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Old 14th Feb 2013, 7:02 pm   #121
Valvepower
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Default Re: Tuac Amplifier modules

Hi Stuart,

Yes, it’s a fair old thread!

I can’t remember the follow-up article on improvements to the Practical Wireless amplifier, but saying that I don’t have a complete set of PW’s from 1967/68/69 though. I remember a couple of hi-fi amplifier projects in PW using the Peak Sound power amplifier circuit and the Henelec (Henrys Radio) PA25 amplifier module.

I remember building an amplifier using the 100 Watt power amplifier (2x MJ2955/2N3055’s) from the 1976? ETI disco system project. This was available as a kit from Maplin.

Eventually the ‘home-brews’ units gave way to professional units like the MM Electronics AP360 power amplifier.

It would be interesting to find one of the Henrys Radio Henelec PA25 & 50 modules.

Terry.

Last edited by Valvepower; 14th Feb 2013 at 7:04 pm. Reason: Edit ...
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Old 15th Feb 2013, 9:33 am   #122
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Default Re: Tuac Amplifier modules

Quote:
Originally Posted by Valvepower View Post
I remember building an amplifier using the 100 Watt power amplifier (2x MJ2955/2N3055’s) from the 1976? ETI disco system project. This was available as a kit from Maplin.
Hi,

I built that amp. It was, originally, the ETI 413, from 1972/73. I have the original article if anyone is interested. Very sturdy amp.

Cheers.

Aub
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Old 15th Feb 2013, 5:58 pm   #123
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Default Re: Tuac Amplifier modules

Terry,
The follow-up article is in PW June 1968 P101.
I remember a guitar combo amp in either PW or PE using the Henelec (Henrys Radio) PA50 amplifier module.
Stuart.
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Old 15th Feb 2013, 7:28 pm   #124
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Default Re: Tuac Amplifier modules

Hi,

Aub, I’d be interested in a scan/copy of the original ETI article please.

Stewart, Ah there was a follow-up article which appeared in the June 1968 PW – I’ll look for a copy. Yes, you’re right regarding the Guitar combo amplifier. This featured in the September 1970 copy of PW and was Called ‘PW Vibrasonic Guitar Amplifier' by F.C. Judd.

Regards
Terry
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Old 16th Feb 2013, 11:33 am   #125
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Default Re: Tuac Amplifier modules

Ok,

I'll try to do it over the weekend.

Cheers

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Old 16th Feb 2013, 12:04 pm   #126
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Default Re: Tuac Amplifier modules

Quote:
Originally Posted by Aub View Post
I built that amp. It was, originally, the ETI 413, from 1972/73. I have the original article if anyone is interested. Very sturdy amp.
It was updated as the ETI480. Dad built a couple of the 50W versions from Dick Smith kitsets - great simple amps, and cheap to fix if you blew the output (I did that a couple of times!).
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Old 16th Feb 2013, 1:58 pm   #127
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Default Re: Tuac Amplifier modules

Hi,

Look forward to a copy of the orginal ETI article - no hurry when you’re ready.

Regarding the ETI/Maplin power amplifier, I have to agree it was a cracking amplifier.

I remember adding the short circuit protection form the Mullard Transistor Audio and Radio Circuits book, I have to say this did save a few output transistors though!

I remember one of these being modified with a Quasi Complementary output using 4x 2N3773’s output transistors, although it increased the power slightly it lost some of the sound quality of the of the original complementary pair (2N3055/MJ2955) unit, which I suppose is to be expected with the use of the Quasi Complementary output even with the ‘Baxandall equalization’ diode.

Terry.
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Old 16th Feb 2013, 9:20 pm   #128
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Default Re: Tuac Amplifier modules

Server is playing up. having to load the Jpegs one at a time.
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Old 16th Feb 2013, 9:31 pm   #129
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Having problems with the jpegs. I scanned the article a few years ago, but i think i will need to re-scan, as page 2 seems to over 25Mb! I will have to dig it out of the loft.



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Old 17th Feb 2013, 10:14 am   #130
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Hi Terry,
With reference to post 124, I already have the follow-up article in question thanks.
Stuart.
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Old 17th Feb 2013, 3:18 pm   #131
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Page 2. The PCB layout is missing.

Page 3.

Page 4.
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Old 17th Feb 2013, 3:32 pm   #132
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Also, there was a 200w bridged version:-
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Old 17th Feb 2013, 8:52 pm   #133
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Default Re: Tuac Amplifier modules

Hi Aub,

Many thanks for that – it’s greatly appreciated. I didn’t realize the original circuit dated back to 1973, plus for use as guitar amplifier! I do remember using this power amp with a hook-up preamplifier with a bass guitar and it did sound ok – maybe the complementary output helped here.

I’ve seen that method of bridging in a few commercial amplifiers over the years, but going by the date this might be the original article describing this method of bridging.

