TDA2030A Audio Amp

[Neil WyattModerator @neilwyatt]

Posted by John Haine on 12/02/2018 20:15:49:

Wharfedale speakers – remember them? – was started by a chap called G A Briggs, who wrote a couple of very good early books on hi-fi loudspeakers. In one of them he describes setting up a sound system in the Albert Hall and driving it to produce the same SPL as a symphony orchestra. IIRC the power needed was in the region of 10 – 20 W through using efficient loudspeakers. One of his points was that small loudspeakers have to be heavily damped to get good frequency response which makes them inefficient.

I read his book as a schoolboy and have been trying to find it ever since because non-one believes that figure!

Neil

Loudspeakers by G A Briggs  – Amazon £42 hardback, £82 paperback!

Edited By Neil Wyatt on 12/02/2018 20:53:43

[john swift 1Participant @johnswift1]

the TDA2030 IC was the audio amplifier used in the Forgestone Colour Developments F500 colour TV kit that I built during the 1981 Christmas holiday

Forgestone was one of the component suppliers for the Televisiom magazines DIY colour TV project that started April 1971

John

[Neil WyattModerator @neilwyatt]

Not quite the same as wiring a Raspberry Pi up to a TFT display!

Neil

[john swift 1Participant @johnswift1]

no the TFT displays don't X-ray your delicate bits

if you don't adjust the 143V HT rail correctly to obtain the 24Kv final anode supply to the CRT

a few more HT volts and the EHT goes over 24Kv and emits harder X-rays !!

John

PS

you also get a few hundred solder joint to practice on

[David Standing 1Participant @davidstanding1]

Posted by peak4 on 12/02/2018 17:01:10:

Don't bin the speakers, the foam surrounds can be replaced.

Bit busy at the moment, I'll explain later.

Bill

Yep, they probably can.

I am about to send my Acoustic Energy AE1 (classic) speakers back to the factory for a refoam.

[Mark RandParticipant @markrand96270]

Has anyone else wondered about Britain's Silicon Valley or may be "Germanium Valley" in the 1970's? The likes of Maplin, Bi-Pre-Pack, Amstrad and a few others I can't remember, Even E. K Coles (echo televisions) and others in the London-Southend corridor.

Got all the units of my Monitor Audio MA2's re-rubbered (not 'foamed) 20 years ago, The foam was not a good design decision. I was amused when I brought the midrange units in and was told 'Ah yes, they're a standard KEF base unit'

PPS:-

Auditioned a Linn Sondek LP12 and thought is was awful. It rang like a bell compared with my Pink Triangle (made on a clapped out Colchester triumph!)

Edited By Mark Rand on 12/02/2018 23:35:25

[peak4Participant @peak4]

OK, sorry for the delay and keeping you in suspense. I was out patching the inner wings on the Disco.

Last year, I dug my old JPW AP-2s out from the attic, ready for the new house, but the foam surrounds had perished quite badly. I used replacement foams from a specialist shop In the Netherlands; See Here though there are other suppliers and they even come up on ebay. The supplier I've quoted seemed competitively priced and delivered promptly, as well as accepting paypal. See also Goodhifi.com

It's not a difficult job, but make sure you've got a large number of spring clothes pegs to hold the glue whilst it sets between the foam and the metal surround.

Have a look at their video, under the Instructions tab.

For the joint between the foam and the loudspeaker cone, I managed to find a kitchen basin the correct size, but I guess most folks on here will have a lathe to custom make something if need be.

The web site contains instructions and photos, but there's plenty more advice on the net.

There is debate on whether to use foam or rubber rings, but from what I remember, most advice is to use foam for most applications. The exception being if you live near the sea, as salty air attacks the foam and shortens its life.

For the price of the bits, and a couple of hours work, it's got to be worth doing. Sorry I don't have any photos of me doing the job,

Bill

p.s. With care, the job is reasonably easy and might be the route to the more impecunious amongst us buying a pair of known knackered speakers for a song, and refurbishing them.

p.p.s. no idea why my typing's shrunk !!

Edited By peak4 on 12/02/2018 23:46:23

Edited By peak4 on 12/02/2018 23:47:23

[David Standing 1Participant @davidstanding1]

Posted by peak4 on 12/02/2018 23:41:49:

OK, sorry for the delay and keeping you in suspense. I was out patching the inner wings on the Disco.

