Flapping / distortion from rig combinations

[bigjimmyc]

Hi all. Please save my brain from exploding with this issue. 
 

I’m experiencing an unpleasant noise in the lower register. I’m calling it flapping or distortion but you could call it farting.  It happens at medium volume and flat eq. 
 

In trying to isolate the problem I’ve eliminated the (passive) instrument and there’s nothing in the signal chain in front of the amp. 

I have 3 amps (traynor all valve, Orange OB-1 class A/B and Ashdown class-D) and 3 cabs (Ampeg 4x10, Barefaced Compact, GK 1x15). 

Here‘s the head-scratcher: With the Traynor and any cab, no flapping. With Orange or Ashdown and any cab, it’s there. 
 

I got the Orange amp looked at by an Orange-approved tech. No problem. 
 

What am I missing? 
 

Cheers for any help.
 

PS. Gig Saturday so I’ll be lugging the big iron to the pub 😖

[Downunderwonder]

Farting is an excess of low frequency energy sent to a cab.

 

Some amps are better than others at filtering. Some amps have overall much less power. I suspect the Traynor might tick both boxes.

 

A highpass filter aka HPF is very useful for nipping farting while maintaining a solid bottom end.

[bigjimmyc]

11 hours ago, Downunderwonder said:

Farting is an excess of low frequency energy sent to a cab.

 

Some amps are better than others at filtering. Some amps have overall much less power. I suspect the Traynor might tick both boxes.

 

A highpass filter aka HPF is very useful for nipping farting while maintaining a solid bottom end.

I follow your logic here, but in reality the Traynor is delivering a lot more power and low end than the others. It doesn’t make sense that a credible amp like the ob-1 can’t push the same signal to the same cabs without making them fart, even at lower amplitude & eq. 

[Downunderwonder]

13 minutes ago, bigjimmyc said:

I follow your logic here, but in reality the Traynor is delivering a lot more power and low end than the others. It doesn’t make sense that a credible amp like the ob-1 can’t push the same signal to the same cabs without making them fart, even at lower amplitude & eq. 

The cabs told a different story!!!!

 

If it's happening at  very low volumes it could be your incoming signal is too hot and what you are hearing is plain distortion.

 

Still, it doesn't take much 40hz to give many cabs the heebie jeebies.

 

One test you could make is to take the fx out loop from the Traynor and put it into the fx return of one of the others. Any amp that is a tube amp will need a cab hooked up so it doesn't fry.

[Dan Dare]

If it doesn't happen with the more powerful amp, that would suggest clipping to me. If you are boosting the lows especially, the amp could simply be running out of steam. The Traynor, being all valve and with a meaty power supply, can simply deliver more sustained current than the other two.

[Twincam]

So other than one amp.

All the other amps do this and with any cab. 

 

Has this just started to happen?

 

Have you checked its not a bass or lead issue! 

Because I have repaired amps for  myself and others to find its a lead. Doh!.... 

In 2 cases was an issue with the instrument itself. Doh! Again lol. 

 

Also have you tried moving the cabs. Sometimes noises can come from a different place. But you could swear it's coming from the cab. 

[Bill Fitzmaurice]

8 hours ago, Dan Dare said:

If it doesn't happen with the more powerful amp, that would suggest clipping to me. If you are boosting the lows especially, the amp could simply be running out of steam. The Traynor, being all valve and with a meaty power supply, can simply deliver more sustained current than the other two.

Knowing what model Traynor would help, but it's certainly possible. Another consideration is that the natural compression of the valve amp is the difference. That compression is what gave rise to the valve watts versus SS watts nonsense, which gave rise to the even more nonsensical TC watts.

Edited February 18, 2022 by Bill Fitzmaurice

[Downunderwonder]

Did you try backing off the input gain on the 'farting' amps?

[Lozz196]

20 minutes ago, Downunderwonder said:

Did you try backing off the input gain on the 'farting' amps?

That’s what I was thinking, similar happened to me using a GK MB500 a few years back, instead of pushed into breakup it sounded like the speaker was being slammed.