Terry.
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Old 17th Feb 2013, 10:45 pm   #134
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Yes,

Strange that it was originally a guitar amp when it's perfectly capable of good reproduction of music. We used one in our mobile disco in the 70's.

All the best

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Old 21st Jul 2013, 8:21 pm   #135
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Default Re: Tuac Amplifier modules

Hi All,

Another addition to the TUAC thread.

I’ve copied out and attached the circuit of the TUAC VA08 pre-amplifier as used in complete (guitar/PA) amplifiers. I figure it’s aimed more for guitar use though.

It looks to be a fairly straight forward two stage affair with a combination of passive and Baxandall like active tone controls and a FET first stage, which gives a high input impedance. I find the reversed volume controls interesting, although I’ve seen this method used elsewhere in a few other transistor amplifiers. This method may enable the paralleling the outputs of a couple of the units to make a basic mixer.

Regards
Terry.
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Old 22nd Jul 2013, 5:34 pm   #136
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Default Re: Tuac Amplifier modules

Hi All,

I've just joined in order to post a reply to the TUAC thread as I knew them well. Well, at least I did at the time!

I first used some TUAC modules when I built one of my first disco set ups in 1972. They were really rugged, which was great because at that time, so many people ended up blowing up the output trannies with a duff speaker cable or something similar. The TUAC ones had short and open circuit protection, so if some one tripped over a speaker cable (no health and safety in those days - LOL!) and the jack plug came out or half out and shorted, then there was no problem.

The amps discussed earlier in this thread were all using 2N3055 output transistors with either 2 for the 60W module or 4 for the 125 watt module. Yes, they supplied amplifier modules to several other companies who put them into their gear with their name on, because everyone knew that they were bullet proof!

I got to know the guys (Dave and Geoff) who owned TUAC very well because they realised I knew what I was talking about in terms of electronics and in fact they used me and one of my friends who also ran a mobile disco as "test beds" for new ideas. We were the first to get our hands on their TR-1000 which was one of the first 1000W amplifiers out there that was actually affordable. It was based on the Quad Acoustic "current dumping" principle used in the Quad 405 and delivered 500w RMS into 2 ohms. To be honest I rarely used the TR-1000 as my TR-300 (150W RMS per channel was easily loud enough for most venues with the speaker systems of the day.

We were also the first to get our hands on the Starchaser, which was one of the first digital light units, using an EPROM for the sequences and it simply scrolled through the various sequences within the EPROM memory with the speed being altered by changing the clock speed or triggered by sound.

All the amplifiers I ever used were from TUAC all the way through from 72 until I gave up discos in 1984 when I moved from Crawley to the Midlands. I tried but didn't like their mixers. The main reason was that with a decent speaker system with mid-range and tweeters they sounded very boxy. People like me using a full range speaker system were the exception at that time. Basically, TUAC were designing their mixers to provide the right roll off to drive 4 x 12" type cabinets, so they had harsh treble lift. I used a Citronic mixer, which when driving a decent speaker set through the TUAC power amps, was fantastic, almost hi-fi quality.

Unfortunately, by the early 80's the shop in London Road was not doing a good trade and the factory around the corner was suffering too. They went out to get business building electronics for other companies and I remember them building a load of gadgets that you could type with despite it only having half a dozen keys or so. For the life of me I can't remember what they were called. The guys remortgaged their houses to try to keep the business afloat, but sadly it went to the wall.

Here's a little blast from the past showing me 30 years ago with the disco in 1982.

Regards,

Gordon
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Old 5th Nov 2013, 12:35 am   #137
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Default Re: Tuac Amplifier modules

I've just been scanning through some of the comments about TUAC modules - very interesting... I also ran a disco in the 1970s, and used their 125W amplifier modules and light sequencer board for years. They never failed me, and I can confirm that the sound quality was actually very good, in a subjective sense. Anyway, the reason I posted is to say that I run a service centre for live music equipment on the Isle of Wight, and I've just received a Baker 100 amplifier for repair. Guess what - it has a TP125 amplifier module installed... If anyone would like the schematic, I'll draw it out. Cheers, Mark
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Old 6th Nov 2013, 8:13 pm   #138
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Default Re: Tuac Amplifier modules

that would be great if you can
trev
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Old 8th Nov 2013, 8:32 am   #139
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Default Re: Tuac Amplifier modules

I have a scan copy of the original circuit diagram , with installation instructions as supplied with the TL100 and TP125 .
Chris.
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Old 8th Nov 2013, 8:43 pm   #140
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Default Re: Tuac Amplifier modules

Hi,

It would be really nice to see an original TUAC TP125 circuit. I did draw one out (in post #32) but there seemed something rather strange about the series and parallel combination of resistors in the feedback circuit notably the resistor connected to the output, and it would be nice to see a pukka circuit.

Terry
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