Last year, I dug my old JPW AP-2s out from the attic, ready for the new house, but the foam surrounds had perished quite badly. I used replacement foams from a specialist shop In the Netherlands; See Here though there are other suppliers and they even come up on ebay. The supplier I've quoted seemed competitively priced and delivered promptly, as well as accepting paypal. See also Goodhifi.com

It's not a difficult job, but make sure you've got a large number of spring clothes pegs to hold the glue whilst it sets between the foam and the metal surround.

Have a look at their video, under the Instructions tab.

For the joint between the foam and the loudspeaker cone, I managed to find a kitchen basin the correct size, but I guess most folks on here will have a lathe to custom make something if need be.

The web site contains instructions and photos, but there's plenty more advice on the net.

There is debate on whether to use foam or rubber rings, but from what I remember, most advice is to use foam for most applications. The exception being if you live near the sea, as salty air attacks the foam and shortens its life.

For the price of the bits, and a couple of hours work, it's got to be worth doing. Sorry I don't have any photos of me doing the job,

Bill

p.s. With care, the job is reasonably easy and might be the route to the more impecunious amongst us buying a pair of known knackered speakers for a song, and refurbishing them.

p.p.s. no idea why my typing's shrunk !!

Edited By peak4 on 12/02/2018 23:46:23

Edited By peak4 on 12/02/2018 23:47:23

I am tempted to have a go at doing my AE1's myself, but they are horrendously expensive to replace if I goof them up!

[peak4Participant @peak4]

I do remember Wharfdale speakers, though I've never owned any; I went to audition some at a local dealers in Sheffield when I was a student in the mid 70's.

It was an interesting conversation with the shop owner.

Back then, there was a period when VAT rose to 25% on luxury goods, but educational kits remained at the lower rate. I'd built a Quantum pre & power amp and was looking for some speakers to match it. I was told, by Quantum, to be careful about the loading, as the amp would start to self protect if the load impedance fell too much, and that some 4 ohm speakers could cause issues, though not all. No damage to the kit, just distortion as it protected the output stage.

I'd gone to the shop with an open mind, but a couple of models that I'd like to hear. The owner, quite reasonably, added a couple more into the mix that I wasn't familiar with. Consequently, bearing in mind Quantum's advice, I asked what the nominal impedance was.

He went on to explain; the cheaper end of the market were mainly 4 ohms, as it was much more expensive to construct 8 ohm ones, more wires in the coils you see. Why not have a listen to these Wharfdales, they're mid range quality wise at 6 ohms; I think they were Lintons, can't remember now.

Hmmmmmm, thought I but didn't let on.

During a cup of tea, conversation changed to what I was studying; Electronic Engineering at the University was my reply.

He changed sales patter after that, unsuccessfully I should add.

Bill

[peak4Participant @peak4]

Posted by David Standing 1 on 13/02/2018 00:00:24:

I am tempted to have a go at doing my AE1's myself, but they are horrendously expensive to replace if I goof them up!

Removing the perished foam was easy enough though rather mucky with black sticky foam granules everywhere, but nothing more onerous than that.

I'm not sure how easy it would be to remove good newly attached foam, to make a second attempt.

Why not see if you can find a cheaper pair for the workshop and have a practice on them first.

( I finished up with AR MST's, then the JPWs, one pair in each room, until a friend gave me his Rogers LS-6s, when I retired the JPWs for a while. Now rejuvenated in Buxton, the're working fine, with a pair of Ruark Templars in the other room.)

Bill

Edited By peak4 on 13/02/2018 00:17:26

[Geoff TheasbyParticipant @geofftheasby]

All this talk of unidirectional cables etc., reminds me, if it makes you laugh hysterically, or weep at people's gullibility, look up Peter Belt and his claims.

Geoff

[Joseph Noci 1Participant @josephnoci1]

Did my fair share of amplifier building in the day..while still in school I played in a 'Rock Band', and as an electronics enthusiast even then, ended up as repairman for all the band equipment and built a lot of it too! Pedal effects unit, I made quite a few, with weird effects – I remember one, a white noise generator, using a transistor as a zener diode, and amplifying the zener shot noise – it was not noisy enough during one gig, so got the bass player's cigarette lighter and heated the transistor ( BC107, I think..) till it was red hot, cooled it, and voila! Heaps of white noise…

Built a 10W Class AB1 Valve amp using EL84's, then the JLH 10Watt Class A amp with 2N3055's, Then about a dozen JLH 82watt amps, 2N3055's and fitted them into our bass speaker cabinets..Also built the A Bailey 30watt stereo HiFi amp , music in the bedroom at home..And a few dozen amps of various powers and varying success..