[agedhorse]

A couple of things to try...

 

Does it make this noise with either the 410 or the 115?

 

What are the cabinet impedances?

 

What are the amp's minimum allowable load impedances?

 

Are you SURE your cabinets haven't been modified or repaired incorrectly?

 

Different amp types have different protection circuits, some can cause the noise that you are describing.

[Dan Dare]

15 hours ago, Bill Fitzmaurice said:

Knowing what model Traynor would help, but it's certainly possible. Another consideration is that the natural compression of the valve amp is the difference. That compression is what gave rise to the valve watts versus SS watts nonsense, which gave rise to the even more nonsensical TC watts.

 

Sound advice (pardon the pun) from Bill as usual. I would also suggest not pushing the extreme low end. It makes little difference to the sound in the room and trying to get your rig to do the job of a subwoofer is a great way to soak up amplifier power and possibly do damage to your gear.

 

Very few cabs can reproduce 40hz cleanly and at volume and you need serious power to drive those that can. In practice, sensible levels of boost at 80-100hz is as low as you need to go.

[Bill Fitzmaurice]

If his Traynor is a Fender copy (that's how they started off back in the 60s) the passive EQ can't give much bass boost, while significant high passing is built in.

[bigjimmyc]

It’s a yba-200. 
 

I have tried backing off the gain on the other amps. Makes no difference. 
 

All 3 cabs are 8 ohms. 

[Chienmortbb]

On 17/02/2022 at 19:21, Downunderwonder said:

Farting is an excess of low frequency energy sent to a cab.

 

Some amps are better than others at filtering. Some amps have overall much less power. I suspect the Traynor might tick both boxes.

 

A highpass filter aka HPF is very useful for nipping farting while maintaining a solid bottom end.

Correct.

[Downunderwonder]

1 hour ago, bigjimmyc said:

gain

Input gain or output 'gain'? Big distinction.

[Lfalex v1.1]

Maybe it's the various amps' Damping Factors being wildly different.

 

Power makes the drivers move. 

A higher damping factor stops them more swiftly once the signal has stopped. 

 

A combination of higher power and greater damping factor should yield better driver control. 

 

I've had good experiences using HPFs, too.

No point in amplifying frequencies your poor old cab can't produce. Gives you more headroom for further up the frequency range, too.

[Dan Dare]

52 minutes ago, Chienmortbb said:

Correct.

 

Not always. Amplifier clipping causes a similar effect. It effectively means the cab is sent a square wave, which sounds very nasty indeed and will not do your drive units any good.

[Bill Fitzmaurice]

1 hour ago, Lfalex v1.1 said:

Maybe it's the various amps' Damping Factors being wildly different.

Power makes the drivers move. 

A higher damping factor stops them more swiftly once the signal has stopped.

That's a straw that an oddiophile or amp salesman might grasp, but unless you're running 50 meter or longer speaker cables damping factor is a non-factor. Besides, the damping factor of valve amps being much lower than SS it wouldn't explain the OPs situation. However, while his YBA-200 amp doesn't have Fender/Marshall circuitry it does have the same style of passive tone controls, which along with natural compression and high passing leaves me to believe that's the difference. It's not without good reason that heavy iron valve amps remain the standard for tone, if you can manage to lift them, or even better have roadies to do it for you.

Edited February 19, 2022 by Bill Fitzmaurice

[Bill Fitzmaurice]

1 hour ago, Dan Dare said:

 Amplifier clipping causes a similar effect. It effectively means the cab is sent a square wave

Not exactly. Clipping doesn't send a square wave, no more than a pristine signal sends a sine wave. In all cases what's sent to the speaker is a complex wave form. What differs when the signal is clipped is that there's a lot of midrange and high frequency harmonic content present that's not in the original signal. With bass that can sound nasty, especially if you have tweeters. With guitar it's the Holy Grail.

[Dan Dare]

33 minutes ago, Bill Fitzmaurice said:

Not exactly. Clipping doesn't send a square wave, no more than a pristine signal sends a sine wave.

