Aleph-X: High-Power Version

[Edwin Dorre]

Originally posted by carpenter
What are Watt/puppies?

You gotta be kidding ....

Wilson Audio Watt/Puppy in his +/- 7's incarnation at the moment!

http://www.wilsonaudio.com/products/...ppy/index.html

It is one of the most 'talked' about speaker in speakerland as far as my world goes...

Edwin

[vuki]

What are Watt/puppies?

very expensive, audiophile-loved, two-parts floorstanders that have real trouble to play music. I listened them few times in various iterations and even with high-powered 600W/8R amps they sounded like small ineficient minimonitors on steroids - clean, sterile and dynamicly flat even at low volumes.

[Blitz]

...looks like we are off now with Grey's and Nelson's help. I would like to ask one of my earlier questions again: Will a 044n sound better at 1 A / 22 W or 2 A /44 W per piece ? Since we are in DIY, it is not such an issue to exchange them every 5-10 Years when that has a significant impact on sound. I have read Nelson's article in Audio express where he suggests to run a 044 ( which has nearly double of the capacity) with 2 A / 44W. I guess with a reason. Has made any one own listening experiences to share with us ?

[Bricolo]

Off topic (but not off forum ):

Does the Watt puppies exist in DIY?

[Blitz]

Yes.

It is off the topic and it is not really a great speaker and yes Thorsten has put together a kit:

http://www.fortunecity.com/rivendell...avid/david.htm

And now back to the subject...

[MEnsing]

Blitz,

This is what Nelson wrote to almost the same question.

It has been my experience with Mosfets that the total
bias is the key element to performance. Within reasonable
limits it can be through 1 device or distributed through
parallel devices, but the total remains the prime factor.

Too few devices and you might cook the parts. I like to
stay around 25 watts or less, but I have successfully used
the IRF 150 watt parts up to 50 watts without seeing
many failures.

With more devices, it's easier to get the current up there,
but you reach a limit in the amount of capacitance you
want to try to drive. Practically speaking, for something
like an Aleph circuit, this limit is less than 12 devices in
parallel, and usually I prefer half that.

Within those boundaries, if you want the best performance,
you crank the bias up all you dare.

[Bricolo]

Originally posted by Blitz
Yes.

It is off the topic and it is not really a great speaker and yes Thorsten has put together a kit:

http://www.fortunecity.com/rivendell...avid/david.htm

And now back to the subject...

What do you call "not reeally a great speaker"?

I'm thinking about biolding a pair of proac response 2.5
Are the puppies worse?

[Bricolo]

Originally posted by MEnsing
Blitz,

This is what Nelson wrote to almost the same question.

so, according to the wanted power, we should always use the less devices possible.

[Blitz]

On the mosfets: I know the theory through reading through other threats, but in this concrete application: Will we have an even better sounding Aleph X with 100 Watts if we would use only half of the 12 Mosfets ? And how much better ? Any real listening experiences ?

On the speakers: Obviously a question of taste. I heard once a pair on real big Krells and I didn't like them. Harsh trebles, technical sounding and a badly integrated woofer. Clearly the tweeter is not bad for the money (100 $; but listen to a Philips Magnetostat or true ribbon like an expolinear www.expolinear.de ..), the scan-speak-mid-ranger is to slow, but OK ( compare this to an Eton 5" or Focal and you forget this chapter; they are great for bass, but for true imagining in the mids ?) and on bass ...well...listen once to something like an active exponential horn subwoofer (fairly small to put in the corner of a room) or maybe Nelson's new woofer and we talk again about a complete different class. I have nothing against Wilson, but it is an OK speaker for far too much money. By the way: The ceramic enclosure-legend: TAke an MDF-enclosure and stick some ordinary ceramic plates ( like you would use in your bathroom) into it and you have it. A german DIY-Magazine has made the measurements regarding this material mix and it is extremly good. But why paying 40000 $ for it ? If you are interested into this stuff further, let's start a new threat under "speakers".

