Yamaha YBA-100

The Yamaha YBA-100 consists of a head [Model BE-200] and a powered cabinet [Model BS-100]. It was designed and built during the 1960's by the Nippon Gakki Co. Ltd. Hamamatsu, Japan. I first saw it introduced in North America during the early 1970's. It was Yamaha's premium bass rig and billed as their 'Ampeg SVT killer.' It represents some of the best industrial design that era had to offer but was quite expensive, which I credit being the reason they didn't catch widely.

The BE-200 head is a 2 channel solid-state preamp with no channel switching. Each channel has a high and low input, volume, bass, middle and treble controls. The controls are linear tapered slider controls in, what appears to be, one of the first implementations of a "graphic" style of EQ.

Channel 1 has the addition of an EQ "preset" bank, which consists of 4 push-buttons [similar to the transmission selector buttons on my Grandpas '57 Plymouth] - Cancel, Deep, Mellow and Bright. When any of the last 3 are engaged, the graphic EQ settings are disabled, allowing 4 tonal settings at the push of a button. The names are descriptive of the tones they generate. The back of the head has 4 x 1/4" phone jack outputs, wired in a simple gang-array fashion.

The BS-100 powered cabinet features a 100 watt RMS solid-state power amp, 3 x Yamaha 12" 50 watt 8 ohm bass drivers wired in parallel, plywood construction with a MDF baffle, recessed side handles and castor's. There is a 1x3 wooden block connecting the middle of the baffle to the middle of the back of the cabinet so they move together. The amp has a power switch and 2 x 1/4" phone input jacks on the back.

A word about the overall industrial design is in order, as this is one of the neater features. The head and cabinet together have a very cool "Jetson" vibe to them, as they were designed during that era. The have a 1.5" strip [of what appears to be aluminum] running around the edge that provides a great design look, but serves the function of protecting the pieces from damage in transit. [Looking straight on at the unit, they run up both sides, around the top, down the back to the bottom where the 2 ends meet.] I got the unit used in 2007 and, while it sports some war wounds, it has stood up extremely well and is a testament to the brilliance of the design. Head and cab are covered in a medium gray tolex. The cabinet came sporting Yamaha's blue pin-striped grill cloth that was current during that era.

The unit was designed to be "extensible" in a very simple, yet brilliant way. The cabinet has 4 molded plastic indents on the top which match to the 4 molded plastic "feet" on the bottom of the head AND to the 4 castor's on the bottom of the amp. This allows cabinets to be stacked as high as you dare. The 4 outputs on the head allow you to connect directly to 4 separate cabinets and the 2 jacks on the back of the cabinet allow you to chain as many cabs together as you want without serious signal degradation. The cabinets are stackable, so you can easily build a wall of 100 watt RMS power modules as high and as wide as you could afford!

I'm giving this category a 10, not because it has all the features we've come to expect in a modern amp, but because it was at the bleeding edge of bass rigs in the day it was designed and is still a brilliant implementation of most of what a gigging player needs - versatility!

The YBA-100 was noted for 2 things - huge volume and a "hi-fi" [in a good way] tone. Even though the power module is rated at 100 watts, it's old-school transistor RMS - there isn't an IC anywhere to be found.

The huge volume, and I mean HUGE, can be attributed to how they selected and wired the speakers. The 3 x 50 watt 8 ohm speakers are wired in parallel. This equates to a 2.667 ohm load which is roughly equivalent to the output of a 230 watt amp!

The "hi-fi" nature of the tone can be attributed to a combination of the 12" drivers, the MDF baffle and lack of sound absorption materials in the cabinet. The tone was perfect for the era it was designed for, which was prior to extended range bass guitars.

I use a Yamaha BB-405 bass with Q-Tuner neodymium pickups. It is a 5 string bass [low B] and the Q-Tuners provide the best sound quality available from any pickup.

When I first got the amp and plugged in everything was fine until I got down to the low end of the E and the B strings. The sound turned to flub as the speakers simply could not deal with the low frequencies my bass was giving them. A bit of a disappointment, but not the end of the world.

As luck would have it I had a vintage JBL K-140 15" bass driver looking for a home, so I undertook a speaker swap. I prefer the sound of 10's and 15's for bass, so I scouted out a couple of Peavey Neo 10's, which I felt would complement the neo pickups in the bass. I replaced the stock MDF baffle [they must have chosen that material on purpose since the rest of the cabinet is plywood] with 3/4 birch ply and the blue pin-striped grill cloth with black Marshall cloth. I also took the opportunity to stuff the cabinet with insulation to help deaden any cabinet reverberations.

The JBL and Peavey's are 8 ohm speakers but didn't sound very good wired parallel as the stock configuration. After some experimentation I settled on the 2 Peavey's in series and those in parallel with the JBL [or something like that]. Whatever the wiring [I'd have to take the back off to verify and there are a million screws, so that's not gonna happen] I ended up with a 5.33 ohm load which translates to the equiv of a 182 watt amp.

How does it sound?

Like GOD in a box.

It handles the low B with aplomb and literally shakes the building. While I lost a bit of the volume, the tone more than makes up for it. It has no trouble keeping up with a Marshall 1/2 stack and a heavy-handed drummer.

Ranking on sound quality depends on how you view the amp - in context of the day it was made, today in stock configuration, or today with some modern updates.

It clearly gets a 10 for the sound in context with the day it was made. It was designed to be a vintage Ampeg SVT killer, and it delivered on that promise in spades.

In it's stock configuration with a 4 string bass today, it might not deliver the low end some have come to expect and it certainly won't keep up with an extended range instrument - so here I would have to give it a 6 to 7.

But, with a few upgrades to the speakers, baffle and a bit of cabinet damping, and you simply will not find a better sounding bass rig anywhere. With upgrades, I give it a 12!

This thing has been in service for over 35 years. When I got it one of the input jacks was intermittent [easy fix] and the head of the volume control on the second channel was broken off - but the control still works.

I'm not sure many, if any, modern amps would fair as well after 35 years of hard use. This amp will continue to operate long after I'm gone.

You certainly can't expect much by way of support when buying a 35 year old electronic device, but I must say Yamaha [Canada] is an absolutely fabulous company to deal with. They maintain a library of manuals of all the equipment they've ever carried. I ordered the service manual for the unit and had it delivered for under $15.

While this unit is long out of warranty, I do happen to be personal friends with the former service manager for Yamaha. We went over the unit from head to toe and could not find a single problem with it, aside from a bit of dust that had accumulated over the years.

We did do a search through Yamaha worldwide to try and find a replacement volume pot, but none could be found. It was a long shot, and the people at Yamaha were very good in at least trying to see if one was hidden away somewhere. Since the pot still works, this was more of a cosmetic than functional thing anyway.

I've been playing on and off for about as long as this amp has been in service - 35+ years. I remember lusting over these when they were released, but it simply wasn't a financial reality. As luck would have it, one finally did find it's way to me and I'm ecstatic the karmic wheel of life has been so kind to me.

The tone I get out of this thing is simply second-to-none. Unfortunately it's way to big to move around without help, but then, that can be said about most 1x15 combo's as well. If I need a hand moving a rig, it might as well be a rig worth moving and this is it/

I've looked long and hard over the years for the perfect bass tone. I found it in the Yamaha YBA-100.

I'm posting this, not because there are a lot of these around, but because there are NOT a lot of these around and most people don't understand what they are. If you find one, snatch it up, swap the speakers and enjoy bass-bliss.