Nothing. What I mean is that we not necessarily need to use opamp circuit design approach in discrete audio circuits. And I can see opamp circ. des. trends here, which I count not necessary.
BTW, simulator semiconductor models are not well fitted for noise analysis.
BTW, simulator semiconductor models are not well fitted for noise analysis.
john curl said:
That's easily accomplished with just a couple lengths of wire and some nickel. No active components necessary. 😀
Not only would you have better common-mode rejection than your active balanced input, you'd also have similarly high common mode rejection even with single-ended sources.
And the icing on the cake would be galvanic isolation which would save people ground loop headaches.
se
jcx said:
No, I see no need to include R3 and R10. That is why I prefaced my remark with something like, "for those who prefer this approach".
These resistors were not included in my original MOSFET power amplifier. I showed the approach using R3 and R10 to address the concern about lack of open loop bandwidth expressed by John Curl.
You are exactly right about the increased gain applied as global feedback decreasing all distortion products.
Cheers,
Bob
PMA said:
No, I mean just a simple 1:1 input transformer. Like a CineMag 15/15B or a Jensen 11P-1. At the amp's input. Everything else would remain essentially the same except the active input would go back to back to being single-ended.
se
PMA, Bob Cordell and I are both, OP-AMP designers. What do you think that we design, and how does the noise contribution from various sources differ between OP-AMPs and any other type of audio amplifier?
Fellow designers, many of you are using versions of SPICE that I am not personally familiar. It might be that you can't separate the noise contributions to the total output noise in a complete circuit. Can you do this with the SPICE available today to most of us? Or do we have to buy the PROFESSIONAL version of SPICE to get this added benefit?
john curl said:
Hi John,
Who is "we"?
It is my understanding that Jim Bonjiorno conceived the complementary differential input pair while he was at Dynaco, put it into first commercial product in the SAE XXXIB in early 1973, and subsequently published it in PE as the Ampzilla in 1974.
Can you point to any commercial product that predates those?
Perhaps Charles Hansen can shed some light on this, as he seems very interested in audio history.
Is it possible that you are only laying claim to the implementation with JFETs that has the floating tails?
Cheers,
Bob
No, Borgorino did not invent the complementary differential input stage when he was as Dyna, to the best of my understanding. In fact, he offered the Dyna circuit to Southwest Technical Products, and learned about it from the designer there. This is what I have been told in detail.
I designed the complementary differential transistor input 39 years ago, and my old friend Jon Iverson, designed it at the same time or even earlier.
We did NOT publish the circuits for good reason, at the time. In 1969, I did have a full complemetary symmetry balanced bridge, current out power amplifier designed and running in the Ampex Research Department that was capable of several thousand watts DC output.
I designed the complementary differential transistor input 39 years ago, and my old friend Jon Iverson, designed it at the same time or even earlier.
We did NOT publish the circuits for good reason, at the time. In 1969, I did have a full complemetary symmetry balanced bridge, current out power amplifier designed and running in the Ampex Research Department that was capable of several thousand watts DC output.
john curl said:
With circuits like these, it is certainly possible that multiple people came up with it, independently. But the first person who comes up with it independently and makes a commercial product out of it, or publishes a paper on it, is generally credited with it.
Many of us engineers, at one time or another, have had this sort of thing happen to them. That's life. You could invent Cold Fusion in your lab and not tell anybody about it, and you would not get credit for it. If you invent something and keep it under your hat, you don't get to claim it - that's just the way the world works.
SWTP was Dan Meyer, and as far as I know, he did not have any product with that circuit in it, at least in that time frame, and certainly not the Universal Tiger.
Cheers,
Bob
john curl said:
Hi John,
My 108 dB in my 50 Watt amplifier is 20 dB better than the JC-1's S/N. 20 dB is a factor of 100 in power. If your amplifier was a 5000 Watt amplifier, your argument about speaker sensitivity might make sense.
The proof is in the pudding. My circuit cannot have much of a noise "problem" if it delivered 108 dB S/N, beating the very good Boulder amp by 3 dB.
I haven't made any claims about my circuit for use in a phono or mic preamp, as the discussion in this thread is about power amps. Although it might be very suitable and low in noise, I did not design it with that in mind.
Cheers,
Bob
Bob, please don't go crazy with this. You are not using the same circuit gain or features that the JC-1 has. It can be proven, even with SPICE that my circuit topology is slightly quieter than yours, all else being equal.
Guys,
How significant is device noise contribution to sound quality as compared to the contribution of non-linearity to sound quality? I seldom see noise quoted on audio amplifier datasheet.
Thanks.
How significant is device noise contribution to sound quality as compared to the contribution of non-linearity to sound quality? I seldom see noise quoted on audio amplifier datasheet.
Thanks.
Bob, you will find the first 'in print' description of the complementary symmetry bipolar transistor input stage as an advertisement in ' The Audio Amateur' by SWTP in early 1972. Check it out. It is the Tiger .01.
Noise, per se, is rarely a problem in an amplifier unless you have pretty efficient speakers. Horn fans are more likely to have complaints about noise than other folks. My speakers are more modest--efficiency in the mid to upper 80s--and noise is just not that much of an issue to me. The same is true for most people.
A more subtle point is the interaction of noise with the music in somewhat the same manner as IM distortion, but since noise is generally so low in high fidelity amps it's not that much of an issue.
Now, if you want to talk noise, let's talk about phono stages for moving coil cartridges. That's a valid discussion.
Grey
A more subtle point is the interaction of noise with the music in somewhat the same manner as IM distortion, but since noise is generally so low in high fidelity amps it's not that much of an issue.
Now, if you want to talk noise, let's talk about phono stages for moving coil cartridges. That's a valid discussion.
Grey
john curl said:
I don't think I'm the one going crazy with this, John. It is very simple: the proof is in the pudding. You assert that there must be a noise "problem" with the circuit, and yet that circuit delivers better S/N than most of the amplifiers ever reviewed by Stereophile. I do not rely on the mediocre noise performance of the JC-1 to make that point.
Until you or someone else goes to the trouble to make all else equal and simulate the two topologies for noise, I don't think that you can assert that one or the other is quieter. Now that you have SPICE up and running, why don't you give it a shot and let us know what you find?
Cheers,
Bob
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