A big Acoustic tower...

Introduced in 1967 the Acoustic 360 tower (commanding views in all directions?) was a solid state bass stack with all discrete components, built around mainly silicon transistors**. But the Model 360 Bass head had no power output stage - it contained just the solid state pre-amp with tone stack - well, it also had a rotary switch “Variamp” tone control, a fuzz circuit and even an “electronic tuning fork”. The matching 361 cabinet housed not only the speakers but also a 200 watt power amp. Audio output in the large “W bin” cabinet was handled by a single, rear firing, Cerwin Vega L-187 special design 18” speaker, in a folded horn construction - not unlike Altec Lansing’s “Voice of the Theatre” bass reflex cabinet designs for cinemas in the 1950s. The choice application of these various amplifier design elements was to good purpose and the sound quality of these ACC rigs was soon causing a stir. Despite their transistorised circuit there was no harshness in the treble range and they were exceptionally articulate in the low end. But more than anything the 360 series was loud. The folded horn cab was extremely efficient and, get this Stonehenge fans, you could connect up to four 361 cabs to one 360 pre-amp head unit. And the 361 powered cabs also had a speaker output with high-pass filter to feed a passive extension cabinet. 

The ACC company had been founded by Steve Marks and his father Robert in 1965 in a shotgun shack on Sunset Boulevard, before moving on to Van Nuys, CA, where the company was incorporated. Following on from ACC’s first guitar amp, the Model 260 head & 261 cab - which gave Acoustic their first big push when Robbie Krieger of The Doors started using it - the 360 was designed specifically as a bass amp, largely by a guy called by Russ Allee. Early adopters of the new Acoustic tower were John Paul Jones, Larry Graham and John McVie, which certainly speaks for their sound quality, but they weren’t exactly flying out the door. It might have had something to do with the price tag: the 360/361 set cost $1250 when it was released, that’s nearly $10k in modern money. No wonder Jaco Pastorius would sleep on the beach while his bandmates motel-ed up, in order to save up for one. Jaco is of course the man most famously associated with “the big Acoustic tower”. And while you can talk about the type of epoxy he used to fill the empty fret slots and seal the fingerboard of his ’62 Jazz Bass or the way his right hand would dance over different pups, there is one further thing we can say about his tone. He would have had a hell of a job trying to get it with any other amp rig in 1971. 

There was a panel on the back of the 361 cab where a mains power cable went in, with a rotary connection power switch, an orange indicator lamp, an input jack and a 5A fuse holder. This back plate of the 361 cab proclaimed in one column of white lettering “600 Watts, 120 Volts and 60 Cycles”. And then underneath that the same column of three ratings was repeated but with the output revised to 200 Watts. I don’t imagine anyone familiar with amp power ratings would be able to make sense of these numbers or how they might equate to each other. However in one of their early brochures for the “Model 361-Bass Amplifier”, Acoustic opened the specifications with “440 Watts Peak, 200 Watts RMS” - a ratio that sounds more like it. By the time they brought out the Model 371 the brochure claimed “730 Watts Peak, 365 Watts RMS” back to confusing numbers again, RMS ratings are never exactly half of peak-to-peak, so should we blame the marketing department? Maybe that’s the real reason Jaco Pastorius didn’t like the 371, it lied to him. Whatever the reason, he refused to convert to the 370 after trialing it for Acoustic and stuck to his favoured 360. He did however like the Acoustic 320 when it came out around 1978, but still used it in conjunction with the 360 preamp. The 370 was matched with the 301 passive cab which had the same 18” folded horn design as the powered 361. But while the 361 had a module with the driver that bolted into the middle of the cab, the 301 cab had an integral chamber for the driver accessed by a rear plate; though on later models this could only be accessed through the front grill. The 370 could sound a bit nasal in the mid range and some versions had a volume jump in the first half of it’s range, oh and it’s Bright switch was most definitely bright.

