Matti had a pretty good gig with Harmon, after they got rid of me. He made plenty of money and got to make an amp.
He still did significant work with the peak current requirement for speakers, IIM, and PIM during and after his Harmon tenure. Let's not sell him short, it was just that he was a born politician. In fact, I am surprised that he did not go into the govenment of Finland in his later years. He was a 'born' congressman, or whatever they elect over there.
He still did significant work with the peak current requirement for speakers, IIM, and PIM during and after his Harmon tenure. Let's not sell him short, it was just that he was a born politician. In fact, I am surprised that he did not go into the govenment of Finland in his later years. He was a 'born' congressman, or whatever they elect over there.
Christer said:
I don't mean to nitpick here, but Barrie Gilbert is his name. If you do a Google search on "Gilbert cell", you'll get lots of hits referring to mixers. The transistor mixer was named after him, even though the circuit supposedly existed in vacuum tube form many years before his time. He took the basic mixer cell and did a lot of work to figure out how to turn it into an accurate analog multiplier. But he got credit for the mixer idea, much like Cooley and Tukey got credit for the FFT, even though Cornelius Lanczos invented it in the '40s before anybody could make good use of it.
Given the caliber of Gilbert's work, it doesn't surprise me that he knew about this stuff years before audio designers knew about it. In his prime, he was one of the cream of the crop of analog designers. I suspect "the gurus of analog IC design already knew about it" may be more accurate than "everybody except the audio people knew about it".
Well, I did in my earlier post 🙂. In the '70s he wrote an article called something like "TIM distortion in audio power amplifiers" for the American magazine Audio. I read this when I was a young person trying to figure out what to do with my life, and became very interested in the idea. I decided to become an EE after reading this article and corresponding with Dr. Leach. That article was an attempt to take Ottala's work and write it in such a way that it's understandable to the layman.
This article is conspicuously absent from Dr. Leach's site, even though all the other Audio articles are there. I suspect this is so because it contains some of the same errors as Ottala's original article - namely the statement that wide open-loop bandwidth is required to eliminate transient distortion. Ottala did eliminate transient distortion from his design using a wide open-loop bandwidth, but his technique was sufficient but not necessary.
Exactly. His original article in the February 1976 Audio http://users.ece.gatech.edu/~mleach/papers/lowtim/feb76feb77articles.pdf had the resistors R20 and R21 and R22 to reduce feedback. Later, in a class I had with him in the late '70s, he admitted that these were a mistake. Later amplifier versions omitted these resistors, resulting in increased feedback over the original design, and reduced sine wave distortion without sacrificing transient performance.
andy_c said:
I have always been surprised how long it takes the audio designers to understand what the circuit designers have known for long time.
The truth is: Barrie Gilbert thought that I was NUTS when I mentioned TIM to him at a ISSCC conference 30 years ago. He had NO idea what I was talking about. LATER, he figured it out and admitted to it. This is normal with traditional circuit designers.
That's amusing. I remember.... on second thought I don't.
Oh yeah, now I remember - the well known (but herein
nameless) academic audio authority who publicly laughed at
the concept of TIM at AES. Several years later I saw him lecture
on how every problem was caused by TIM, including loudspeaker
distortion.
😎
(but it was really analog jitter all along.... 😉 )
Oh yeah, now I remember - the well known (but herein
nameless) academic audio authority who publicly laughed at
the concept of TIM at AES. Several years later I saw him lecture
on how every problem was caused by TIM, including loudspeaker
distortion.
😎
(but it was really analog jitter all along.... 😉 )
What I meant in my comment was how long it took the CCS, LTP, current mirrors to get into audio designs.
I have just simulated Cordell's circuit. I have loved Linsley Hood ,Randy Slone and Douglas Sefl.And now, i also love Hawksford and Cordell
The Admin!Thanks you!😀
I hope i can view the schematic which has not any distortion in near day!
The Admin!Thanks you!😀
I hope i can view the schematic which has not any distortion in near day!
If you think that i'm not right ,let you will not be crazy!
t.i.d :'transient intermodulation distortion'
One of the early treatments of t.i.d. may be responsible for some of the misunderstandings. It was published as an appendix to an article by Daugherty and Greiner entitled 'Some Design Objectives for Audio Power Amplifiers' (March 1966, IEEE Transactions on Audio and Electroacoustics.) The main conclusion of the analysis was that the 'open-loop response' of an amplifier using overall negative feedback should be at least 20kHz if this is the bandwidth of the signal source
t.i.d :'transient intermodulation distortion'
One of the early treatments of t.i.d. may be responsible for some of the misunderstandings. It was published as an appendix to an article by Daugherty and Greiner entitled 'Some Design Objectives for Audio Power Amplifiers' (March 1966, IEEE Transactions on Audio and Electroacoustics.) The main conclusion of the analysis was that the 'open-loop response' of an amplifier using overall negative feedback should be at least 20kHz if this is the bandwidth of the signal source
Hi Pedja,
This is a very good example to remind us where we are. It gives a accurate distance for discussion on what figures of THD are important. I have heard 0.1% and not 0.01% - with single ton. With mixed I would have a trouble with interpretation.
