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Good "victim" for a Soul Transplant

Started by R.G., August 28, 2009, 08:35:29 AM

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It's getting on 15 years now since I first noted on usenet, then later the web that the mechanical, not electronic, part of building effects is the hard part. This is even more true for whole guitar amps. Physically constructing an enclosure which will hold speakers, making and fitting a chassis into the enclosure, mounting a heat sink and power devices, and making a good (enough!) looking front panel are far more difficult than building a circuit board and getting it to run.

However, the process of Technological Cannibalism can speed things up a bit. Finding a commercially available product that is **physically** close to what you want to do and then modifying it to be exactly what you think you want is much, much easier. Think about it - even custom car builders don't, as a rule, start by machining up frames, engine blocks, wheels, etc. Instead, they take an existing car and "improve" it, even if their idea of improvement doesn't match yours.

Thanks for staying with me through the intro. We're getting down to the meat of the issue.

I ran into a happy accident that prompted this note. Some industrious searching may make you the happy recipient of something similar. In scanning the local craigslist, I noticed an ad for a "Rogue" guitar amp. I would not normally give a no-name amp a second look, but I did read the ad. The ad claimed a Rogue GS-100R amp, with 2-12" speakers and 100W output. I did a search on that and found that these were a house-brand made for Musician's Friend in 2001-2005. They still sell an upgraded version, the GS-120R. They're around $200 new.

But old and used? They're CHEAP! The craigslist ad had an asking price of $40, and said it worked, with some crackles. $40 might, maybe, possibly buy a single power transformer for a 100W amp. And I get for my money not only a power supply, but also heatsinking (which may need improving!), a chassis, enclosure, speakers which speak if not perfect, knobs, AC power wiring done? Such a deal!

In short, I picked it up and it's a beautiful candidate. The enclosure is as nicely done as I could do. The chassis is big, roomy, and easy to modify. The power amp is a discrete-transistor design on a single PCB with the power circuitry. The power transformer is big (always good for power thingies!). The heatsink is enormous, probably because they neutered it by placing it where it can't get airflow through the box, so they made it huge.

The physical arrangement is such that you could easily put in your own circuitry and have a working, usable and gig-able amplifier. How many of you have ever played a gig with an amp you've built? It's not that the circuits won't work, it's that you can't box it up well enough to survive transport.

In any case, if you can locate a Rogue GS-100R at a cheap price, it's worth your time. Even if it's completely non-functional. They were only $200 new. How expensive can they be 4-8 years old and unloved?

The one I got had a broken input jack. With a replacement jack, the amp was good as (it ever was) new. It's LOUD as you'd expect for a 100W, 2x12. The clean channel is good for effects users, since what you want with effects is to hear your effects, not the amplifier blender-izing them. The built-in distortion is pure, unadulterated crap, to be listened to as a bad example. But good distortions are a dime a dozen these days. Good enclosures, power supplies and power amps are not.

Try it. You may like it.


Sounds interesting. I have gone through the trouble of building my own chassis and cabinet for a combo amp and fully agree that it is the most tedious process of building the entire amp. Mine was just a little 15W 1x8 practice amp in a 9" x "9 cube and it was still a major pain! Now I'm contemplating a 2x12 120W build and am really nervous about the cabinet build.

You wouldn't have any gut shots of the amp would you? Maybe something to show the front/back panels, heat sink and overall chassis layout?
Thanks for the heads-up, I'll keep an eye out for these from now on!



