Passlabs Aleph 5 project?????

Hello I've been checking out the posts here recently trying to gather up as much info as possible for the project I'm planning. I'm looking at building the Aleph 5 amp then possibly a pre to match with it. I was hoping some of you more experienced folks may be able to steer me in the right direction. Of all the Aleph series of amps I chose the Aleph 5 to build as it meets my criteria for wattage, and component cost. I have been looking at the volksamp 60 which is a very similar amp to the aleph 5 with the exception of the 12 irf244's vs 6 of them on the Aleph 5. I was trying to decide whther to build the Aleph 5 circuit exactly as its given on the passlabs site or make some of the changes that are present in the volksamp 60. Mainly I was thinking about changing out Q5 (mpsa18) and its biasing circuitry to the one on the volks60 (ztx450). My thinking was that the change on the volks60 was probably an improvement of the older circuit. I was also wondering if there are any errors on the Aleph 5 schematics posted on the passlabs site that anybody is aware of?
 
KC,
Keep in mind that Nelson faces problems that we don't have to worry about. His use of the ZTX450 in place of the MPSA18 (MPSA42 in some of the Alephs, I think--MPSA92 in the Zen?) also reflects factors such as price and lead time (how fast can you get the parts once you've ordered them). I have frequently run into delays on Motorola parts (at least ordering from Newark, other suppliers may be faster), whereas I've never been backordered on IRF parts. (I've never ordered Zetex parts, and have no opinion on their availibility.) I used MPSA18s in my Aleph 2s, as I regard that as a stock item, and order them 100 at a time to get the price break (jeez, they're only like 8 cents or something at that quantity, so 100 is $8--you've got plenty to match and they're nice transistors).
As to the Volksamp and how 'improved' it is...I have no opinion, because I haven't heard the Volksamps side by side with the Alephs. That said, I can't count the number of times that I had manufacturers or reps telling me that they made a substitution of a part in a circuit due to price/availibility concerns, but that it was an 'improvement.' (Always accompanied by a slow, solemn nodding of the head to emphasize the gravity of the moment.) Harrumph. There *are* improvements in circuits, but not *every* change is made for sonic reasons. Customers, however, don't want to hear that. They get fretful if the chassis they are considering buying differs one iota from the one that was reviewed in their preferred magazine. (Oh, god, I remember one customer I had...oh, never mind, it's too long a story...) So you gotta tell the customer it's an 'improvement' or he'll get all weak-kneed on you. That's one aspect of the business I don't miss.
Considering that the Volksamp 60 is basically an Aleph 2 running at lower bias, and that higher bias usually sounds better, I'd be surprised if the Volksamp sounded better than the Aleph 2. They had to make concessions in order to get the heat dissipation down when they shoehorned the circuit into the simpler chassis. However, I'm willing to listen to the two, as I've been wrong before. That's where the numbers crowd goes wrong--they make up their minds based on theory, but never bother to check it against reality.

Grey
 
Grey,

I have listened to both amplifiers and the Aleph 60 is slightly better in my opinion, both are excellent amps however.
The assumption bias current is the main criteria of sound is incorrect since other factors come into play eg. circuit board layout, power supply, wire, component selection etc. This would be akin to saying one amp is better than another because it it class A or tube for instance.
The Aleph 2 is a 60 watter and Aleph 2 is rated at a hundred watts. The criteria for my opinion is based on pure sonics and not driving either amplifier into clipping, on the same speakers in the same room.

Jam

[Edited by jam on 06-14-2001 at 04:06 PM]