(Michaels) HH HISTORY PAGE
The following article is based on my own 45 years (limited) experience and involvement with HH, Laney, and also examination and repair of Marshall, Hiwatt, Vox, Fender, Mesa, Trace, Ashdown and other similar product made since 1967. It is written from a totally biased engineering point of view. All copyright is reserved and I would prefer you didn't use this text without prior permission. They might think I said it. Libel, Plagiarism etc. Ask first and I will almost certainly say YES.. Scratch me - I'll see you in court asshole....
7) Have few beers whilst struggling with Dreamweaver and a new laptop keyboard. Windows 7? Isn't it just great?
The
first music range products were the IC100/IC100S/MA100/MA100S/S130
and appeared around the end of 1971 - early1972. They were not
copies or adaptions of any other product and were radical new designs.
The IC100 was drawn up in June 1971, the IC100S
in September 1971, and the MA100/S later in March 1972.
I’m sure production was already in progress at these times. Early
serial numbers had a pattern. 2
prefix was MA100, 3 prefix was IC100S, 4 prefix was IC100 (eg 2081 was
MA100 build number 81, 4054 was IC100 build number 54 etc). Later serial
numbers are quite meaningless and were applied across the whole
HH range for
sales records only.The VS Musician, VS Musician Reverb,
and the VS Bassamp were drawn up around January 1976 and were
available shortly after. The IC100L appeared in mid 1977
as a response to dealers who preferred the IC units to
the new VS range. The MA150 and S150
appeared in the early 1980's and were the last of the Music Range products.
The music range
products are nowadays considered the most interesting and sought after
items from HH so I will
go on a bit in the next paragraph.
1. Op amps, noise and reliability. The HH preamplifiers were all based around the then quite new (to the audio industry) 741 operational amplifiers. Early units used 14 pin devices, later units 8 pin. These are ALL THE SAME DEVICE although there is confusion amongst the no engineering brain (but I have researched it on the Interweb..) assholes - as some were prefixed 2741, A741, shit741, pig741, concorde741, etc, and fostered no doubt by the fact that most HH diagrams including the ones I drew show 14 pin nomenclature. I had realised by as early as 1969 that these were ideal building blocks for audio but even the best ones were noisy, and also even though HH used Military spec devices in the early units, noise levels were high and failures were common. The early HH amps used +/-19 Volt supplies for these devices – I consider that ambitious even with today’s devices as reliability of op amps is loosely a function of the supply voltage. The reduction of the supply to first 16 Volts and then 15 Volts (by the time the VSM/VSB came along) paid dividends. The noise problem in the IC100/IC100s units was tackled simply by the provision of a Stage/Studio (gain reduction) switch. A better power supply layout in the VS units helped once again..
2. Power amplifier failure. This was a big problem. The first units I ever saw in 1971-2 used Darlington based output stages similar to the second series TPA 50D and had driver pcb numbers AO 3073, (and AO3073/2 - second attempt, getting there...) I dont think the transistor based TPA AO3071 was ever used in the music range. The Darlington units were state of the art and well designed but turned out to be totally inadequate from a gigging point of view. There is a slight difference between a TPA 50D being used sensibly by a qualified BBC engineer using a controlled signal source connected to a correct speaker load using impeccable cables and young son hammering a Les Paul or a Strat at full power+++ and then some through an IC100 or S connected to as many speakers as he can find (Impedance? Wosthat?) using dodgy bell wire speaker leads and sellotape wrapped arcing sparking shit jack plugs. That slight difference is that it bangs and costs money to repair and doesn't do your reputation as a manufacturer any good. Ah.. So they changed to using a conventional bipolar output stage (AO 3103 pcb, through issues 2/3/5/6) and the problems grew less, but still didn’t quite go away. I maintained then and still do that the problem was not the actual output devices themselves, but the driver stages. The driver transistor part of a typical Darlington output transistor is fabricated on chip to supply the theoretic need of the output transistor part – not big enough in our thrash music world. The discrete TO-5 drivers used on the AO3103/5/6 were better but still only just adequate. In December 1974 the AO3103/7 pcb with its two grunt overkill RCA 40871/2 plastic driver transistors appeared across the range and the problem was minimised. The AS00014 pcb used in the VS and later units was a further development of this, getting rid of all the TO-5 devices and inheriting more sophisticated short circuit protection courtesy of the S500-D (Crown). This was a great move has proved to be a very reliable design – we still make it as a replacement to this day. Oh in 1974 they added a “D” suffix to the serial numbers of the amps fitted with discrete driver stages.
