Mobius loop again ( should have been my nom de plume ) . At the twist point we get the Nyquist point . Visually I do see a feedback amp as being like that .
I recently built a unique application of a bootstrapped VAS . I could not use a CCS as it a power engineering application and requires nearly 100% positive feedback ( 96.4% ) . The hum levels were atrocious ( and of absolutely no importance ) . Has anyone had poor noise performance from bootstraps ? It is not talked about . Looking at my results it seems logical they would . This further endorses regulated power to the VAS ( shunt ) . Also the tail resistor is then a possibility rather than a CCS , as one of us said it might behave better at HF ( fas 42 ? ) .
I recently built a unique application of a bootstrapped VAS . I could not use a CCS as it a power engineering application and requires nearly 100% positive feedback ( 96.4% ) . The hum levels were atrocious ( and of absolutely no importance ) . Has anyone had poor noise performance from bootstraps ? It is not talked about . Looking at my results it seems logical they would . This further endorses regulated power to the VAS ( shunt ) . Also the tail resistor is then a possibility rather than a CCS , as one of us said it might behave better at HF ( fas 42 ? ) .
(Bold & underlined by DVV)
This is an assumption most open to discussion. A resistor afrter a zener is preferred by the audio industry for cost reasons only. Those same manufacturers will do it right on their more expensive models.
As we had the opportunity to see here some time ago, somebody posted his own test of 10 or so CCS types tested for PSRR, clearly demonstrating numbers from 38 to 82 dB. Kinda BIIIIG difference, don't you think?
Somebody else mentioned the fact that this is outside the NFB loop, so it it what it is, no subsequent corrections. While I cannot pretend to know just how audible this is per se, I am ruled by the logic that everything matters, that effect included. The most difficult thing ever, in any field of technology, was to make a well balanced product.
Because of this, I am not very keen on all-in-one power amp chips and prefer those which require external power devices. The key reason is that in such a case, I can use fully electronically regulated power supplies for the chip and separate unregulated supplies for the output stage.
In case of a discrete CCS, the transistor separating the zener voltage from the input stage rules supreme no matter what anyone says. Preferably two transistors in a cascode topology, and still more preferably with a FET separating the BJT from the supply line (but because of generally low FET voltages, this usually requires an extra resistor, zener diode and filtering capacitor. Thank God I am not the industry.
I wonder how many very boring / competent amplifier out there might be improved by simple PSU upgrades ? Fit a larger toroid transformer and upgraded capacitors . Next a few tweaks to the power amp VAS supply . Graft 4700 uF next to output transistors . If knowing virtually nothing about electronics this should be possible and rewarding. If space allows use the old transformer to power the VAS etc (and preamp section if an all in one design ) . Rotel told me that their cheapest amplifier was simply a smaller transformer ( I think I recommended it and they did it about 1985 ) . It sounded very different ( anemic ) !
I might tell a sad twist to that story . Comet was where I bought my Akai AA 8080 receiver when aged 15 ( 1971 £139 ) . Comet probably launched the reborn Rotel of Stan Curtice and Tony Morpath . When I had a shop I used to send students to Comet to buy a Rotel amp ( RA 820 Silver ) ,then return to me to buy the rest ( 10 % student discount and all cables supplied ) . I was so impressed I phoned Rotel and became a dealer . I was I think the only independent then who sold it in the UK ( 1980 ) ? Comet were like Walmart , most shops wouldn't touch it if sold there . I didn't give a dam if it made money directly as it made money for me selling other things . Truth is it did make money and Rotel liked having an enthusiast to talk to who got involved with circuit design .
My shop closed in 1997 . Student grants were cut and parking became impossible . My little shop turned over £400 000 at the peak and £ 210 000 when we closed . Even by UK standards it was a small shop . It cost £38 000 from the profit just to open the door per year .
Comet ( all UK ) closed about a month ago . Rather than them being competition we shared business , the manager was astonished and I am sure he sent me twice what I freely sent him ! We both noticed if recommended by the other usually the sale was made . It was like the film Miracle on 34 th street ( 1947 ) . Opposite the shop was Pizza Hut , it was a prime secondary site . Also Jessop's the top photographic chain . Jessop's also have gone just after New Year .
I am told John who took the business I lost now has to do £ 1000 000 to survive ( Oxford Audio Consultants , I presume still there ) . No wonder we have no hi fi industry . Talk about the vampire drinking the blood of their cash cows .
