http://www.diyaudio.com/forums/chip...tors-amp-tda7293-come-also-8.html#post3992306
Just read this by Andrew T when searching for TDA 7293 in PP bridge ( 60 R load +/- 37 V DC ). Really impressed Andrew says it this way. It is what Dejan has been asking. Andrew has simplified a very difficult question. He also sugests how transformers should be looked at. I recently ran out of space for a transformer and had to use some Andrew thinking to solve it. Not able to say the solution as I am being paid for it. Andrew more or less says what I did. Douglas Self does not support this idea by his numbers. Andrew very clearly states why it could be other than the world of Douglas. I must say I slightly side with Douglas and against myself and Andrew. I have managed to build nice amps with very small PSU caps almost out of wanting others to be wrong. Seems to me if the clipping point is at high output then it is OK. I suspect Andrew is saying we all like to clip amps and need heat sinks to be small. By experiment we find big transformers important. However Andrew is 100 % right as far as I know in his picture, Bob Carver might see it in the same way. Andrew seldom likes a compliment so I exspect none.
One of my designs was taken to task and thought to be inspired by a Neumann phantom PSU. The reviewer stated it must be a floating PSU using a resonant circuit over-damped. The evidence was a AP graph where mine almost clones the other. A friend translated it for me so some of this must be Chinese whispers and I may be very wrong. The difference being mine is 4600 watts. The thing is it was sent to me via someome as the reader infered it meant mine was nothing special. I think the doubt was I had copied something as it seemed a total clone. The weird bit is my friend John has a Neumann or two. He has shown me the PSU. Maybe I took something from it? I was questioning if something so simple was good enough ? It looked like ripple could be high. It isn't.
Just read this by Andrew T when searching for TDA 7293 in PP bridge ( 60 R load +/- 37 V DC ). Really impressed Andrew says it this way. It is what Dejan has been asking. Andrew has simplified a very difficult question. He also sugests how transformers should be looked at. I recently ran out of space for a transformer and had to use some Andrew thinking to solve it. Not able to say the solution as I am being paid for it. Andrew more or less says what I did. Douglas Self does not support this idea by his numbers. Andrew very clearly states why it could be other than the world of Douglas. I must say I slightly side with Douglas and against myself and Andrew. I have managed to build nice amps with very small PSU caps almost out of wanting others to be wrong. Seems to me if the clipping point is at high output then it is OK. I suspect Andrew is saying we all like to clip amps and need heat sinks to be small. By experiment we find big transformers important. However Andrew is 100 % right as far as I know in his picture, Bob Carver might see it in the same way. Andrew seldom likes a compliment so I exspect none.
One of my designs was taken to task and thought to be inspired by a Neumann phantom PSU. The reviewer stated it must be a floating PSU using a resonant circuit over-damped. The evidence was a AP graph where mine almost clones the other. A friend translated it for me so some of this must be Chinese whispers and I may be very wrong. The difference being mine is 4600 watts. The thing is it was sent to me via someome as the reader infered it meant mine was nothing special. I think the doubt was I had copied something as it seemed a total clone. The weird bit is my friend John has a Neumann or two. He has shown me the PSU. Maybe I took something from it? I was questioning if something so simple was good enough ? It looked like ripple could be high. It isn't.
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I'm thinking Thunder Ute, and a shag in a swag at a B&S.
(life is loads easier with a 50-year old mind in a body of 18)
I'm happy with the mind of an 18 year old in the body of a 46 year old
. I decided long ago that acting my age was over rated.
Yeah, that's what I always see first when I go to London. Funny, huh?
This August I plan to investigate Nigel's habitat in Oxford, who knows, maybe there it's different.
Oxford is still a bit polluted. I detest the place, but love it also. I doubt if in my life I have seen 50% of it. Cambridge is very similar. Cambridge has more 1500's red brick buildings. Around Cambridge is a bit boring I find except Ely. Essex which receives so many jokes can be very beautiful when away from the Ford factory etc ( And the dreadful Rega Research Ltd ). Roy helped design the Ford Mexico I was told. His boss took the credit so he set up Rega with Tony Relph. Tony's mum worked there until her 90's I think and was the motor setup expert. Mr Akemanns sister also the same age tied the nylon for the SME bias weight. She was the expert also.
The Moon is going to eclipse the Sun in 15 minutes. I think that it is on the Equinox is the more interesting. The Druids must think so ? Svalbard should have the best view a little later.
The Moon is going to eclipse the Sun in 15 minutes. I think that it is on the Equinox is the more interesting. The Druids must think so ? Svalbard should have the best view a little later.
