the range of frequencies that trigger compression. The ET has a spare OTA, so if you used that to make two in the same box then you could arrange one to compress the bass, the other the treble, and mix the outputs. I could see that making an exceptional bass compressor...

Me too! Awesome idea!

So, would you simply add the treble boost mod to one of them, or would you filter somehow closer to the input of one?

~ Charlie

Not sure abotu Merlin, but I was thinking more along the lines of using a low-pass and high-pass filter to split your signal prior to any compression and then running two compressors (bass and treble) in parallel before mixing at the output.

[merlinb]

However, IF one wanted to get max headroom with a stompbox compressor, then this might not be the way to go.

True. If you want extraordinary amounts of headroom from an ordinary stompbox, then optical compression is the way to go.
It's a moot point in this case, as the ET has enough headroom to handle active bass pickups already.

I might be missing someting about the supply voltage/clipping issue, but isn't that getting quite unlikely if both the op-amps and OTA are running at +/- 9V?

The trouble is that it is not so much the supply rails that limit an OTA, but the input signal to it, which starts to distort around 150mVpp. So if you want the circuit as a whole to handle larger signals than it already does, then you have to scale the divider that feeds the input of the OTA, and scale down the current per V of the envelope detector (as you pointed out), so you end up sacrificing threshold. In other words, it would become a line-level compressor rather than an instrument level compressor. Making a device that can do both with equal ease requires a good deal more expense, and is probably beyond most peoples needs anyway.

[samhay]

OK - thanks Merlin. Seems like a typical case of me over-thinking something again.
Kipper - sorry for the thread derail. Have you made any progess?

[Kipper4]

Nope no problem guys. its all intresting.
I have to wait for my buddy to return home. he's working away right now.
As soon as i hear anything i'll ressurect the thread.
It has made me think how it would be good to have an all in 1 box for bass for me though.
inc
preamp
compressor
distortion with blend function
dual output (maybe one of them with compatable with line level, for direct to FOH board when gigging)
switching for Active/passive bass or dual input

Is this even a possible?