|Neil Wyatt||12/02/2018 12:50:30|
12517 forum posts
The TDA2030A is one of the 'classic' linear ICs. which although technically obsolete still has a reputation for its very low distortion and transparent sound combined with near-indestructibility - just limited by modest power output.
Back in 1979 I made a stereo amplifier with a pair of TDA2030s and a spilt power supply using a 12-0-12 transformer I wound myself. I built it into an old and very robust aluminium instrument case.
Yesterday I found it in my dad's loft, along with my twin-cone speakers (sadly their synthetic rubber surround has rotted away).
It saw me though university until I got and old 'Tripletone' which I re-cased and that lasted until i got a proper new(!) Panasonic amp.
A bit nervous of 16-year old me's idea of safe mains wiring :-0 but I think I will try to resurrect the old beast
|525 forum posts|
Neil, watch out for exploding electrolytic capacitors. Always a risk of this with old equipment. I had one make a large dent in the ceiling.
|Martin Kyte||12/02/2018 13:57:44|
|1209 forum posts|
At least your hands are probably better insulators now than in your sweaty fingered youth.
You probably shouldn't listen to anything recorded after mid 80's through it but then you probably don't anyway.
Go for it at least for old times sake.
|2450 forum posts|
Forget trivial disputes like Metric vs Imperial and Brexit, we're about to have a proper argument.
Can a semiconductor amplifier like Neil's ever be High Fidelity? No of course not. Only a complete ignoramus would think so.
In my loft I have one of these fine beasts, circa 1970 the ultimate in home-built stereo amplifiers. All valve (aka tubes in the USA), with transformer output from matched pairs of EL84s in push-pull. One of these would cost big money today.
As an amplifier I remember it working very well apart from a bit of hum and a tendency to pick up Radio Moscow after dark.
My mates who were seriously into audio all hated transistors and the smelly hobbits who owned them. One friend was deadly serious about sound quality, rejecting Stereo recordings outright because they're inferior to Mono, and going so far as to convert a chimney into a speaker enclosure to get the extra bass response needed to hear low notes "properly". He used 807s. Audiophiles claim semiconductors inevitably produce a soft mushy sound with bad distortion compared with the crisp clarity of valve amplifiers.
Admittedly I have a poor ear, but I reckon the differences are undetectable. I'm deeply suspicious of gold-plated oxide-free speaker cables and much else that high-end music lovers hold dear. Am I right, or am I just an uncultured yob?
|Neil Wyatt||12/02/2018 14:06:56|
12517 forum posts
For an audio amplifier, you want it to put as little of its 'character' into the sound as possible. Bluntly, valves are crap at that and sillicon is good at it. People who like valve audio amps are enjoying the subtle distortions that only poor linearity and multitudes of transformers etc. can bring.
There are people who insist that valve rectifiers for the PSU sound better than diodes (shakes head slowly) the whole top end valve hifi market is about making valves perform as nearly like a transistor amp as possible...
Now when it come to instrument amplification, it's a whole different ball game where those influence on the sound put valves head and shoulders above the vast majority of transistor amps. Equally top end transitor amps are all about trying to get a tube sound...
|An Other||12/02/2018 14:19:21|
|75 forum posts|
Remember these arguments from years ago in 'wireless World'. Fascinating reading all the arguments for both sides. SoDs comments about chimneys as speaker enclosures, etc made for big laughs - especially when you found out the protagonists were building these things in rooms with huge windows, wooden floors, vibrating doors and rattling ornaments.
It never has seemed much sense to me to insist on extreme linearity, frequency response to N Megahertz etc, when the normal listening environment for much of the music, when performed live, was in the presence of a noisy audience - and nowadays I much prefer a 'live' recorded performance, because to me it seems to add something to what is otherwise a flat, featureless performance - but thats my opinion.
SoDs comments about the price of valve equipment nowadays is a good one - I have even seen gold-plated chassis (chasses?) offered - I wouldn't dare take it out of the safe! - but then you can receive Radio Moscow with it! - a good example of the brilliant (?) linearity of these gas-powered devices.
|Martin Connelly||12/02/2018 14:27:20|
602 forum posts
In the days of cars that came without built in sound systems it always amused me that some people wanted hifi quality equipment to put in the noisy passenger compartment.
403 forum posts
I think thats called 'adding colour' Neil
I still prefer my ReVoX PR99 to cassette tho, and thats got ic's in it
|John Haine||12/02/2018 15:19:09|
|1694 forum posts|
An old colleague used to work for Neve making top end mixing desks. When people went on about the evils of transformers in amplifiers, he used to ask them how many transformers there typically were between the microphone and the LP master cutting lathe. Apparently the average was about 15...
Anyone remember an article called "Dynamic Range Versus Ambient Noise" that was in Wireless World 30-odd years ago? Worth a read and a chuckle here. A whimsical article explaining why you need at least 1 kW per channel for proper stereo and the problems in designing a system. Written by one George Izzard o'Veering.
|Martin 100||12/02/2018 15:44:36|
|216 forum posts|
Of course all this valve vs transistor stuff is total nonsense. What you really need is fifty grands worth of assorted stuff from Russ Andrews.
