Yeah, like null-test elephant and mosquito and adjust the elephant so it can fly.
Easy!
Welcome back new Wavebourn . I missed you . New tougher Wave I think ? What the hell , good to have you in the fight . Dvv and I held the fort a lot .
There's a word: competent. In the late 80's and early 90's I gave up on commercial audio amplifiers, Krell and the like included - they were all incompetent. I had a test CD that I took around that easily exposed their lack of capability - at various, quite ordinary volume levels they started to obviously distort ... I gave up on the audio game for about 10 years, because it all seemed to be going nowhere ...
But, progress has been made in the interim! At the recent hifi show in Sydney a reasonable number of units showed true competence - it was an encouraging sign ...
Strewth Frank, "...-they were all incompetent." is a bit strong , don't you think? Most, I can understand, but ALL?
I would agree that the 80ies were a sort of a black hole for audio, the heyday was gone by 1980, exceptional growth rates, which made some companies giants in just 4-5 years previously, were also gone, the video threat was upon them and now a new "thingie" called PC was looming and taking off like a rocket by mid-80ies. They didn't know what to do, so they decided to put just about everything on hold, except the gem they had, which was the CD.
If you look back, it was not before 1988 that they tried a comeback. Everybody and their dog had completely new models on display by then, some even had completely new series out. Regarding competence, I do believe some very good new models appeared about that time from several sources all at once, and there were some creditable efforts before that as well.
Example - Yamaha A1000. Possibly the last of the heavyweights (except for Sony, who tenaciously held on a lot longer than most), built like a tank and offering a manual or automatic choice of pure class A or class AB.
But after the onslaught in the late 70ies, lack of impetus was more than obvious, sort of like a drizzle after torrential rain.
I would agree that the 80ies were a sort of a black hole for audio, the heyday was gone by 1980, exceptional growth rates, which made some companies giants in just 4-5 years previously, were also gone, the video threat was upon them and now a new "thingie" called PC was looming and taking off like a rocket by mid-80ies. They didn't know what to do, so they decided to put just about everything on hold, except the gem they had, which was the CD.
If you look back, it was not before 1988 that they tried a comeback. Everybody and their dog had completely new models on display by then, some even had completely new series out. Regarding competence, I do believe some very good new models appeared about that time from several sources all at once, and there were some creditable efforts before that as well.
Example - Yamaha A1000. Possibly the last of the heavyweights (except for Sony, who tenaciously held on a lot longer than most), built like a tank and offering a manual or automatic choice of pure class A or class AB.
But after the onslaught in the late 70ies, lack of impetus was more than obvious, sort of like a drizzle after torrential rain.
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David Hafler, Erno Borbely laid down the goods. I've a stable with DH220 types, XL280 (including clone), PRO2400 (which is based on XL280), and PRO1200 (based on the SE design of DH120. Nothing incompetent in any of these.
Lots of DIY attempt simplifications and variants that share these roots, only to increase distortion 1 or 2 orders of magnitude, and still be in realm of competent.
Lots of DIY attempt simplifications and variants that share these roots, only to increase distortion 1 or 2 orders of magnitude, and still be in realm of competent.
Well, can't speak for the units I didn't come across, and sample,
. To be fair, and parochial, a couple of Oz units did very well , but they didn't become mainstream ... which sort of says where people were at back then ... .To demonstrate real progress has been made lately, the top of the line Brystons show complete composure at high impact levels, very impressive ...
Well, can't speak for the units I didn't come across, and sample,
To demonstrate real progress has been made lately, the top of the line Brystons show complete composure at high impact levels, very impressive ...
Actually Frank, give an amp sufficient drive for what you consider low impedances, i.e. 3 or 2 Ohms, and beef up its power supply without looking back, and many will manage the same or very similar.
Don't get me wrong, I am an admirer of Bryston, but I am also a guy who has beefed up regular, plain vanilla amps to something better, and witnessed the transformation. On occasion (e.g. Marantz 170DC power amp), just replacing filter caps does wonders for the device.
Of course, all this cannot turn a plain vanilla device into a High End one no matter what I stick in, but still, it does a lot, I mean a LOT.
I'll drink to that! Although I've heard it said that quite a bit of Hafler models was in fact designed by Erno Borbelly - don't know if that's true.
I'll drink to this as well!
My greatest beef with the DIY people is that they miss out so much by providing people with just the schematics, no walk-though, very little (if any) instructions, no hints and tips, not even the basic protection circuits ...
People are reduced to deaf and dumb copycats, when in fact they should be made aware of what they are making by the authors. But nobody seems to care ...
Fully agree - modifying, tweaking, optimising are powerful tools to achieve much more satisfying results. What the Bryston did was to show that a manufacturer can create a stock standard, straight off the shelf unit which delivers all the goods - something which has eluded the majority of audio companies for years ...
On the negative side, a lot of highly reputable audio names at the show had dreary, "small", instantly forgettable sound - the very thing to guarantee that the next generation of possible audio enthusiasts will think, What's the point of this? ...
And are so confident in their design and build quality, that they offer a 20year guarantee.