 

I see. Thanks Bill. I thought that, when an amplifier fails to deliver sufficient power, the peaks and troughs are cut from the signal, as in the illustration. Not exactly a square wave, but approaching one. I gather it's rather more complex from what you say. Certainly doesn't do drive units many favours.

 

[Bill Fitzmaurice]

That's what happens to a sine wave, but music doesn't consist of sine waves. With music content what happens is that whether it's an amp, a stomp box or a speaker there comes a point where there's not enough rail voltage and/or driver excursion to go any louder in the low frequencies, so they don't get louder with additional signal applied. The midrange and high frequencies do get louder, and that changes the tone. When you do that using a Les Paul through an AC30 and Greenbacks that tonal change is for the better. When it's a PBass through an SS amp and tweeters it's like nails on a chalkboard. This is why you shouldn't use tweeters if you employ distortion, and why AC30s don't have tweeters at all.

[Downunderwonder]

1 hour ago, Dan Dare said:

Certainly doesn't do drive units many favours.

 

Tweeters get the heebie jeebies from clipping.

 

Woofers don't mind unless the overall signal gets them too hot aka overpowering/heating, not farting.

 

Jumping on a distortion pedal doesn't cause bass speakers any problems unless you are at the bleeding edge already with the clean tone.

 

Squarewaves are not squares.

[agedhorse]

21 hours ago, Dan Dare said:

 

I see. Thanks Bill. I thought that, when an amplifier fails to deliver sufficient power, the peaks and troughs are cut from the signal, as in the illustration. Not exactly a square wave, but approaching one. I gather it's rather more complex from what you say. Certainly doesn't do drive units many favours.

 

 

That's a (very) far cry from a square wave.  

 

On a sine wave (a fundamental with no harmonics) it looks more "spectacular" than it is, but on a complex (real world bass) signal, the signal is built up of varying amplitude sine waves comprised of the fundamental and its many harmonics. Because the amplitude varies by a large amount between component signal elements (which is what makes up the envelope of the composite signal), clipping affects only some of the signal.

[Phil Starr]

On 19/02/2022 at 20:38, Bill Fitzmaurice said:

 However, while his YBA-200 amp doesn't have Fender/Marshall circuitry it does have the same style of passive tone controls, which along with natural compression and high passing leaves me to believe that's the difference. It's not without good reason that heavy iron valve amps remain the standard for tone, if you can manage to lift them, or even better have roadies to do it for you.

Whilst it is almost impossible for us to know what is going wrong at a distance and without more details I think Bill has probably nailed your issue and you need to eliminate this first of all.

 

Your Traynor is lower powered than the other amps, has no bass boost and intrinsic to it's design it a lot of the bass frequencies filtered out. (Forget it sounding louder and bassier for a moment)

 

Your other amps can drive higher powers at lower frequencies into your speakers and that is the classic cause of speakers 'farting out'. Of course we can't hear it so there is a possibility it is something other than the speakers.

 

The thing is to understand how your tone controls work. Your Orange for example boasts +/- 15db of bass control and 'flat' is probably at 12 o'clock, turning the control to 6db of boost will deliver four times the power to your poor speakers (and demand it of your amplifiers output stage. The passive controls in the Traynor can't boost the bass, they only adjust it relative to the mids and treble. Everything full up is the nearest to flat it will do. It's a system that worked for many years and it's kind of intuitive to use because it isn't unlike the way our brains perceive sound. What we hear as 'bassy' is where the bass part of the spectrum is louder relative to the upper ranges. Most of what we hear as bass is upper bass low mids anyway. The really deep speaker flapping frequencies we are nearly deaf to and the valve amp sidesteps this issue by leaving them out and giving the speaker an easy ride.

 

Try using a bit/ a lot of bass cut on your solid state amps and then seeing if the speaker flapping goes away. If so then you are just pushing them too hard. To restore your tone you might need to trim your mids and tops and/or buy an HPF but at least you will know where the problem lies. Our analogue brains weren't really made for the digital world