Converted some 100watt Marshal Amps to circuitry based on JLH designs – I thought they sounded nicer..And I have to add my 10p worth regarding valve versus transistor sounds – For a Rock Band, you could not beat the valve sound. A high power Lead Guitar piece , with all the nuances and peak energy, through a perfect reproduction Transistor amp had the same effect as root canal…With a valve amp, the clipping is so nicely rounded, the edges softened, and it soothes you along – Just listen to the early years of Pink Floyd!

So what if the sound , viewed on a 'scope, is not a true reproduction! Its the sound's effect that matters!

I made a transistor amplifier using constant current sources in the feed to the upper and lower transistors in the amp output – this gave very similar effects to the soft clipping of the valve type amps, hard to hear the difference, but there was no glow, so scrapped it..

Joe

Edited By Joseph Noci 1 on 13/02/2018 07:05:30

Added:

And the best of both worlds:

Transistors up front and BIG valves where it matters – an East European Marshall knockoff, but very well made, and very good sound, and made in East Europe, not PRC..Cleaned and serviced for a local Chap here in Swakop…

Edited By Joseph Noci 1 on 13/02/2018 07:12:09

[I.M. OUTAHEREParticipant @i-m-outahere]

There has been somewhat of a resurgence in valve amps here in Australia with one of the local electronics mags offering some designes and kits they also did some very low distortion transistor designs as well .

I can still remember peering into the back of the telly or radio to watch the valves heat up and i will never forget the smell ! This probably explains why i like vintage radios . Anytime you can smell anything from a transistorised unit you have problems ! Once the smoke gets out nothing can put it back in !

[Neil WyattModerator @neilwyatt]

Hmm the refoaming looks cheap enough to have a go – the speakers (twin cone units) were decent enough in their day, in unfinished conti-board boxes made to the specified volume.

I have a Vox Valvetronix VT20 modelling amp that uses a valve preamp to get decent distortion sounds. For the convenience of having about twenty effects and 33 distinct amp models it's brilliant as a 'bedroom blaster'.

One think I like about Vox is they eschew all the 'music power' exaggeration nonsense. Even the VT20 is 30W RMS…

My bother came across a test of a large Fender combo, Marshall 100W combo and a Vox AC30. The AC30 was the loudest…

Neil

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by John Haine on 12/02/2018 20:15:49:

One of his points was that small loudspeakers have to be heavily damped to get good frequency response which makes them inefficient.

Absolutely. A small driver in a small enclosure must have a relatively high resonant frequency when compared with a bigger speaker. Below the resonant frequency the response falls off rapidly so, in order to obtain a flat frequency response down to low bass frequencies the response at frequencies above resonance must be reduced to match. Hence the efficiency must be lower and they must need more input power for the same level of sound output.

Yes Neil, you can get good bass response from a small speaker but at the cost of efficiency. There is, however, another problem: To get loud bass notes you must have a large cone excursion. That's fine with a pure tone (provided you can maintain linearity) but with a higher frequency note present at the same time there will be a kind of inter-modulation distortion as a result of the Doppler effect. This can be heard as a sort of muddling of the sound.

I'll stick with my floor standing Rogers speakers even though my old ears can probably no longer hear the nuances!

Russell

[Neil WyattModerator @neilwyatt]

Posted by Russell Eberhardt on 13/02/2018 09:40:26:

Posted by John Haine on 12/02/2018 20:15:49:

One of his points was that small loudspeakers have to be heavily damped to get good frequency response which makes them inefficient.

Absolutely. A small driver in a small enclosure must have a relatively high resonant frequency when compared with a bigger speaker. Below the resonant frequency the response falls off rapidly so, in order to obtain a flat frequency response down to low bass frequencies the response at frequencies above resonance must be reduced to match. Hence the efficiency must be lower and they must need more input power for the same level of sound output.

Yes Neil, you can get good bass response from a small speaker but at the cost of efficiency. There is, however, another problem: To get loud bass notes you must have a large cone excursion. That's fine with a pure tone (provided you can maintain linearity) but with a higher frequency note present at the same time there will be a kind of inter-modulation distortion as a result of the Doppler effect. This can be heard as a sort of muddling of the sound.

I'll stick with my floor standing Rogers speakers even though my old ears can probably no longer hear the nuances!

Russell

I'm not claiming that modern small speakers are the ultimate. I prefer my 25-year old KEFs, but the fact is that today you can buy speakers that fit in the palm of your hand that sound way better than the foot-high speakers supplied with most consumer hifi thirty years ago. Small-cone large excursion speakers and cleverly matched enclosures do sound remarkably good, often managing to sound louder than they really are.

I recall going into Tandy where they would always be selling speakers 'with 12" woofer for bass you can really feel'. The 6" speakers in my old Mondeo's doors had more guts than any of those awful Tandy ones!