When the shop was doing OK the UK was 60% non productive ( not making things ) . Now I guess 90 % ( UK = Greece with banking safety net ) ? In 1997 I went into manufacturing and never looked back . I was forced and also told a white lie at my kids school . When a teacher was having a go at my boy I said it's not surprising as I am an inventor and he is used to an eccentric life style . I never regretted that forced change of life . It has made me many friends and I have seen the world due to it . Never had any money and I guess I never will ? I am try to pass through the eye of needle without volunteering I guess ?
I might tell a sad twist to that story . Comet was where I bought my Akai AA 8080 receiver when aged 15 ( 1971 £139 ) . Comet probably launched the reborn Rotel of Stan Curtice and Tony Morpath . When I had a shop I used to send students to Comet to buy a Rotel amp ( RA 820 Silver ) ,then return to me to buy the rest ( 10 % student discount and all cables supplied ) . I was so impressed I phoned Rotel and became a dealer . I was I think the only independent then who sold it in the UK ( 1980 ) ? Comet were like Walmart , most shops wouldn't touch it if sold there . I didn't give a dam if it made money directly as it made money for me selling other things . Truth is it did make money and Rotel liked having an enthusiast to talk to who got involved with circuit design .
My shop closed in 1997 . Student grants were cut and parking became impossible . My little shop turned over £400 000 at the peak and £ 210 000 when we closed . Even by UK standards it was a small shop . It cost £38 000 from the profit just to open the door per year .
Comet ( all UK ) closed about a month ago . Rather than them being competition we shared business , the manager was astonished and I am sure he sent me twice what I freely sent him ! We both noticed if recommended by the other usually the sale was made . It was like the film Miracle on 34 th street ( 1947 ) . Opposite the shop was Pizza Hut , it was a prime secondary site . Also Jessop's the top photographic chain . Jessop's also have gone just after New Year .
I am told John who took the business I lost now has to do £ 1000 000 to survive ( Oxford Audio Consultants , I presume still there ) . No wonder we have no hi fi industry . Talk about the vampire drinking the blood of their cash cows .
When the shop was doing OK the UK was 60% non productive ( not making things ) . Now I guess 90 % ( UK = Greece with banking safety net ) ? In 1997 I went into manufacturing and never looked back . I was forced and also told a white lie at my kids school . When a teacher was having a go at my boy I said it's not surprising as I am an inventor and he is used to an eccentric life style . I never regretted that forced change of life . It has made me many friends and I have seen the world due to it . Never had any money and I guess I never will ? I am try to pass through the eye of needle without volunteering I guess ?
In my experience, quite a lot of so called budget amps will benefit from beefed up power supplies. Some more, some less. When any one of my friends decides to refresh his gear, the first thing I tell them is to carefully investigate whether installing larger caps is possible, and if so, to go for them.
Sometimes, it's also necessary to change the bridge rectifier, so it can handle the eadded capacitance.
Several times, the power transformer had also been changed, but that's very rare as usually there's not much spare space, or if there is, the basic device is simply not worth the trouble and expense. I mean, if you own a 30 WRMS Technics, what's the use of investing more than its purchase price into beefing it up?
Why even consider it? Usually, for one of two reasons. Sometimes the owner is most attached to a device and will not give it up for any reason. Secondly, even in the budget sector, you occasionally come across an uncut diamond, so to speak, a design which you would never expect to find in that price bracket. Toshiba R45 comes to mind, exactly such a product, designed and made MUCH better than its price would lead you to believe. Its only real failings are a ridiculously small power transformer and a U shaped piece of aluminium which acts as the "heat sink". Both can be changed for better without too much hassle, resulting in an integrated amp purchased for a princely sum of € 35 (app. $50), requiring about €100 (app. $130) for the whole list of works (new power transformer, new proper heat sink, new caps up from 8,200 to 15,000 uF, new output devices, etc, all of which will make it play music like a modern integrated amp about 7-10 times its total price.
You won't have a remote, but you will have the music. Who knows Toshiba's transistors better than Toshiba?
My dad has a Kenwood ( Trio ) 10 W receiver . It is out of this world good . The power supply looks to be for a train set . I studied the design and feel it must be a 30 W design chopped down in price . The FM is astonishing , as is the build quality . The sound is fantastic apart from obviously low power . The tone controls in the power amp ( nice ) . Nothing in the power amp would say it is less than 50 W . This receiver was sold when 10 W was already below acceptable . I bought it by listening and being totally amazed . Stranger still it drives LS3/5A which are considered to need 100 W ( 500 transient was said by a BBC designer , Meridian 105 is very good ) . I remember the Kenwood raising the roof on Proms night . It can be clipped without any distress to itself or speakers .
