Help ZEN's cousin to come to life!

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
B

bobsinclar

Member
Joined 2006
Zen suggested a coil as CCS:rolleyes: what about an impedance" transformer ?would it make sense? I have one here that comes from a broken old JBL bipolar amp from the 70'sI have to fix...
this outpot Xformer has 2 secondaries 16ohm /8ohmand but where I could get the signal :confused: maybe worth to be tested...this would look a bit like a tube amp topology if I'm correct...any idea?
Vince
 
Zen Mod

Zen Mod

Official Court Jester
Joined 2003
zenmod.in.rs/
Paid Member
bobsinclar said:
Zen suggested a coil as CCS:rolleyes: what about an impedance" transformer ?would it make sense? I have one here that comes from a broken old JBL bipolar amp from the 70'sI have to fix...
this outpot Xformer has 2 secondaries 16ohm /8ohmand but where I could get the signal :confused: maybe worth to be tested...this would look a bit like a tube amp topology if I'm correct...any idea?
Vince
Click to expand...

just in case:
be sure that this is "proper"xformer,not autoformer as in McIntosh amps.....
regarding "where I could get the signal" it's same as any SE tube stage with OPT....click on my www button,go on "my WOT preamp " page and you'll see plain old SE stage;
drawing is almost nice as yours ;)
 
J

JCM

Member
Joined 2005
... there is something special about the sound of a Power resistor loaded Single end output!
Click to expand...

My experience to date is too limited to comment about the sound, but I like simplicity; the notion of having fewer parts, the most direct practical path from the source to the speakers. It's the easiest and most natural thing to put a current source in there, take out the resistor - but then it starts to not be quite as simple...
And resistors are more linear than any semiconductor ...
Click to expand...

That's true, but in an amplifier, my understanding is that a current source is going to force the amp to be more linear than a resistor. Still, I liked the concept of the Zen-light so much I was willing to consider building a 5 watt version. I remember looking at it, but the power dissipation even for that output was - monstrous, by my standards.
Zen suggested a coil as CCS what about an impedance" transformer ?would it make sense? I have one here that comes from a broken old JBL bipolar amp from the 70's I have to fix...
Click to expand...

It looks like NP got almost 10 watts out of a cascode design, Zen V9 with 2.2 amps idle current and 50 volt supply using light bulb filaments - the resistance was said to be 11 ohms. There might be no way around increased idle and supply. Five watts output is pretty good with that layout. Transformer ... not sure. He got almost 10% efficiency out of that, which is the same as you're getting. I'm doubtful more power can be squeezed out without turning up the juice.
 
lineup

lineup

Member
Joined 2005
JCM said:

Still, I liked the concept of the Zen-light so much I was willing to consider building a 5 watt version.
I remember looking at it,
but the power dissipation even for that output was - monstrous, by my standards.
.
Click to expand...


I have praised the genius ZenLite by Pass several times before in this forum.

Not many would get this idea to solve power handling issue.
And even only a brave man would be willing to try it, in reality.
It was a real Bright ;) moment in audio history, in my opinion.

( ... but I would not be much surprised if Nelson got his inspiration from some even older tryout,
by some other real pioneer.
Seems like whatever some of us come up with these days, crazy or not,
it has been done before :xeye: somebody has been there first)

I am surprised not many more of those posting here
have built one ZenLite version of their own .....

Besides, it is a spectacular amplifier to show to your friends
with that glowing bulb on top!

An externally hosted image should be here but it was not working when we last tested it.



I already had this idea, after thinking about this very thread yesterday:

Why not try the same concept for a Single Supply single ended Class A
PREAMPLIFER

Could be called
----------------------
PreLite
----------------------

I am already thinking about what lower wattage bulb
with a suitable resistance could be fit for such an amplifier.
Maybe something used in cars ... ??
Preferably should be a a light bulb with some nice and attractive colour.

;)
lineup
 
J

JCM

Member
Joined 2005
It was a real Bright moment in audio history, in my opinion.
Click to expand...
Definitely !

:soapbox: I had been looking at some amplifier designs, all class AB. One thing bothered me (besides xover T.H.D.), it was the issue of power supply voltage dropping in sync with the load demand. Even with a high VA tranny, it still happens. Of course, one could regulate it - and then that becomes part of the design - and more complexity. I minimized the effect in the early stages of experimental amps using not just decoupling resistors and caps, but diodes, and that, as a simple stop-gap, improved performance a lot. But still, the power stage - no getting around it, it can and does modulate the supply.

I kept thinking there ought to be a good class A design, some kind of push-pull, something, I imagined different schemes. But I found it had already been done. And the efficiency far surpassed the textbook examples of 5 or 6 % efficiency. With a class A amp, drawing the same current constantly, the power supply drooping issue is disposed of, and I can filter the supply with resistors, which I greatly prefer to do - something unthinkable with an AB.

And who doesn't love tubes ? A light bulb is ~ sort of ~ a tube - and the first triodes were created in a light bulb factory. Using bulbs for part of the circuit has its own kind of charm - I love the idea, but I was looking at 60 watt bulbs with a filament resistance of 240 ohms - way too high - even 2 is 120 ohms; four is 60 - still too high. That was why I abandoned that notion, plus I was thinking of using bipolars, which seemed to make the whole idea practically impossible. But with that Zen-light, I think N.P. has pulled a rabbit out of a hat. :wiz: I wasn't able to afford the transformer power for it, and of course I shied away from the high dissipation. But it remains a design I admire.

Seems like whatever some of us come up with these days, crazy or not, it has been done before somebody has been there first)
Click to expand...
Yes, seems to be the rule, actually.

Why not try the same concept for a Single Supply single ended Class A PREAMPLIFER ... Could be called PreLite. [/quote]

I guess one could do that. Bulbs with high enough resistance would be easy enough to find. That would be the perfect name for it, I think. :angel:

Beautiful amp there ... sweet music from a class A amp. :bulb:
 
B

bobsinclar

Member
Joined 2006
Hehe guys, hat an interesting debate! yes I'd be tempted to try all of them bulbs/ xformer and CCS even modulated CCS(just as in the Alephs...
I am building a Zen with CCS straight from Nelson's schematic...and then I'll have a reference amp to compare to my schematic...By the first listning sessions this is much encouraging, but the amp shows great linearity...but i am curious to see what can be diffrent compared to an original Zen...
anyway I'll come soon with picts and results!and the final schematic if it turn out good...
Vince;)
 
lineup

lineup

Member
Joined 2005
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom