Drive Block In Parallel Causes Phase Issues

muleskinner

muleskinner

Inspired
Hi,

I've finally figured out why I can't get the bass tone I'm after.

I need a drive block running in parallel with a clean tone. The 'mix' knob on the drive block doesn't work as (as has been discussed) it filters the signal removing a lot of the low end which is hopeless for bass.

I can get a nice driven tone but as soon as I switch the clean tone back in to bring the bottom end back everything sounds like a phasey mush to me. On analysing the recorded waveform in Logic I can clearly see that the drive block is shifting the phase of the signal (and/or introducing latency, whatever the correct terminology) therefore causing phase cancellation issues with the clean tone. Probably a lot more obvious on bass than on guitar.

Is there any way round this? I tried adding a bypassed drive block to the clean tone but that doesn't seem to make any difference, and I can't get a 'true bypassed' signal out of an active drive block.

Maybe I could add some latency to the clean tone with a digital delay to try and get them to match? Seems like using a sledgehammer to crack a nut though...

cheers
 
muleskinner said:
Maybe I could add some latency to the clean tone with a digital delay to try and get them to match? Seems like using a sledgehammer to crack a nut though...
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Not sure how that will sound. Seems like an odd and very cumbersome solution to me. Why does the phasing appear when using the Drive block mixed with clean? Is this normal? and isn't there a simpler solution?
 
javajunkie said:
Delay block time is not fine enough. Either use the delay in the cab block or place a compressor in line (1:1 ratio) and use the look ahead time.
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Thanks - good tip on the compressor!

Is the latency always the same whatever drive type is used in the drive block - and if so do you know what it is by any chance to save me messing about with a lot of trial and error? ;)
 
perhaps you could add another drive block to the clean chain...maybe the FET boost...which would leave the tone uncoloured
 
Bodde said:
Not sure how that will sound. Seems like an odd and very cumbersome solution to me. Why does the phasing appear when using the Drive block mixed with clean? Is this normal? and isn't there a simpler solution?
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I think it is normal - it's introducing latency to the signal, thus screwing with the phase of parallel signals where there's no such latency. I find it really obvious on bass - totally kills the tone.

I guess ideally we want latency compensation for each column in the grid but I imagine that would be a ballache to implement.

Simeon - FET boost is another good idea, I will try that. I was trying the tape dist but that has a massive affect on the tone even when drive is at 0%. I just want the simplest and lowest-cpu solution.
 
muleskinner said:
I think it is normal - it's introducing latency to the signal, thus screwing with the phase of parallel signals where there's no such latency.
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Is this phasing also the case for other effect blocks? never experienced such a thing.
Also never really liked the clean/drive blend thing you get when running a drive in parallel. Same thing applies to the blend knob that many bass overdrive pedals have these days. It always sounds like you hear two instruments and not 'one voice'. That's never sounds right for me. So I would rather find an drive model for bass that you can run in series as Simeon suggested.
 
Bodde said:
Is this phasing also the case for other effect blocks? never experienced such a thing.
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I have no idea which blocks cause latency and which don't but it would be interesting to know. I'd imagine the effect is a lot less apparent on modulation fx as you expect some kind of 'phaseiness' with these anyway.
Bodde said:
Also never really liked the clean/drive blend thing you get when running a drive in parallel. Same thing applies to the blend knob that many bass overdrive pedals have these days. It always sounds like you hear two instruments and not 'one voice'. That's never sounds right for me. So I would rather find an drive model for bass that you can run in series as Simeon suggested.
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I respectfully disagree ;)

My favourite drive pedal for bass (Barker Assmaster) uses a blend control and IMO they're fundamental for not mushing up the bottom end - unless the pedal itself has some other multiband-type tricks going on of course.

The bass big muff also uses some kind of parallel circuit I believe.

cheers
 
if you are in mono try this:
use two amps: amp1 -> cab1, amp2 -> cab2
- amp1 is set driven [from the amp rather than a drive pedal]
- amp2 is clean
- cab1 is a 4x10 that's punchy and bright
- cab2 is a 1x15 that is deep and thick [ingore the hi end]

cab1 low cut: set this to around 550Hz [or higher] so that amp1 / cab1 provides the driven mids and highs
cab2 high cut: set this to around 350Hz to 450Hz so that amp2 / cab2 provide a very clean, very tight and deep low end
the cab level controls will essentially act like a 2-band EQ where cab1 is your mids/ hi's, and cab2 is your lows
 
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I was going to suggest using two separate amps//cabs running one clean and one w/ some drive or dirt like clarky did above..
 
Even adding a FET or NULL clipping drive block could still result in some phase differences since the blocks do not have linear phase (most filters, analog or digital don't), and differences in the blocks (especially due to EQ settings) will result in different phase responses.
 
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rsf1977_again said:
If the drive block has variable latency. It would be nice to display the time offset within it or have develop an "offset" block that you could use and select another existing block and mirror its latency.
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Yeah. Except it's not linear phase, in other words the latency is different for different frequencies and it would be fairly complicated to have one block compute its phase response and report that to another block. I'd say I'm splitting hairs, but the OP's issue is due to phase differences, so it's probably a valid point.
 
jdosher said:
I'd say I'm splitting hairs, but the OP's issue is due to phase differences, so it's probably a valid point.
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My issue is to do with phase problems caused by latency, one parallel signal is 'out of phase' with the other due to the latency introduced by the drive block - simple as that.

I am NOT talking about phasing issues caused by blending a filtered signal with a unfiltered one. As you say, there's really not much that can be done about this unless Cliff were to introduce linear phase filters.

I haven't had much time this week but will be trying to sort the problem tomorrow using some of the suggestions posted above. Thanks.
 
Compressor block. Look ahead 0.69ms. Mix 0%.

That seems to sort it - compressor block seems to delay the dry signal by the same amount as the lookahead value so no need for any other shenanigans.

Amazing what a difference 0.69ms makes - haven't tried all the drive types but the ones I did try all appear to have the same latency.

Even the 'null' clipping type in the drive block affects the tone so there must be some filtering going on even when levels are at zero.

cheers all
 
muleskinner said:
Compressor block. Look ahead 0.69ms. Mix 0%.

That seems to sort it - compressor block seems to delay the dry signal by the same amount as the lookahead value so no need for any other shenanigans.

Amazing what a difference 0.69ms makes - haven't tried all the drive types but the ones I did try all appear to have the same latency.

Even the 'null' clipping type in the drive block affects the tone so there must be some filtering going on even when levels are at zero.

cheers all
Click to expand...

Yes, the look ahead is just a micro delay so the compressor can react as quickly as possible. The detector detects in real time but the signal is delayed slightly to give the compressor a chance to react to very fast transients.
 
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