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Old 20th Mar 2011, 7:13 pm   #101
Trevor
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Default Re: Tuac Amplifier modules

Welcome Seymore
Let us know if we can be of help
regards Trev
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Old 20th Mar 2011, 9:09 pm   #102
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Default Re: Tuac Amplifier modules

Hi,

Yes, they bring the global feed back to the base of the first transistor and not the emitter. I may be wrong but seeing T2 is being fed from the collector of T1 the overall phase relationship of the amplifier will need to be opposite to that of the TP125?

I thought they used 2N6254’s

I’ve found a nice TUAC “glossy” back cover advert from 1976, I’ll scan and post it.

I feel quite a few on the forum had a miss spent youth dabbling with various bits of audio, radio and electronic equipment!

Terry.
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Old 20th Mar 2011, 9:35 pm   #103
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Valve power
yes I agree But I personally have never believed in absaloute phase it can always be corrected by connecting the spk in reverse polarity
However I have seen a no of good amplifiers that do not worry re this particular item
The shame of this design like most transformer coupled amplifiers is that the bias is via a simple resistive chain and as such varies according to the supply volts
I have in the past replaced the bias resistors in this case 500 ohm with constant current sources this eliminates the varying bias effect
However despite being a crude amplifier when opened up these things really sing !!!
regards Trev
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Old 25th Mar 2011, 8:26 pm   #104
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Well the Tuac power module has completed a week of playing All in all I have replaced the driver transistor an uncooled to39 device that dissipates 1.5 watts and the output devicesas I think they are over-run I shall attempt to take a few pictures befor sending it back
regards Trev
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Old 26th Mar 2011, 9:51 pm   #105
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Default Re: Tuac Amplifier modules

Hi Trevor,

As promised I’ve attached the back page glossy TUAC advert from the 1976 Radio Constructor mag.

I’ve often found it’s the simple & straightforward amplifiers, which sound good. The Linsley Hood Class A amplifier is testament to this.

Terry.
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Old 26th Mar 2011, 10:39 pm   #106
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I wish I had a time machine I would go back and get a dozen
regards Trev
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Old 27th Mar 2011, 10:42 pm   #107
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Time constraints have meant that I can-not post any further pictures or comments re the Tuac
However I must say that I would have no problems in using these remarkable amplifiers that can deliver a great sound for the money its a shame that they are no longer available.
Regards Trevor
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Old 28th Mar 2011, 9:59 pm   #108
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Default Re: Tuac Amplifier modules

I used run a mobile disco years ago We used to use TUAC equipment we had a couple of the 100w modules and the mixer in these ads. We also had their 3 channel sound/light with sequence chaser module which I still have in the loft. All bought from their shop in Mitcham Rd. Garland Bros in Deptford ( still there )also were stockists.It was always reliable and never let us down.
Ian
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Old 29th Mar 2011, 8:15 am   #109
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Default Re: Tuac Amplifier modules

I have put out feelers for a pair of these modules I would love a stereo power amplifier using these
The sound is very dynaamic and punchy in the bass !
Should any one have a pair please advise are you selling your Seymour?
best regards Trev
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Old 30th Mar 2011, 8:21 pm   #110
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Hi,

I do wonder if the lower impedance source provided by the driver transformer contributes to the sound of these amplifiers. A friend used a TUAC pre-amplifier and power amplifier for his bass guitar back in the late 70’s, and it sounded rather nice, but it just didn’t have that valve sound I got from my Roost amp.

There must be a few of these amplifiers out there in Disco and PA units. If I remember righty amplifiers sold under the “Norman” brand name used TUAC modules.

Great adverts – sure does bring some memories. My friend who used the TUAC amplifier modules in the 70s’ also used the sound to light and chaser units. The last time I saw his TUAC power amplifiers was back in 1982 when I bought a Mullard 5-20 he had in the workshop, sadly I feel the TUAC amps would have been skipped a few years later in the late 80’s when he sold his workshop/factory and it was converted into flats!

Terry.
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Old 30th Mar 2011, 9:34 pm   #111
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Heart breaking when you think about it !
The use of a driver transformer does indeed change the dynamics of a power amp
its very complicated but when i have some time i will try to explain how I think it works
regards for now Trev
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Old 30th Mar 2011, 11:31 pm   #112
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Hi Trevor, I've been following this thread with interest. I know what you mean about the difference in the sound. I won't pretend to understand it but, I have experienced this with HH TPA 100 amps. Long story short, I've been collecting a few of these, mostly from ebay. I made the mistake of letting someone else bid for me before I had a computer and ended up with 3 of the original TPA 100 amps. These have a driver transformer and the whole board is completely different to the TPA 100 D which I thought I was buying. They have problems but the sound compared to the D amps is a lot warmer. I really preffered them but they have a slight distortion problem. It could be the wire wound resistors which are hot all the time. I assume these are providing the bias but I have not been able to get any info on them. Don't suppose you're familiar with them?
I also have a Hill LC 800 with transformers. These have 1K 15 watt resistors in series with the transformer and are reknowned for going out of spec, this results in DC on the output and then protect mode on the channel.
Any thoughts on any of this?
David.
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Old 31st Mar 2011, 6:48 am   #113
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Wow
did not know re the H+H amplifiers I would love to see inside one !
As for the hill I have repaired a few of these and yes those resistors can be a problem!
Do you want to sell an H+H or loan it me I will repair it F.oC if you want toloan it to me for study!
regards Trev
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Old 31st Mar 2011, 8:46 am   #114
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Default Re: Tuac Amplifier modules