I still have Mike Harrisons original A0 pencil drawn circuit diagrams of the original IC100 and IC100S . First series IC units can be identified by the lack of the stage studio switch and AO3078/A front end (in the IC100S). Second series amps followed shortly after and had the Stage /Studio slide switch on the back panel, and the more familiar toroidal transformer and AS3078/B preamp. Early examples also had solid aluminium knobs with grubscrew fixings, the rear panel was fixed with Allen head set screws, and the pre amp Zeners were MZ (these look like a TO-92 transistor with 2 legs).The definitive version with the Stage/Studio switch in the centre of the front panel came I think at the end of 1972 and stayed cosmetically the same until discontinued in 1976. The power amplifiers were updated constantly. These amplifiers are quite noisy compared to modern stuff. Thats the way it was, thats why they fitted the Stage/Studio switch. Oh, and the S in IC100S meant Standard, not Sustain. See MA100S etc. (You cant tell me this was a PA amplifier with Sustain old chap. Get a life..)
!First series IC100S units had a totally different preamplifier, pcb 3078/A. This is essentially similar to the more common 3078/B used in the later units, but many component values were different and a transistor driven filter preceded the power amplifier stage. These amplifiers have a totally different sound to later issues.
If you are trying to emulate Mr Bolans sound, you'll have to consider this one.
Full details of other important differences/changes and how to date your IC100/IC100S/VSM/VSMR/VSB are given in our service manual M101.
The VS Musician, VS Musician Reverb, and the VS Bassamp were drawn up in January 1976. Early versions can be identified by having two input jacks on the main channel, in lieu of the single jack plus "Effects Input" DIN fitted on later units. These were a natural progression from the IC range, and demonstrated HH's response to the necessary "Valve Sound" then beng requested by certain factions. These amplifiers all contained a sealed "Tone Correction Module" aka the "Valve Sound Module" which was promoted as the heart of the Valve Sound of these units. Used correctly it actually worked very well. Used incorrectly by the set the controls for the heart of the sun brigade, the transistor power amplfier took over and the subltey was lost. The non reverb VS Musician was produced in small numbers and is now quite collectable. A reader points out, quite correctly, that the perspex panel on my first edition VSB pic above is different to the later issues. Spacings are the same, but a box is drawn round the bass boost control on later issues. We live and learn...
The idea of the tone correction module and its contents was patented by HH, and a schematic diagram was never published by them. Nor will it be by us as we (truthfully) do not have one. We build replacement modules from an original pattern. And as it exists only as a replaceable module, a schematic diagram of the internals is unnecessary for servicing and repair purposes.
And thats why I'm here son... But for any interested geeks:
What I will tell you is that this module is not a complex holy grail integrated valve sound device. It actually contains six completely separate unrelated electronic mechanisms. They are:
1) The inductor and support electronics for the Middle control
2) The inductor and support electronics for the Presence control
3) The inductor and support electronics for the "Voice Switch" function
4) The harmonic generator for the "Valve Sound" function (the important bit, but actually a very simple junction FET stage)
5) The electronic FET switching necessary for the Valve sound switch/footswitch function (revolutionary in 1976)
6) Channel 1/2/reverb mixing stage (nothing works if this fails)
The AS00015/A is the VS Musician variant, the AS00015/B is the VS Bassamp variant. They are identical apart from two gain set resistors we fit when they are made.
Our replacements are not sealed, so you are quite welcome to buy one and draw it out if you are sufficiently interested...
Early tape machines used a short tape loop similar to a Copicat (but not the same length..) and a simple jockey arm tensioning system. Very reliable in operation but tape life was short. Later machines had a much longer 3m. loop and a transport mechanism not unlike the Roland units. These can be recognised by the large perspex tape house you see when you remove the lid. All machines are capable of excellent performance, and are much sought after today. The later transport mechanism is crude but effective - given constant fiddling and maintenance.. These machines are NOT in any way to be considered "plug and play" - the top cover will be off more than it is on... You've bought a classic car, son... Get on with it.
OPINION: Tape Echos - Superb performance if you can find a nice one and afford it. We have the spares and the tapes.
Digital Echos? - Fancy a second mother in law? Perhaps not. Thats what you might as well BUY.. And don't ask ME to fix it or set it up. Or "Calibrate/Tune" it (Another F stupid internet word...).
The MA100 and MA 100S (basic non reverb, that S again) although not considered very interesting now, probably accounted for the majority of early HH music range sales. A first class 5 channel 100 Watts+ PA with reverb, electroluminescent front panel - it had to sell, and it did. They sold SERIOUS numbers of these... Not overtly collectable but still a good working PA even now. And useful for guitarists with all the sounds in the floor pod. Note these amps are extremely noisy by todays standards - gain levels were set very high. Do the MA series (only) noise reduction mod detailed in the service manual. The MA150 was the later version, sported a switchable effects loop, and used a mains transformer borrowed from the Performer amplifier to provide the extra gruntitude. The S130/S150 were the power amplifier only versions.
