DBX 120

wiz1der · Oct 18, 2007

Had a search, but wondering if anyone has attempted this:

dee bee ecks 120

I know it can be done, depending on interest, or maybe it would be better to just hunt one down from a jamaican sound system??

I think i need one of these in my life....

SonsOfThunder · Oct 18, 2007

They can be bought used pretty cheeply. Peavey makes a similar piece, the Kosmos. Or Audio Control EpiCenter.

They all work basically the same I think.

BPF -> Square Wave Conversion -> Divide by 2 -> Integrate back to Sine -> Mix w/ original full range signal or Low passed signal.

The BPF is something like 80 to 200Hz.

HTH!
Charlie

clintrubber · Oct 19, 2007

Hmm, looks interesting - but haven't had hands on boxes like this...
do boxes like this sound 'real' (...) as in fuller + fatter - or more like octaver-pedals ? (more of an FX)

Despite using just little amounts of it I never could use octavers for adding some whoomph under a signal; it immediately made the 'oops, there's an octaver in the house'-bell ring.

So am curious to the result of 120-ish boxes; as it seems the circuit-principle of that 120XP is not unlike say the Boss OC-2.

I saw there are a lot of 120-somethings, saw various 'which-120 is the best' discussions around (fwiw, among others followed by recommendations for other brands as well)

Regards,

Peter

BTW, http://www.pat2pdf.org/patents/pat4182930.pdf

gyraf · Oct 19, 2007

Could we rename this thread into something readable?

See:

http://www.groupdiy.com/index.php?topic=19276

Jakob E.

jensenmann · Oct 19, 2007

I used it a lot for livesound.....well, reggae of course. It gave me always the fatter sound than all the other mixers at festivals had. Care has to be taken for indoor use because it attacks roommodes heavily.
For studio use it only makes sense if your main monitors go down to 20 Hz. Otherwise you can´t judge what you are doing. And this box goes all the way down, hehehe :grin:

clintrubber · Oct 19, 2007

[quote author="jensenmann"]I used it a lot for livesound.....well, reggae of course. It gave me always the fatter sound than all the other mixers at festivals had.[/quote]
And just curious, how about that box/schematic as above
for electric bass ? (in 'real time')

Bye,

Peter

jensenmann · Oct 19, 2007

Electric bass was what I´ve been using it for. To seperate kickdrum and bass I fattened the bassdrum in the 100Hz area with EQ while pushing bassguitar way lower with the 120XP. There were some bassguitars which didn´t work good with the 120. I remember a Warwick bass where the boombox always added the fifth, not the octave. That was pretty disturbing

clintrubber · Oct 19, 2007

[quote author="jensenmann"]Electric bass was what I´ve been using it for. To seperate kickdrum and bass I fattened the bassdrum in the 100Hz area with EQ while pushing bassguitar way lower with the 120XP. There were some bassguitars which didn´t work good with the 120. I remember a Warwick bass where the boombox always added the fifth, not the octave. That was pretty disturbing[/quote]
Good to hear it could be of use for elec bass :thumb:
Did you notice any 'octaver-FX taste' in the sound or was it like it could have been as deep ? (so without a processed- feel)

No worries w.r.t. the brand, no Warwicks here :wink:
Was that a low-B bass perhaps ? Just passive 4-stringers here.

Regards,

Peter

solder_city · Oct 19, 2007

is it useful?

ask any dj who was working during the vinyl era!

hell yeah, its useful!

jensenmann · Oct 19, 2007

Yes it was a low B bass but that wasn´t the reason. Other low B basses had no problems.
If not overused the 120 sounds natural, no Moog-overdubbed sound at all. I met two older (than me) engineers who told me that the dbx500 sounds better than the 120 but I never had the chance to check it since they are pretty rare.
If you´re seriously interested in checking the 120 out drop me a pm, I could send you mine for a few weeks.

SSLtech · Oct 19, 2007

[quote author="SonsOfThunder"]They all work basically the same I think.

BPF -> Square Wave Conversion -> ...[/quote]

Bzzzzt!

No square-wave conversion. That would generate too many harmonics, and they'd re-invade the spectrum at-or-around the original fundamental. It would also lose any dynamic information.

It's MUCH cleverer than that... and simpler, too!

they just use a zero-crossing detector and mute every alternate half-cycle. (which mis-tracks occasionally and randomly flips the polarity, but that's all part of the charm...)

That way, you get to retain dynamic information, as well as some other harmonic structural nuances.

The corners at the mute transitions are a little bit spikey, but the filtering removes that, and it's MUCH better than a square!

Keith

clintrubber · Oct 19, 2007

[quote author="SSLtech"]they just use a zero-crossing detector and mute every alternate half-cycle. (which mis-tracks occasionally and randomly flips the polarity, but that's all part of the charm...)[/quote]
Hmm, still sounds like the way the Boss OC-2 does it (OC-2 et all; for instance the old Pearl OC-7? is very alike... and so will a plastic $2 Uli B.-pedal be I guess).
The Boss flips the polarity at half frequency (and at one fourth for the 2 octave down).
Maybe the dBx does some smarter filtering, who knows.
I should look more at the waveforms in the patent though, maybe there's a bit more going on.

Regards,

Peter

clintrubber · Oct 19, 2007

[quote author="jensenmann"]Yes it was a low B bass but that wasn´t the reason. Other low B basses had no problems.[/quote]
Hmm, that's a bit puzzling. But OK, no low-B here, so all fine in that respect.

If not overused the 120 sounds natural, no Moog-overdubbed sound at all.

Good to hear!

If you´re seriously interested in checking the 120 out drop me a pm, I could send you mine for a few weeks.

That's a nice offer, will keep that in mind, thanks ! :thumb:
Let me start with having a relisten to some of those FX-pedals first again, since they seem to do this in a very alike fashon as the dBx-method.

Cheers !

Peter

wiz1der · Oct 19, 2007

[quote author="gyraf"]Could we rename this thread into something readable?

See:

http://www.groupdiy.com/index.php?topic=19276

Jakob E.[/quote]

Sorry Jakob, I've been here since forever, and thats how I've always seen it done,,, so I thought i was doing the right thing.. .... renamed.

gyraf · Oct 20, 2007

thanks! It makes searching much easier at a later stage.

..And for interesting stuff like this, if at all possible, always remember to email a backup copy to our email address - groupdiy at gmail com

:grin:

Jakob E.

bcarso · Oct 20, 2007

[quote author="SSLtech"]
they just use a zero-crossing detector and mute every alternate half-cycle.
Keith[/quote]

Could you elucidate? It's not quite clear to me from that description. Are you counting zero-crossings independent of the sign of the slope, or....?

CJ · Oct 20, 2007

There might be an Blackmer AES paper that walks you thru every stage of development by the inventor.

I will see what I can find...

JohnRoberts · Oct 20, 2007

I love all these one sentence explanations for how products work.. :roll:

I am not a fan of the PV Kosmos (or any of this genre) but it too is based on a patented technology.

JR

wiz1der · Oct 20, 2007

Could one of these possibly fit on a card small enough that will fit into a 900 series rack??

I rememebr there being talks of 900 series projects a couple years ago, but it never materialized. Good to see how big the 500 series format has goten though....

HMMMMM dbx 120 in a 900 rack size.....

StephenGiles · Oct 20, 2007

Have you seen this?

http://www.rolls.com/data/rp221man.pdf

DBX 120

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