London is much better now. Cars of the high pollution type are contorlled by charges. This is made complex by having to pay on the day via a terminal in a shop or electronically. Many catch a bus as it is cheaper anyway. I can drive to St Pancras station without crossing the zone. It is a few metres away. I haven't been for a while so may be wrong. Oxford read 4 out of 10 for pollution yesterday as did my small town.
Did a small mod on my OB speakers that was a step in the right direction. The midrange coupling cap increasd from 100 uF to 570 uF ( 470 uF low grade and 100 uF high grade ). This moves the - 3dB point from 200 Hz to 35Hz. The drive unit has a natural roll off of 100 Hz. It was a stab in the dark and seems about right. The amp now has a tougher time. The mathamatical additon of two drivers makes for OK bass. Really quite surprising how different it is. Almost sweet and lush.
Next step is an inductor to roll off the top a little of the 12Lta midrange ( > 250 uH ). Next a two pole 5 kHz filter for the tweeter. After that active seems the best route. The tweeter might need 6 dB gain when active.
The sound is still 1960's cinema. I wanted that. Micro detail is still poor compared with what I hoped for. Adding bass helps that. Obviously we can't hear micro detail if the bass is missing? As far as I know the baffle resonance being wood looses some micro detail. The additional 15 inch driver is just a delight and did no additional harm.
Did a small mod on my OB speakers that was a step in the right direction. The midrange coupling cap increasd from 100 uF to 570 uF ( 470 uF low grade and 100 uF high grade ). This moves the - 3dB point from 200 Hz to 35Hz. The drive unit has a natural roll off of 100 Hz. It was a stab in the dark and seems about right. The amp now has a tougher time. The mathamatical additon of two drivers makes for OK bass. Really quite surprising how different it is. Almost sweet and lush.
Next step is an inductor to roll off the top a little of the 12Lta midrange ( > 250 uH ). Next a two pole 5 kHz filter for the tweeter. After that active seems the best route. The tweeter might need 6 dB gain when active.
The sound is still 1960's cinema. I wanted that. Micro detail is still poor compared with what I hoped for. Adding bass helps that. Obviously we can't hear micro detail if the bass is missing? As far as I know the baffle resonance being wood looses some micro detail. The additional 15 inch driver is just a delight and did no additional harm.
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Actually, Nige, London was doing something right way back in 1984, when I was there last. For a kick-off, people were swimming and bathing in the river Thames, an unimaginable thing to do in 1970, unless you wanted to get in as a man and come out as a skeleton. True, this was just BEFORE the suburbs, private houses on the river banks.
This prompted me to investigate, From that time, the UK non-pollution law had all of TWO paragraphs. From memory (for the gist of it):
People livng and working in the UK will not pollute the natural environment.
All creeks and rivers in the UK will flow down the natural stream.
The second article may seem to be silly, but it cut short the "it's not us, it's the guys before us" argument. As is usual in Anglo-Saxon law, it was left to the courts to fill this in from their practice, using the precedence factor. I imagine they have done quite a job over the last 29 years.
This prompted me to investigate, From that time, the UK non-pollution law had all of TWO paragraphs. From memory (for the gist of it):
People livng and working in the UK will not pollute the natural environment.
All creeks and rivers in the UK will flow down the natural stream.
The second article may seem to be silly, but it cut short the "it's not us, it's the guys before us" argument. As is usual in Anglo-Saxon law, it was left to the courts to fill this in from their practice, using the precedence factor. I imagine they have done quite a job over the last 29 years.
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The big change was no industry. So a bitter-sweet reason. My dad swam the Thames in the 1940's. His mum was vey unhappy he did. He is 84 now. He worked with dangerous chemicals also so shouldn't be with us ( benzine )!
I will have a bath in a minute. It is the Thames. We get it before Oxford so still very clean. It was said our drinking water had passed through many other humans starting in Birmingham before we get it. Stupid how people will believe things. It never did. Why Birmingham I ask ? If it was the Oxford Birmingham canal perhaps so. That runs nearby and is very beautiful. The Cherwell also. Cherwell is more the Oxford river than the Thames. The Thames is called Isis in Oxford. Oxford was formed by a gravel deposit. The river branches into many fingers. Thames at Abingdon ( MG Cars ), Henley and Reading are notable points. I think in French a river like the Thames is called a Fleurve? It means important river.
