CMI Electronics SG 410

A hybrid solid-state and tube power amp (rated at 100W) combo, made in 1973 and purchased new in 1976. Designed by Bob Crooks, founder of Standel amps in the '50s, for CMI Electronics (who owned Gibson at one time and later became Norlin Music) after he sold Standel to CMI. Two channels, one clean and one effects channel with two inputs each (Hi and Lo impedance). Channel two includes a Maestro Phase Shifter with 3 speeds, reverb, "wave form" distortion, and a "Notch Shift" feature that simulates an equalizer with 4 pre-sets (all effects controllable via an optional footswitch that I do not have). Both channels include separate volume, bass and treble controls. The effects channel adds a Midrange tone control and an Accent control, the latter acting somewhat like an attack or presence control. A master volume knob controls both channels.

It's difficult to get this amp to break up, even at high volume settings. It's very quiet thanks to a polarity-reversing toggle switch on the back panel, which also features a stand-by toggle switch, speaker-out and preamp-in jacks, an AC accessory outlet, a circuit breaker reset button, and footswitch jacks. I play a Strat Plus with Gold Lace Sensors and a Les Paul Classic with Burstbucker Pros. The amp is versatile in that it works well for many musical styles. The built-in effects, however, are not up to modern standards, so I use a basic effects loop consisting of stomp boxes for distortion/overdrive, chorus, flanger, and sustain. If I didn't already have those, the amp's built-in effects would still be usable (they were the reason I bought this amp back in the day, but processor technology has progressed tremendously since then). Using overdrive and sustain pedals, this amp sounds awesome with the volumes both set at 4 or 5. Feedback is easy to control, and the tube power section really delivers warm tones. Running clean, it's great for jazz and country. Even after 30+ years, the four 10" speakers sound fine.

I recently replaced all the tubes (two RCA 8417 power tubes and an RCA 12AX7A) and had an amp tech reset the bias, clean the pots, replace a failed transistor and a few caps. When it was new it had some problems, necessitating several trips to the shop (but repaired while still under warranty). Over the years features stopped working such as the reverb. Since it has recently been repaired everything is working as new. Some of the issues were due to abuse or power surges.

Gibson may still be able to provide schematics for these products since they inherited the CMI line. But these amps have been out of production for half a generation now.

I'm a 40 year "noodler" with other amps including a solid-state Fender Stage 100 running into two DT-412 cabinets. I had retired this lump years ago, but decided to try and have it repaired in preparation for selling it. The more I researched its history while trying to locate parts, the more I liked what I found. So now that it's working, I'm postponing any sale and enjoying it once again. The biggest downside to this unit is its weight, so it doesn't leave the house often. The look is unique and the construction is solid. But this amp is not something I would look to purchase because there are so many options to choose from these days. It's a terrific piece of history, though.

SG-410 By CMI electronics. 4x10" 'custom voiced' speakers... Master Volume with 2 channels (not switchable) 1 for clean(?) one for the other effects (waveform control, reverb - 1/4" footswitchable, built in Maestro Phasor, Power Amp input (to use as a powered speaker cab), Special Footswitch for the Phasor w/proprietary plug (I don't have it). 2 power tubes (mine came with KT-100's in it, currently running 6550's - see other reviews for mention of the other industrial numbered tubes that were OE). Solid State Pre, one tube (I think, for reverb driving). The reverb and the phasor sound sweet. Lot's of power and volume in this puppy. Built on casters. A little unmanageable, but weighs about the same as other same-era 4x10 combos I think.

Not really using it much as I aquired it to save it from the junkyard. Great clean, and the reverb is excellent. Phasor is great too. Sounds great when demo'd by good players. I expect it should stand out in the mix well. 'Waveform' control is not worth much by modern tube-gain standards though, for crunch or metal you'd need a pedal. (hey that ryhmes!)

