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ORNJ 2nd October 2012 01:45 PM

Pass Class A/B designs for HT?
Hey guys, I have been looking at building/buying amps for a while for my HT system as I didnt really know the direction I wanted to go with it.....

However, I think I have decided that I dont want to try and integrate my music system into my theater system and just build some good Class A/B designs.

I know that Pass has a Class A/B 5 channel amp but I haven't been about to find much information on it. However, It may be better for me to just make some 2 2channel and 3 channel at first because I use my receiver for all audio now as the built in speakers in my TV are terrible.....and I am now spoiled with audio.

and there is no reason to have all five channels turned on if they are not being used....

Also, can anyone tell me how much it approx. costs to build one of the class A/B designs? Not including the case...

I ask cause I am looking at how to budget everything. I know there are premade cases out there but I may be able to just get ahold of some heatsinks and build a wooden box...

Zen Mod 2nd October 2012 01:53 PM

X3 and X5

ORNJ 2nd October 2012 03:58 PM

yea thats the only thing I have been able to find in the past as well. But I havent been able to find anything about building one. granted, Passlabs website has the hardware facts but there are no circuit design plans from what I can see.

Zen Mod 2nd October 2012 04:23 PM size
2. which speakers
3.your presumed power per channel and how many of them
4.listening habits

then we can talk

ORNJ 2nd October 2012 05:10 PM

1. its a pretty small room, I dont have exact measurements as I am at work but I only have room for a couch and a single chair in my family room. But the room does open up to the kitchen, hallway, and entry way and has high ceilings. I am driving everything from my receiver right now which only has about 75 watts I believe.

2. I currently have some SVS bookshelf speakers but I am also working on some High efficiency 2 way speakers with the goal of having them be about 90db 1w/1m sensitive or higher with a 1.4" CD and 8" woofer with the plan to cross no lower than 60hz to the subwoofer

3. I only see the need for 100-150 wpc as I am more about having efficiency then having enough power running through the room to be able to power half of new york city....I want Pass amps though for their quality of power they can feed my speakers.

4. in the room that these amps will be going in is about 70% movies/tv and 30% music. Most music is listened to in my office where I currently have a bottlehead quickie preamp, adcom 6000 amp, and JBL 120ti monitors....I hope to build some frugal horns or some sort of full range horn for this room along with an F5 or bottlehead amp.

Zen Mod 2nd October 2012 05:16 PM

90db/W/m spks will sing with F5 amp , if helped with some nasty active subwoofer

regarding AB Pass amp , probably best/most easier thing is exactly F5 , made with laterals and biased lower than original

or something as that , made on F5 Turbo basis , with higher voltage , lower bias and laterals , for lesser Klunk!


anyway - 100-150W/ch is somewhat too optimistic , if you're counting on PL basis , without much heat

ORNJ 2nd October 2012 05:23 PM

Thats fine. I dont need 100-150 watts as I subscribe to the "first watt" theory.

Simple logic to me that other disagree with...but 90db 1w/1m is loud in most situations and if that is only with 1w....I just want to make sure it can handle any peaks.

I thought about the lower bias approach that you mention because from what I understand, the lower the bias the more power available but the higher amount of distortion is present....correct?

So I would just need to choose a "sweet spot" of balancing distortion and power....

Zen Mod 2nd October 2012 05:38 PM

if you're going to stereo + active sub ( mostly for movie shake) , then even A class augmented F5 will fulfill your needs , without too much sweating

I'm speaking of 2SJ201 & 2SK1530 as outputs , because they're better if bias is lower , comparing to IRF mosfets; that in case you can't afford so much heat

as you said , first watts are most important , so even with lesser A class amount you'll be good

ORNJ 2nd October 2012 06:10 PM

Any idea what my target watts should probably be? Im wondering what a good compromise in bias would be....especially since lower bias means lower power draw while running compared to the massive 100w draw from higher bias designs.

AudioSan 2nd October 2012 06:14 PM

F5 turbo V2 with low bias. say 0.8A bias. and +/-38V rails?:)
that will give you just over 60W dissipation pr ch. at idle. and 10W classA at 8ohm. and about 75W or higher class A/B at 8ohm.

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