John Curl's Blowtorch preamplifier part II

[john curl]

It is important to note that I am NOT an amateur audio designer. I have been designing audio circuits for over 40 years, am a Lifetime member of the IEEE, and I am working on 3 separate audio projects as we speak. I released two new designs within the last 60 days, a phono stage, and a power amp. Bob Cordell knows this. He was in the room where we were showing our new power amp at RMAF in early October of this year. I spoke with him, myself. He could have met my associates and tested their mettle, IF he had chosen to do so, when they were there, later that day. He chose not to. NOW, because I quoted out of a textbook written by a colleague, Ed OXNER just because it was conveniently located my side, I am 'name dropping'? Give it a break, please.

[janneman]

Originally Posted by simon7000

Jan & ikoflexer

One often confused point is the difference between a regulator and a filter. A regulator provides a constant voltage or current. A filter shapes or removes components of signal variation.

A series regulator can act as an active capacitor (gyrated capacitor), or inductor as part of it's design. It cannot damp down reflected energy from the load. Reflected energy can come from reactive loads. The classic example is an inductor being driven by an amplifier and suddenly saturating.

A shunt regulator can control a current source to be a precise voltage and damp excess energy. In some designs of active shunt regulators, capacitors are added to the feedback loop to increase the filtering action. In this case it behaves as a capacitor.

There probably is a reason why E.B. designed his version of a shunt regulator with someone using headphones to listen to a preamp. That most likely was a non-linear inductive load.

In a regulator we can look at how it behaves with level and frequency. This allows us to use and model it better. When you start using a regulator as a filter it becomes a more complex problem. Two inches of wire is a small inductor, a smaller resistor, a tiny time delay but a reasonable antenna.

So I think the design issue is are you aiming for a point of load regulator or filter? I think the answer is filter as I feel that very precise voltage accuracy is not as important as low noise and source impedance.

Well, one good reason for a shunt reg is that it allows you to localize returned ground currents so there is less chance to induce ground current noise and/or instability elsewhere in the circuit. That is in addition to the reasons of active clamping of reflected energy, which as I see it is less a problem if you have a lood with some minimim load current. Unless the load current goes down to zero, a series reg wouldn't have a problem in this respect.

jd

[janneman]

Originally Posted by ikoflexer

Filter. More specifically extremely high line and load regulation. In my particular case, besides low noise and excellent line regulation, I'm trying to have very flat, very low output impedance up to high frequencies (say, for instance, 200kHz). Am I dreaming?

Precise voltage control and absolutely no drift in the span of a few months is not important to me. I would venture to say, to most audio circuits.

Fully agree.

jd

[janneman]

Originally Posted by john curl

[snip] NOW, because I quoted out of a textbook written by a colleague, Ed OXNER just because it was conveniently located my side, I am 'name dropping'? Give it a break, please.

It was name dropping and and a sneaky try to switch the discussion, which was about whether feedback produced TIM, to another subject.

jd

[GK]

Originally Posted by Joshua_G

I'm not the only one. For example, look here: Cometh Bosendorfer! The $25,000 Bosendorfer VC 7 horn-loaded loudspeaker system - Equipment Reviews - Dagogo .

LOL! Veracity by numbers.

Originally Posted by ikoflexer

Now you make me cite Homer

And here's wisdom, some more Homer quotes.

Is this B.S. supposed to have a point?
Joshua now says that he can actually demonstrate his ability to discern ppb differences between resistors. Elves and fairies.

[ikoflexer]

Originally Posted by GK

Is this B.S. supposed to have a point?
Joshua now says that he can actually demonstrate his ability to discern ppb differences between resistors. Elves and fairies.

It was a joke. Unrelated to whatever technical or whoever here. Lighten up.

[Curly Woods]

Originally Posted by ikoflexer

It was a joke. Unrelated to whatever technical or whoever here. Lighten up.

Thank you Ikoflexer. A voice of reason

[ikoflexer]

It's funny and sad in the same time.

How about another classic.



John, you mentioned a power amplifier that you just released. Do any of your ideas explored in the BT preamp made it in the power amp? Is the new power amp a fair subject? Others may not be, but I'm genuinely interested in your designs as a learning source. Occasional mannerisms aside, I like your blend of engineering and insight.

[simon7000]

Originally Posted by janneman

Well, one good reason for a shunt reg is that it allows you to localize returned ground currents so there is less chance to induce ground current noise and/or instability elsewhere in the circuit. That is in addition to the reasons of active clamping of reflected energy, which as I see it is less a problem if you have a lood with some minimim load current. Unless the load current goes down to zero, a series reg wouldn't have a problem in this respect.

jd

Jan,

Under some load conditions the load current not only goes to zero but reverses! The classic example is a relay driver. If you do not put a reverse diode across the coil you can see very large spikes. A cored inductor that is fed current for too long will saturate the core have a sudden drop in inductance and possible on the return cycle dumps some energy backwards. That is why many commercial amplifiers have reverse diodes across the output transistors. I try not to underestimate the ability of people to do stupid things.

So for almost all users a series regulator is great, but when driving inductors such as earphones, speakers and most importantly transformers some provision should be made for reverse currents.

[janneman]

Originally Posted by simon7000

Jan,

Under some load conditions the load current not only goes to zero but reverses! The classic example is a relay driver. If you do not put a reverse diode across the coil you can see very large spikes. A cored inductor that is fed current for too long will saturate the core have a sudden drop in inductance and possible on the return cycle dumps some energy backwards. That is why many commercial amplifiers have reverse diodes across the output transistors. I try not to underestimate the ability of people to do stupid things.

So for almost all users a series regulator is great, but when driving inductors such as earphones, speakers and most importantly transformers some provision should be made for reverse currents.

Yes you are right of course. And I use the reverse diodes as a matter of routine in my power amps. But in the case of a regulated supply these are rarely used on power output stages but more for small signal stages where it is not really an issue. But for inductive loads etc I agree with you.