First Foray Into Cerrem's Resistor Mod

[mr.twistyneck]

Oh. My. God.

Hour 1: no fried amps. one fried resistor. build a heat sink - it gets mega hot. the sound....is....wow.

[gnugear]

MUST. POST. SOUNDCLIP.

[mrbeasty]

MUST. POST. DETAILS ...

[ToneToDaBone]

Who's mod?

[mr.twistyneck]

Hours 2 and 3. gratuitous wanking. only casualties so far are a 2K resistor and a B string.

I first hooked up the 2K resistor to short wires coming out from under the chassis. With no heat sink, I smoked it. So I found a small heat sink in my piles of crap and used a pair of vice grips to hold it to the heat sink, with heat sink creme in between. That was no fun. So then I found the nice big heat sink in the pictures [with conveniently routed mounting channels that AS FATE WOULD HAVE IT, were exactly the right distance to mount the resistors. I had ordered a whole slew of different values from Allied Electronics last Friday, and they came in today. SOOOOO, I mounted five resistors next to each other: 470 ohms, 560 ohms, 680 ohms, 1K ohms, and 1.5K ohms, all rated at 50 watts [does this sound correct? anybody?]. Then I had to solder in some longer wires [12 gauge] so that they could reach the resistor block, which was standing on an old music stand.

The 2K resistor sounded good until I blew it, and the 1.5K sounded great. So did the 1K and the 680 ohms. I put the 680 ohm and 560 ohm in series to get a little over 1K, and that sounded good too. 560 ohms is VERY quiet compared to full blast with no resistor.

Don't get on me about soundclips just yet - I sold my minidisc 4 track on eBay a couple of months ago. But I still have my old cassette 4 track, which works fine. So I'll have to drive to Murfreesboro with the kiddo and get an SM57, an XLR cord, and a converter. Then I'll have to mix it somehow into my computer and convert it to mp3. I'm sure the result will be turd-acious, but you'll get the idea.

Man, this turns a Super Lead into something scary. It sounds compressed. ALL harmonics - tapped, pinched, plucked, palm rolls, all that stuff LEAP out, whereas they usually get lost. And let me tell you - my speaker setup in the garage SUCKS - it's an old Randall 4x12 wired at 8 ohms, with two 200 watt EV speakers and two Celestion G12T75's. A very harsh cab. I stuck a Phase 90 in front of it. WOW. I can't wait to get this into some of my Marshall cabs!

No Hotplate used so far. No reason to, unless I can incorporate it for it's line out feature and rig up a new wet/dry setup.

I'm thinking about wiring up the resistor block with a heavy duty array of switches, or a nice fat rotary switch. all in a box with a fan. or maybe in a mini fridge. the resistor block gets HOT! [duh]. below are pics of the setup, a closeup of the resistor block, and just for grins, my garbage filled garage. more soon.

Thank you to Cerrem and Marshall Maniac. Bless your hearts. I am so happy!

<img src="http://www.twistyneck.com/marshallnoise/mpics/DSC05979.JPG" alt=" - " />

<img src="http://www.twistyneck.com/marshallnoise/mpics/DSC05980.JPG" alt=" - " />

<img src="http://www.twistyneck.com/marshallnoise/mpics/DSC05981.JPG" alt=" - " />

[Dai]

!!!Careful with those exposed alligator clips!!! Keep small pets and any young 'uns away mon!

Dai

[jusky]

twisty-

are those all stage props in your garage???

[Gainfreak]

Twisty, You continue to be my hero!! Man do I want to hear some clips !!!

[drewl]

Hmmmm........we have a whole bunch of those gold resistors here at work.........
so Twist, you collect acoustic guitars, or are they all firewood?

[DreamTone7]

I dunno Twisty....with the "luck" you've had with amps in the recent past.......

[godotzilla]

More detail! Where are you placing the resistor(s)? This sounds like an ultra-cool mod, but I have no clue what goes to what. Spell it out for us techtards please!

[fzh1yv]

In a nutshell:
Connect a power resistor (anywhere between 500 and, say, 1.5K and at least 25W power rating) across the full primary of the OT.

Read in all it's glory >>here<<

[Marshall Maniac]

Great report, Twisty!

As for the resistor wattage, a 100w Marshall normally puts out well over 100 watts at full tilt, probably closer to 150w or more. With a resistor equal to the OT impedance (1750?) half of the power would go to the resistor, which is why you smoked your 2k. To be safe, I would go with a 100w resistor, maybe higher (or use two 100w Rs), even with a sink.

I was playing around some more last night with some resistors and my 2204, but I kept worrying I was gonna fry something. I know the tubes have got be be stressin' with those kinds of loads. I was trying to get a good sound with 2-3k, but I fear I need to go lower. My 30w 1k with no heat sink was getting too hot too fast!

I'm kind of torn on this. So far I'm not getting the right sound with this mod in my 50w MV amp. I like my 2204 as it is, so I don't want to reconfigure it as a 1987. And even if I did, being 50w it won't have that 100w sound. So maybe I'll just have to find me a basket case 100w cheap and build me an "EVH tone" amp.

Or I could just keep using my SD-1 for high-gain stuff. I love that VH tone, but I'm really more of a KT66 AC/DC kind of guy.

I'll keep workin' on it and post sound clips as I go. I'm gonna pick up some more higher-powered resistors today.

[mr.twistyneck]

well, i've probably played with it for about five hours of playing with no ill results. I dug out the old cassette 4-track, and it is ICKY! we'll see if it works. Good news follows, however:

1. Gig tonight in Nashville. Last one for the band, as a matter of fact, at a bar called "The End" HAW HAW HAW. I'll be using the resistor mod tonight on stage. Can't wait. Maybe I'll use the 4-track to get a crappy mix off the board.

2. Friday is "GO IN THE STUDIO DAY". We'll be recording thru Monday, and perhaps afterwards [just recording the last originals we wrote and everybody's favorite covers]. I couldn't remember when we were going in, so perhaps I'll just record some tone clips in the studio - probably better and easier to post.

I'll be going over to Murfreesboro shortly, and will stick the mod wires in the rest of the heads and play around with them. I'm bringing every head into the studio [except the '73 ST, which is waiting for it's new PT].

Checked into some 100 watt resistors from www.alliedelec.com - looks like they have some fixed values and some adjustable resistors. that'll have to wait until next year.

gotta go; much wanking to be done in the next several days!

[outtahear]

Whatever you do-don't even think about trying to take that thing on a plane....