Power follower 99c Vs Zen

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I am very curious how does a power follower 99C sound compared with a Zen? Some may know what I am talking about.
The circuit looks very simple. There are some advantages I know:

1: Lower value capacitors
2: Lower output resistance which means good dampling factor.
3: Higher output power.

Is it reallyworthy to spend money to built it? I plan to use it with a BOZ.
 
I've build Andrea's Follower some years ago - an original one and with some modifications (I've tried to use current source on mosfet and bipolar, I've tried to use bipolar power supply without the output capacitor, with DC-Servo), and I've tried original PassZen V3,V4, V3+tube input stage - and as for me (not only for me, but also for some of my friends) - the sound of Zen is better!

Thank You Nelson, for the genious design!

BTW, In my V3+tube there is some differencies from the original V3 shematic.
One of the differencies (according Fig.3 in Zen V3 pdf) - I take off C5 and put the upper pin of the R11 to the drain of the Q5 at first, then - to a separate lowpower supply (10 volts higher then Zen's main supply voltage)

The sound is better, as for me.
 
The one and only
Joined 2001
Paid Member
I think that the sound of a follower is generally better,
as it has the 100% degenerative feedback and the
distortion and bandwidth are better. The damping factor
is a little higher on the follower, but I haven't noticed
much difference in bass control.
 
I compared the follower (not Andrea's) and the ZEN (1st version) some 3 years ago. I would add to what Nelson said that the sound of follower did not depend that much on speaker used - probably because of the lower output impedance (0.3 Ohm approx) and the sound was more clean for complex music. But I have never heard ZEN V4.
 
Maybe I'm off base on this one, but isn't it playing with words to call a follower a single stage with low distortion when you have to put some voltage gain stage (with it's distortion) in front of it to get it to work? Seems like an apples/oranges comparison when you are talking about the follower vs. zen circuits.
 
nobody special said:
Maybe I'm off base on this one, but isn't it playing with words to call a follower a single stage with low distortion when you have to put some voltage gain stage (with it's distortion) in front of it to get it to work? Seems like an apples/oranges comparison when you are talking about the follower vs. zen circuits.

You bring up a valid point, it's true that the follower will have less distortion in the output stage than a Zen or any other output stage with gain. The trick here is to build a gain stage with very low distortion to drive the follower. This shouldn,t be to hard because now the "gain stage" doesn't need to supply much power, just enough to drive the output stage. That's how it is with creaping eligance, just add this little thing and make it better, you know. I point to Zen V1 to V7. Just add one little thing. HAHAHAHA

I built a power follower many years ago, about 1973 or 74 and drove it with a cheep Zenith stereo. It sounded way better than it had any right to.

Later BZ
 
jh6you said:
Question:

Is the final distortion value at the speaker teminals of the follower is independent of the (high) gain stage distortion?


No. Every stage adds it's own distortion. As the signal goes through the amp. the distortion becomes a composite of all of the stages distortion. That's why loop feedback works.

The point here is that the power follower type output is very low distortion compaired to other types of output stages. At the same time it is easyer to make a low distortion voltage gain stage if it is loaded into a high impedance load (the gate, grid or base of the follower device). The driver can also be DC coupled in many cases. Because of these things a no loop feedback amp can be built that can sound very good and be low distortion.

Later BZ
 
Nelson Pass said:
Well, if you need more voltage, you need it.

??
OK... I don't see what you're getting at.
:confused:
I guess I see the point made above- the voltage stage isn't heavily loaded, so it is easier to design for lower distortion.
Has anyone here used both outputs on a BLS to drive two amps into a speaker differentially? I suppose you could even X it fairly easily, and also it would get rid of the output coupling caps, right?
 
The one and only
Joined 2001
Paid Member
HDTVman said:
No. Every stage adds it's own distortion. As the signal goes through the amp. the distortion becomes a composite of all of the stages distortion. That's why loop feedback works.

There are those who would argue that this is the weak part of
loop feedback. The composite nonlinearities of many stages
within a loop creates a more chaotic situation for feedback to
deal with, and the result is less predictable. The paradox of
feedback is that it works perfectly with systems that are
perfectly linear, and of course because they are linear, they
don't need feedback. The more you need feedback, the less
reliable the result.

:eek:
 
nobody special said:


??
OK... I don't see what you're getting at.
:confused:
I guess I see the point made above- the voltage stage isn't heavily loaded, so it is easier to design for lower distortion.
Has anyone here used both outputs on a BLS to drive two amps into a speaker differentially? I suppose you could even X it fairly easily, and also it would get rid of the output coupling caps, right?



What tells you if you need voltage gain? If you don't need it you can go on with the follower and nothing else ...

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

BLS into a differential amp? YES !
I made experiments with SOZ as a follower , and differently drived as an amp for biamplification with output caps !
 
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