Yamaha B100 II

Made around '81 or beginning of'82, according to "guitare magazine" in my own library.
Excellent for playing Rock/Punk-Rock!!!
1 channel, no switch, no headphone jack.
I use this head for playihg on a bi-amplified Classic 410E Peavey cabinet. Excellent for a gig at the pub! 100 watts it's enough! solid state, good conditions and vintage of course.

I play it with my Fender Pr??cision or Fender Mark Hoppus not so old.
I do not use the equaliser, flat sound but a Boss Fender Bassman '59 as pre-amp. And play it Rock! Rock! Rock!

I use it on a gig and i don't need a backup.
It seems to be a strong building, even the electronic circuit is good quality as Japan use to produce.

I bought it in a guitare shop as second hand, 3 months of warranty. No need to be repaired at this moment. Very good conditions.

I have already a big Woodstock 200B (looking for informations...) and it sounds good. But i wanted something else and i found this amplifier, i want to keep it, i enjoy playing it, so simple to use especially on the Peavey cabinet, as a real Bassman '59.
I bought it as an impulsive choice, this waited for me...i saw it and fall in love with it! It's a love story between Yamaha and i for a long time...

This is a Japanese-made solid state bass head dating from the 1970s. Power consumption 250 watts, output vaguely between 100-150 watts, I mean its anybody's guess. Styling is Fender-like. Case is black tolex covered, tilted black-face control panel, fabric-covered vented front, white metal corners, handle on the top, very solidly built. Its a good looking compact amp but heavy. Measures 21x9x11 inches deep. The weight comes from the massive transformer and over-engineered heatsink for the two output transistors. It is not very well balanced for the handle so quickly gets uncomfortable when carrying it.

On the front panel we have high and low level inputs, controls for volume, treble, middle, bass, then a 5-band eq with rotary knobs, power neon, power switch. Round the back theres the cable for the mains inlet, voltage selector for 110, 130, 220, 240v, fuse, speaker 1 output, speaker 2 output, and lastly a 3-pin XLR line out which is transformer balanced.

Switch-on and it takes a few moments for the sound to come through. This has led some people on guitar forums to question whether the amp is in fact a tube amp, and it does have a bit of a tube-like sound. Well I have had it to bits and I can say for definite that its a 100 percent transistor design. The delay is due to the capacitor on the output needing to warm-up. The speaker is coupled to the amp via a large-ish capacitor in an old skool quasi-complimentary circuit. It sounds vintage because thats the way they used to build them. Theres 105 volts between the terminals of this cap, so keep your fingers away from it if you wanna go poking around inside the amp. Inside by the way, it looks like a muscular version of a hifi amp that Japanese companies turned-out in the 1970s. Theres a pair of 150W 2SC1586 transistors giving the thing its power, and all the other transistors in the preamp are unfamiliar too. A nice feature is the balancing transformer on the line-out. I don't think this is present on version III of the amp, which has a line-out driven by op-amps.

Decent ribbed and welded chassis, generally speaking its a very well built amp.

This was an impulsive buy for me - I saw it was underpriced at 25 pounds and snapped it up. Initially I was disappointed with the sound. I am not a bass player but even I saw immediately that the eq didn't go high enough in the range. The five knobs are marked 60hz, 150hz, 320hz, 640hz and 1250hz, for cut or boost. Sure you get all the notes on your bass but then it stops short on the harmonics. I think Trace Elliot amps go up to 15k. The treble mid and bass controls are for boost only but these work pretty well. So you can set your tone and then do some tweeking on the bass and mid-range. I think its basically a rock amp. You can get thunderous amounts of room shaking rumble, but then maybe this amp wouldn't be your first choice for funky slap bass.

Theres only one volume control but it doesn't go very far up before things get seriously loud. The tone has a slight warmth to it which you could call vintage - hell its a vintage amp! I'd say thats a good thing, an amp with character is better than one thats clinically clean and unforgiving of cack-handed playing. I don't know the power output on this amp and I don't think anybody does. I've read the reviews of version 1 of the amp and it seems pretty much in line with what they say there. It is very very loud. The first amp had a distortion control which seems to be disliked among reviewers; thankfully this one has no distortion control, and in fact it didn't distort with the volume up loud. When I say loud by the way, the volume wasn't fully up, it was only as loud as I could stand. It is possible that the amp could clip with an active bass, but as I was testing it with a generic Fender copy with passive pick-ups, this didn't happen. Perhaps somebody who has been using this amp for a long time could give a more objective review??

The quasi-complimentary design of amp is known for its efficiency as essentially the amp only needs to draw power for the first half of the cycle, so you can't simply rate the amp by reading the power consumption at the mains and saying, no more than half of that. Yamaha rate their amps by the power put into an 8 ohm speaker, as they mostly trade in combo amps with one speaker. They have provision for a second speaker to be connected and this will bring the load down to 4 ohm - but then on this amp theres a capacitor between the speaker and amp so who knows? The amp will take a 4 or a 8 ohm load, but not 16ohm. If anyone was to connect two speakers to this amp then it should be done from the two output jacks at the back of the amp, and not by daisy-chaining the speakers together. There is a small resistor across the second jack socket, and this is not switched-out when speakers are daisy-chained together.

I guess for the time this would have been quite a smart little amp with its 5-band eq and line out. But these days you notice what is missing. No level/gain on input, no effects send and return, no compressor, no footswitch for the eq. That said, it is good at what it does, and remember Yamaha did go on and develop the amp further in later years. With my limited testing it would seem to be a good choice of amp if you were looking for a mellow 70s sound.

By the looks of things Yamaha only support the version III bass amp. You can download the schematic for that one from the Yamaha website. It is possible they will send a schematic on special request, but I haven't tried myself. The tone controls on mine were cracking and popping all over the place, but meanwhile the eq worked like a dream. I guess that says a lot about how often the eq had been used by previous owners. The jack sockets are enclosed in squared plastic cases just like your old hifi. I can imagine problems obtaining spares for these, the obscure transistors and the line-out transformer. Maybe get ready with the switch cleaner before ripping anything out.

As stated before the amp is super-heavy duty in build quality, so should survive the rigors of the road. The amp I have looks clean inside - no repairs done to it so far and that is saying something for a 30+ year old amp.

Yamaha are not likely to go bust just yet. Never tried customer support but there are extensive links and downloads and things on their websites (there are lots of Yamaha websites).

Can't really give an opinion on this as I haven't used it very long. It seems pretty much OK. A bass player might get real excited by it, the way it can shake a room down. But I don't think I will be hanging on to it as its not something I would use that often. If you took the badge off the front you would have something that looks essentially like a fender amp. The lack of effects loop, and pre gain is a shame, but not the end of the world. Ideally suited for playing rock.