One interesting exception to the small can be good rule are the early iPhones which had noticeably poor sound compared to many cheaper phones. I have never understood why Apple took so long to get the sound of iPhones dialled.

Neil

[Martin Shaw 1Participant @martinshaw1]

Back in the day when I worked for BBC Engineering the almost universal loudspeaker amplifier was a Quad 405, usually in bi-amp configuration. It was the amp of choice because, in the late Peter Walker's maxim the ideal amp was a piece of wire with gain, and it was solidly built and wholly reliable, day after day after day. Very little else originally designed for the consumer market has come anywhere near, my own example some 25 years old still outperforms most things on the market. Valve amps are just a pain, certainly in the wallet as revalving on a regular basis is essential, but unless you've got a high efficiency speaker design, horn loaded for preference, then they invariably have insufficient welly. Of course if your seduced by the hi-fi gurus, may you enjoy the dubious statements of betterment at your own considerable expense.

Regards

Martin

Edited By Martin Shaw 1 on 13/02/2018 21:05:43

[Mark RandParticipant @markrand96270]

What I would really like is a house that was big enough to house a pair of Quad ELS's

[peak4Participant @peak4]

Posted by Mark Rand on 13/02/2018 22:49:46:

What I would really like is a house that was big enough to house a pair of Quad ELS's

The most realistic sound I ever heard was in a hi-fi shop in Southport, probably in the early '70s, when my ears were young enough to appreciate it.

I can't remember the signal source, but the speakers were stacked Quad electrostatics (the original ones), two per channel, one above the other, driven by Quad valve amps. Crystal clear orchestral music that was quite mesmerising, even though I didn't appreciate "Classical" music then.

[Ed Dinning 1Participant @eddinning1]

Hi Gents, split bobbin transformers tick all the boxes for the H&S brigade in terms of leakage pri/sec etc BUT, they have much worse regulation and higher losses, which could, with a poorly designed power supply increase distortion.

A correctly designed "sec over pri" transformer (earth screen and correct creepage and clearances) will give much better performance, use less total power and still be safe.

Note that the split bobbin design is virtually never used for the "holy grail" ~ output transformers.

Ed

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Neil Wyatt on 13/02/2018 20:51:27:The 6" speakers in my old Mondeo's doors had more guts than any of those awful Tandy ones!

Probably did. I agree that Tandy speakers were rubbish but don't you think that the size of enclosure you were in had something to do with it? Add in the ambient noise from a Mondeo engine and I doubt you could hear the distortion!

Quad electrostatics were excellent. They had diaphragms with a large area and very small excursion but needed a big room as they had to be sited well away from a wall for best results.

I like your KEFs. I seem to remember that Rogers used KEF drivers in their speakers.

Russell

[John HaineParticipant @johnhaine32865]

I had a couple of ESLs, the original version, one made in 1957 the other in 1963. Probably spent over £2000 having them serviced, once by Quad the second by "onething audio", but last year the treble panels went again, so popped them on eBay and sold to an enthusiast who reconditions them himself. Now got a pair of Quad 21s which to my ageing ears sound excellent, though the ESLs when they were working properly were fantastic.

[Neil WyattModerator @neilwyatt]

Posted by Ed Dinning 1 on 14/02/2018 08:00:11:

Hi Gents, split bobbin transformers tick all the boxes for the H&S brigade in terms of leakage pri/sec etc BUT, they have much worse regulation and higher losses, which could, with a poorly designed power supply increase distortion.

 

A correctly designed "sec over pri" transformer (earth screen and correct creepage and clearances) will give much better performance, use less total power and still be safe.

 

Note that the split bobbin design is virtually never used for the "holy grail" ~ output transformers.

 

Ed

Bear in mind (1) I'd never wound a transformer before (or since) (2) it was the only type of kit Radiospares sold…

Fully regulated supply rails and caps the size of beer bottles (well not quite)

Edited By Neil Wyatt on 14/02/2018 09:55:20

[Neil WyattModerator @neilwyatt]

Haven't seen electrostatics for >30 years. I saw one speaker that had a small electrostatic tweeter run off the valve O/P line before the impedance matching transformer.

[Gordon WParticipant @gordonw]

Reminded of a man I was talking to a few weeks ago– He asked me if I knew where to get lead shot. He needed it for some sound system he was building, had to pour the shot into the speaker stacks to get balance. he then went into his set -up at great length, most of which I didn't understand, his amp etc. etc. Turns out he lived in a 12ft caravan.

[Author]

Posts