Endless fight? No, thank you. I was surprised that people writing in this endless thread don't read answers. And did not start testing own theoretical musings in reality.
Endless fight? No, thank you. I was surprised that people writing in this endless thread don't read answers. And did not start testing own theoretical musings in reality.
Happy to see Wavebourn back, with another smoking primate as his avatar.
Endless fight? No, thank you. I was surprised that people writing in this endless thread don't read answers. And did not start testing own theoretical musings in reality.
One of your better mussing was symmetry of slewing ( If I read you correctly ? ) . I think this is saying something interesting ? I espeacailly like it challenging some long held beliefs . Doesn't make it true . No harm in asking the questions I feel .
IMD - Something New
Slewing rate distortions eminate principally from the Class A voltage gain stage of an amplifier where loading effects of stray capacitance come into play.
When such stages are fully complementary ideally the stray capacitance is driven equally in plus and minus directions by each voltage stage half (avoidance of modulation effects). Some even order distortion cancellation will also accrue from push-pull operation.
The test set-up in the link uses unbiased signal diodes inwhich the signal switching is non-linear. I am not convinced that using these back to back is precise enough or proves anything.
Michael J
When such stages are fully complementary ideally the stray capacitance is driven equally in plus and minus directions by each voltage stage half (avoidance of modulation effects). Some even order distortion cancellation will also accrue from push-pull operation.
The test set-up in the link uses unbiased signal diodes inwhich the signal switching is non-linear. I am not convinced that using these back to back is precise enough or proves anything.
Michael J
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@mjona
Michael, you may have missed that specific part of the discussion, In fact, we were talking about the theioretically ideal symmetry between rise and fall times, noting that few people even speak about it, Keith Johnson of Spectral being a notable exception, and of course, us here.
As for the classic voltage slew rate, we sort of settled that 40 V/uS was realistically more than enough anyone would ever need in real life to be free of slew induced distortion, and even that was with a big, fat "just in case" add-on.
Michael, you may have missed that specific part of the discussion, In fact, we were talking about the theioretically ideal symmetry between rise and fall times, noting that few people even speak about it, Keith Johnson of Spectral being a notable exception, and of course, us here.
As for the classic voltage slew rate, we sort of settled that 40 V/uS was realistically more than enough anyone would ever need in real life to be free of slew induced distortion, and even that was with a big, fat "just in case" add-on.
Endless fight? No, thank you. I was surprised that people writing in this endless thread don't read answers. And did not start testing own theoretical musings in reality.
Exactly!
I figured that about the same, so I FINALLY did things to make my amp become reality. I was a little bogged down by the logistics of having to split the whole thing up into two piggybacked boards (I've never done that before), but I should have it all figured out by this afternoon. Then my colleague can get on with the PCB art.
And, as you suggested, I have an unholy list of things I want to try out, most of it originating from you gentlemen here.
Thanks DVV,
I did read that part.
My immediate thought on referencing the link provided by Nigel was the test set up was based on a couple of back to back signal diodes shunting a signal to earth.
This was to do with intermodulation distortion which arises when any signal is passed through or is shunted by a non linear circuit element.
An unbiased diode is not linear in the switching region and this has implications in the above regard.
By contrast a full complementary symmetry voltage amplifier operating in Class A is close enough to perfection that it forms the heart of many advanced designs.
I should have left out my broken record replay on slew rates but how valid is it to subject a low distortion amplifier to a piece of test gear that is based on switching diodes.
Michael J
I did read that part.
My immediate thought on referencing the link provided by Nigel was the test set up was based on a couple of back to back signal diodes shunting a signal to earth.
This was to do with intermodulation distortion which arises when any signal is passed through or is shunted by a non linear circuit element.
An unbiased diode is not linear in the switching region and this has implications in the above regard.
By contrast a full complementary symmetry voltage amplifier operating in Class A is close enough to perfection that it forms the heart of many advanced designs.
I should have left out my broken record replay on slew rates but how valid is it to subject a low distortion amplifier to a piece of test gear that is based on switching diodes.
Michael J
I'm not sure what Rod Elliot was puzzled about (in that link). To get sum and difference frequencies you need second-order distortion, which means asymmetric distortion. Symmetric distortion is odd-order (lowest is 3rd) so you get 'sums of sums' and 'differences of differences' etc. instead. The reason he found this 'puzzle' never spelled out is that it is obvious to anyone who understands distortion.
In general, textbooks omit things for various reasons:
1. they are not true
2. they are true but so obvious (to the writer) from what has been said that they need not be stated explicitly - note that they might not be obvious to all readers
3. the writer did not think of them
4. the writer thought of them but was running out of space or time
5. the writer thought of them but knew he could not give a good explanation in that level of textbook
In general, textbooks omit things for various reasons:
1. they are not true
2. they are true but so obvious (to the writer) from what has been said that they need not be stated explicitly - note that they might not be obvious to all readers
3. the writer did not think of them
4. the writer thought of them but was running out of space or time
5. the writer thought of them but knew he could not give a good explanation in that level of textbook
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