A well kept secret: the Yamaha G100 212 II

Yamaha G100 212 II

Yes folks, one of the best kept secrets in the wide world of guitar amps is the late-70’s to early-80’s Yamaha G100 model (and similar) amps. They appeared in three series of models – series I, II & III – our pick would be series II which are very robust and obviously built to last the distance. Yamaha’s cosmetic approach is very conservative, but also quite distinctive.


check out the chassis – Yamaha G100 II

Yamaha obviously marketed these amps to compete primarily with the Roland JC120 series amps, and also the Fender ‘Twin Reverb‘. You can pick the Fender ‘Twin’ influence in the G100’s tonality, but in our opinion the G100 has a somewhat warmer tone and very powerful and flexible EQ. There are two channels, as you might expect in such an amp, each with volume treble/middle/bass controls and some ‘pull-on’ options. Common to both channels is (spring) reverb and a 3-knob parametric EQ.

Yamaha’s power amp module can be removed for repairs

This is a channel-switching amp. Channel A is warm and clean. Channel B has additional gain on board for some overdrive. Like any solid-state amp from this era, clean sounds are the main strength of the Yamaha. However, you could employ this amp effectively for most playing styles, excepting hard-rock, grunge and metal, etc. The power amp is modular and plugs into the power supply board. The module is fastened to the chassis via the large heatsink and is easily removed for repairs. The power amp design is quite an old-school 1970’s design, ie quite LO-FI, with a single-ended power supply which necessitates the use of a large output coupling capacitor to the speakers to block the DC voltage present at output (ie an electrolytic capacitor). Perhaps these are contributing factors to the Yamaha’s warmer sound ??

the G100 chassis is very serviceable

This example G100 was recently acquired by our regular customer, Ian Astill. We inspected the chassis and boards, as well as testing for electrical safety. The amp came up trumps apart from some very scratchy pots. Getting access to the pots for cleaning is not especially difficult. We removed the board behind the front panel and gave the offending pots a blast with FaderLube. These pots are the commonly used PCB mounting split-shaft/splined-shaft which facilitate a push-on style of control knob. Unfortunately, the shafts are often damaged and bent. Even worse sometimes the previous repairer has glued on some knobs, making removal without destroying the pot quite a challenge ! The bent shafts can be carefully straightened so there is no excuse for this approach.

parametric EQ on a guitar amp

Some say the original Yamaha speakers play an important part in this combo’s tonal response. If you are looking at acquiring one of these amps, this is probably something you should check out first. The parametric EQ is not easy to use – it takes time and effort and some experimentation to get a result. But the controls can be set for 12 o’clock and instead rely on the very functional channel (passive) EQ instead.


A well known user of these amps back in the day was American jazz guitarist Mike Stern. Americans Pat Metheny and Robben Ford are also said to have used these amps. I can recall seeing some Aussies using these amps back in the day including Rick Springfield. There is a rumour that these amps were designed by Paul Rivera, but the power amp design looks exactly like a standard Yamaha design, so who knows ?? The standard of assembly is very high, it’s little wonder these amps have survived so well, requiring very little in the way of service and repairs – mainly just damaged pots. IR.


One Response to “A well kept secret: the Yamaha G100 212 II”

  1. john Says:

    i got a series 1 for free back in 2010! had been sitting in a crawlspace for years i got it home and twisted all the knobs a bunch to work the dust out and it has been fine ever since. factory distortion channel sucks so i ran a boss ds1 in front of it played an es335 and a squire 51 and had good results! other guys in the band i played with poo pooed it cuz they were tube amp snobs but i could smoke their hundred watt combo amps mine has both original 12s in the cab clean tone is awesome and it does great with pedals they are getting scarce nowadays too good time to sell cuz i don’t gig anymore

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