Jaco Pastorius famously continued to use 360 pre-amp heads throughout his career even after moving to the 320 head and 4x15” Acoustic 408 cabs. Interestingly the only other amp he is known to have approved was made by Amplified Music Products. In 1985 Pastorius visited Hartke Systems in Bloomfield, NJ, and was so impressed by AMP’s Model BH-420 that he ordered one. The AMP serial #1166 shipped to Jaco in May ’85, but it was only much later that he learned that it had been designed by Russ Allee - the same man who had designed the Acoustic 360. After the AMP company folded the BH-420 was restyled as the Gibson Model GB440 which later morphed into an independently built 440 copy, the Thunderfunk by Bob Gunnison, aka Dave Funk, who had bought up all the unused GB440 parts. 

So can we say that Acoustic instigated a solid state revolution in the low end world? Well Acoustic’s 360 was hardly the first transistor bass amp. Back in 1962 Vox had brought out the T.60, which was also the first amp they designed specifically for bass players. Prior to this Vox had only offered their bass tone modified AC15 and AC30 combos. Indeed the T.60 may be the very first transistor bass amplifier. It has been claimed that the Kay Vanguard was the first solid state guitar amp of any kind, but if that’s true it was only first by a very short nose, as it also came out in 1962. The development of a new solid state power amp design came from Les Hills who had worked on Vox’s Continental organ. The T.60 was a germanium transistor amp head that put out about 35 watts RMS and was originally paired with a 2 x 15” cabinet. It was hardly a tower of power, with a speaker box just three feet high and rising another half a foot with the head on top. In 1963 this was followed by the 50w Foundation Bass rig consisting of an AC50 valve head into a 1 x 18” cab. Both bass cabinet designs were closed back for better low end response, unlike the open-back AC bass combos. The T.60 cab was then changed to a 1x15” with 1x12” formation and had a simple capacitor crossover; which in turn became the AC100 2x15” cab in 1964 (but was often referred to as the T.100). It was rated to handle an AC100 head - which is what Paul McCartney drove it with eight days a week for the next couple of years. Vox had stepped up to the plate alright, but a 100W bass rig was hardly going to hit it out of Candlestick Park. But before we move on, let us remark on the fact that Vox made a 100 watt valve head in the year before Marshall were persuaded to do so by The Who. As the Beatles became bigger than Jesus their need for volume was greater than other bands. No other “popular beat combo” was playing baseball stadia in 1964. 

If the Acoustic 360/1 put out 200 watts RMS, and you could have four stacks of it in one system, was it the loudest bass amp around when it came out? Well, you might compare that to the 300 watts RMS put out by the all valve SVT — but then remember that Ampeg didn’t release the SVT until 1969. Ampeg have always been associated with bass, and I mean always, because they were there at the very start of bass amplification. It all started with the Michaels-Hull Electronic Labs’ double bass amp system. The first ever “Bassamp” and double-bass pickup appeared around 1946 which they followed with their 770 system. The pickup was fitted to a modified spike for an upright double-bass and this “amplified peg” was advertised in 1947 as “The New model 770 Bassamp with Ampeg pickup - The answer to the bass man’s prayer”. The company name soon changed and in 1948 the The Ampeg Bassamp Company’s 800 models were released. The same brochure for the Model 770 advertised the specs as 18 watts “usable” from a 6L6 output pair. The first stage was 3 x 6SN7 and the rec was a 5U4. You know, the first Fender amps and their K&F precursors variously used the same tubes. This new amplified bass sound came out through a 12” GE speaker - and through a rather fetching bass clef cabinet front grill. Of course Rickenbacker were already making wireless style amplifiers with valves for their revolutionary electric guitar pickup, but although they would become famous for their bass guitars they hadn’t yet built a dedicated bass amp. 

