Rockett Allan Holdsworth Overdrive

[mirosol]

So. Anyone has any information on this one? It seems to be a nice sounding overdrive.

I stumbled on a blog post with a few photos, but there's not much that can be done with those. Anything more than guessing.
http://thoughtfulguitarist.com/2012/12/ ... ve-review/

I'll throw in my 2c with speculating about the JRC4558 having 1N4148s and Schottkys in the feedback loop. Gain pot at A50K could point the gain setting to be closer to Marshall Bluesbreaker than a TS. 5 transistors in all, could be two AMZ mini-boosts or any other muamp configurations. Could be a lot of other things too.

[micromegas]

I would go with mosfet clipping due to the smooth breakup the circuit presents, and a mosfet booster for the boost section. Notice there are 6 transistors.

[mirosol]

You're correct, there are six. Those pairs could be muamps, or they could be clippers. Too bad angle and light on the photo to tell for sure. Haven't seen any of these for sale as used around here, but i'll keep an eye out. Let's just hope someone can snap a decent shot of the board at some point.

[MoonWatcher]

You're correct, there are six. Those pairs could be muamps, or they could be clippers. Too bad angle and light on the photo to tell for sure.

Well, luckily the resistors are regular carbon film types, so it's super easy to make out their values. For mu-amp-type circuits, I'd expect to see more 1M resistors than I do, unless they are obscured by stuff. But I'm probably going to conclude that it kind of looks like evidence against them being mu-amp-based.

What I do notice is that there seems to be a lot of 1k5 resistors. What immediately springs to mind are thoughts of FET-based derivatives of tube preamp stages, because 1k5 has to be one of the most common cathode resistor values that there is. The only issue is that I don't see trimmers for biasing, but it could be an instance of measuring and sorting so they can be avoided.

So maybe if there are instances of other somewhat common cathode resistor values - 820R, 1k8, 2k7 - it might give some ideas.

I have no doubt that there are more standardized parts of the design that use the 4558 and diodes for clipping, and it might even be possible that the 50K gain pot is similar to what is used in the Blue Note. Isn't John Scofield using the Blue Note now? Both he and Allan have that very mild breakup sound, so there may be at least some similarities.

Or - if you can find somewhat common values for the tone and volume controls with other pedals like the Blue Note or Animal, it might give you a rough idea of what at least part of the foundation might be like. It looks like many of the capacitor values are pretty clear as well, and they look like the standard variety of 100n, 22n, and so on.

Maybe comparing this pedal to another Rockett that uses two footswitches - to see if there's anything in common with how the second one appears to be wired up?

Despite it being a signature pedal, I would think there might be a foundation similar to other Rockett pedals - that's just a hunch. A buddy of mine had the Tim Pierce OD, and internal inspection showed that parts of it looked similar to other stuff of theirs (but neither of us had enough interest to trace anything - just wanted to take a brief glance).

[MoonWatcher]

I went back and looked into the Tim Pierce OD a bit, and even found a gut shot of it.

The layout looked flipped compared to the Allan Holdsworth OD, so I went and looked into videos of it, and found that the gain/vol and bass/treble are basically flipped left to right, as well.

The biggest exterior difference between the two is that the Allan Holdsworth pedal has the pair of switches that go with the boost.

The biggest interior difference is that the Tim Pierce pedal appears to have just one transistor for the boost side. I think it also has a 500K gain pot.

When I listen to the demos of the Tim Pierce, it kind of sounds like mostly a higher gain OD version, and the boost obviously is a LOT less flexible. With the higher gain, I think it's sort of clear that the bass control is most likely handled like with something like a Timmy, or a pre gain arrangement. So the treble is probably like a post gain arrangement. The tone control in both the Blue Note and Animal is certainly like that.

So my best guess is that the Tim Pierce probably is a variation on the Animal, and is paired up with what looks like a variation on a Vex SHO - a single mosfet (I see what looks like a pair of 1 meg resistors near it, and what are probably similar drain and source resistor values). And then the Holdsworth is probably a variation on the Blue Note, but is paired up with a much more comprehensive boost section, and it must have made sense to utilize more than one FET-based stage to get the headroom that Allan probably wanted.

The Holdsworth pedal also looks to be the first from Rockett (in this sort of format) that has a lot more capacitors for EQ shaping versus the others, including the Pierce.

With listening to the demos of the OD with the Holdsworth, it doesn't sound particularly unique besides being low gain. I think the boost side is a lot more interesting, and may be handled somewhat differently than a lot of boosts in other pedals.

[MoonWatcher]

there are six. Those pairs could be muamps, or they could be clippers.

Let's just hope someone can snap a decent shot of the board at some point.

I was looking at how those pairs are oriented, and it made me think of parallel FET's. Wasn't there some Toneclone kit for the Cranked AC? I know that used parallel FET's. I also know that Allan favored Vox amps many years ago. Maybe Rockett provided some existing stuff for Allan to try, and it included something that used this type of platform? I think it was also mentioned that the copper colored Rockett boost didn't use a conventional FET setup like you'd find with a Vex SHO or a minibooster?

I don't have the Cranked AC schematic or layout handy, but I think that one had six transistors. It looks like the Holdsworth only has what looks like they would be two parallel pairs - that must be plenty for what is supposed to be more like a boost and less like an amp.

I think it was also mentioned that the Cranked AC uses 15k and 1k resistors for the parallel pairs. Maybe the crappy photo might reveal that? Maybe what I thought were 1k5 are actually 15k?

So that leaves the other two transistors. I guess it could be as simple as them being in and out buffers.

But another decent shot of the board should include what the transistors are. That would tell a lot.

[Tmidiman]

Careful. While this may be an overdrive it does not, IMHO, offer the "Holdsworth" you are thinking of.

Allan backed this because of the clean boost. He gets his signature tone from the preamp of the amp he's playing through. He boosts the input of the preamp and then shapes that tone with a parametric EQ.

Watch the demo. No one gets that tone just using the pedal, Allan uses only the clean (transparent) boost that the pedal offers, and few videos when you hear the tone are the few people who have figured this out.

BTW if you're interested in that tone it can be achieved using a Zoom MS-100BT.

[okgb]

Or just allot of mid-range and less treble? He's endorsed allot of things over the years and always sounds
like himself , clean chorused sound mid range shaped overdrive , not a complex formula, but a complex player
I love in one of his video's he offer's 20 most useable scales and of course not one is the major scale or any of it's modes

[MoonWatcher]

Watch the demo. No one gets that tone just using the pedal, Allan uses only the clean (transparent) boost that the pedal offers, and few videos when you hear the tone are the few people who have figured this out.

It doesn't surprise me that he only uses the boost side. Someone probably figured that it would be a better seller if it was more than just that, so must include an overdrive option.

I found this link, which probably gives a really good idea of how Allan's entire rig will probably typically be set up:

http://www.seymourduncan.com/forum/show ... it-his-rig!

According to what that person said, it's been the same booster from the 70's and is nothing special. So at this point, Allan probably just uses a modular approach and exchanges parts of his rig for what he finds is most useful.

The overdrive part of the rig sounds very basic, and is probably mostly aimed at just not sounding too distorted. He has no need for a traditional distorted amp sound - he just needs one that works for his style.