I will have a bath in a minute. It is the Thames. We get it before Oxford so still very clean. It was said our drinking water had passed through many other humans starting in Birmingham before we get it. Stupid how people will believe things. It never did. Why Birmingham I ask ? If it was the Oxford Birmingham canal perhaps so. That runs nearby and is very beautiful. The Cherwell also. Cherwell is more the Oxford river than the Thames. The Thames is called Isis in Oxford. Oxford was formed by a gravel deposit. The river branches into many fingers. Thames at Abingdon ( MG Cars ), Henley and Reading are notable points. I think in French a river like the Thames is called a Fleurve? It means important river.
Hah, Reading. It was my byway crossover station, when coming to England, I went from Heathrow to Reding, shoter and much faster route than to Paddington), then caught the West Country train to Taunton. Ah, those were the days, my friend.
Just on my CD player, Leapy Lee and "Little Arrows" - remember him, Nige? 1968, I believe, actually hit No.1 on the charts, but didn't stay long. I am listening to a compilation called "One Hit Wonders", just as he was.
Struth, I do miss old Blighty!
Just on my CD player, Leapy Lee and "Little Arrows" - remember him, Nige? 1968, I believe, actually hit No.1 on the charts, but didn't stay long. I am listening to a compilation called "One Hit Wonders", just as he was.
Struth, I do miss old Blighty!
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Colleen and I were talking of the Welsh ( ? ) wonder and little arrows recently.
New Somerset and Dorset Railway
https://www.youtube.com/watch?v=zTFcN8RsJbs
Mr mothers name is Beeching. Same family alas.
New Somerset and Dorset Railway
https://www.youtube.com/watch?v=zTFcN8RsJbs
Mr mothers name is Beeching. Same family alas.
Water is a closed system, your bath will have passed through every human who has ever lived.
You would have enjoyed the Buffalo DHC-5D I used to fly in the Canadian Air Force back in 1968. Empty weight was 25,000lb, max take off weight was 49,000lb. Typical take off weight when unloaded was around 28,000lb. With 3150 shaft horsepower from each of the two GE turboprops this translates to 4.4 lb/hp. This, coupled with the very low stall speed enabled by the double slotted Fowler flaps meant we could get off the ground after a very short run, especially with any headwind at all.
I remember it having 4 bladed 14' diameter props, but all the pictures I see show 3 blades. In any event, the props were huge and at cruise speed the props would be turning around 1100 rpm, and you could easily see the rotation when looking at the hubs. Part of the overall design of the Buffalo involved acoustic stealth, and due to the low prop rpm and the light prop blade loading due to their large blade area, the plane was all but inaudible from the ground when approaching at altitudes of around 1000'.
I now waht you mean, Russ, propellers of any kind with four blades appear at the rate of wisdom teeth appearance. Mine was not an airplane prop, it wasn't even turbo, it was a modest two stroke British Seagull outboard motor rated at "2.5-3.5" hp. Also four blades, and straight, except for vertical angling. It was not fast, but th weight it had to push didn't seem to make any sense to it, it just went on about its job.
AS a matter of fact, that was easily the best piece of mechancs I have ever seen anywhere, by anybody. Incredibly simple, there is prescious little to break down if you juist remember to check for the oil in the horizontal-vertical drive shaft. The only similar engine I saw was its only real competitor, British Anzani.
It was purchased in 1966 and still works like clockwork to this day, I gave it to a mad fisherman friend. He swears by it, claims it's more effective on the rivers (Sava and Danube) than his outboard 5 hp Johnson. In a lightly loaded boat, on still water, the Johnson will outpace him easily, but like a lot of local river fishermen, he never goes out alone, it's a social event so the boat is almost always full.
AS a matter of fact, that was easily the best piece of mechancs I have ever seen anywhere, by anybody. Incredibly simple, there is prescious little to break down if you juist remember to check for the oil in the horizontal-vertical drive shaft. The only similar engine I saw was its only real competitor, British Anzani.
It was purchased in 1966 and still works like clockwork to this day, I gave it to a mad fisherman friend. He swears by it, claims it's more effective on the rivers (Sava and Danube) than his outboard 5 hp Johnson. In a lightly loaded boat, on still water, the Johnson will outpace him easily, but like a lot of local river fishermen, he never goes out alone, it's a social event so the boat is almost always full.
Yes, the Seagulls were always designed for push, not speed, and had props as large as 13" (on the "barge pusher") but always with fine pitch, so lots of push but no speed potential. There was almost nothing else but these used around here as auxiliary motors for sailboats, for which they were ideal, easily pushing 25' boats 4 knots or so and, as you say, Dejan, a model of simplicity. I think they were displaced by the little Hondas and Yamahas which were more complex but ran cleaner - the Honda 4 stroke, especially.
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