Turntable Signal to Noise Ratio

[Primalsea]

The Maplins kits I used were the 200W kits for £14.00 each. They are actually more like 50W, the 200W is a bit loose and wild. They use darlingtons for the output stage instead of a CFP. I bought extra darlingtons and parralleled them in 3's. This is quite a simple design and I was not expecting much. However once I powered the amp amp I was very supprised. I've herd all sorts of amps at different price ranges and these are my favourite at the moment.

I have not seen the mosfet modules so can't comment on them.

Ever since I read about Bob Carver and how he got his $600 solid state amp to sound identicle to a $20,000 valve amp to the point where Stereophile could not tell the difference, I have stopped paying too much attention different amp designs.

[petercom]

That 'Carver' trick was back in 1985. It was up against a Conrad Johnson in a test and listening environment of his, not Stereophile's, choosing. He is not the only one to have done it. I remember a similar exercise in 1972 by a UK manufacturer keen to launch his new budget amplifier design.

Carver is full of all sorts of claims like this. I suggest you stop reading and start listening for yourself!

[Primalsea]

"I suggest you stop reading and start listening for yourself!"

Aaaaaaaawwwwwww, Meeow!

As you are actually someone who has a solid technical background I have some respect for you. Far more than many reviewers who admit themselves they are ignorant and indifferent about technical aspects of items they review.

But.... the idea that you can modifiy an amp to sound like any other using Carvers methods, albiet in a controlled environment is interesting. This sort of stuff could really sort the wheat from the chaff of the mods and tweaks and component changes etc etc that we all do. Also the idea that changes in amps characters can be bought about buy different topologies as modifications to them is another interesting point. It can also give insight to how subjective improvements match engineering changes.

I do not take what carver did to be a crowning moment for the skeptics. The guy is great at marketing and like the 1972 excerise you mentioned was just another piece of marketing.

This has gone a bit off topic, innit

[pre65]

Hi-what Peter says is really the best advice we can all have.

so much of what is written is marketing hype and because of the way our surroundings alter the sound we can only really rely on our own ears.

that is the beauty of this forum because we mostly use what we make or buy at home so our views and opinions are more relevant.

you will be better to keep an open mind on what you read and many of us have sold equipment that was supposedly the dogs whotsits and replaced it with much cheaper AND better performing gear.

If you are happy with your equipment then no problems but you owe it to yourself (as i hope to do ) to attend the next gathering (Nov ?) and hear what can be achieved in several different ways.

Philip

[Primalsea]

From what you said I think I came across slightly differently to how I intended in the previous post.

I agree with what you and Peter said, I,m just looking at it from a slightly different angle.

What gathering in November are you talking about and where might it be? I would like to meet others and hear their projects as well as maybe bring some of my own. I presume this is what happens.

[petercom]

Absoloutely, that is exactly what happens.

As for topology you are right, the topology of a circuit affects the sound in very distinct ways, especially when you are working at reduced feedback levels.

Todays amps tend to sound very close in character to each other largely, I suspect, because modern transistor amps are chasing vanishingly low distortion specifications with higher and higher levels of feedback.

Since loop negative feedback arrived on the hi-fi scene in a stable manner in the Williamson amplifier, the 'goodness' of amplifiers has been determined by the distortion figure.

But, as I pointed out in another post, if harmonically related distortion below 2% is difficult, if not impossible, to detect, what is the point?

I note that around the time of the Leak Point One, amplifier manufacturers started putting the level of loop negative feedback used in their amplifier specs. So, for example, one would see 'feedback 30dB' in an advertisment as if it was something to be prized.

Before this new amplifier designs were characterised by their topology and the character of sound that this produced. So a Lowther amp would sound very different to a Panphonic and so on.

With our low feedback valve amps we are getting back to that stage. As a result there is as much personal preference amongst amplifier types as there is amongst speakers. But all of them play music in a much more enjoyable manner than any modern transistor amp.