Hi,

I’ve kept the below brief as it’s off topic. If the subject of HH and TPA’s is of interest we’ll have to start a new post for these amplifiers.

When I’ve needed info on HH amplifiers I’ve obtained the info from MAJ Electronic. http://www.majelectronic.co.uk/

I didn’t know HH used driver transformers in the very early TPA amplifiers. The TPA amps I’ve seen either had a 741 input with a standard voltage amp driving darlington’s. And the early ones with a standard transistor based input circuit driving the same style output stage as above. I’ve seen some TPA’s with an output transformer to match 100V line installations. They also did an option of a transformer balanced input.

Terry.
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Old 31st Mar 2011, 7:34 pm   #115
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I agree with you valvepower
I have repaired a few H+H units andthey have been as you describe I even repaired the H+H pa amp for Peters and Lee in there hayday while they were touring
It was a simple job
I always thought the H+H were all dc coupled jobs and very fine in their day!
Teetune can you post a diagram of the tp100 power amplifier either on this thread or indeed a new thread if you would prefer
best regards trev
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Old 1st Apr 2011, 12:24 am   #116
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Hi Trevor, re the HH TPA series power amps. To be honest I could easily live without a pair of these original TPA 100 amps. I've not done anything with them after realising the distortion problem and they are just taking up room. I started robbing the third one for spares. The problem with getting them to you is the weight. I think I paid £30 each for them but with postage on the 3 it came to £125! As Valvepower pointed out, these are fitted with 100v line output transformers and did have Gardners input isolation transformers which I removed as they are worth keeping. Maybe the FCS could help getting them to you. I don't have a diagram for them but I will try to get some pictures up.
A point of interest regarding the driver transformer on these, they have a connection like an extra winding that goes to a reed relay which mutes the audio briefly during power up. As I said, a completely different beast to the TPA 100 D. I gather the D stands for Discrete, and these are DC coupled.
Maybe I should start a new thread if anyones interested in more info. I have 12 amps in the TPA series at present, my favourites being the TPA 50 D. Sound great in my shed from a Sony Discman through a pair of Tannoy 603s. The model number of these amps refers to output into 15 ohms, so they are a lot more powerful into lower impedances.

Regards David.
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Old 10th Apr 2011, 9:54 am   #117
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I am still after some Tuac modules any model provided they are transformer coupled any out there I am prepared to pay a fair price
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Old 2nd May 2011, 9:28 am   #118
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After about 10 years of thinking about it I have last made a novel transformer coupled amplifier that has been inspired by the tuac modules .This I have decided to call the 2uac in honour of these please look up the homebrew section where you will find it you will I am sure be delighted by some rather unororthadox solutions
it uses only 4 active devices involved in the signal path and an extra device for thermal compensation
the main feature is the unusual use of a mains Tx as the driver transformer
regards Trev
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Old 12th Feb 2013, 8:59 pm   #119
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Hi,

This thread has been dormant for about 18 moths, but I felt it worthwhile to post a recent TUAC find.

I recently bought a Norman amplifier, which from memory were made by TUAC in the 1970’s. These were sold to the radio trade alongside Norman radio parts like switches and pots etc. I clearly remember Norman parts being sold in my local radio parts shop in Southend.

I must admit I took a gamble buying this amplifier as my memory of TUAC making Norman amplifiers was a vague one, so there was a risk I could have bought a ‘pup’, but on opening the case and looking inside, to my surprise, I found a TUAC TL60 and a V08 pre-amplifier lurking inside . The power module could be a TP50 though, which is very similar to the TL60.

Going by the date code on the capacitors I date it at something like 1974/75.

I’ve given it quick check with the DVM and the transistors appear ok.

I’ve attached a few pictures of the amplifier.

Regards
Terry.
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Old 13th Feb 2013, 7:32 pm   #120
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Hi All,
I have just found this thread and read it through (yes all 119 posts).
Just out of interest, see a thread "Anyone remember this DIY amplifier?"
There was a follow-up article for this series in Practical Wireless, where it was suggested that the HT on the output pair could be raised to increase the power. This worked very well. I used the power amplifier as a built in amp in an early disco console, but then invested in the two TPA 100Ds.

Stuart.
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