By stuff I mean things like gold plated silver cored unidirectional hand knitted phono cables and mains cables polished by nubile nymphs with autoclaved red squirrel tails in a class 1 clean room, and then run in for 500 hours using only the very best sound sources. The leads are then vacuum packed to avoid contamination and then packed in individual cardboard boxes made from sustainable wood pulp sourced from the pristine forests near the arctic circle with the trees only harvested under the misty magic of the northern lights.
All these precautions being 'scientifically proven' to really make a difference to the 'sound you hear'
Laugh? I laughed so much my ears actually exploded.
|Mike Poole||12/02/2018 15:51:59|
1112 forum posts
Everything about recorded music is artificial. A studio recording of rock and pop is a creation of the producer. A friend enjoys recording gigs with a hand held digital recorder. The strange thing is when you play them back you hear all sorts of sounds from the crowd that when you are actually at the gig you don't notice, the ear/brain is remarkable at ignoring the sounds that are not the music you are listening to live. At a rock gig that is mic'd and mixed to a PA the sound you hear is going to the sum of the original sound the mics the amps and the speakers and whatever the sound engineer has added or subtracted. For rock and pop a sound system that sounds pleasant is probably all that's required. Orchestral music I think is another kettle of fish, the instruments of an orchestra have well known and distinctive sounds so the holy grail of fooling you to believe you are at the concert is a very high bar to reach. I was in a revolving restaurant and I was surprised how good the sound of a solo piano was I thought they had an excellent sound system until the guy playing a real piano came into view a few minutes later. I have abandoned hifi for SONOS, it sounds pleasant and is very convenient and after 45 years of howling motorcycles and megadecibel gigs by the likes of Mötorhead and Ted Nugent my part of the hifi chain is probably not in very good shape. No point in spending a fortune on something I can't hear now.
|Russell Eberhardt||12/02/2018 15:55:54|
2147 forum posts
Would that amplifier be two Mullard 5-10 amplifiers on a common chassis? I seem to remember it used an "ultra linear" output transformer with taps for the suppresor grid.
I built a single one - couldn't afford two channels on my pocket money
10 watt was more than adequate in those days. I think our huge speakers were more efficient than modern tiny units.
|2450 forum posts|
Neil's says valves are crap! In their defence, they:
What's not to like?
|2450 forum posts|
Thanks Russell - I couldn't remember what it was called - but that's exactly what it is. Not built by me; I got it from a friend who had to downsize when he got married.
|Jon Gibbs||12/02/2018 16:43:18|
|656 forum posts|
Thanks for making me smile - I'd forgotten all of that valve vs transistor BS from days gone by.
The only disappointment is that there was no mention of Class-A valve amplifiers that would keep you really warm in the winter.
....but as an EE of the early 80's I'm a semiconductor evangelist. So firmly on Neil's side of the argument.
452 forum posts
Don't bin the speakers, the foam surrounds can be replaced.
Bit busy at the moment, I'll explain later.
|Rob Rimmer||12/02/2018 17:26:18|
|9 forum posts|
I'd be interested in foam surround repairs too - my pair of speakers built to a Hobby Electronics magazine design have not aged well.
|Neil Wyatt||12/02/2018 17:39:55|
12517 forum posts
Nice valve story - a friend of my brother had a vintage bass head, he was operating it on its side when vibrations caused the transformer to shake loose. Yes it was at the top, so it broke all the valves on the way down. A full set of replacement valves was £300 BEFORE any other repair work!
|Phil S||12/02/2018 17:42:32|
|8 forum posts|
Probably the greatest risk from home built kit is weakness of the transformer primary to secondary insulation. True split bobbin (side by side) tend to be better than concentric with just a layer of thin card. A megger primary to secondary test and/or ensuring the centre of the 12-0-12 is firmly connected to mains earth go some way to mitigating the risk. I know the latter may result in hum but is preferable to the entire circuit up near mains potential due to flashover.
|52 forum posts|
Back in the mid to late 70,s when i was a teenager into electronics and hifi these BI-KITS modules were a very popular way to build a cheap amp , these AL60 ones in the pic rated at 25 watts rms i think , are spares ive had kicking around in the loft for over 40 yrs in case my original amp build blew up , which it never did ,despite a lot of full volume abuse , well thats what you did back in them days , all you needed were a pre amp module , a power supply module and transformer and a couple of power amp modules , get a suitable case connect them all up with some speaker and din sockets and some switches and hopefully you would have a decent audio amp , wish i still had my original one but it got given away decades ago.
Edited By Kettrinboy on 12/02/2018 18:13:08
Edited By Kettrinboy on 12/02/2018 18:15:50
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
Love Model Engineering? Sign up to our emails for the latest news and special offers!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.