Anonymous asked: Hi, the Model B looks awesome! Pretty huge transformers! May I ask in which way you modified the tone stack?
Not too much — just some very small pot value changes and a lowpass filter on the output that takes off some buzz from the distorted sound. The sweet spot for a lowpass on the output is where it knocks a few dB off of the “fizzy” distortion harmonics, but is still above the resonant frequency of most guitar pickups. That way it doesn’t affect the sound very much when you roll off the guitar volume or turn down the gain, but the drive sound is smoother. Usually somewhere around 7.5-8kHz is a good F3 point.1 note
Orange OR-80 reissue version. This has a PPIMV installed in the spot where the slave-out jack used to be on the back panel. Otherwise, there’s no way to get a distortion tone out of the amp at anything less than earsplitting volume.15 notes
Another custom overdrive pedal. This uses the OCD circuit (which is one of the simplest ever, and pretty much just a RAT/Dist+ with the tone control isolated) but with alterations to the gain/clipping structure. Overall gain is lower and it uses germanium diodes instead of MOSFETs. The range of the tone control is pretty different too, leaving more of the upper midrange intact than an OCD — this is necessary because the clipping behavior in this pedal sounds really dark and fuzzy with the normal OCD tone network. These changes were drawn in large part from my experience building the Klon clone. This pedal ended up like a cross between a RAT and an OCD, combining the snarl of the former with the thickness of the latter.35 notes
Klon clone. Everyone has to try this eventually, I guess. It uses the 2009 trace schematic, with all the same components as the original, and as similar a layout as I could do without a PCB.
I’ve played a lot of “based-on-Klon” designs and never cared much for any of them. Part of the turn-off may have been the enormous number of YouTube videos of people playing through Klons or Klon knockoffs, raving “DUDE BRUH, SO COOL MANNN” while I just thought I heard a sloppy pentatonic scale through a Peavey Bandit. Many of these folks would benefit more from a good tuner pedal than a $1500 overdrive.
I do like this pedal, but not for “that” rock tone (why do I only ever see these used with Fenders?). It’s gooey/squishy and not harsh, with a nice range of usable tone control settings. I actually think it’s a superior front-end boost for single-channel amps, particularly Marshalls — closest thing to getting two channels from an already gainy amp. Not joking: you can get an absolutely amazing death metal tone out of this when you push a maxed-out Marshall 2203. It works really well in front of high-gain distortion boxes that tend toward muddiness.
The OD tone of the pedal by itself is nice, but nothing to write home about. When you look at the topology and weird component values, it’s obvious that it was designed iteratively and with lots of tweaking by ear. Which is probably why it’s often counterproductive to “modify” it, using more engineering-oriented design thinking. The thing is a kludge. It’s really badly designed from a textbook standpoint. It probably sounds good because it has an emergent synergy with other electrical systems that are also badly designed — electric guitars and tube amps. In isolation, it’s boring. In combination with other things, it behaves surprisingly.
People who love the Klon usually talk about how it adds “niceness” even when the gain is all the way down. This seems to be due to very carefully selective frequency emphasis that increases intelligibility and note-separation — sort of like how telephones only operate from 300-3000Hz, because that’s where speech intelligibility is located. The Klon emphasizes the stuff you’re listening for from the guitar. It probably accentuates the differences between different guitars and pickups, which will cause people to talk about “transparency.” It is certainly not transparent. It also appears to affect the attack envelope of certain picking techniques — whether through actual compression or through filtering — which sounds a lot like the sag you get from a tube rectifier in an amp. Combining the extra smoothness of compression with the greater intelligibility, it is going to flatter most players and most guitars.
EDIT: I did not do the powder-coating. These people did.22 notes
crusherdestroyer asked: I had to check to be sure. The 900 in question is a 100 watt jcm 900 dual reverb that came stock with 3 ecc83's (I believe one drives the reverb) and 4 5881 power tubes. Some quick googling is telling me its a 4100.
Yes that’s a 4100, which is truly weird. The 4100 reverb is actually totally opamp-based, like all subsequent Marshall reverb circuits that I’m aware of. The 4100 has a tube for a cathode follower to drive the tone stack, a tube for the phase inverter stage, and a tube where each triode does mostly nothing but cleanly pass already distorted signal (one triode after the FX return’s opamp buffer, and one right before the dual master volumes (which are opamp stages). So it’s a head-scratcher as to where in the circuit those two extra triodes are used, unless they’re cascaded the with the stage right before the master volumes. But even there, you have to attenuate after the stages because of the opamps’ input headroom limitations.
crusherdestroyer asked: A friend of mine had his JCM900 modded by Dennis Kager with an extra 12ax7 preamp tube, with its own level control. Its the loudest gainiest ballsiest 900 Ive ever heard. I wish I remembered more specifics.
I’d bet money it was not a 4100. When discussing the JCM900 series especially, we need to be clear about which model we’re talking about. The 2100 or 2500 is quite easy to modify with extra stages, or I have in some cases modded it right back to the JCM800-2203 circuit. It has diode clipping but there are tubes that distort in it. The 4100 is a essentially a completely different amp, with a front end that’s entirely opamp-based. It’s unfortunate that the 4100 is much more common.1 note
Anonymous asked: hi, i have a jcm900 4100 and I'm looking to have a mod done to it for it to be much higher gain and much more saturation. I use only natural distortion with the eq given on the front of the amplifier. but i want to get a mod done so the amp has far more balls than she has now being a jcm900, i play very very aggressive speed/thrash metal. and need her to sound like a jvm410 red channel with max gain.