[GRollins]

All right, let me see if I can get all the rest of the changes together...
*****
Disclaimers:
--All references are to the original schematic that I posted on the first page of the Aleph-X thread.
--If you're working off of another schematic that someone else posted, you'll have to double check the part numbers.
--If you've chosen to modify the circuit, then getting the decimal in the right place is your responsibility. I've got enough on my plate trying to check (and recheck...) my own numbers.
--No, I don't have any plans to drawn up a full set of schematics at 25W, 50W, 75W, 100W, 150W, and 200W. Please don't ask for a custom wattage design. I might throw a fit. It wouldn't be a pretty sight.
--These values are for the 100W (22.7V rail) version I posted about the other day.
--Unless you're really, really determined, I would not recommend this as a newbie's first project. There's some fiddle factor involved. Start with a Zen or something. If, in spite of this warning, someone gets in over their head, post. There's a fair possibility that the answer can be found. The problem will be that a newbie might not have the diagnostic experience to figure out what's wrong. Until we know what's wrong, we can't suggest fixes. A meter is essential. A freq. generator and an oscilloscope are a real good idea. It won't hurt to have big load resistors and other odds and ends on hand. Not to mention soldering irons, pliers, and your favorite flavor of ethanol. You know, the usual.
--Don't lose sight of the fact that this circuit is based on Nelson Pass's work at Pass Labs and is covered by active patents. Start trying to make money off of this and his lawyers will slide you down a mile-long rusty razor blade into a vat of salt water filled with mutant sharks (lasers on their heads are optional, but likely).
*****
Uh, okay...now where did I put my notes?
Ah, caught them. The pesky things were trying to sneak off.
1) You'll need to increase the wattage capability of R1, R4, R44, and R45. Should you power up the amp without a load, then present it with a signal, you'll toast the 3W resistors in the original design. The power will go to ground via these resistors. Plan accordingly. Note that they'll also get pretty warm when you're setting the DC offset.
2) Match R2, R3, R42, and R43 in value and quantity to the number of Source resistors in your output stage. For an output stage with three device pairs per side, you should have six resistors per side of the same value as the Source resistors. This is part of the Aleph current source. Unless you've got a very clear idea as to why you want to do this differently, don't change things at random. Read Nelson's Patent first. Understand it. Then you can mess with it...but you probably won't want to any more.
3) Don't forget the 221 ohm resistors at the output MOSFET Gates. All added-on MOSFETs will be in parallel with the ones shown on the schematic, just the way the Alephs were.
4) As in the Alephs, the output current source (the group of components clustered around Q3 and Q8) is hooked <i>only</i> to one MOSFET's Source resistor, not the whole bank in parallel.
5) R14, R15, R31, and R32 will now be 1.5k
6) Increase R17 to something on the order of 3.3k. You've got latitude here. I know people went for pages in the Aleph-X thread talking about current sources. Knock yourself out. Put in a battery for all I care. Just kidding. A battery won't work well for this. The point is to get something on the order of 20mA flowing through the front end differential and to make it variable to the tune of, say, +-10%. If you want to obsess about current sources, be my guest. I'm working on the X-preamp and writing on four different stories. I don't have the time or the inclination to get in a dither about current sources.
Note that I posted an alternate set of values for the adjustment resistors for the front end current source on page 8 of the Aleph-X thread:
R24 332 ohms
R26 562 ohms
V2 still 200 ohms
This gives you somewhat tighter control of the current source at the expense of range. Use either set.
7) Somebody said that Nelson said that lower values for R19 and R29 were a good idea. 20K max? I don't remember. Something like that. Just use the same value on each side and you'll be fine.
8) Inevitably, someone will post wanting to know if the amp will accept a single-ended input. The answer is yes. Just ground the unused input or your gain will drop. This is just like the Alephs. Most anything posted about an Aleph front end is true here. I'm just using the output from both sides of the differential, that's all.
9) I think I remember seeing someone complain about using a 3W resistor for R21. If you want to use a smaller resistor, have at it. If you find yourself in a ground loop situation, feel R21. If it's hot, put in a bigger one. You'd be surprised how much juice you can develop in a ground loop.
10) Don't like pots? That's cool. Put them in anyway. Adjust the circuit until you've got it beat into shape. Pull the pots out, measure them, and plug in fixed resistors. Presto! No pots.

I think that's it. I am--as usual--on the run. If anyone spots something I missed, say so and I'll take a look. This ain't rocket science, but it's certainly more than a biplane. Perhaps something along the lines of a 747. It's doable. Any intermediate to advanced DIY critter can follow this trail of bread crumbs and come up with a functioning amp.
Might even sound good...<i>ahem</i>...

Grey