New Pass Labs Website - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 14th August 2004, 10:14 AM   #1
toshiba is offline toshiba  Germany
diyAudio Member
 
Join Date: Apr 2003
Location: Meersburg
Default New Pass Labs Website

@Mr. Pass
@Mr. Harrington

Nice to see that service manual of X2 is coming soon !
Date of publication already fixed ?

Some links dosn't work :
Products -> XA Series -> "Like Peanut Butter and Chocolate"
Products -> X Series -> "Super Symmetric Amplification"

Otherwise, dirty yellow. Why not. Looks good to me.

Regards
  Reply With Quote
Old 14th August 2004, 10:33 AM   #2
diyAudio Member
 
Join Date: Oct 2002
Location: Holland, The Hague
The new XA100 is a beauty. Would love to hear is someday.
__________________
Is that all there is?
  Reply With Quote
Old 14th August 2004, 10:54 AM   #3
Magura is offline Magura  Denmark
diyAudio Member
 
Magura's Avatar
 
Join Date: Oct 2003
Location: Denmark, Viborg
Default Re: New Pass Labs Website

Quote:
Originally posted by toshiba

Some links dosn't work :
Products -> XA Series -> "Like Peanut Butter and Chocolate"
Products -> X Series -> "Super Symmetric Amplification"

Both links works for me....strange???

Magura
__________________
Everything is possible....to do the impossible just takes a little while longer.
www.class-a-labs.com
  Reply With Quote
Old 14th August 2004, 11:01 AM   #4
diyAudio Member
 
Join Date: Feb 2001
Location: Columbia, SC
Note also that the Owner's Manual for the First Watt F1 amplifier has now been posted.

Grey
  Reply With Quote
Old 14th August 2004, 03:10 PM   #5
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
Default Confused with XA100 Specs

I am confused. But maybe it is just my stupidity.

According to the specs on the website, the XA100 delivers a maximum OUTPUT voltage of +/- 25 V, a maximum output current of +/- 12A, but only consumes 300W.

So even if there are no losses in transfomers, rectifiers, CRCRC's (or maybe CLCLC's), ..... we would still need rail voltages of +/- 25+? V, and bias current of at least 12A (total) in order to achieve those ouput values. And then we should then certainly get much more power than 100W at 8 ohms at Class A.

Or would the commercial XA's have 100% efficiency ??
Someone care to enlighten me ?


Patrick
  Reply With Quote
Old 14th August 2004, 03:45 PM   #6
diyAudio Member
 
Join Date: Feb 2001
Location: Columbia, SC
Being a bridged amp, the bias would only need to be about 3A for 100W into 8 ohms. This would lead to a Pd for the amp of about 150W at idle, so I suspect that the amp is biased--more or less--for a 4 ohm load (about 6A). Given heat losses elsewhere in the circuit, I'd guess that it's actually slightly less than that. Hence the amp probably peaks out--wattage-wise--somewhere just north of 4 ohms.
The "maximum" numbers in the literature are going to be peak, not RMS...something that has caused more than one person to get confused over the years. Just be glad that there aren't also average (or any of the other spec schemes developed over the years) numbers to further muddy the waters.
It's not that any of the numbers are inaccurate. You just have to know when to shift gears. Since I tend to think in terms of RMS, I find myself having to squint sometimes when reading spec sheets.

Grey
  Reply With Quote
Old 14th August 2004, 04:23 PM   #7
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
Default Still confused

> Being a bridged amp, the bias would only need to be about 3A for 100W into 8 ohms. This would lead to a Pd for the amp of about 150W at idle, so I suspect that the amp is biased--more or less--for a 4 ohm load (about 6A).


Let's see if I understand you correctly :

6A bias means 3A for each side of the bridge, and at +/- 25V rail, the amplifier consumes 6 x (25+25) = 300W. With the Aleph current source, maximum current going from one side of the bridge to the other (i.e. through the speaker) would be, with the current souce supplying 50% of that current, 6A.

I doubt you could get rail to rail voltages at the output, so let's say 4 V less than rail, maximum output voltage would then be +/- 21V, at maximum output current 6A -- not quite the +/-25V 12 A quoted. And I do understand that these figures refer to peak and not rms.