It would be a No 1 for an upgrade . It has the space . I think a 250 VA toroid is where to start . They are cheap at Rapid Electronics and CPC . Caps after . Good to hear the progress in stages .
Toroidal Transformer 230v Single Primary 225va 0 15v 0 15v ( a guess for a 10 W design , A Japaneses 10 W was often 20 W ) ??
It would be a No 1 for an upgrade . It has the space . I think a 250 VA toroid is where to start . They are cheap at Rapid Electronics and CPC . Caps after . Good to hear the progress in stages .
Toroidal Transformer 230v Single Primary 225va 0 15v 0 15v ( a guess for a 10 W design , A Japaneses 10 W was often 20 W ) ??
This is indeed the mark of a sound design. Plenty of music material which sounds to be of a high order is in fact badly clipped, but I doubt if anyone can pick it at normal levels. For example, that YouTube clip I linked to some days ago, of a live percussion band vs. speakers has a tremendous amount of clipping ... in the speaker section? No, in the initial "live" capture!!
How many people can hear that happening ...?
Frank
Ooooooh, this is totally off topic, but I just have to share it ...
An hour ago, the postman brought me my quarterly fix of CDs from Amazon.com, and this contains the triple CD/DVD package "The Traveling Wilburys".
There's a leaflet supplied, with very well natured and humorous writings of several people, all of whom are signed as per their "academic" titles, one of which is:
Professor "Tiny" Hampton is currently leading the search for intelligent life amongs rock journalism at the University of Please Yourself, California.
))))))))))))))))))))))))))) Caustic!
An hour ago, the postman brought me my quarterly fix of CDs from Amazon.com, and this contains the triple CD/DVD package "The Traveling Wilburys".
There's a leaflet supplied, with very well natured and humorous writings of several people, all of whom are signed as per their "academic" titles, one of which is:
Professor "Tiny" Hampton is currently leading the search for intelligent life amongs rock journalism at the University of Please Yourself, California.
))))))))))))))))))))))))))) Caustic!Our ears clip also in a very similar fashion . Very bad news if so as SPL is very high . I speculate that compression that does similar things as our ears goes unnoticed ?
Here is a tip . Belgians add cocoa to mediocre coffee ( and others I am sure , also coffee to chocolate cake ) . It makes it taste like better quality coffee , yet the cocoa is not obvious . Better quality coffee with it added is often too soft and does taste of it . I am sure hi fi has similar tricks of perception which don't always work . Multiple caps can be less good than one posh cap . Like the coffee sometime multiple is rather good .
I do wonder if Kenwood had done something rather wonderful by de-tuning a more powerful amp ?
Here is a tip . Belgians add cocoa to mediocre coffee ( and others I am sure , also coffee to chocolate cake ) . It makes it taste like better quality coffee , yet the cocoa is not obvious . Better quality coffee with it added is often too soft and does taste of it . I am sure hi fi has similar tricks of perception which don't always work . Multiple caps can be less good than one posh cap . Like the coffee sometime multiple is rather good .
I do wonder if Kenwood had done something rather wonderful by de-tuning a more powerful amp ?
Live music does overload our ears, and automatic gain control in our brain kicks in. So loud, natural sound doesn't sound loud, but rather, intense. And reproduced sound that doesn't fit the profile when the volume is turned up just sounds wrong, our minds reject it as "just being hifi".
We know instinctively, or have learnt over our lifetimes what the SPLs of the real thing is. My wife, a piano player, sometimes turns up the volume of some initially softly playing solo piano music until it sounds right to her, and virtually every time I find the setting to be a couple of clicks away from a particular one: only a few down from maximum volume ...
Frank
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Yes! On the nose! I think that we proved all of that, over and over, in the thread at http://www.diyaudio.com/forums/power-supplies/216409-power-supply-resevoir-size.html#post3096360 .
Along with increasing the transformer's VA rating, it would probably do even more good to also increase its output voltage. But that would be a lot more dangerous for the amplifier, if attempted by someone who wouldn't know how to tell if it would damage the unit. (And maybe it usually would, anyway.)
Putting uF (decoupling caps) right next to the output transistors seems like it would probably very-often provide an amazing improvement.
I was only 14 in 1971. But in late 1978 or early 1979 I bought an HK560. One channel finally went out, about 15 years ago. Wow I loved that receiver. When it died, I replaced it with a Luxman R1050, from eBay, that I think was at least as good. (More recently, I have ended up with what's practically a small museum of more of those plus some of their relatives.
Yes, that is all rather poignant!
