F5 power amplifier

[Nelson Pass]

As many of you know, the F5 power amplifier design is done and is
merely awaiting delivery of the issue of AudioXpress which was
scheduled to be mailed April 10.

I feel that it's important to support AudioXpress, a magazine with
which I have a 35 year history, and which also serves as a
mainstay for the DIY comunity. Lately they have kindly printed
projects that I had already posted on the web, but I decided that
they deserve a little better than that.

Coincidentally, I had surgery of the 10th, and having apparently
survived, I am typing this from my bed.

Do not try to lift an XA200.5.

In any case, I know you're eager to get going and as soon as the
magazines arrive I hope that this thread will become a beehive of
activity. I have no doubt that members here will improve or at
least embellish the design.

Here's a copy of the simplified circuit.

[steenoe]

Originally posted by Nelson Pass
As many of you know, the F5 power amplifier design is done and is
merely awaiting delivery of the issue of AudioXpress which was
scheduled to be mailed April 10.

I feel that it's important to support AudioXpress, a magazine with
which I have a 35 year history, and which also serves as a
mainstay for the DIY comunity. Lately they have kindly printed
projects that I had already posted on the web, but I decided that
they deserve a little better than that.

Coincidentally, I had surgery of the 10th, and having apparently
survived, I am typing this from my bed.

Do not try to lift an XA200.5.

In any case, I know you're eager to get going and as soon as the
magazines arrive I hope that this thread will become a beehive of
activity. I have no doubt that members here will improve or at
least embellish the design.

Here's a copy of the simplified circuit.

Thanks a lot, Nelson. Hope you recover fully, pretty soon.
Wow thats simple enough for a P2P build

[stefanobilliani]

Best wishes for great recover

[EUVL]

All the best for a speedy recovery.

The simplified schematics looks familiar though ?

Profet Amplifier


Patrick

PS I think R4 should also be 600 ohm and not 0R47.

[seventenths]

Nelson,
Yes, best wishes on a speedy recovery and a huge thank-you for your contributions.

sincerely,
7/10

[sandstorm33]

Originally posted by Nelson Pass
As many of you know, the F5 power amplifier design is done and is
merely awaiting delivery of the issue of AudioXpress which was
scheduled to be mailed April 10.

I feel that it's important to support AudioXpress, a magazine with
which I have a 35 year history, and which also serves as a
mainstay for the DIY comunity. Lately they have kindly printed
projects that I had already posted on the web, but I decided that
they deserve a little better than that.

Coincidentally, I had surgery of the 10th, and having apparently
survived, I am typing this from my bed.

Most certainly, GET WELL QUICKLY!!

I congratulate you on your loyalty to TAA publications . The Audio Amateur and its successors have provided ,through the years , a trustworthy platform for the best of the audio DIY minds. Recalling its 4 issues a year in the 70's,the articles it contained opened a whole new world to understanding and construction of top notch audio equipment . Your 1994 original ZEN article ranks as one of the classics. We all await the F5. Hopefully my copy will arrive this coming week!

[Blues]

Have a speedy recovery, Nelson!

Another lesson from Mr. Pass...don't lift more than your body weight.

[MikeW]

Get well soon. Let me know when you are off your medication and I will send you a couple of bottles of wine.

[Magura]

Originally posted by Blues


Another lesson from Mr. Pass...don't lift more than your body weight.

Well body weight, that's usually an opposite linear function to age

Anyhow, get well soon Nelson, it's gonna be an awful lot of trouble, if we will have to tow your bed to BAF 08


Magura

[Nelson Pass]

Thanks very much.

However, I don't want this to become a best wishes thread, rather
it should focus on what I think will be an exciting little amplifier.

In case you haven't already seen the square wave....

[Blues]

Let me guess Nelson...the output stage has 3 pairs of mosfets with about 200mA of bias through each pair?

[Nelson Pass]

No, you are looking at all the gain devices in that schematic.

[anubisgrau]

best wishes for the fast recovery, nelson!

it would be great if you could add a few words on what in particular you've wanted to achieve with F5, what's the sound philosophy behind, whom it is aimed for (what kind of speakers).

this is so distinctive about each of FW amps - a strong philosophy behind each and every of them. but one has to be careful where to apply them!

[Zen Mod]

talking about Profet ;
NFB is bloody different

[Blues]

Originally posted by Nelson Pass
No, you are looking at all the gain devices in that schematic.

What!?...WOW!

[Blues]

Isn't that circuit supposed to be Zv10?

[stefanobilliani]

Originally posted by EUVL
All the best for a speedy recovery.

I think R4 should also be 600 ohm and not 0R47.

Yeah , me too

[Nelson Pass]

Originally posted by Blues
Isn't that circuit supposed to be Zv10?

I suppose that ZV10 would have been the F4.

The Zen Variations were intended as single-stage amplifiers
(although ZV4 had a buffer).

The First Watt stuff is distinguished by being commercial product,
and is not limited to single stages.

14 years is a good long run for the Zen series. I may return to it
some time in the future, but I don't have a specific plans.

[stefanobilliani]

Were we talking somewhere of a nice new preamp in the zens ?

[Nelson Pass]

Originally posted by EUVL
All the best for a speedy recovery.

The simplified schematics looks familiar though ?

Profet Amplifier

PS I think R4 should also be 600 ohm and not 0R47.

Such a smarty-pants. Yes, it's 600 ohms (it's correct in the not-
simplified schematic).

I had not seen the Profet schematic before - when the ads came out
I noted that it supposedly "all the benefits of a current source
and voltage source" and I didn't give it further attention.

An email correspondent some years ago also suggested this
topology, a CFP with voltage gain. If I could remember his name I
would have mentioned him. (who knows, maybe it was the Profet
guy...)

Anyway, it's been around for a while. When you read the F5 article,
you will see "The topology is familiar...". Selectronics has chosen to
bridge the circuit and settled on different values.

Given the differences in measured performance from "Chuck"
Hansen's review in AudioXpress, I suspect that they were using the
same kind of gun to shoot at a different target.

[EUVL]

> Such a smarty-pants.

I take that as a compliment.




Patrick

[Nelson Pass]

As it was intended.

[EUVL]

The first time I saw the circuit (Profet I meant), I was quite impressed by its simplicity. The only concern then was the relatively low gain, espscially with lateral FETs. I guess using high transconductance FETs would solve part of the problem.

There are not that many true complimentary FETs around, which is why I have so far shy from building anything complementary other than a pre with all K170's / J74's.

Maybe I shall try this some time.


Patrick

[bogdan_borko]

Is it class AB? (Vgs 3.6V)

[Nelson Pass]

It is biased at 1.3A, and leaves Class A at 2.6A.