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Post subject: Someone please explain
Posted: Fri Oct 19, 2012 7:06 am
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I'm sure there are many members on this forum who could describe to me what the term "sag" means as it applies to rectifier tubes(in laymens terms). I'm having trouble understanding it. I get almost all the other terminology such as headroom, breakup, top end, etc. but "sag", I just cant wrap my head around it. :?
Thanks in advance.

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Post subject: Re: Someone please explain
Posted: Fri Oct 19, 2012 7:19 am
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Well ya see its what happens when ya get older :wink:

HA could not resist !

It is a condition of tube rectified amps, some rectifiers are more prone to it than others,
Example is 5AR4/GZ34 is more prone to "sag" than a 5U4GB
"sag" happens when an amp is hit hard and the rectifier isnt keeping up with the demand.

Thats about as technical as I can get :mrgreen:

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Post subject: Re: Someone please explain
Posted: Fri Oct 19, 2012 8:38 am
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" Example is 5AR4/GZ34 is more prone to "sag" than a 5U4GB. "

Blues, not quite. The GZ34 has less "sag" than a 5U4GB. Check the chart. The GZ34 has about 10VDC drop. And the 5U4GB is 50VDC drop. This is the "sag."

"Sag" is kinda like a breathing effect in the amp. Gives the tone life. Like singing. Sorta.


http://www.300guitars.com/articles/rect ... rop-chart/


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Post subject: Re: Someone please explain
Posted: Fri Oct 19, 2012 8:48 am
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Sag is super fun!! :wink:

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Post subject: Re: Someone please explain
Posted: Fri Oct 19, 2012 12:34 pm
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Sag is when a amp 'rectifier is slow , or can't to give the voltage / current needed ( to tubes , to be short ) when you play loud. So the voltage drop and tone change.

When you play loud , amps need more voltage / current.

Tube are slower and loose voltage more than Silicon rectifier.

Sag is like with your small car ,you want to pass another car and engine is not enough powerfull to respond as fast as you wish.


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Post subject: Re: Someone please explain
Posted: Fri Oct 19, 2012 3:00 pm
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To me "sag" helps = that Bluesy tone. Not, that solid-state rectification is always bad. But. most "vintage" moderate sized amps (5-40 watts) with that tone-to-die-for, have tube recitifers.

JMO. :D


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Post subject: Re: Someone please explain
Posted: Fri Oct 19, 2012 4:37 pm
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Thanks to all for your explanations. I think that last one was the one that finally allowed me to "visualize" sag.

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Post subject: Re: Someone please explain
Posted: Fri Oct 19, 2012 4:49 pm
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stratele52 wrote:
Sag is when a amp 'rectifier is slow , or can't to give the voltage / current needed ( to tubes , to be short ) when you play loud. So the voltage drop and tone change.

When you play loud , amps need more voltage / current.

Tube are slower and loose voltage more than Silicon rectifier.

Sag is like with your small car ,you want to pass another car and engine is not enough powerfull to respond as fast as you wish.


+1

Sag also contributes (greatly) to how a much the signal is compressed at the output stage. More sag = warmer, bluzier tone.

Arjay

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Post subject: Re: Someone please explain
Posted: Fri Oct 19, 2012 8:50 pm
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Got it bass ackwards OOPS ! :mrgreen:

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Post subject: Re: Someone please explain
Posted: Sat Oct 20, 2012 5:55 am
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BMW2002Ti wrote:
To me "sag" helps = that Bluesy tone. Not, that solid-state rectification is always bad. But. most "vintage" moderate sized amps (5-40 watts) with that tone-to-die-for, have tube recitifers.

JMO. :D


+10K...Steve you got this perfect and the reason I think I like the tone of the SR, Princeton, and Champ so much...I think the rectifier is directly related to the Best tones. I also think it is what's missing in some of the newer tube amps and why their tone is lacking.

T2

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Post subject: Re: Someone please explain
Posted: Sat Oct 20, 2012 7:29 am
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Good article on adding a "sag" resistor to a solid state rectifier power supply to simulate tube rectifier power supply sag:

http://www.justinholton.com/hotrod/sag.html

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