But getting back to 1969 and the year that Ampeg released it’s new bass guitar rig: a massive 95lb (40Kg) head containing no less than 14 valves (and it wasn’t even valve rectified), stacked on top of a cabinet as tall as a short singer and with 8 — that’s right 8 — ten inch speakers! No wonder it was called the Super Vacuum Tube amp, and you know, it went on to be quite a successful model. Ampeg reckoned it could pump 300 watts into a 2 or 4 ohm load. These towering new cabs were loaded with CTS speakers with a declared total power handling of 240 Watts, so Ampeg tried to sell you on the idea of buying two cabs if you thought you were going to really crank the amp. Sixteen speakers totalling 480 watts power handling would more than cope of course. Those early “flat-back” 8x10 cabs are sought after for their sound in a way that the later higher rated SVT-810 cabs are not. A lot of old timers reckon that an original cab was quite capable of handling the SVT at high levels and that we can’t be certain that the original CTS speakers were only 30W since their specs have never been published. Indeed the Eminence speakers put into the first “towel bar” Magnavox era 810 cab were rated at 70W - and they were supposedly based closely on the original CTS unit. Even if the CTS units were only rated at 40W then eight of them could handle a 300W head. And anyway, many of the the old “flat back” cabs can still be found with their original speakers since they rarely blew out. And here's another thing, the significantly better low end response of the original cabs means that their power handling is more efficient and they have a wide, smooth frequency response. So did the Ampeg marketing dept. under-sell the original cab in order to try and double sales? As the years passed the changing companies that controlled Ampeg kept putting in sturdier speakers so that a single cab was given a higher and higher wattage rating, but not really any better power handling, especially if you were playing below the 41.2Hz of a low E string. It wasn’t just the speakers that made earlier 810s sound good though, the construction was also a big factor. As the years went by the cabinet construction quality went down the toilet.*** 

So that night at The Marquee, I don’t know what amp Nick Lowe was using as a bass rig “in a bid to save a bit of power” but I doubt it was a big Acoustic 361 tower, and it probably wasn’t louder than 100 watts and almost certainly no louder than 200. And while I think that the SVT was formally revealed at the Chicago Namm of June ’69, it was still in development in July. Down the road at the great Hyde Park butterfly massacre there were no Ampegs on stage either. All the amps were either WEMs for the PA or HiWatts for the various guitars. Bill Wyman’s bass rig was driven by 200w HiWatt DR 201 heads as well as Dave Reeves slave amps. In amongst the WEM columns you can see the various HiWatt rigs that Keith Richards and Mick Taylor were also using. One of the great anecdotes of the SVT story was that the Stones turned up in America to start their 1969 tour in November and somebody blew up all their amps with the wrong voltage. Whatever the truth of the matter The Rolling Stones took Ampeg’s prototype SVTs on the road for their first big US tour in three years. It was a run across the pond that would become truly legendary. In 1966 the Beatles had made their own decision to never tour America again, but the Stones had been banned since '66 by US authorities. The SVT was used for all guitar & bass amplification for the entire '69 US Tour (the V4 wasn't finished yet) and Ampeg’s Rich Mandella went with them to keep them running. The V series amps expanded in 1970 and though the Ampeg V4B head only put out 100 watts it’s a great sounding bass amp. (Actually, on PJ Harvey’s Hope Six Demolition tour of 2016-17 we used John Parish’s V4B and matching 4x12 mainly for the Mellotron and only on a couple of songs for bass guitar.) 

Sunn Musical Equipment Company’s Orion amps were built in 1968 with more than a nod to Acoustic. To quote an advert from the trades at the time it featured “application of a modular concept, built in buzz tone, solid cabinetry, versatility of sound reproduction and JBL D15S speakers. The Orion control amp drives a 175-watt RMS power amp mounted in the bass (sic) of the speaker enclosure. If additional power is required, a PMI (175 watt power module) can be added to the initial Orion PMI to develop a total power output of 350 watts RMS. Another PMI can be added for 525 watts and so on to infinity." Now that really smells like marketing bullshit! As with the Acoustic 360 driving 4 x 361 concept - you’re getting a louder rig with more coverage by having 4 x 200W amps, but that’s certainly not the same thing as one 800W amp! The Who used the Orions in ’68 in the US. But then Entwistle & Townsend between them used just about every monster amp that was made as soon as they could get their hands on it. 

