Battery sag/rectifier sag?

[Artie]

I just read a thread that mentioned the "battery sag" thing, relative to an effects pedal. I've seen this mentioned before and it reminded me that Jack Orman has a circuit that simulates that function. My lil ole technical brain doesn't get this. Can someone explain the benefit of a dying battery to tone please?

And, if you feel talkative, rectifier sag also. (In a tube amp.)

Thanks.
Artie

 

[Rich_S]

Re: Battery sag/rectifier sag?

There's no such thing as a perfect voltage source. Any voltage source can be modeled as a "perfect" voltage with a series resistance. As the current drawn from the source increases, the voltage drop across this series resistance increases, having the outward effect of causing the terminal voltage (to the load) to sag.

Old-fashioned (or simply old, worn-out) batteries exhibit higher series resistance, and therefore sag more with load than do new-fangled, fresh alkaline batteries.

Similarly, tube rectifiers exhibit a voltage drop that increases with load. So, as you play louder, the amp draws more current, and the B+ sags. Solid-state recifiers exhibit a fairly constant voltage drop regardless of load, up until you fry them. So, SS recifiers don't sag appreciably. A cheap and dirty way of simulating tube-recto sag with SS-recto reliabilty is to stick a power resistor ~100 ohms in series with the amps B+ supply.

 

[STRATDELUXER97]

Re: Battery sag/rectifier sag?

I just read a thread that mentioned the "battery sag" thing, relative to an effects pedal. I've seen this mentioned before and it reminded me that Jack Orman has a circuit that simulates that function. My lil ole technical brain doesn't get this. Can someone explain the benefit of a dying battery to tone please?

And, if you feel talkative, rectifier sag also. (In a tube amp.)

Thanks.
Artie

It's hard to explain really,but it is something that is true...Basically it's just the effect working differently due to an "overall" lowering of the working voltages inside the pedal...I'm not Eric Johnson,but I too have experimented with Alkaline vs carbon batteries and it's effects on effects! The carbon battery offers a larger or higher output voltage and sometimes I feel like the carbon batteries make things warmer or sweeter...I trust my ears on these findings though!

I find in a Tube Screamer that the pedal is smoother and sweeter sounding when the voltage is at or around 9 volts...At higher voltages the same pedal is a bit harsher,not as smooth,and has slightly more overall output and is tighter sounding...Almost like the differences I hear between ss and tube rectifiers in the same amp,but not as extreme...I had a Dual Rec Mesa Tremoverb and I use this as my reference...

 

[Artie]

Re: Battery sag/rectifier sag?

This is interesting. Would this affect be different if I just dialed the voltage down to 6 - 8 volts?

 

[STRATDELUXER97]

Re: Battery sag/rectifier sag?

This is interesting. Would this affect be different if I just dialed the voltage down to 6 - 8 volts?

Below 9 volts things start getting bad overall in the tone and feel dept.,but you can experiment?

 

[Artie]

Re: Battery sag/rectifier sag?

Rich's explanation was good from a technical point of view, but I think I knew that part. I meant more in terms of how it "improved" tone. Why is it desirable?

 

[Artie]

Re: Battery sag/rectifier sag?

It's hard to explain really,but it is something that is true...Basically it's just the effect working differently due to an "overall" lowering of the working voltages inside the pedal...

Cool. I may have to build Jack's circuit, and play with this.

 

[Vasshu the humanoid typhoon]

Re: Battery sag/rectifier sag?

Well Thomas (my productionchief)and me have been playing with a voltage regulator for the plexi, for those who wanted more swamp than glass

 

[STRATDELUXER97]

Re: Battery sag/rectifier sag?

Rich's explanation was good from a technical point of view, but I think I knew that part. I meant more in terms of how it "improved" tone. Why is it desirable?

Rich's explanation is excellent for us techie nerd guys! Yep...:laugh2:

 

[kmcguitars]

Re: Battery sag/rectifier sag?

O.K. here's the not so technicial explaintion. According to Producer Tom Dowd. He claims that while a session guy in Mussel Shoals,Duane Allman use to collect dying 9v batteries. He would put them in his fuzz device with it off,And then crank his Twin. The dying battery created for lack of a better word (A Buffer between the Guitar and amp. I imagine this way he could crank the amp and get cranked tone without blowing everyone over.