Velleman K4010

[WikiBoy]

Sorry I am a silly arse, should read Hitachi not Toshiba. Well it was 28 years ago

I produced the first non Toshiba application note mosfet output power amp, the Tresham Audio SR402 in 1980. .

[StanleyB]

Why are some engineers quick to blame the parts when it is really their ability that is at fault? The classic one so often heard is: "if I had a bigger knob I would be a better lover" .
I use 3 semiconductors in my product that most engineers complain about in terms of performance they are able to extract from those parts. I don't have any problem with getting them to work properly, and bring delight to the ears of many. Does that make me a genius or my fellow engineers a bunch of circuit copiers who should be taking up a different trade?

I got a set of emails stored away from a guy who I asked to carry out a certain mod on something he bought off me. He gave me a whole lecture about why it won't work, and how I was a useless quack pretending to be a designer. He was a top engineer with a big US electronics company and had designed components used by NASA. So I asked him to back up his claims that the thing would blow up if he did it the way I told him to. If it blew up, I would give him a refund and a new unit FOC.
Two days later a had one long apologetic email about how smart I was and how much he appreciated my patience. And he was over the moon big time with the results.

The moral of the story is that some engineers won't know what to do with a bigger knob.

[WikiBoy]

Why are some engineers quick to blame the parts when it is really their ability that is at fault? The classic one so often heard is: "if I had a bigger knob I would be a better lover" .
I use 3 semiconductors in my product that most engineers complain about in terms of performance they are able to extract from those parts. I don't have any problem with getting them to work properly, and bring delight to the ears of many. Does that make me a genius or my fellow engineers a bunch of circuit copiers who should be taking up a different trade?

I got a set of emails stored away from a guy who I asked to carry out a certain mod on something he bought off me. He gave me a whole lecture about why it won't work, and how I was a useless quack pretending to be a designer. He was a top engineer with a big US electronics company and had designed components used by NASA. So I asked him to back up his claims that the thing would blow up if he did it the way I told him to. If it blew up, I would give him a refund and a new unit FOC.
Two days later a had one long apologetic email about how smart I was and how much he appreciated my patience. And he was over the moon big time with the results.

The moral of the story is that some engineers won't know what to do with a bigger knob.

You obviously haven't a clue about the basic properties of transistors.

Crystals are grown and different crystals grow differently and have different properties, both advantages and disadvantages. Everything in audio design is setting preferences and making compromises. A power fet amp from the hands of an intuitive and capable of listening designer will clearly out perform a bi-polar design from a designer who isn't. My point is all other things being equal fets have severe problems in terms of linearity and balance. It can be seen quite clearly on an oscilloscope and can be heard quite clearly. This non linearity is endemic and incurable with the present semi conductor state of the art.

BUT things change, we had to start with germanium crystals and really couldn't get going until we grew silicon crystals. Fets will give you the ultimate in transistor linearity if you configure them for single ended class A as long as you put up with the compromises that design inflicts. Very low power levels and need for high heat dissipation. And the shear advantage of a device that doesn't go crack splutter bang and loads of smoke from the burnt out emitter resistors when grossly overloaded or short circuited is well worth having. The manufacturers of power fets have been trying for years to get over these non linearity problems in the growth of the crystals, so far with little success otherwise they would have taken over from bi-polar the same way as silicon took over from germanium.

[StanleyB]

You obviously haven't a clue about the basic properties of transistors.

There we go again. Don't blame the properties of the transistors. Do you complain about the properties of valves as well? Your comments only go to underline what I am stating that many engineers are brainwashed with: blame the tools they have to work with for not being able to produce a better end product. The reasons tend to be obvious in many cases. If you start thinking out of the box instead of trying to build the same structural design day in and day out, new components are not going be be any good to you. You are supposed to use the properties of the new part to your advantage.
In the case of MOSFETS, amplifier designers rushed out and designed class B amps in the believe and hope that it would sound better. How many people outside Japan started from scratch and looked at ways to design new types of audio amps circuitry?

[WikiBoy]

There we go again. Don't blame the properties of the transistors. Do you complain about the properties of valves as well? Your comments only go to underline what I am stating that many engineers are brainwashed with: blame the tools they have to work with for not being able to produce a better end product. The reasons tend to be obvious in many cases. If you start thinking out of the box instead of trying to build the same structural design day in and day out, new components are not going be be any good to you. You are supposed to use the properties of the new part to your advantage.
In the case of MOSFETS, amplifier designers rushed out and designed class B amps in the believe and hope that it would sound better. How many people outside Japan started from scratch and looked at ways to design new types of audio amps circuitry?

If you want to be thought of other than a complete idiot perhaps you should be more specific instead of generalising, what audio circuits? what do you do that is different? Name me an amp or designer where he has started from scratch with mosfets and what he has produced. Amp design is like a game of chess, it has to have rules or you can't play. Each of the chessmen (components) has usage rules, otherwise the device wont play or self destructs in a cloud of smoke, good fun but it plays no music. Individuality comes in how you play the game in regards to sequence and pattern. Same with amp design. Anyway in reality all this about output stage configuration is small beer compared with other parameters like power supply as so succinctly put by anthonyTD in another thread, who is not just some pseudo wanna look big knowledgeless prat.

[johnrtd]

How many people outside Japan started from scratch and looked at ways to design new types of audio amps circuitry?

We did!

[WikiBoy]

We did!

Just about everyone does, otherwise they are not worth their salt, which is why the statement / question was so stupid. Very few people just ape application notes, though they are a good start point, at least you know *that* works.

It is normally in the early days of a new genus like the Hitachi power mosfets in the early 80's that people use purely the application note but as time goes on new things are seen and done and others build on it, like a pyramid of the possible. It is even fun when things go wrong, especially if you are a secret pyromaniac like me, my early teenage fun in components working for G.W.Smith and Co Radio Ltd in Lisle St (which is now part of London Chinatown, I went for meal in my old shop a couple of months ago) as Saturday boy was finding out which components make the biggest bang when wired across a mains block. good thing I wear glasses, otherwise I would be my avatar.

But to quote Dr. Bunsen Honeydew "who needs eyes when you have glasses".

[karl43]

How much bias needs a SR402b to sound well ?

[johnrtd]

The Crescendo resp. Vellemans amp is NOT a "High End"design. Of coarse it's fun to make it, but don't expect something better then an average commercial amp (say Onkyo, Harman Kardon, Bryston etc.).
Not yet mentioned in this thread is that there are newer mosfet's from Hitachi which are a lot faster so bandwidth and slew rate both improve in a design.
Some mentioned the "loudspeaker protection" circuit as offered by Velleman. In that circuit there's a relay contact at the output of the amp. IMHO there's no need for that. We deliver mosfet based amps since 1989 and NEVER heard of any problem (blowing up the loudspeakers).
The real fun for an audio amateur is to construct something (an amp) that outperforms most commercial products at a reasonable price. If someone is interested I could publish the circuit of our famous A-18 on these pages. In that amp there even are NO source resistors so the fet's are directly connected with the loudspeaker.

John

[Marco]

Hi John,

Good to see you back. Where have you been old chap, and what's happened to your avatar?

Marco.