What Carver did is what most manufacturers do when trying to out clout the competition. By arranging a switch box between the loudspeakers and two amplifiers, and making sure the tonal balance and volume levels of both amplifiers was identical, listeners could not hear the difference when switching from one amplifier to another.

The problem with this type of test is that switching only allows you to hear the change in volume or tonal balance. It will not allow you to hear the musical character of the amplifier. That is because musicality is an all enveloping aspect of a musical performance. As such you have to listen to a passage of music on each playback system to assess its musical character.

There is an interesting corollary to this going on in the pro music business. You can now buy software boxes that will turn any electric guitar into the sound of a Les Paul or a Stratocaster or anything else through DSP. But whilst the output of the box might sound 'tonally' like the real thing, there are grave doubts that it doesn't emulate the real instrument musically. And should we be surprised? If sound reproduction was all down to frequency response, distortion and volume level then hi-fi would have been 'perfect' decades ago.

[Primalsea]

That's some interesting points you've made Peter.

I would'nt be so interested in hifi if it was'nt for the differences that you can hear. and how supprised you can be with stuff that has been written off just because it uses yesteryears technology.

When I got the Maplins kits home I saw to my dismay they used just a basic topology:- LTP with no current sources, VAS with a boot strap current source and a Darlington output stage. If this was mentioned on somewhere like the DIY Audio sight people would either scoff or ignore you. replys would tell you to stick in some active current sources and sinks and remove the old style boot strap source. Other would say dump it and go for a symetrical non global feedback design with current feedback etc etc etc. I think sometimes there is a kind of blind faith that things with better specs are better in everyway.

However when I fired them up they sounded fantastic! With what I read about Carver / Stereophile incident I decided to spend some time just exploring what can be got from working with this basic amp circuit rather than agonising other whether I should "upgrade" to a more complex design. It was really the idea that you can make dramatic changes to how an amp sounds by modifying it rather than making those changes by completely changing the amp with one that has been engineered to have the lowest distortions, highest current capability blah blah.

To go off topic a bit more, The 773e's. I think thay are great speakers but I do feel that they can sound a bit closed in and dull at lower volumes. At higher volumes they seem to really open up and become more enjoyable to listen to.
Have you noticed this too with them?

[petercom]

I agree, it is amazing what you can do with some basic circuits just by making sure the layout is excellent and the power supply is sensibly designed.

773e - yup, they were engineered to sound good at highish volumes, like most speakers with small cones they find it difficult to manage transient information faithfully at low volumes.

You can improve treble detail by replacing the treble capacitors in the crossover with Soniqs PXX polyprops, and improve the midrange clarity by replacing the bass coils with the larger ferrites we have at on the WD catalogue.

Have a read of the speaker upgrading articles in Hi-Fi World this and next month's issues.

[Primalsea]

I've read this months article which was quite interesting.

I was'nt sure if the increase in volume excited the room modes given the impression of better sound or if it was the speakers.

By the way, I like the way you sneaked in an advert for WD, Hifi Chioce and a reference to what I suspect are 2 of your articles. Well if you've got a big trumpet, blow it!!

[Ianm2]

I am afraid most makers either plainly lie, mislead or blind us to specs.

there needs to be absoulte comparitive standards well understood and explained in laymans terms, makes me laugh and cry a bit all these meaningless specs. you get it in computers too, and who knows what they mean? you have to understand it all b4 you can judge, and when you begin to, you realise the hoodwinking going on.

Its disgusting really.

specification masturbation.

I have a bk elect 1000 watt pair of modules.

I calculated it accurately to 247 watts rms into 8 ohms, based upon voltage rails, input sensitiviy, feedback resistors, and load!!

1000 watt is probably peak to peak into 4 or even 2. Fortunatly, despite that, they sound great, and do have loads of current into lower load nasty speakers

having said that, it really makes me wonder what these small hifi amplifiers are capable of, if a monster transformer and output stage can only provide that. I reckon, you can probably 2/3 to half most power specs.