ZV9X : A JFET input ZV7

[Magura]

Originally Posted by rsdio

Hey, Z.M., you're back to bragging about your Donut.

Seriously, if there is a non-transformer output version of the Donut amp,

For that matter, why isn't there a schematic on some web site?

apparently only intended to show off your prowess as the Choky Donut creator.

1) No, no, you got it wrong, he is bragging about MY Donut

2) There is AFAIK no transformer output version of the Donut, as I find that straying just a bit too close to something Choky would like (hollow state).

3) The schematic is not published the usual places, as I for one am done supporting rip-off artists. The same goes for the fluffy Serb. If we feel somebody is genuine, and so forth, we hand out schematics, usually followed up with help and advice.

4) ......and yes, the Donut is made by me, with (great) support of Choky, a bunch of other less fluffy Serbs (you know who you are), a nationality confused Frenchman, a Dutchman, a German, and a couple of Americans, so actually there are a whole bunch of Donut creators.

Sadly, there is only one Donut owner/builder (till the fluffy Serb gets going).


Magura

[rsdio]

Originally Posted by Magura

The inductors are the load, not the output.

A simple toroidal transformer can do, with no problems added.

What am I missing out on when I hope to make the speaker the only load?

I should add another item to my NICE-TO-HAVE FEATURES:

C) Current Output Stage (hopefully as an option, since I don't know yet whether my speakers will like this)

Seems to me that a current output amplifier would do best when the speaker is the only load, but this area of amplifier operations is the newest concept for me.

Originally Posted by Magura

3) The schematic is not published the usual places, as I for one am done supporting rip-off artists. The same goes for the fluffy Serb. If we feel somebody is genuine, and so forth, we hand out schematics, usually followed up with help and advice.

I totally understand this. One of the things I learned after reading hundreds of postings on this forum is that there are too many rip-off products. If it's too easy to just download the finished plans, then the IP violations are increased. Nelson tends to keep each idea in a separate article, sometimes combining a couple of ideas together, but he never really puts all of his techniques into one public schematic. The Pass Laboratories products are where all his tricks go into one bag. Not to mention the fact that he's always trying new things, and thus new tricks appear all the time. I noticed that his lawyers had him remove some of the First Watt schematics from the web site manuals section because they were a bit too much of a giveaway. All of this makes perfect sense.

Hand in hand with "not feeding the IP rip-off artists," I also see a theme here on diyAudio that veterans don't do a lot of hand-holding with newbies. The ethos is that DIY folks should learn by doing, and not have every answer provided without requiring at least a little thought.

I actually had a mind to build my amplifier without ever sharing. You'll note that I did not include resistor values on my schematic (partly because they haven't been dialed in yet). My primary reason for putting my schematic here is that I plan on making some boards, and given the minimums required, I might as well share them with other interested folks. Thus, it seems prudent to share my design before I make the boards so that folks have a chance to make suggestions for a reasonable amount of flexibility.

One thing I decided to do after reading Choky's comments is to put degeneration source resistors on the input JFETs, and capacitors on the inputs, even if I have to solder wire jumpers in the event that I decide I don't want them. I'd rather solder jumpers than cut traces and have a mess.

P.S. I read every page of Bob Cordell's book, enjoyed it immensely, but was not interested in building anything but Class D. Funny that my two DIY interests turned out to be Class A balanced SE SUSY and Class D, spanning the spectrum from fairly inefficient to highly efficient. The Class D amp would go in my electric car for longest battery life, and the Class A would go in my main, stationary listening position.

Maybe in my next update I'll restate my goals, requirements, and other features I'm interested in, just to be clear. I've mentioned almost everything I'm looking for so far, but my comments are rather spread out in this thread.

[jacco vermeulen]

Originally Posted by rsdio

whether my speakers will like this

If you don't know, the most likely answer is not.

[rsdio]

Originally Posted by jacco vermeulen

If you don't know, the most likely answer is not.

Ah, well, I am willing to rip out the crossovers. In fact, these speakers are designed for normal wiring, bi-wiring, and bi-amping. Conversion involves changing or removing the crossover. Apart from a lack of schematics for the crossovers, there's nothing stopping me from doing a little homework to see what changes would be needed for driving them via current output.

I hope I am not being too naive when I believe Nelson when he says that speakers react most directly to current, not voltage. Thus, with proper connection, any speaker should work, provided you're willing to alter or remove the crossover. I should read those articles again, though...

My plan is to bi-amp these speakers eventually, since I have at least 8 DAC outputs available. The DAC has non-volatile memory for various DSP effects, so I could program in the appropriate active crossover frequencies and have them available immediately upon power-up.

If I can successfully build one amplifier, I should be able to build four or five.

[Magura]

Originally Posted by rsdio

What am I missing out on when I hope to make the speaker the only load?

I should add another item to my NICE-TO-HAVE FEATURES:

C) Current Output Stage (hopefully as an option, since I don't know yet whether my speakers will like this)

Seems to me that a current output amplifier would do best when the speaker is the only load, but this area of amplifier operations is the newest concept for me.

The inductors in the Donut are simply replacing a CCS, giving much higher efficiency. We are approaching 20% efficiency in real class A by using an inductor load.

So what is the point of using an inductor as load VS. a CCS you might ask?

It is so that if you want real class A, as opposed to pseudo class A, you will end up with a huge power demand, offering a relatively limited power output.
Now if you go with a CCS, the effort needed for heatsinking and PSU, is going to be massive. Using an inductor, makes those demands much lower, as in less than half, for the same output.
The other solutions like active current source, are still in the pseudo class A category (let the flaming begin), and in comparison quite dull IMHO.
I have built quite a number of amps over the last 15 years, starting out with class AB PP, over single ended class A, and balanced single ended class A.
Of those, most of them have been built in many iterations, testing among other things current output, transformers, SUSY, you name it.

The only way to find out what really pleases you, and fits your speakers, is to experiment.
Mostly current output only works well with full range drivers, but can also be of benefit with band tweeters.

The Donut can easily be configured to run as current output amp, so makes no big difference to the amp choice.

In your shoes, I'd build a simple Zen V1 , a Aleph, an AX, a Zen 9, and a Zen 7. Play around with them, and find out what pleases you, and find out how to reach that goal.

The Donut is made to please me. It fits my speakers well (full range horns), and that's pretty much it.
It was never the intention to make an amp that anybody else likes.

Magura