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Old 6th December 2012, 10:39 PM   #31
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by Bigun View Post
I would suggest reading about the SEWA amplifier
I guess its among the best of its kind....didn't he also design the ONO, to start with
who was it ? norwegian guy, mats, mads, or something ?
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Old 6th December 2012, 11:37 PM   #32
ide2003 is offline ide2003  Indonesia
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just read the whole post, simpler better in class A, in my limited experience, yes

after more than a year hard tweaking my Aleph J clone, listening to many friends F5, F4 etc. and after 2 weeks enjoying CCSed 2SK82 SIT amp,

just as Vladimir says somewhere here about our perceptions on output power, THD, no output cap, my old perceptions is surely on a shaky ground now
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Old 7th December 2012, 12:31 AM   #33
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by tinitus View Post
I guess its among the best of its kind....didn't he also design the ONO, to start with
who was it ? norwegian guy, mats, mads, or something ?
mads_k
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Old 7th December 2012, 02:00 AM   #34
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Does LM317 have enough bandwidth?

You said don't mind component value so I wont, but in my experience those switching MOSFETs have horrible non-linear gate capacitance, making simple circuit difficult to sound good.
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Old 7th December 2012, 11:47 AM   #35
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Quote:
Does LM317 have enough bandwidth?

You said don't mind component value so I wont, but in my experience those switching MOSFETs have horrible non-linear gate capacitance, making simple circuit difficult to sound good.
Not sure about the LM317's bandwidth. It doesn't have to be a switching mosfet. The circuit drawing just showed the design not saying anything about what kind of components that are used, the LM317 represents an adjustable regulator. I later got that a regulator might not be the ideal current source so I then wanted to assume an ideal current source instead just so I could understand what was "flawed" about the actual one-stage mosfet output. But I understand now that it is the unlinearity of the mosfet that's the bottle neck, but that's why I'm wondering how a op-amp input stage with the feedback taken from the output of the amp won't fix a lot of this.
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Old 7th December 2012, 11:52 AM   #36
AndrewT is offline AndrewT  Scotland
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for a good explanation of composite read W.Jung.
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Old 7th December 2012, 02:10 PM   #37
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by tinitus View Post
I guess its among the best of its kind....didn't he also design the ONO, to start with
who was it ? norwegian guy, mats, mads, or something ?
The SEWA is basically a POWER FOLLOWER 99 by Andrea Ciuffoli, with normal/ordinary power supply (Ciuffoli used virtual ground). Key element is the use of IRFP150. A little improvement can be made with current source a-la VladimirK.
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Old 7th December 2012, 04:06 PM   #38
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Quote:
Originally Posted by Plecto View Post
I've been wondering about this. I've been reading about mosfets at university and I think I have a decent understanding of them. Take this class A amp circuit as an example:

http://i50.tinypic.com/10hugp5.png

Don't mind any of the component values. When I look at many class A amp designs out there they seemed to be littered with components and I often see a minimum of 5 transistors used in all sorts of ways, but I'm wondering why? I can see some problems with the circuit I linked though like the output cap and current source, but if we assume an ideal output cap and an ideal current source, what is flawed with this design? What kind be done to further increase the quality of the sound?
check out the pictures by post #1 and #2 about
ZEN include active crossover without additional OP AMP for ultimate sounding PHL1230
the based schematic is here:
http://cygnus.ipal.org/mirror/www.pa...ages/zenf2.pdf
the air coil on the images are 10 mH (choke) and the caps behind this choke 2x 10.000uF (Kendeil)
Supply voltage behind the 10 mH inductor is 25V and the idle current is 3,5A (3500mA)/each channel.

The outdoor power supply for one channel (no pictures) consist of two light transformers (each 12V 500VA), rectifier, 1x 10.000uF Siemens Sikorel and a small air coil inductor. The distance for wire lead between power supply and 10 mH choke on the actually ZEN amp from the mentioned images is 5 meters (~16 feet).

Additional very strong increase of the sonic quality is reached by introducing of additional choke and additional caps (6,8mH/75mF = additional 12db lowpass) so as additional caps of 200mF in parallel to the exist ones behind the 10 mH choke.

The unwanted capacities arround the Gate, Drain and Source from the gain MOSFET on ZEN (Grounded Emitter) seems to have had no negative unwanted and audible effects cause a unity gain preamp in front of this power amp with 1A idle current (Vdd: only 9V) - inside there is Andrea Ciuffoli's Power Follower (redesign for 9V supply voltage).
the Power Folllower

The answer to the headline is from my view clearly yes, despite any unwanted inherent properties like very bad power supply rejection ratio (PSRR) and large non linear input-reverse capacities of typical power MOSFETs from the good known IRF series.

Last edited by tiefbassuebertr; 7th December 2012 at 04:17 PM.
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Old 7th December 2012, 07:13 PM   #39
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by Jay View Post
The SEWA is basically a POWER FOLLOWER ...
I would guess that simple power followers go back a long way before Andrea but there is something about the SEWA that captured my imagination more than the others. I have a short list of amplifiers I want to build and this is one that's still on the list. Mads developed versions with and without current sources - somewhere there's a thread he started called OTA (one transistor amplifier) which might have been the inspiration for Mark's ZCA (zero component amplifier).


Quote:
Originally Posted by Plecto View Post
I'm really curious about having an op-amp ...
Take a peek over on the chip amp forum, lots of stuff over there along these lines.
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