hi,
I think there was an IEEE article too
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1162523
and two authors.
örjan
I think there was an IEEE article too
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1162523
and two authors.
örjan
orjan said:
This paper has the same contents as the AES paper, same authors (Lohstroh and Otala):
Preprint NO. H-6 (R)
AN AUDIO POWER AMPLIFIER FOR ULTIMATE QUALITY REQUIREMENTS
by
Jan Lohstroh and Matti Otala
Philips Research Laboratories
Eindhoven, The Netherlands
PRESENTED AT THE
44th AUDIO ENGINEERING SOCIETY CONVENTION
FEBRUARY 20-22, 1973 - ROTTERDAM
Jan Didden
It is interesting how people apparently connect the terms 'Otala amp' and 'high quality' for no obvious reason (not obvious to me at least).
Otala's amp is NOT the worlds best amp. It isn't even a very good one in spec terms. It was a 'reference design' to show one way to build an amp with low or close to zero TIM.
There are other ways, and now that we understand the real mechanisms of TIM we can build very high feedback, very linear, very low distortion amps that are as free of TIM as anything proposed by Otala.
If, for instance, the PGP would be no better than Otala's low TIM amp, we would have been spinning our wheels for 35 years. Thankfully, that is not the case!
Jan Didden
Otala's amp is NOT the worlds best amp. It isn't even a very good one in spec terms. It was a 'reference design' to show one way to build an amp with low or close to zero TIM.
There are other ways, and now that we understand the real mechanisms of TIM we can build very high feedback, very linear, very low distortion amps that are as free of TIM as anything proposed by Otala.
If, for instance, the PGP would be no better than Otala's low TIM amp, we would have been spinning our wheels for 35 years. Thankfully, that is not the case!
Jan Didden
Some people just enjoy making stuff up to stir the pot.
From that AES paper:
"The approach chosen is to avoid all apparently “elegant” tricks frequently employed (bootstrapping, positive feedback, distortion compensation, higher feedback for dc than ac, gliding bias etc.)....."
You’d never better even the “Blameless” linearity benchmark with this prescription.
From that AES paper:
"The approach chosen is to avoid all apparently “elegant” tricks frequently employed (bootstrapping, positive feedback, distortion compensation, higher feedback for dc than ac, gliding bias etc.)....."
You’d never better even the “Blameless” linearity benchmark with this prescription.
Oh really now, do your homework, do you really think I didnt do any improvements, for instance take the pioneer circuit Os posted, that one is already a very good performer THD wise .003 at 200 w output 20 khz, actually that amp measures a bit better than what is stated on its specsheet, up the loopgain use different compensation scheme and see what you get 
.
Glen are you still toying with self based amps, I dumped them long ago, was building very low distortion so called Self amps 12 years ago, but not according to Self but John Linsey Hood ideas from 1970s , which is where most of Self s theories comes from. That Pioneer circuit dating from the 80 s measures better and is much faster and clips beautifully than any Self based circuit that you have shown in this forum upto date with a little more than half the parts of your designs. Do you really think you are the only person that can design amps that measure or sound good,
Janneman the PGP is miles ahead of otalla amp, that doesnt mean we cannot improve it, the basics is good, I use higher feedback than otalla, have no case against feedback like some.
. Glen are you still toying with self based amps
, I dumped them long ago, was building very low distortion so called Self amps 12 years ago, but not according to Self but John Linsey Hood ideas from 1970s , which is where most of Self s theories comes from. That Pioneer circuit dating from the 80 s measures better and is much faster and clips beautifully than any Self based circuit that you have shown in this forum upto date with a little more than half the parts of your designs. Do you really think you are the only person that can design amps that measure or sound good, Janneman the PGP is miles ahead of otalla amp, that doesnt mean we cannot improve it, the basics is good, I use higher feedback than otalla, have no case against feedback like some.
homemodder said:Oh really now, do your homework, do you really think I didnt do any improvements, for instance take the pioneer circuit Os posted, that one is already a very good performer THD wise .003 at 200 w output 20 khz, actually that amp measures a bit better than what is stated on its specsheet, up the loopgain use different compensation scheme and see what you get
Glen are you still toying with self based amps
Janneman the PGP is miles ahead of otalla amp, that doesnt mean we cannot improve it, the basics is good, I use higher feedback than otalla, have no case against feedback like some.
More :bs:
That Pioneer circuit isn't an "Otala" amplifier and there is nothing special about the front-end circuit at all. It owes it's linearity to a non-switching output stage and multiple parallel output devices, not to any magic of the "Otala" front-end. As for the linearity and slewrate of some of the circuits I have presented, I guess you haven't been paying a lot of attention.
Also, if you use higher feedback just for one, like you claim, then it is a departure from Otala's design philosophy, which, to reiterate:
"The approach chosen is to avoid all apparently “elegant” tricks frequently employed (bootstrapping, positive feedback, distortion compensation, higher feedback for dc than ac, gliding bias etc.)....."
This 'Otala' amp was designed over 36 years ago. I bought the prototype from Electrocompaniet and used it as my reference for years, while developing preamps , xovers, etc. It is a wonderful little design, and I own and use one, today. It will sonically beat most better sounding amps. I know this from direct comparison with electrostatic headphones.
The real 'secret' behind the success of this design is because it has a 20KHz, open loop bandwidth. I know that many of you will hiss at this, but it is true, nevertheless.
Just yesterday, an engineering colleague, a video engineer, has made a break-though in measurement of PIM in amps of this type. He is getting a patent, so it might be awhile before more will be divulged. I am very happy with this, as it proves what the ear has known all along, and even if Matti Otala could not completely 'prove' it in his lifetime, what he initially was trying to find, has been measured. Hurray!
Just yesterday, an engineering colleague, a video engineer, has made a break-though in measurement of PIM in amps of this type. He is getting a patent, so it might be awhile before more will be divulged. I am very happy with this, as it proves what the ear has known all along, and even if Matti Otala could not completely 'prove' it in his lifetime, what he initially was trying to find, has been measured. Hurray!