Delivered to m with KT-100's and I swapped in 6550's (on a guess... the pin-outs were similar if not the same I think) and it's still working. I would not expect ever to have a problem with it unless you dropped down a flight of stairs and smashed the entire thing, or dropped it off a truck. (This one won't bounce, I expect that it would just make a nice big hole in the earth where it lands)

Great for clean loud playing, the speakers give some nice color to it. The bass response also is pretty respectable for an open-backed 4x10 config. Ideal for someone with 3 roadies to carry it. Probably only out-classed in bulk by the ampeg vt-22. Definately a fixed-installation type piece, but a powerhouse nonetheless. and the tall vertical size probably add's to the good projection characteristics of the 10's. Mine's too big for me to handle so it's for sale if you want to email me: gear@hotfreaks.net . If the email is still around when you read this, I'll let you know if I still have it!

This antique tube amp I got from my 8th grade science teacher in the early 1980. He got it from his grandmother who tought him electric guitar on a Gibson ES 135.(How cool is that?) I was told this amp was made in 1969(1 year after I was born) for the Gison SG guitar. It must be a unique short run amp cause I am unable to find much info on the manufacterer(CMI Electronics).
I loved this amp for its' looks and sound. It has huge silver and black knobs with a high and low input channel for guitar and s separate channel for a mic. It has two chrome domed 12" speakers which produce the nicest warmest sound I've heard especially when using humbucking pick-ups. There are 3 built-in phase switches with three speeds fast, medium, and slow. There is sort of a distortion knob called wave form and there is a nice big reverb knob with treble and bass knobs as well. There is a huge master volume knob near the middle and separate volume knobs for each channel. To the right there is the puzzling Knotch shift knob with four settings which sort of changes to response-tenor range to the sound. I was never explained this feature fully but it's fun to mess with with different effects. The back of this amp also allows for a line out and in with a tremolo pedal foot switch input. The tremolo input is strange looking and akins to a phone jack.

I like to play just about anything from blues to pounding grunge and this amp is able to deliver a wide range of sounds and is LOUD! I use it at home mostly for messing around but have mic'd up to a PA before. The phase and reverb sound excellent on the dual 12's especially when using a Cry Baby. For distorting I use a DOD overdrive going into a DOD compression sustain and you can ony image the extended warm fuzzy sound I produce with this setup due to the dual power tubes in the back. Since the speakers are old at high volumes you can get some tonal distortion and I don't want to blow them.

I would definitely keep this one at home due to it's uniqueness plus it is really not a touring amp. I had the transformer replaced a long time ago and last year the rare vac tubes toasted because a (*#%(*#*!!@!!! meat-head friend of mine touched one of the tubes and when I powered on they both blew. I've looked into replacing them and they are really rare and need to be matched. We are talking at least $80 a piece. Yow! But other than that this amp has been a solid workhorse and I've thrown this big boy around in car trunks before as a youth. I now treat it with the respect it deserves.

I don't know what happened to CMI elctronics and there is no other known manufacterer or info on this amp.

Of course I got a unbelievable deal on this family heirloom and intend to pass it on to my kids if I have any. It is truly a unique piece of work to see and even better one to play on. I only hope I can maintain it's orginal stock parts and there are enough Vac tubes out there to keep it running.

This is an old amp,because it just broke down on me!! It's probably a fuse or something, so don't worry. The amp has got a clean channel (1) and a sort of distortion channel(2).The distortion is created by a so-called wave-form. Further,there is a built-in phaseshifter. Two Tubes amp. The appereance of this amp is ultra-cool!! Big silver volume controls, coloured-phase-frequency-knobs and shining speaker-centers!!!

Usely I play on humbuckers (gibson-sg, squier super-sonic and some cheap left-handed ibanez' and epiphone's) and it sounds deep,full and so on. Esspecially when I use my mooger-foogers it's a lot of fun.

It just stopped working, so...

Who built these, then...

This amp I use at home, for fun and practice. At training and live performance I abuse my Hughes & Kettner 120 watt (yes, a non-tube-amp, but it's better then a Marshall) plus 2 H&K 4*12 speakerbox. Further a Boss AW,DD-5,OC-2,TR,old yamaha phase shifter and Mooger foogers, anything that doesn't fuck up the original signal..