G.Kleinschmidt said:
Ah, I see. That's different from what I remember from last year. Here's an earlier post from Jan where he attaches his AES preprint.
http://www.diyaudio.com/forums/showthread.php?s=&postid=1061447&highlight=#post1061447
You can see Rodolfo's related post further down the page.
darkfenriz said:
I think you'd only need to roll-off the EC loop gain above a certain frequency to ensure stability, just as is required when applying EC to the output stage only.
In fact, you'd want to ensure that the actual amplifier itself has as wide a bandwidth and as little phase shift as possible.
Cheers,
Glen
andy_c said:
D'oh! I downloaded that AES preprint from his website a while ago too - just haven't read through it yet.
http://www.linearaudio.nl/beenthere-1.htm
Cheers,
Glen
Originally posted by G.Kleinschmidt
---Now here’s an idea – why not design an amp with EC applied around the entire thing instead of conventional global NFB?---
Is this a low power implementation ?
http://www.diyaudio.com/forums/attachment.php?s=&postid=1183839&stamp=1176634068
---Now here’s an idea – why not design an amp with EC applied around the entire thing instead of conventional global NFB?---
Is this a low power implementation ?
http://www.diyaudio.com/forums/attachment.php?s=&postid=1183839&stamp=1176634068
Re: EC applied around the entire thing
Sorry!
When I first opened your pax pdf, the circuit looked at first glance (before zooming in) like conventional opamp-front-end power amp, with EC applied around the whole thing.
???
Not exactly the same thing - it looks like an attempt at error correction applied to a frequency compensated amplifier with global NFB.
Cheers,
Glen
janneman said:
Don't steal my idea!. Instead, come to SF in Oct to the Burning Amp festival and you can listen to the thing!
Jan Didden
Sorry!
When I first opened your pax pdf, the circuit looked at first glance (before zooming in) like conventional opamp-front-end power amp, with EC applied around the whole thing.
estuart said:
???
forr said:
Not exactly the same thing - it looks like an attempt at error correction applied to a frequency compensated amplifier with global NFB.
Cheers,
Glen
G.Kleinschmidt said:
Hi Glen,
Although EC applied globally around an entire amplifier may indeed work in principle, my belief and experience says that EC works as well as it does because it is around a very fast group of components. Speed is really king in the way EC seems to work, and its ability to correct accurately at high frequencies (where it is needed the most) is very dependent on speed and phase.
Cheers,
Bob
Bob Cordell said:
Hi Bob.
I agree, hence my comments on the bandwidth and phase shift of the voltage amplification part of the amplifier.
I doubt that such an approach could be demonstrated to be generally more effective than conventional global NFB, but I think a decent performing amplifier could be built this way, on the condition that particular attention is paid to open loop linearity.
Cheers,
Glen
Hi, Mr. Cordell,
I'm very interested in this. Actually, I'm thinking alot about an EC based on floating opamp like this one :
http://www.diyaudio.com/forums/showthread.php?postid=1230139#post1230139
or this one :
http://www.diyaudio.com/forums/showthread.php?postid=1271976#post1271976
Because (before I read your post above), the OL gain is the important factor in how well an EC will do its work. And opamp provides very high gain.
Now comes a factor of "speed and phase". Opamp based cannot beat simple discrete transistors in these terms (like Hawksford EC).
What is your opinion on opamp based EC (floating +/-15V). Will it work better or worse than discrete EC?
lumanauw said:
I've never tried any kind of op-amp-based EC. I don't think it saves much complexity at the end of the day and I believe that in most cases it will compromise speed that the EC loop can work with. Discrete-based EC can work remarkably well, and is really not that complex. It adds only about four or six small-signal transistors to what you need to have there anyway. It is particularly effective with vertical MOSFETs because of their lightning speed, but also appears to work well with RET bipolars.
Cheers,
Bob
Hi, Glen,
About your schematic in here : http://users.picknowl.com.au/~glenk/CLASSA.HTM
I got some things that I don't understand.
1. Why is the anode of D1 (and katode of D? = 1N4148) are tied together to R1/input? If it is part of current limiter, maybe connecting those 1N4148 to collectors of Q29 and Q30?
2. After input R1 (750ohm), the signals are level shifted via VR (LM336B-5V). Is this makes the base of Q1 sitting at +5V (and base of Q4 sitting at -5V), or these 2 LM336B-5V at input are just voltage limiter?
About your schematic in here : http://users.picknowl.com.au/~glenk/CLASSA.HTM
I got some things that I don't understand.
1. Why is the anode of D1 (and katode of D? = 1N4148) are tied together to R1/input? If it is part of current limiter, maybe connecting those 1N4148 to collectors of Q29 and Q30?
2. After input R1 (750ohm), the signals are level shifted via VR (LM336B-5V). Is this makes the base of Q1 sitting at +5V (and base of Q4 sitting at -5V), or these 2 LM336B-5V at input are just voltage limiter?
lumanauw said:
G'day
The two LM336-5's just bias the first emitter follower (Q1-Q3, Q4-Q6). The two 1N4148's from the collectors of the I-limit transistors connect to R1, because it is from here that the "error voltage" is sensed by the EC. Clampling the signal (with respect to the output) here stops the EC transistors from conducting harder when the current limiter operates.
Cheers,
Glen
Hi,
I have posted the conceptual diagram of my error-corrected Vas stage on my website. Currently hard at work to complete the prototype for the Burning Amp festival!
Jan Didden
I have posted the conceptual diagram of my error-corrected Vas stage on my website. Currently hard at work to complete the prototype for the Burning Amp festival!
Jan Didden