A VS Musician Mk II was planned – I have the original unfinished works diagram and but it never made production. Strangely it also bore no resemblance to the impending Performer range amplifiers. They just changed direction overnight. Odd. Very odd. What a mistake they made. (Perhaps they were all pissed?)
By late 1975 I was becoming very familiar with the Crown DC 300A power amplifiers that Slade had bought back from America following their first tour. These were to replace the ageing WEM power blocks which formed the basis of their PA. I noted the Crowns were virtually flawless in performance, and could deliver 340+ Watts/channel into 4 Ohm loads. Down side was that these units were 4U tall and about 9” deep, and they required forced rack ventilation – having no cooling mechanism of their own. The build quality was only fair. An internal mains fuseholder attached only by double sided stickytape? God. And like everything else they went WRONG. There was no load protection in the event of a catastrophic failure and DC on the output terminals… But they were the most powerful amps I had ever seen and they sounded superb and I was getting used to working on them...
In late 1975 for reasons I will not bore you with I personally handed a copy of the Crown DC 300A technical handbook (with schematics) to one of HH's senior representatives - he had explained to me that they were looking at producing a similar high power amplifier and any relevant data would be useful to them... (Didn't get me that free dinner though Clive did it..)
The S500-D
was unveiled mid 1976. It was 2U high, 15” deep, had its own cooling system
on board, looked mean, sounded perfect, green light front panel, and delivered
believe it or not 340+ Watts/ channel into 4 Ohm loads. It could also
work into 2.6 Ohm loads (3 x 8 Ohm speakers), delivering 440 Watts per
channel. Wow. I took a great interest in these, even
at that time. The driver pack was in the form of a potted block, apparently
to stop people copying.. When they unsealed the driver module 12 months
later, and published the circuit diagram I looked at this carefully and
I really had to smile. This was no more than a straight copy of the DC300A
but with minor changes to the output stage to make it quasi complementary.
They even retained the American sourced 739 input op amp and high voltage
driver stage with exactly the same resistor values! Dohh.. But what they
had done – and this is creditable – they took the unworkable 4U Crown
package and put it into a highly useable 2U format. The S500-D
is a great amplifier. Not many people will work on these now. I do lots.
BUT if it goes wrong it WILL destroy your speakers. There is NO
load protection.
Arguably
the most successful power amps in history, these were built around the
then new Hitachi power mosfet output devices. Looking at the apparently
simple drive stage, which I attributed at the time to HH,
I noted that although there were some failures hardly any involved the
output stages. Well done. And the performance was neutral and flawless,
with overkill spec transformers and power supply components (13600uf/rail
to start with, most later amps had 30000uF/rail. Great bottom end then...
It was only many years later that I was given a Hitachi
Power Devices data book and realised that these designs
were a straight application of the supplied data but with obvious
HH embellishments. I still have the book. In fact, only
problem with the Hitachi fets was the price – they were
very expensive, even at the time. Wish they were still made now though
dammit...
When
these arrived for evaluation and comment on my bench as the replacements
for the superb music range products, I opened them up expecting something
else (in the words of Eddie Cochran). Not so, I was very disappointed.
The build was again awkward, with a thick wiring umbilical between front
and rear panels, and the whole build method appeared to be a backward
step from the previous fine efforts. But they had used junction fets as
building blocks, mixed with bipolar transistors and op amps, and had a
mosfet output stage. They sounded very good, and the Bass Machine
with its 250 Watts output was the most powerful Bass amp going. Great.
But the input fets were gate unprotected, and they went down EVERYWHERE.
By the time HH issued an
official protection fix (A year later!) we’d been doing this anyway. These
amps cosmetically strongly resembled the American Acoustic
amps being imported at that time – with the pastel colour front panels
- although they were electrically quite different. No disrespect to anyone
but I don’t think HH should
have been concerned at all, or chased this particular dragon – the
Acoustic amps were good
working stuff but blandly uninteresting and just about as unreliable as
everything else of the period.
These were being produced as HH
passed into Carlsbro’s hands around 1982/83 and production continued into
the late 1980’s. They were good working amplifiers based on traditional
Carlsbro and HH
values but were pretty unexciting products. Far cry from the original
music range efforts. A couple of notes: The build quality was very good
throughout, and whoever dreamed up the B100 got it smack
on first time. What Bass player even now could want more sensible features
than this, other than a sub harmonic dedicated
owner. Dont ask - Its a quiz. Aspidistra etc. etc.
Schematics, footswitch data, fault finding hints, and more detailed dating info can be found in our SERVICE MANUALS which are available by email or CD rom if you prefer to pay extra for the postage.