ODS' Clarification

Phostenix

Phostenix

Power User
So, based on the wiki here:

Amp: all models - Axe-Fx II Wiki

Am I correct that:

ODS-100 Clean is an HRM clean channel
ODS-100 Mid is an HRM OD channel with Mid Boost engaged
ODS-100 Lead is an HRM OD channel with none of the option switches engaged
ODS-100 Lead 2 is a non-HRM OD channel with the tone stack bypassed
ODS-100 Lead 3 is a non-HRM OD channel with the tone stack in
 
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Also, I did a bit of research on the ODS & it sounds like the "Ratio" control in the OD channel on the real amp allows you to mix the OD channel and the clean channel. Am I understanding that correctly? If so, would we need 2 amp blocks in parallel (ODS-100 Clean & one of the ODS-100 Lead channels) to accurately reproduce the Dumble overdrive sound?
 
From an interview:

"Ratio adjusts how much of the overdrive circuit's signals is fed back into the preamp circuit"
 
yek said:
From an interview:

"Ratio adjusts how much of the overdrive circuit's signals is fed back into the preamp circuit"
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Fed back into the clean preamp circuit? As in, the clean channel is always on and when you switch in the OD channel, the OD gets added in?
 
There is no "OD channel", it's a pair of extra gain stages.

If you look at the schematic of an early ODS, it's very very very (did I say "very") similar to a Boogie Mark II. One difference is that there is feedback from the plate of one of the triodes back into its own grid. It's done through a large (5M, in the early amp) resistor. Sort of local negative feedback.

I suspect the control in question varies the value of that resistor.
 
AdmiralB said:
If you look at the schematic of an early ODS, it's very very very (did I say "very") similar to a Boogie Mark II.
Click to expand...

That explains why I was thinking last night how much it sounded like an early Boogie. Very (old) Carlos Santana-ish. I just happen to really like that tone. :)
 
FractalAudio said:
"Ratio" is simply the Master Volume for the overdrive channel. It allows you to adjust the relative volume of the OD channel.
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So, LEVEL on the amp is the gain control for the OD gain stages and RATIO is the level control after the OD gain stages?
 
Phostenix said:
That explains why I was thinking last night how much it sounded like an early Boogie. Very (old) Carlos Santana-ish. I just happen to really like that tone. :)
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This made me remember an interview I read with Santana a few years ago after he started using Dumble amps. He was talking about using Boogies and about how hard they had to work with them in the studio to get the sound he liked to get with them. He said when he got his Dumble(s) (don't remember any details about what Dumble he got) suddenly the sound he wanted was instantly and easily available. Kind of interesting that it took him so long to get to Dumbles given that you'd think he'd have had the capital and the access to try out Dumbles of his various Dumble-playing pals for decades.
 
I have to think that Randall Smith happened on to an ODS early in the life of Mesa/Boogie. If you look at the Mark II as compared to the Mark I, they're almost totally different aside from being Fender-based.

The Mark I was a BF/SF Fender circuit with an extra gain stage stuck on the front end. Distortion happened before the tone stack.

The Mark II splits the two 'stock' Fender gain stages and adds two more, in-between. Distortion post-tone. Identical to the early ODS, aside from a few details that Randall probably didn't understand.

There's no way you get to the Mark II as an evolution of the Mark I. Since the ODS was around before the Mark II (maybe before Randall was building amps at all), and they were in the same geographic area, it seems most likely that Randall had an 'epiphany'.

Not that that's necessarily a bad thing; there's nothing new under the sun, everyone copies something, and it's not like Mesa and Dumble were ever competing in the same market space.
 
I found this schematic:
http://i1.wp.com/pdfelectronics.com/wp-content/gallery/ods-hrm-build/ods-hrm-schematic.jpg

Don't know how accurate it is, but....

The thing I found interesting in regards to the OD 'Ratio' control is that when (according to this schematic) you switch on the OD, the Master Volume pot's wiper is disconnected from the circuit and the Ratio control becomes the Master Volume.

Also, the post distortion tone stack has pots for Bass, Middle, and Treble controls but they aren't exposed to the user.
 
That's a much later version than the one I'm talking about. But the amp 'as modelled' is probably much more like that one.
 
AdmiralB said:
If you look at the schematic of an early ODS, it's very very very (did I say "very") similar to a Boogie Mark II.
Click to expand...

Different circuit paradigms - here just basic gain stages design, no tone stacks etc....both designs would have a tone stack between V1 and V2 before Clean Volume (Input drive in our axes)
Mesa
Mesa.jpg


Dumble

Rumble.jpg


if the skyliner tone stack is in (check out ODS Lead 3), only the 4th gain stage will be driven into saturation...on a boogie, saturation starts much earlier, this result in a different overdrive characteristic....a Mesa Mk2 is not a dumble, but there is a chance to revoice a Boogie Mk2 or similar into D-Style tone....

http://forum.fractalaudio.com/lounge/62122-mesaboogie-overdrive-special-still-beta-stadium.html
 
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AdmiralB said:
I have to think that Randall Smith happened on to an ODS early in the life of Mesa/Boogie. If you look at the Mark II as compared to the Mark I, they're almost totally different aside from being Fender-based.

The Mark I was a BF/SF Fender circuit with an extra gain stage stuck on the front end. Distortion happened before the tone stack.

The Mark II splits the two 'stock' Fender gain stages and adds two more, in-between. Distortion post-tone. Identical to the early ODS, aside from a few details that Randall probably didn't understand.

There's no way you get to the Mark II as an evolution of the Mark I. Since the ODS was around before the Mark II (maybe before Randall was building amps at all), and they were in the same geographic area, it seems most likely that Randall had an 'epiphany'.

Not that that's necessarily a bad thing; there's nothing new under the sun, everyone copies something, and it's not like Mesa and Dumble were ever competing in the same market space.
Click to expand...

Don't let him hear you say that :roll
 
PacoCasanovas said:
Different circuit paradigms - here just basic gain stages design, no tone stacks etc....both designs would have a tone stack between V1 and V2 before Clean Volume (Input drive in our axes)
Click to expand...

You're saying that the use of a potentiometer, rather than a fixed pair of resistors, in-between stages qualifies as a 'different paradigm'?
 
AdmiralB said:
You're saying that the use of a potentiometer, rather than a fixed pair of resistors, in-between stages qualifies as a 'different paradigm'?
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No

Leaving out the tone stacks, the difference illustrated here is overdriving V3 in the boogie vs. V4 in the Dumble.
 
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