Home » Sponsored » Pi Speakers » Output Impedance of my Son of Zen amp - Compatibility with Pi 7 setup
Output Impedance of my Son of Zen amp - Compatibility with Pi 7 setup [message #33758] Fri, 31 August 2001 01:24 Go to next message
Super_BQ is currently offline  Super_BQ
Messages: 37
Registered: May 2009
Baron
In response to http://www.audioroundtable.com/PiSpeakers/messages/1116.html

Nelson Pass has replied to me and said that the SoZ has an output impedance of "about 16 ohms".

So I'm not sure what that means in terms of damping factor or it's ability to drive 15" size woofers (low zmax?) at high SPL ?

If you're there Wayne - is 16 ohms pretty high?

Re: Output Impedance of my Son of Zen amp - Compatibility with Pi 7 setup [message #33760 is a reply to message #33758] Fri, 31 August 2001 08:20 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18790
Registered: January 2001
Illuminati (33rd Degree)

Output impedance of 16 ohms is pretty high. Even speakers with low Zmax will peak higher than that. I would expect some response fluctuation using any speaker on that amp.
Re: Output Impedance of my Son of Zen amp - Compatibility with Pi 7 setup [message #33761 is a reply to message #33760] Fri, 31 August 2001 10:48 Go to previous messageGo to next message
Crazy Dave is currently offline  Crazy Dave
Messages: 67
Registered: May 2009
Viscount
Keep in mind that there are two differnt (at least) Zen amps out there. One is a triode wired, single-ended, EL34 tube amp. The other one, designed by Nelson Pass, is a single-ended mosfet amp. Both have a low damping factor.

Dave

Re: Output Impedance of my Son of Zen amp - Compatibility with Pi 7 setup [message #33762 is a reply to message #33761] Fri, 31 August 2001 11:47 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18790
Registered: January 2001
Illuminati (33rd Degree)

Most amplifiers act like constant voltage sources. Amps with high output impedance are more like constant current sources. As such, I would think they probably work best with high efficiency speakers that don't fluctuate much in terms of load impedance with respect to frequency.
Nelson Pass's "Son of Zen" is like a differential MOSFET pair [message #33763 is a reply to message #33762] Fri, 31 August 2001 12:29 Go to previous messageGo to next message
AudioLapDance is currently offline  AudioLapDance
Messages: 40
Registered: May 2009
Baron
Tooooo many Zens!! "Zen this" and "Zen that"! "What the Zen?"

To clarify...

Steve Deckert of Decware (www.decware.com): Single Ended Tube amps: Zen A, B, C and Select; and Zen Monos

Nelson Pass of PassLabs (www.passlabs.com): MOSFET power amps: Zen, Zen revised, Son of Zen, (maybe even Zen Cousins)!

The Son of Zen is a single gain stage differential MOSFET pair biased by power resistors. To see the circuit:

Web page
http://www.passlabs.com/projects/sonofzen.htm
or PDF (page 2)
http://www.passlabs.com/pdf/sonofzen.pdf

Hope this helps,
I like to be of assistance now and zen, ;-)
Cheers,
Jeff


Re: Nelson Pass's "Son of Zen" is like a differential MOSFET pair [message #33766 is a reply to message #33763] Fri, 31 August 2001 16:53 Go to previous messageGo to next message
Super_BQ is currently offline  Super_BQ
Messages: 37
Registered: May 2009
Baron
Thanks for the clarification and URL's. You're right about the confusion all those Zens cause.

Mine is shown at my homepage (below). I will take an updated picture as soon as I get back to New Zealand (in a months time). I get e-mails every week or so inquiring about where I got those heatsinks from.

Re: Output Impedance of my Son of Zen amp - Compatibility with Pi 7 setup [message #33768 is a reply to message #33761] Fri, 31 August 2001 16:58 Go to previous messageGo to next message
Super_BQ is currently offline  Super_BQ
Messages: 37
Registered: May 2009
Baron
The Son of Zen (by Nelson Pass) is a balanced line mosfet amplifier.

http://www.passlabs.com/images/projects/sozenf1.jpg

shows a + and a - output (unlike single ended).


Re: Output Impedance of my Son of Zen amp - Compatibility with Pi 7 setup [message #33769 is a reply to message #33762] Fri, 31 August 2001 17:03 Go to previous messageGo to next message
Super_BQ is currently offline  Super_BQ
Messages: 37
Registered: May 2009
Baron
Hi Wayne,

Here's a quote from the circuit design of the amp taken from Nelson Pass's website (Son of Zen project):

"First, the damping factor is quite low, on a par with some of the tube amplifiers on the market. If you need an amplifier with a high damping factor, look elsewhere. You can improve the damping factor of the amplifier by scaling the resistor, but only at a heavy efficiency penalty."

Re: Output Impedance of my Son of Zen amp - Compatibility with Pi 7 setup [message #33772 is a reply to message #33769] Sat, 01 September 2001 00:04 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18790
Registered: January 2001
Illuminati (33rd Degree)
Low damping factor means high output impedance, moving closer to constant current and away from constant voltage. Just like he says, that's like a tube amp.
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