I agree that using an old amp is a good way to start, but it doesn't have to be a Rogue, it could be a beat up Charvel, Fender, Dean Markley - pretty much anything you can get for cheap and looks half decent.
Life is what you make it.
Still rockin' the Dean Markley K-20X


Yeah, the Rogue is just what I happened into. However, it's a bit of a bluebird since it's got a lot of space and is uncluttered, as well as being made out of stock parts. It's easy to put in your own stuff. And you're unlikely to have any competition for buying them.  :)

I did take a couple of photos.
Front view:

Back view:

I think Dr. Frankenstein would have been proud of his assistant for digging up this one.  ;D

J M Fahey

Quotethe mechanical, not electronic, part of building effects is the hard part
Couldn't agree more!
In fact, among my clients I often have Electronic Engineers/Musicians.
When I ask them the obvious question: why don't they build their own?, they always reply the same: "I can't build *just one* that both is "carryable" with safety,  has  reasonably good looks, and costs less than a new amp or even worse, a good used one"
This idea of getting garage sale specials is excellent.
This particular Rogue one is an example.
Looks very good , clean, and roomy, with the only exception of the puny "ventilation slots", nothing some top and bottom slots can't cure.
I think that the "R" stands for reverb but I don't see it.
┬┐Does it have a conventional spring tank or some chip?


Yeah, it has a short spring unit in the bottom.

My personal interest in this one is that I have recently made PCBs for the preamp section of the JMI Vox Supreme and 7120 amplifiers. I intend to put one or both in this chassis. I may also graft in the limiter and perhaps even a transformer-driven power amp.


Wow, that's a lot of room inside it. I like how it's mostly "modular", so you can e.g. save the power amp board and just refit your own preamp - or something along those lines. There's also room to stack boards on top of each other if neccessary.

Edit: Am I looking at it correctly; are all of those power transistors contained on their own little boards? Wow, that's something I've never seen before.


wow, that does look ideal. there are plenty of holes on the front panel for expansion and the fact that the front panel is simply has the labels  painted on the raw metal makes it easy to have a custom front panel made to sandwich between the pot nuts and the chassis.

Unfortunately there are none of these available in my local craigslist or on ebay. Maybe we could start a list of good salvage amp models. I know what my criteria are for such a thing but I'm not sure what everyone else is looking for. I would like something that is kind of "generic" looking (like this rogue amp). Preferably without any logos embedded in the grille cloth/cabinet (or at least are easy to remove). Also a nice standard rectangular chassis is nice. Many chassis have slanted fronts or internal structures that make it difficult to install custom components. Of course, any helpful reusable parts such as the transformer or a separate power supply board are helpful as well!

I've attached a picture of my first (and so far only) attempt to build a cabinet from scratch for comparison :)


That's a way better looking cabinet than anything I've ever built. I wish I had jigs and tools to make those finger joints. So far I have only managed to make butt joints reinforced with dowels and screws.

In my former work I made a bunch of plywood roadcases with steel reinforcements in all angles. You know, the sort of JC-120 look but with steel reinforcements instead. They ended up looking so tough that I might have to build something along those lines the next time I ever build myself a cab. I like that look a lot and it still looks "right" even if all worn out and beaten to pulp.


On on-topic note, I have found out that generally the chassis of things like domestic audio and video equipment (VCRs, CD players, integrated amps etc.) are not a good platform to build anything. They are almost always either too flimsy or heavy and large, and they tend to need a good deal of mechanical modifications to be turned into anything useful.

For example, if you strip the PC boards and all the stuff out from a non-working CD player all you got left is a flimsy chassis that lacks a decent front panel since the front panel is almost always without exception made out of plastic. Plus these things are often constructed in a way that all the parts that you need to strip out tend to be the ones that stiffen the chassis and keep it in part.

Those integrated amps with tuners, CD players and cassette decks are about the worst if plastic ghettoblasters are not included. About the only things you can recycle from them are the internal parts whereas the chassis will likely end up being nearly worthless scrap metal.


Well, I bought the finger jointed box at my local IKEA. It's a flower pot :) Of course, that just got me the basic shell. I had to cut the bottom out of the flower pot, install additional internal bracing for the baffle, build a frame for the grille cloth, stretch the cloth. I also had to cut out the opening for the control panel at the back. Overall not TOO bad of a project. The "chassis" is simply an L-shaped aluminum bracket I made by cutting the sides off a cheap project box from Radio Shack.

Your amp does look rugged indeed! Is that a combo amp?


