Adventures in Fractal's Dual Rectifiers

[MirrorProfiles]

Just remeasured and verified.

Red channel

Gain=240k
Bass=1M Ω (I think)
Mid=23k
Treble=214k
Presence=100k
Master=190k (same for orange channel master)
Global Master=240k

 

[SwirlyMaple]

Those values are consistent with an early '90s Recto. The MV was changed to 1M later on.

Did I just hear "Early 90s Recto Red coming soon to the Axe-FX?"

 

[SwirlyMaple]

There's your answer. Some Rectos had 150K pots, most had 1M. With a 150K pot (yours is slightly out of tolerance at 190K) you get a LOT less bass out of the tone stack.

Here's a graph of the difference between a 1M and 150K MV pot:

View attachment 15604

Blue trace is 150K pot.

 

[MirrorProfiles]

There's your answer. Some Rectos had 150K pots, most had 1M. With a 150K pot (yours is slightly out of tolerance at 190K) you get a LOT less bass out of the tone stack.

Here's a graph of the difference between a 1M and 150K MV pot:

View attachment 15604

Blue trace is 150K pot.

Definitely checks out with my experience of this amp vs later recto’s where they get very bassy quickly and you have to keep the bass down low to avoid the flub. I often use this without a boost and it’s absolutely fine.

Interestingly both Orange and Red master volume pots read the same value - either they’ve drifted the same amount or Mesa found 2 that had somewhat similar values when building it.

While it was out the box again, got a few more photos:

output transformer code 562 105 EIA 606 516:

Power transformer (hard to read because the engraving is very light and the dust obscures it a lot). Think the code is EIA 606 422

Older style outputs:

attached power cable/parallel loop:

Transformer codes line up exactly to this (at least from what I can make out). Can just about see 6114 on my power transformer

 

[deathbyguitar]

So if I've been reading this thread correctly, it seems like the models in the Fractal are accurate compared to the amps they have on hand and any discrepancies are due to pot tolerances and different pot values depending on the revision?

Do I have that correct? If so, seems like "Why your amp doesn't sound like our amp" all over again.

 

[dean701]

What's the impedance curve for 5 pounds of dust?
Dammit, clean that amp.

 

[SwirlyMaple]

Just remeasured and verified.

Red channel

Gain=240k
Bass=1M Ω (I think)
Mid=23k
Treble=214k
Presence=100k
Master=190k (same for orange channel master)
Global Master=240k

Probably a stupid question as I've not poked around much inside of tube amps, but is there anything else in circuit with the pots that would invalidate a reading unless you disconnect them first?

 

[MirrorProfiles]

What's the impedance curve for 5 pounds of dust?
Dammit, clean that amp.

ha that dust is pretty attached to the transformers annoyingly. Maybe a bit of elbow grease will help but that’s for another day…

 

[JiveTurkey]

ha that dust is pretty attached to the transformers annoyingly. Maybe a bit of elbow grease will help but that’s for another day…

Don't wipe off the mojo

 

[dean701]

ha that dust is pretty attached to the transformers annoyingly. Maybe a bit of elbow grease will help but that’s for another day…

I'm just teasing you. I'm a clean freak. Except for my car, dirt is the glue that holds it together

 

[MirrorProfiles]

So if I've been reading this thread correctly, it seems like the models in the Fractal are accurate compared to the amps they have on hand and any discrepancies are due to pot tolerances and different pot values depending on the revision?

Do I have that correct? If so, seems like "Why your amp doesn't sound like our amp" all over again.

Essentially yes, besides Cliff’s amp having a different taper pot to what the model has.

But the point of the thread wasn’t so much “why doesn’t my amp sound like the Fractal model”, it was more a dive into how to best tweak the advanced parameters to get them sounding similar. Can’t speak for others, but I’ve certainly learned a lot, both about Rectifiers and Fractals modelling so I think it’s been pretty worthwhile.

 

[Orvillain]

So if I've been reading this thread correctly, it seems like the models in the Fractal are accurate compared to the amps they have on hand and any discrepancies are due to pot tolerances and different pot values depending on the revision?

Do I have that correct? If so, seems like "Why your amp doesn't sound like our amp" all over again.

I think that might be a little uncharitable given how interesting some of this has been. But yes.. more or less.

 

[MirrorProfiles]

I'm just teasing you. I'm a clean freak. Except for the dirt on my car, dirt is the glue that holds it together

the amps that stink get the most cleaning attention. My 1992 Mesa OS cab still has a bit of a smell that won’t budge. I had a Peavey Triple XXX that I probably wouldn’t have sold if it didn’t smell like a kebab shop.

 

[dean701]

Can’t speak for others, but I’ve certainly learned a lot, both about Rectifiers and Fractals modelling so I think it’s been pretty worthwhile.

I learned a lot. Even got a warm fuzzy feeling that caused me to order an axefx3. The fm9 is going to be upset.

 

[MTB1973]

 

[la szum]

So if I've been reading this thread correctly, it seems like the models in the Fractal are accurate compared to the amps they have on hand and any discrepancies are due to pot tolerances and different pot values depending on the revision?

Do I have that correct? If so, seems like "Why your amp doesn't sound like our amp" all over again.

Yup, there is no THE Amp. It's all very deep and dripping with Zen.

 

[Orvillain]

Yup, there is no THE Amp. It's all very deep and dripping with Zen.

Change yer pants boyo.

 

[la szum]

Essentially yes, besides Cliff’s amp having a different taper pot to what the model has.

But the point of the thread wasn’t so much “why doesn’t my amp sound like the Fractal model”, it was more a dive into how to best tweak the advanced parameters to get them sounding similar. Can’t speak for others, but I’ve certainly learned a lot, both about Rectifiers and Fractals modelling so I think it’s been pretty worthwhile.

Why did so many Cats go into the studio with multiple variations of the same Amp Model to
try and find "the one?" And then add in different Cabs, how we are micing them, and with what
Mics?

It's all really a lot of variables, and kind of makes exactness and precision a flawed outlook from
the jump. Mostly.

 

[OrganicZed]

It might be a cool topic for @2112 to make a video covering some of the tweaks discussed in this thread.

 

[JiveTurkey]

Pimp My Recto