Actually as far as I can tell the issue is what is an operational amplifier.
I use both VFA and CFA. CFA has the advantage of better open loop bandwidth, all else being equal. I like high open loop bandwidth, always will! If I have a choice between IC's for a particular application, I always choose the IC with higher open loop bandwidth. Should give lower PIM, all else being equal. '-) In recent years I helped design a new power amp made with IC's. There I chose a high open loop bandwidth IC, sampled to me by Scott Wurcer at a Burning Amp meeting years ago. Still find it very good. Sorry Scott, I am not using any of your IC's these days, except in my test equipment.
This is as good place as any to get a quick understanding:
https://en.wikipedia.org/wiki/Current-feedback_operational_amplifier
https://en.wikipedia.org/wiki/Operational_amplifier
No worshiping... just understanding.
THx-RNMarsh
Last edited:
I've designed and built both types (nx-Amp, sx-Amp, e-Amp and my earlier Ovation 250 and other blameless type VFA's in the late 70's and earlier 80's. I have remained scrupiously even handed and agnostic on both topologies and enjoy listening to all my amps. My musings on their characteristics on this forum and on my website has and is driven purely by the desire to understand amplifier topologies more fully. It's clear that VFA does some things better than CFA and vice versa and the designers personal choice is driven by their priorities. And, if they feel one is better than the other, or subjectively is more pleasant, then that's their business.
Like I said, it's just a circuit. Suggest we leave this subject because it's likely to end up in endless circles again.
Like I said, it's just a circuit. Suggest we leave this subject because it's likely to end up in endless circles again.
Ah fairy nuff. As I said this part was so far ahead of the bandwidths we had been discussing that there was something else at play.
Absolutely. I can't understand this controversy. Both are just electronic topologies, both are working and old enough to have proven everything. Both have their pro and cons, advantages and inconveniences. Everybody is free to chose his poison and express his preferences.
Well, I also can't understand the controversy until somebody starts glossing about (to quickly name only a few):
- The "open loop gain" advantage of the CFA.
- The CFA can provide more loop gain, and hence has lower distortions.
- 1000V/uS providing the last 1% of audio performance improvement.
I've mentioned this before (and provided a link to a thread on this forum), a few years ago CFAs (and in particular the Alexander amplifier) were demonized as the worse thing that can happen to audio, delivering a harsh, raspy sound.
No, and if you think Ron's papers said anything different you didn't understand them.
Yes. I've heard the same things said about other topologies as well.
As Richard says, measure and then judge.
Due time to put your 4 decades' worth into Words of Wisdom, Mr Russell.
(more amusing would be to add up the total number of years of the ones present at this thread, I'd guesstimate Mr Macura is good for at least 35, and surely you must have heard the rumors of/on Mr Marsh)
Last edited:
I think maybe it might be worth adding up all of Dick's post numbers and playing it in the now 1.3B lottery.
Two people shared the UK's ~$85M lottery this weekend.
Unfortunately, I was not in that number.
Someone in the US is going to be very rich in the next few weeks or months.
Unfortunately, I was not in that number.
Someone in the US is going to be very rich in the next few weeks or months.
- Status
- Not open for further replies.