TUAC?

[Mike Honey]

Dont know if there any Sarf londoners on here but in the early seventies I was living at Tooting and there was a shop in the high street run by a couple of guys who built amplifiers. One, Dave, was a guitarist and one was a drummer. they were developing a pink covered amp and 4 x 12 cab ,transistorised but with a brilliant sound. I used to go to the shop at night and play with them and each time you would notice the little tweaks they had made to the amp. I believe they went on to make disco equipment, lighting etc. Whatever happened to them? Anybody heard of this brand?

mike

[John Boyd]

Mike,
I remember the brand from when I subscribed to 'Practical Electronics' magazine. Tuac regularly advertised amps, along with audio mixer modules
and lighting modules which enabled a constructor to custom build sound and lighting gear. From memory they were very well priced and at one stage I even contemplated importing some mixer modules.
Cheers,
JB

[JimN]

I certainly remember Tuac amplifiers. They were one of the makers who followed in the footsteps of Marshall when the "stack" became popular. Others doing the same thing at various levels of quality included Hiwatt, Sound City, Impact, Simms-Watts (London-based) and several provincial makers including Carlsbro, Park and even Miles Platting (named for an area of north Manchester which had just been flattened by slum clearance).

Tuac amps were advertised in the music press - notably the Melody Maker (which at the time was the weekly bible of rock and pop music) - but I don't think I ever actually saw one in use. My guess is that not many were made.

JN

[RayL]

TUAC (the Transistor Universal Amplification Company) had a shop in Mitcham Road, Tooting, close to Amen Corner, with a small 'factory' round the corner in Bickersteth Road. Back in the 1970s and 1980s I bought quite a few of their 100w and 125w power amp modules to build into my own cases (and for others too). They also sold preamp modules and sound-to-light units. (I've still got a few around in my workshop shed). From the TUAC shop you could also buy their modules built into cabinets and they sold a lot, particularly in the South London area.

As the name implies, they only made transistor gear. Their amps were fairly reliable (they used a transformer to drive the output stage, which avoided the 'curse' of transistor amps at that time, which was a fault in the output stage that, in a domino effect, wiped out the preamp transistors because of direct coupling). However, the output transistors were prone to failure under heavy load and I replaced many, many of those over the years!

For more than 10 years I used a couple of TUAC 125 watt modules and six of their preamps in a metal case for a PA amp. The metal case helped to absorb the heat so although there were amp module failures every so often, I could soldier on with the remaining module.

Times were hard for music shops in the late 1980s and I think they closed at that time.

If anyone needs a TUAC circuit diagram I've got quite a few in the 'Amps' folder in my workshop.

Ray

[Mike Honey]

Thanks guys. it's nice to know that they went on to be 'fairly' successful. I remember them as really nice blokes and they didnt give a toss about the noise we would make in their shop of a night time. I lived in Rookstone road, nearly opposite the shop and my missus could hear us playing from 100 yards away!

mike

[stevejustin]

Hi, I am trying to obtain an RCA power transistor part SP507 for a TUAC 125 amp can anyone help me out or suggest an alternative. I m very attached to this piece of kit and would love to keep it alive. Tried everywhere no joy, perhaps someone will have a cherished piece they dont want. Steve

[geoff1711]

I bought a Fender F series Strat from a music shop in that location around 92/3 and they were still around for a while after that, probably 95/6, which to my mind was when valve amps stared to rise in popularity again.

In the early 90's I was playing through a Peavey Bandit with the Scorpion speaker, and if I'm honest (and take my valve head off) it sounded great, I still have one nestling in my garage.

Those output transistors were fairly common, if they're what I'm thinking of, I had them on my 1970's Disco Sound unit and later on a couple of Maine heads, they had a habit of going quiet when they got hot, which was a pain given that come the end of the evening you'd want to be giving things a fair amount of volume, by which time they'd got hot and wouldn't give it to you.

Modern PA amps are often rated at full output on 4 ohms and I've found that if your at a gig where you need a lot of output and run them into 4 ohms rather than 8 the thermal cutouts start doing their work, which is largely why I've gone over to powered speakers, they'll still cutout if you work them to hard, but they're unlikely to all do it once, and whilst I notice if a speaker goes to sleep for a couple of minutes generally the audience doesn't.

[RayL]

Hi, I am trying to obtain an RCA power transistor part SP507 for a TUAC 125 amp can anyone help me out or suggest an alternative. Steve

The 2N6254 was usually fitted to the 125 watt modules, although I've found one circuit that specifies the 40636.

I've got a number of old TUAC 100w and 125w modules lurking about in the workshop and they could possibly be cannibalised for their power transistors (both used the 2N6254). They would need checking because if one transistor blew in a module I would swap the module for a spare and have a big 'repair session' when I had a few modules that all needed fixing.

Ray

[AJAUDIO]

Hi Steve

You do not need to worry about the precise devices to fit as replacements in the TUAC TP125 as they are configured as a quasi complementary output stage being all NPN Devices, we have 2 of these modules one has MJ15015 fitted and the other has SP507 fitted in the output stage, both of these devices are pretty lousy by todays standards as the fT of an MJ15015 is .8 MHz, I suspect they just got hold of a job lot of whatever devices were the cheapest at the time and used them.

I would fit -

MJ15024 - 16 A, 250 V, 250 w fT 4 MHz
or
MJ15022 - 16 A, 200 V, 250 w fT 4 MHz
or
MJ15003 - 20 A, 140 V, 250 w fT 2 MHz

Dump the mica washers clean all the heatsink compound off and fit new silicone insulating pads, make sure there is no contact between the heatsink and the cases of the transistors, also you might have taken out the fusistors (little wire links) they can be replaced with .25 ohm 5 w resistors.


Regards

Alex

http://www.ajaudio.co.uk

[scuddmann]

Hi just stumbled accross this thread about T.U.A.C, I'm a newbie on this site so hi how are you I'm David, and "sorry" have been a mobile Dj/sound engineer for some 30 odd years, since the late 70's well 79/80 actually, and wow what fond, not sure that is the right word, memories I have of T.U.A.C, I had 2 stereo amps that I built up from there 125 watt modules and 2 of there stereo 4 channel mixers, the grey one and the black one, and i can remember many a disco where halfway through the show a module would go down so off came the top of the amp casing out came the module 2 new mosfets bunged in and of we went again, all whilst still using the amp live and running the show. and the amount of heat they threw out, even with a fan I swear you could cook an egg on the amp casing, ahh sweet memories, anyway as a dj I loved the kit, you got exactly what you paid for and no fancy gimmicks that are of use to about 1 in a 1000 of us, it preamped then it amped, job DONE!
cheers, for now, David