That is truly sad, and I truly hate what has happened, politically (not to even mention culturally), over here, and over there, and I am truly worried (or in a state of despair) about what it all means for today's kids and future generations, and I am so utterly sad for what they have lost in the future (or had taken) and for what they and the world will now never know or experience or produce, and maybe especially for the fact that most of them will never even know the difference, or even think about it.
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I had a crazy thought, the other day, when I suddenly wondered if perhaps the counterculture of the 60s was helped-along by a Soviet and/or Hollywood communist plot that has now succeeded beyond anyone's wildest dreams. (Or maybe they knew exactly how it would turn out.) Alas, I think it's more due to clue-less politicians who found out that they could buy votes, with our money, and didn't understand the basic characteristics of positive feedback loops.
You've no idea just to what extent you're right, Tom. But, that's politics, let's not do it here.
Nige might remember that in the 70ies, it was a crying shame when your electronics did only as specified - it was a point of honour to do better than specified.
Today, all the honour has been spent and the leftovers discarded because they cannot be turned into dollars, or euros, or yen, or whatever, so who needs it?
The most important thing about positive feedback loops is chaos . It says something will happen sometime and we will know afterwards ( turbulence ). Great .
I was at a meeting as a guest of our Roundtable ( bit like Free Masons for charity ) . I met Dr Evan the Historian at Oxford ( his counterparts at Cambridge is Dr Evans also ) . The fat cats at the meeting thought Dr Evan a bit light weight , I thought him absolutely brilliant . I asked one of the cats about the crash and why none of them saw it . They said " it is a well known fact that money grows exponentially ( thinking I have no idea what that meant , to say it is to show no understand , the mathematical equivalent of blood letting ) . Always has and always will " . I said bacteria grows exponentially , they die in their own waste products . I never got invited again ( phew ) .
Positive feedback hey .
Seriously . Positive feedback seems to cause common mode problems .
Positive feedback I suppose is optimism . The fat cat told me without optimism we all would at best be living the 18 th century life . It was his near religious belief in what he was saying that worried me .
When in Vagus I was asked by a lady serving drinks if I gambled . No . she smiled and said " I knew you didn't " . how come I asked ? " you don't look like a looser " ! My answer was did the casino's build themselves ? I like Vagus , I am an exploiter when there (cheap food , beer , hotel , winter sun and nothing else , CES show ) . I met some old ladies from NY , I doubt any below 85 . They had a loosing budget for each day . Sometimes they would win by loosing slower . They calculated the heating cost more in NY so why not ?
When in Vagus I was asked by a lady serving drinks if I gambled . No . she smiled and said " I knew you didn't " . how come I asked ? " you don't look like a looser " ! My answer was did the casino's build themselves ? I like Vagus , I am an exploiter when there (cheap food , beer , hotel , winter sun and nothing else , CES show ) . I met some old ladies from NY , I doubt any below 85 . They had a loosing budget for each day . Sometimes they would win by loosing slower . They calculated the heating cost more in NY so why not ?
Those types of people rarely rate others based on intellect.
You, however, are delightfully intellectual, and do, and I tend to be that way too.
But we have to realize that being intellectual is a luxury. And for a society or culture to have people like you in it is a luxury, for that society or culture. But to be able to have the conditions that enable us to afford such luxuries, we need the fat cats, and as many others as possible, to remain very fat.
I would beg to differ ... it's about time for mankind to grow up a little bit, to use a touch more intelligence and rely a little less on pure greed to get things moving. The earth itself is giving us a few warnings that this "path" is fast running out of manouvering room ...
OK, off the soapbox now, naughty boy ...
Frank
When talking to Dr Evens he reminded me of my maths teacher Chris Bartrum . They seem to have an intellectual gearbox that can happily stay in first gear to please others and especially themselves for everyday life . The Roundtable mistook his gentle ways for incompetence I feel . He hadn't amused them . I was asking Dr Evans about Herodotus . He was delighted and said between 400 AD and 1900 I would have been one of a handful of Englishmen to read it . It would have been required reading before 400 AD . If wondering Herodotus is a great alternative to the other great book of antiquity . One that many here would love , Egyptian engineering especailly . Some say the deserts were water filled at the time of building the pyramids , not exactly so if you read Mr H .
These fat cats do good locally and I am sure England is only fed by what they do ? Problem is it makes me feel a bit like a pimp . 90 % of my money comes from outside of the UK . If I had to live on my UK money I would no problem passing through the eye of a needle .
These fat cats do good locally and I am sure England is only fed by what they do ? Problem is it makes me feel a bit like a pimp . 90 % of my money comes from outside of the UK . If I had to live on my UK money I would no problem passing through the eye of a needle .
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