Not my amp, unfortunately. I just posted that pic for example for the llok I likely aim the next time when building something. But yes, that's an old Redmere Soloist combo. They basically built those amps into cabinets that were rugged like roadcases. As you can see, you can even fit a lid to the front, which covers the controls knobs and the speaker. I don't understand why this type of rugged construction isn't too popular. It mostly seems to be reserved for racks.

The roadcases I built had metal L-profile brackets running along all angled sides. They were made in a metal workshop that was integrated to the wood workshop where I worked. I had to cut the L-brackets to right lenght and angle myself, though. ..As well as drill the holes to them. The cabs had not corner protectors but they didn't really need them since I interweaved the L-brackets. Ones could have been fitted but my boss thought that all the neccessary hardware was limited to handles, hinges and casters. Some of these ended up as toolboxes and some ended up as real roadcases for stage lights. I wish I had pics but I never took any at my work. Damn, I wish I still worked there. The access to all tools and the space was awesome compared to the small basement where I work on my own projects.


Quote from: teemuk on August 28, 2009, 01:35:44 PM
Am I looking at it correctly; are all of those power transistors contained on their own little boards? Wow, that's something I've never seen before.
Yep, you're seeing it correctly. Actually, that's one of the problems with this amp. Since I now own it, I did some checking on the reputation. They seem to inspire only two reactions - "good value for what I use it for" and "... cheap, nasty sounding junk".

I think both of those are correct. The entire amp is interconnected on those little white plastic connectors so the boards can be connected with stick-in cables for fast assembly. First of all, small connectors can't carry a lot of current. The output transistors have to put out on the order of 11A peaks, and that's going over *1* of the pins in a little square-pin connector. Get some dirt on it, let it heat up and get loose, and you have a power intermittent.  Then there's what vibration do to the connections. On top of that, every single control and jack is PCB mounted - in some cases, the PCBs are also "jack-mounted". The proximate cause of mine being $40 was an intermittent input jack - and it was obviously because someone bent on a plugged-in plug hard enough to crack the plastic jack and PCB. PCB mounted jacks, pots, and switches are a Very Bad Thing in guitar amps.

I just received a couple of pairs of Toshiba power transistors to replace the marginal TIP3055/2955 pairs, and I'm going to solder the wires to them, not PCB- and plastic-connector interconnect them.

I believe the all-PCB, all-the-time construction was a manufacturing saving. You could use a break apart PCB which contained ALL of the circuitry, including traces interconnecting the various little boards, then populate, wave-solder, and test the complete board. Once a board was known-good, the boards were broken apart, screwed into place, then connected with cables. Less handling, less labor, cheaper.

I'm *glad* they did it that way - it gave me a bargain.

J M Fahey

Hey guys !! You really impressed me !! You *must* post them in the homebuilt contest.
It's not for the competition itself but to see the intelligent ideas everybody has to solve building problems.
Well, they say that necessity is the mother of invention.
That fingered cabinet was great, also the road-armoured combo.
Teemu: I've often seen those individual miniboards in Korean amps, made by some giant OEM manufacturer, who builds for everybody including Ross,Hartke, etc. and their "house brand" is Samick.
They are used in TO220, TO218 and similar plastic cased transistors, both to keep pins firm and separated from each other, and to allow servicing by plug-in transistors.
The miniboards themselves usually have no extra components, only the connector, or at most a reverse biased clamping diode .


I may well have an canditate for a soul transplant. I have a crate dx212, was a great amp with nice models,a really nice amp and what makes this worse is getting another one like this is out of the question. Getting someone around here to work on it is almost impossible. I have a local tech and the only guy I know that is capable of fixing it  likes to take amps apart, put them in a back room and think about them for a longgggggg time, two years its been there.This is whats sitting there in pieces with other amps sitting on top of it,http://www.gear-vault.com/crate-dx-212-guitar-amplifier-review/  at the very minimum I have a solid case, speakers, knobs,and transformer although I"ll miss those other goodies. But hey I think I can do something with it now.