Interesting — most people want JCM900/4100s to have less gain, not more. It’s quite straightforward to reduce gain, because there are several places in the circuit you can do it. It’s a totally different matter to increase gain, because you quickly run into stability problems and complete loss of dynamics. It’s important to remember that the 4100s distortion comes ENTIRELY from pedal-style solid state opamp circuits with diode clipping, and no tube in the amp distorts until you’re loud enough for power amp clipping. It’s so different from a JVM, which uses a more traditional 12AX7-based preamp with significantly more gain, that you really can’t get from here to there.
If the issue with ‘balls’ is that the amp is losing attack at high volume, that can be addressed by installing a larger output transformer and a choke, and in some cases recapping the supply. But there, you’re looking at hundreds of dollars. And it won’t get you the additional gain and saturation you’re looking for.
I think it’s best to let the 4100 be a 4100, and if you’re looking for the sound of a JVM, then either hunt down a pedal that can get you that sound, or purchase a JVM.
Your question brings up an interesting point about modification — mods are effective when you’ve got a baseline performance that you’re happy with, but you want to make small changes to get from 95% to 100% happy. But trying to change one amp into another amp is not generally cost effective, and only to be attempted out of curiosity.
Custom distortion pedal. Basic volume/tone/gain setup with selectable symmetric/asymmetric clipping (really compression). The symmetric uses germanium 1N34As, the asymmetric uses a violet LED and 1N914s. Both sets use series resistors to make them act more like a compressor. Most of the actual clipping comes from overloading the 4580 opamp, which has no diodes in its feedback loop. The diode compressors give it more of a “touchy” vibe. It’s not a great design for low-gain, since it gets gainy really fast, but for high gain it’s got massive punch and manages to get both saturation and note separation.5 notes
Anonymous asked: DM-2 would it be ok to daisy chain to newer pedal or is it better to convert to the psa
Daisy-chaining the DM-2 APPEARS to fix the ACA ‘problem,’ but actually creates a worse one.
Here’s the deal: the pedals marked ‘ACA’ have a resistor and diode in series with the power supply, which are chosen in tandem with the pedal’s specific current draw to create a 3V drop on the supply. So you use a 12V adapter and the pedal sees 9V. The benefit is that all the power supply grounds in the effects setup are isolated from the signal grounds by this small amount of resistance. You don’t get ground loops when you daisy-chain pedals together.
BUT for it to work, ALL the pedals in the setup have to be wired this way. Obviously, that means your whole daisy chain has to be Boss ACA 12V. Not happening. So when you use a 9V adapter with an ACA pedal, the LED is dim and the supply craps out early. Daisy-chaining with other standard 9V pedals makes the LED get bright again, but the reason is that other pedals don’t have their supply grounds and signal grounds isolated from each other. So the ACA pedal’s resistor/diode network is being bypassed, THROUGH the patch cable shield and through the supply grounds of the neighboring pedals, back through the daisy chain. So now you have supply current running in the signal ground, which is a very bad scenario for noise or even squealing/howling and oscillation.
You really only have two options with ACA pedals: give them their own isolated supply (or only daisy-chain them with other ACA pedals), or modify them to PSA specs by shorting out the resistor/diode network.
2004 Ibanez Destroyer (DT-200). Fun weekend project after a grinder of a work week. Completely made over with parts on hand.
I have a thing for “pawn-shop” guitars. I’m not talking about Fender’s inspired-by-Urban-Outfitters line of fake thrift store guitars (Fauxnder?). There’s something very attractive to me about souping up weird, poor-selling budget guitars that nobody wants. Sure, they’re sometimes irredeemably terrible. But sometimes gross overinvestment in an undeserving instrument can get you to really interesting places. The fact that something is not “sought-after” just means that nobody’s gotten famous by abusing it — yet. Look at what Sonic Youth did for Jaguars and Jazzmasters. Or what doom metal did for Sunns and V-4s.
I tend to think of guitars in two-dimensional terms — sound and playability. Both of these axes depend on some elements you can change and some you can’t. You can’t change the wood. You can’t normally change the neck or frets. But you can change the pickups, electronics, nut, tuners, bridge, overall setup. If the stuff you can’t change is decent — like this very nice chunk of mahogany here, with a comfy maple neck and rosewood board — then you can change all the other stuff and come out with a unique and exciting instrument. That’s the essence of a “player’s guitar:” placing no inherent value in tradition or resale price, but appreciating the thing for what it does, to the extent that it is an interactive vessel that smoothly facilitates inspiration and expression. In short, its being and doing are one and the same. Collectors might puke, but wow is that kind of guitar fun to play. It’s worth asking: if a guitar’s value, looks, and perfect sound & adjustment make me LESS likely to pick it up and play it, then what is the point? Is it even still a guitar, or is it a guitar-shaped sculpture?
Lots of fancy words for a budget Ibanez. Whatever, it does what I was hoping — sick 80s thrash and old-school death metal tones, in a lightweight and couch-friendly package. Sounds similar to my Les Paul that has the same pickups (a very good thing), but with more snap from the maple bolt-on neck. Great for meedly-meedly with lots of punch. Nice clean tone too, not sterile at all. Way better than the last Ibanez superstrat thingy I played. The neck feels good and the frets are in good shape, and much better leveled than the MIM Fender I bought new in 2007. Remember that this is a Korean-made guitar!
Dork info: 1980 Gibson Dirty Fingers pickups w/ covers added & mild wax potting, swapped out all hardware, Gotoh TOM bridge & tailpiece, Switchcraft switch & jack, Alessandro 500K vol pots & CTS 1M pull-shaft tone control to coil-split the neck pickup. New handmade unbleached bone nut. Set up to my specs here. Feels GOOD, man.38 notes