Unless of course that the XA100 is operating with 75% current delivered by the current source.

Or am I missing something ??

P.S. It was mentioned on the website that reducing speaker impedance would NOT increase power, so I understand that as the XA100 being set for maximum power at 8 ohm. Which makes it even more confusing.


Patrick
  Reply With Quote
Old 15th August 2004, 02:22 AM   #8
diyAudio Member
 
Join Date: Feb 2001
Location: Columbia, SC
Nothing like a good bottle of wine to cloud the mind. Lemme see if I can straighten this out. I'll just throw out some random factoids and maybe you can put them together in a way that makes sense to you.
A bridged class A amp is biased for the current you intend to use. For an 8 ohm load and 100W, that's roughly 3A. For 4 ohms we double it, of course, so that'll be 6A. Now, the thing to remember is that a bridged amp acts like a see-saw. Each half sees only half of the load. That means that if you're running an 8 ohm load, each side of the amp will see a 4 ohm load, which means that the doubling of the current that you'd expect from push-pull operation (speaking broadly--yes, I know the Aleph CCS is single-ended) gets used up by the "4 ohm" load.
In a 'normal' Aleph, the output stage is biased for all the voltage and half of the current that you expect to use. In a bridged Aleph (e.g. Aleph-X), you're swinging all the current and half the voltage. The other half of the voltage comes from the other half of the amp--the other end of the see-saw, if you will.
Imagine the fulcrum of the see-saw as being "ground" and the two halves of the amp swinging up and down relative to that point. It's not grounded in reality, naturally, it's sort of a virtual ground. Yes, in principle you could tap the voice coil at the midpoint and the amp would continue to behave exactly the same. In fact, it would reduce distortion by reducing even harmonics. Odd harmonics would remain, unfortunately, and the tone of the amp would change as a result. By all means, try it if you have a two identical drivers or a dual voice coil woofer hanging around. Wire the voice coils in series, connect the amp to each end, and ground the center tap. I traded e-mail about this with Nelson for a bit, but decided not to pursue it. Feel free to give it a whack, though.
As a practical matter, Nelson seems to shoot for max power at about 5 ohms, plus or minus a bit. The Aleph 3 was an exception in that it would actually double into 4 ohms. It would not surprise me if the XA100 was biased in the same manner. I haven't done a lot of math on this, mind you. It's all just rule of thumb stuff and having watched Nelson do his thing for a while. He has his own rules of thumb and it's our job to guess what they are. I've got a half-dozen hypothetical rules that I think Nelson works by and they usually seem to pan out. The exceptions are usually things where he consciously tries to do something off the wall to keep everyone else on their toes, e.g. the F1.
It keeps the game more interesting for him, you see...

Grey
(and here comes Grey toddling along behind, moving as quickly as he can)
  Reply With Quote
Old 15th August 2004, 04:48 AM   #9
moe29 is offline moe29  United States
diyAudio Member
 
moe29's Avatar
 
Join Date: Dec 2002
Location: Florida
Send a message via AIM to moe29 Send a message via Yahoo to moe29
XA30... can't wait to see that!

The Aleph 3 is my favorite all time Pass Labs amp, so it'll be neat
to see how the XA30 compares.

Love to see new stuff coming from the Lab
  Reply With Quote
Old 15th August 2004, 08:24 AM   #10
Netlist is offline Netlist  Belgium
diyAudio Moderator Emeritus
 
Netlist's Avatar
 
Join Date: Jan 2003
Grey
I notice your post become more and more enjoyable again.
Itís nice to read a well written story now and thenÖ
The idea of the dual voice coil seems very tempting.
It would take a bit of rewiring but what would be the effect in a dual woofer speaker system, e.g. B&W 800 matrix, supposing only both woofers would be wired like proposed? Or both midís?
Oh well, this is OT, if it's worth it I'll start another thread.

/Hugo
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
FS: Pass Labs X-250 jtwrace Swap Meet 0 17th June 2007 02:20 AM
Pass Labs S/Ns ? dejanm Pass Labs 8 26th January 2007 07:35 AM
My opinion on Pass Labs and Mr. Pass (Nelson) himself b_online Pass Labs 11 21st May 2003 12:39 AM


New To Site? Need Help?

All times are GMT. The time now is 10:01 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2