This is a very good example to remind us where we are. It gives a accurate distance for discussion on what figures of THD are important. I have heard 0.1% and not 0.01% - with single ton. With mixed I would have a trouble with interpretation.
Jarek,
this is a single tone. Consider real complex music and the new distortion products created. Very different from the single tone test. Remember what I spoke about - audibility of single tone through the amplifier with distortion of 0.05% spread to high harmonics.
BTW - what is the distortion of your amplifier, is not it higher than 0.01%?. To declare any conclusions, you must have possibility to compare several designs in one time.
You will recognize 0.003% distortion at high harmonics on the real music - that's what I have meant.
this is a single tone. Consider real complex music and the new distortion products created. Very different from the single tone test. Remember what I spoke about - audibility of single tone through the amplifier with distortion of 0.05% spread to high harmonics.
BTW - what is the distortion of your amplifier, is not it higher than 0.01%?. To declare any conclusions, you must have possibility to compare several designs in one time.
You will recognize 0.003% distortion at high harmonics on the real music - that's what I have meant.
BTW, I have my own test discs too.
I have 2 CD players. One of them is able to reproduce -80dB FS signal quite well. The other one does not play it at all. Shall I make any conclusions from testing on the second player?
I have 2 CD players. One of them is able to reproduce -80dB FS signal quite well. The other one does not play it at all. Shall I make any conclusions from testing on the second player?
Hi Pawel, good morning, for us of course 🙂
Pavel, for me this is only your own interpretation of influence of THD on the sound. Maybe you right, maybe not – I don’t know. According to your statement all amps with below 0.03% specification of THD should sound the same. But is not true. I think, how Nelson said before, there was TIM, jitter, and others - now we talking about THD. IMO the situation is more complex particularly with a use of feedback. There is no one answer and no one way.
Pavel, for me this is only your own interpretation of influence of THD on the sound. Maybe you right, maybe not – I don’t know. According to your statement all amps with below 0.03% specification of THD should sound the same. But is not true. I think, how Nelson said before, there was TIM, jitter, and others - now we talking about THD. IMO the situation is more complex particularly with a use of feedback. There is no one answer and no one way.
jarek said:
Never I have said that, this is a complete misunderstanding!! As the designer I very well know that there are many influences on the amps sound.
What I declare is that low THD is a necessary condition of good sound Not sufficient. And I am saying that it makes difference if amp has 0.003% at high harmonics or the low ones. This is based on the experience of the same amp topology differing only in the output stage. The stage with and without Hawksford correction, designed by Pavel Dudek. Compared to my completely different class A amp. All of them with ultimate low distortion. Pavel's class AB with Hawksford correction and my class A sound very very similar. Pavel's class AB without Hawksford correction sounds different. Just the case of cross-over phenomena in standard class AB stage. Should be inaudible, isn't it?? Perfectly audible.
Comparing of our very different amps (but quite same sounding) to the well known but distorting ones we can easily hear "tail", "masking" of the other designs. Especially an experience with classical music CD is more than interesting.
Maybe your amps are the best on the world, but is still only your interpretation.
BTW, how do you measure the THD? Did you analise sound wave from the speakers?
Jarek, if you will hear sometimes any amp without this " tail " ( which will be probably any class A amp ), you will know whatabout is Pavel talking. Unfortunately this have absolutely most of amp, including ones, which is realy well known 😉 .
Hi Pavel,
I give up this childish discussion. Makes no sense to argue with people who have hardly ever had any chance to hear what we speak about.
Cheers, Pavel
I give up this childish discussion. Makes no sense to argue with people who have hardly ever had any chance to hear what we speak about.
Cheers, Pavel
Upupa,
I agree, that there are differences in sound. But I am not sure there is direct correlation of that with level of THD. We talk about level about 0.01% of THD. And where the THDs are, at the output of amp or in the real sound wave? I do not have a simple answer.
Regards
I agree, that there are differences in sound. But I am not sure there is direct correlation of that with level of THD. We talk about level about 0.01% of THD. And where the THDs are, at the output of amp or in the real sound wave? I do not have a simple answer.
Regards
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