At the start of the ‘70s Simms-Watts brought out their A.P.200 Super (for “All Purpose” 200W). Twin channels labelled Normal and Brilliant, each with 2 inputs that could be linked with a slider switch, and controls for Presence & Master Volume. It had an ultra linear power transformer (like the Silverface Fenders of the time) that could provide a plate voltage of over 670v to it's quartet of KT88 tubes. It was also very similar in design to the KT88 loaded 200W (nominal) Marshall Major, though tonally it sounds much more in the realm of a HiWatt DR 201 (also powering 4 x KT88). David Simms had a music shop on Ealing Road called Music Bargain Centre (“I wish I could be like David Simms” as my Guv'nor almost used to sing) about 200 yards down the road from Jim Marshall’s! There he was joined in 1968 by Richard Watts, who designed the circuits, and soon after Jim Marshall’s son Terry. Terry was famously the T in JTM but had fallen out with his old man, who promptly started labelling his amps JMP instead. Actually the A.P.200 has a much better layout than the Marshall Major, particularly the positioning of that huge output transformer. This and the excellent screening between pre-amp & power stages, much like some Matamps, gives it a much quieter noise floor than the Major. Simms-Watts cabs of the time were usually loaded just like HiWatts with the cast frame Fanes, but sometimes with RCFs. But best of all they had bright red faceplates that often had big exploding cartoon speech bubbles which said things like POW! and SUPER.

Pete Traynor the Canadian amp pioneer of Yorkville Sound, and a bass player himself, did more than most to develop bass amp design. He may have started out by copying Leo’s Tweed Bassman in the magnificent Traynor YBA-1 back in 1963, but by the turn of the ’70s he was dreaming about something big, and his pet project would be solid state to boot. Back in 1967 when the ACC 360/1 came out Pete was still squeezing more and more juice out of tubes. That same year he produced the powerful YBA-3 Custom Special, and to handle it he paired it with a new cabinet design. The huge YC-810 was rated to handle 250w at 4Ω, but there’s a clue in the name that was not such an obvious indicator in 1967. That’s right, everybody thinks Ampeg invented the 8 x 10” speaker cab for the SVT, but Pete Traynor had already done it two years earlier. The fan cooled YBA-3 used four 6CA7 valves (EL34 variant) to output 130 watts RMS sine wave into 4 ohms. Traynor power ratings were for non clipped signals allowing plenty of headroom and I’ve heard it could comfortably put out well over 200 watts flat out. I would be interested to know if anybody ever had the chance to compare a YBA-3 with a 361.

By the time Nick Lowe gave his nod to Acoustic Control Corporation in 1976, if such it was, there were a host of colossal amp rigs for bassists to choose from. Not only that, but the fad among the more adventurous bass players for using large stereo power amps had led to dedicated bass guitar amps along the same lines. Andy Hefley of Great American Sound built a set of four 2,500 watt RMS amps (2 for stage and 2 for backup), weighing 250lb each, for Phil Lesh of the Grateful Dead. These Precision Innovative Electronics Model M87 Wideband Power Amplifiers were souped up versions of the GAS Godzilla solid state behemoths Hefley was already making. Bass players are spoilt for choice these days for high powered amps thanks to the Class D revolution. For example the Bugera BTX3600 Bass Amp Head is called The Nuke and they reckon it’ll do you 2 x 1800W in stereo or biamped mode, or 3600W bridged. If that’s true it’s an atomic bomb of a rig alright. So Lowe singing about fifty thousand watts is exaggeration, of course, even by todays standards - but you could get close to fifteen thousand though. How about a Lab Gruppen FP14000 touring PA amp… 7000w per channel into 2ohms! You could probably bridge them, and as the website says, it’s “Built to Handle Extreme Low-Frequency Loads Effortlessly”. 

And what happened to the Acoustic Control Corporation? Well, they continued into the 1970s. The 450 series for instance, made between ’73 & ’77 were 170 watt 4 ohm heads with a 5 band graphic, a feature that had migrated from the 370 head and went on to the twin channel Model 320. They also tried their hand at valve amps with the 160, 164, 165 Models. But then ACC folded in 1983 and either morphed into, or was taken over by, True Tone Audio manufacturing PA amps. In 2007 the name was revived as Acoustic Amplification, again making bass amps and in 2011 a new company set up as Acoustic USA making reissues of their classic models. And what was the first thing they remade? They got Russ Allee in to redesign the 360/1 big Acoustic tower of course. 

So I was going to talk a bit about electrical safety and the risk of electrocution but I’m going to leave that for another day. It’s not the sort of thing that should be rushed, especially with anecdotal wisdom to impart.