Which one should I build?

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I have a nice system that I've built up over several years.

In college I built about every type of electronic circuit
except an amplifier.
I have a choice of building my own amplifier or buying a
$2000 amp from McIntosh.

So, my main concern is no noise and extremely clean/fast sound.
I'm going to power my Legacy center channel with it.

I don't really want a tube amp. Everything else I have
is transistor/op-amp.

So, any suggestions? I'm looking at a Class-A from Pass
Laboratories right now. It looks simple enough, and it
claims very low distortion. Anyone try it?

Better? The Power Follower isn't bad.

I've also built a Class AB amp, capable of >100W at 8 ohms load.

My Power follower produces 55W RMS at 4 ohms load, it's more than enough for me.

You can find some interesting, more powerfull amplifiers here:

But I think that simple Class A amps (SE no NFB) sounds better, than more complex Class AB amps.

and here's another interesting class AB amp, without NFB.


[Edited by Freddie on 10-12-2000 at 01:40 PM]
Re: How did you get that much power?

>48Watts into 4ohms?

>Mr. Pass says it only supplies 28Watts.

>Did you make any modifications?

I HAVEN'T built ANY of Mr. Pass designs. The Power Follower I was talking about, is the design made by Andrea Ciuffoli. I'm running it with one 38V 500VA transformer/channel (higher voltage than he uses). And with that powersupply voltage it can swing 15V RMS which produces about 55W into 4ohms.

BTW: What Pass Design are you thinking of building?
The Zen amp?

Son of Zen

Well, yes. The Son of Zen actually.

OK. Now, let's get straight. What amplifier are you
talking about, and can you give me a link to the design?

Of course, I started looking for the parts for this thing,
and I couldn't find the main components. I need a matched
pair of MOSFETs for this thing. I looked at Digikey and
only found 20V 200mA matched MOSFETs. The parts suggested
by the design were 200V 20A MOSFETs.

So, now what?


Aount the Fet amp

Dear Pixie

Both design of the Pass Zen and the Andrea Ciuffoli hot follower ar very good, but in yr case, i think u should build the Pass Zen Amp, coz the design of Mr. Ciuffoli just a sourse follower circuit, that means it doesn't has voltage gain, the result is, u need to design another voltage gain stage to drive it to get the full power output..

For the Pass design, it only need around 2.5V Rms to get the full output, the output level of a normal CD player is around 2V Rms, so u may only build this amp and no need to build another pre amp....In the circuit that u can find in passlabs.com, the voltage that mr. pass using is around DC34V, it can given out around 15-18W into 8 Ohm load, don't worry, 15w is very enough for normal listening....

About the matching of MOSFET, u don't need to matching the output device of this 2 circuits ( both pass Zen amp and AC hot follower), since they both working in single end, and they are only using 1 pair of FET....
I wouldn't want to pass the wrong "2 cents" off to you, but
I blew my commercial amps not long ago (sony) and as a
"nuubie", wanted something better.

I looked and looked, "lurked", then joined DIYaudio , when I discovered
the D. self "blameless amp" . It is well documented, it's "bible"
is available here :http://ts1/pdf1/Electronics/Electronics_engineering/
(look for Self D.)

I am listening to this "leap of faith" right now and I'm glad
I did for it sounds heavenly as compared to the garbage I

If you are interested , "power amp under development" or
"brother of Quasi" are amps that will please to the core.
I am listening to a "scary" 150W /250 peak that sounds
awesome, made out of the "garbage" of my blown amps.

They are not hard to build and are very "forgiving'' designs.
I am so happy I found this website so there would be music again!!
The Dx is a nice simple amp but the self design is more refined
and (in my opinon) capable of a more accurate sound.

I did consider the DX as my main amp as a noobie, but found
the self design as a better documented one that would
allow for advancement.

BTW , my rear channels are Dx's because I wanted a simple
low parts count amp to quickly build.

All this is just my opinion , but having both topologies to
listen to ,the Self amp wins.(You can read the book to
make design changes, too...) ;)

Yes Dx are easy to built, and the Dx precision are a bit more complex but for better sound.

For the Self book, it is a must to read, here is the link for those who want to read it;


There is also this much complex amp by roender , with a high end amp sound;


Btw, for any amp, it is very important and worth to do, to match closely the HFE and the VBE of the input transistors. I did it in my last amp and get much better sound.


We can't forget about the Leach amp, bulletproof triple
darlington amp, awesome for college dorm parties and
other beer soaked outings.. ha ha :D :D
By gaetan :to match closely the HFE and the VBE of the input transistors
the self amp uses current mirror to force sharing so match isn't as critical, > than 10 mv DC offset without matching is possible.
On the Leach amp with it's fully complimentary input stage
matching IS desirable.

A georgia / tennessee local amp... go prof. leach ,party on!!

BTW . gaetan8888, the link you placed is the condensed
version of self's book . This is the FULL book :


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