IIC+, GEQ and coupling capacitor

[VanHalen]

Hi,

Found in the Mesa Mark V manual :

"... In our endless comparisons of many original II C+’s - both EQ and non-EQ samples - alongside this golden reference, we discovered that I wasn’t just Tone-dreaming. There was actually a difference between the EQ model and those non-EQ models. It all came down to a coupling capacitor at the end of the EQ circuit that feeds the driver. In the EQ model, it was a great big cap that let a lot of sub-low pass, slowing down the sound and making it fatter. In my amp - a non-EQ version - this cap was smaller and didn’t let as much sub-low through - which speeds up the sound and makes everything tighter and more urgent. There it was, a simple part…but it made all the difference in the time domain..."


As IIC+ models in the Axe have a GEQ, I assume the coupling capacitor is the big one.

BUT

If I remember correctly the photograph of IIC+ combo Cliff acquired, it didn't had any GEQ.


So my questions are :

1/ Do the models of the IIC+ in the Axe match a IIC+ with a GEQ (smaller coupling capacitor, thighter) or a IIC+ with no GEQ (big cap, fatter) ?

2/ Is there a parameter in the Axe that enables me to change the value of this coupling capacitor (and have the best of both worlds) ?


Sorry if this has already been discussed ?

 

[Wolfenstein98k]

Watching thread out of interest

 

[yek]

Documented here, including the story about the difference between the GEQ and non-GEQ versions (p 264):

https://dl.dropboxusercontent.com/u/10338746/Yeks_Guide_to_the_Fractal_Audio_Amp_Models.pdf

The modeled IIC+ is one without GEQ.
There's still a GEQ in the model because every amp model has it.

 

[VanHalen]

Documented here, including the story about the difference between the GEQ and non-GEQ versions (p 264):

https://dl.dropboxusercontent.com/u/10338746/Yeks_Guide_to_the_Fractal_Audio_Amp_Models.pdf

The modeled IIC+ is one without GEQ.
There's still a GEQ in the model because every amp model has it.

Thanks for your answer Yek but this doesn't really answer my question.

In fact for the IIC+ models I think the smaller cap was considered (not sure) but what about the IIC++ ?

Having a parameter to adjust the value of the coupling capacitor to control the tightness/fatness of a the IIC+ model (or even any models) would be cool.

It's disappointing to think I'm using a IIC+ model (for high gain sounds with classic V shape on the GEQ) that has not the fatness I'm looking for because the smaller cap was modeled.

I'm sure there's a solution.

 

[Wolfenstein98k]

I wouldn't lose sleep over a single capacitor. There's multiple ways to add fatness.

Why not take the time to learn some of these? You might get a better result than an accident present in the old amp... and certainly more tailored result.

 

[shredi knight]

One thing that won't help get the fatness is the Depth control (page 2 of the Amp block), as it is non functioning on all the Mesa Boogie Mark series amp models. I always chuckle when I try a patch off of the AxeChange that uses one of those amp sims and I see that the Depth control is turned up to any degree, knowing that that parameter does absolutely nothing on those models.


It been that way for quite awhile (I think since Cliff G3'd the amps way back when), but I don't think a lot of people know that.

 

[electronpirate]

I would like to hear the difference in between the various values of this 'coupling capacitor'.

We do have various ways to 'make everything tighter and more *urgent*'.

 

[Brownmatthall]

One thing that won't help get the fatness is the Depth control (page 2 of the Amp block), as it is non functioning on all the Mesa Boogie Mark series amp models. I always chuckle when I try a patch off of the AxeChange that uses one of those amp sims and I see that the Depth control is turned up to any degree, knowing that that parameter does absolutely nothing on those models.


It been that way for quite awhile (I think since Cliff G3'd the amps way back when), but I don't think a lot of people know that.

http://forum.fractalaudio.com/threads/6-00.121232/#post-1444137

 

[VanHalen]

There's multiple ways to add fatness.

Why not take the time to learn some of these?

We do have various ways to 'make everything tighter and more *urgent*'.

OK guys, gimme your recipes

 

[dpeterson]

the way I tighten up stuff, is lower sag, turn up power amp hardness, and raise lowcut on amp model.

 

[VanHalen]

One thing that won't help get the fatness is the Depth control (page 2 of the Amp block), as it is non functioning on all the Mesa Boogie Mark series amp models. I always chuckle when I try a patch off of the AxeChange that uses one of those amp sims and I see that the Depth control is turned up to any degree, knowing that that parameter does absolutely nothing on those models.

I've just tried and you're right.

 

[VanHalen]

I would like to hear the difference in between the various values of this 'coupling capacitor'.

Me too.

The Mark IV has the big coupling capacitor but the Mark IV models don't seem to sound fatter than the IIC+ models. Does this mean that the IIC+ models are made with the big capacitor ? Maybe the comparison doesn't make any sense

 

[Ed DeGenaro]

Thanks for your answer Yek but this doesn't really answer my question.

In fact for the IIC+ models I think the smaller cap was considered (not sure) but what about the IIC++ ?

Having a parameter to adjust the value of the coupling capacitor to control the tightness/fatness of a the IIC+ model (or even any models) would be cool.

It's disappointing to think I'm using a IIC+ model (for high gain sounds with classic V shape on the GEQ) that has not the fatness I'm looking for because the smaller cap was modeled.

I'm sure there's a solution.

This is where the craziness of the internet comes in.
If you read what Doug West (and he should know) said about it is that he always preferred the immediacy of non EQ version.

Regardless a coupling cap is there to block high voltage from the gain stage to the plate... And acts as a filter. Hence more bass/mud on a Mesa with a .47 uF coupling cap as compared to .22 on a JMP.

If I take a look at most suggested settings on a Mesa I'd say it lets enough bass through (and very well might have had the bigger cap in the amp that Cliff modelled).
You start adding this you might add plate, cathode resistor and cathode bypass cap value then.

 

[firmani99]

Me too.

The Mark IV has the big coupling capacitor but the Mark IV models don't seem to sound fatter than the IIC+ models. Does this mean that the IIC+ models are made with the big capacitor ? Maybe the comparison doesn't make any sense

I think that the Mark IV does sound fatter than the IIC+ model.