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Old 8th February 2006, 12:17 PM   #11
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Hi Mad-K,
Mmmmmh,

SE: power follower 99 have quiete good damping factor ( I believe).
Limited current: If I need ,to say ,2 watt peak, I do not see
current limitations with PF99 (20-30W- 8 ohm) and a good
efficence speaker.
This is the "strange" I do not understand........

Inertial
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Old 8th February 2006, 01:05 PM   #12
Mad_K is offline Mad_K  Norway
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I haven't buildt the PF99, but I have a design which is very similiar, except for the PSU. Basically I have a version of the PF99 with the psu depicted earlier in this thread (With 600VA trafo, Ultrafast rectifier and Evox-Rifa electrolytics) I think the bass is rather good and "slammy". Not as good as a good PP slam, but still. Try another PSU with it and you might be enlightened I can't remember any significant difference in bass slam going from this (OTA) design to a PF99 design. The differences where more towards greater clarity, less tubey sound (lower distortion). Anyways both designs are great and I believe it is very subjective/system dependent which one you'll prefer.
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Old 8th February 2006, 01:22 PM   #13
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Thanks for the advices , Mads

Really I have tried various PSU:
Regulated and unregulated
C only and CLC
Massive transformer and capacitors.
NADA, Zero differences ( on the bass). The "carachter" is always the same.
I only constate the evidence. Bass is "anhoressyc" !!
So I have biamplified and now all is OK. An old Threshold 4000
20-400Hz and the PF99 400-20000Hz. Outstanding result!!
Now I am full satisfied.
But the question remain......

Cheers,
Inertial
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Old 8th February 2006, 01:26 PM   #14
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Default Re: Re: Re: OTA - One Transistor Amplifier

Quote:
Originally posted by lineup


For a push-pull or CCS class A, midpoint is most effective.

But
when using a single end with power resistor
it is different.

Say 8 Ohm resistor and 8 Ohm load.
At negative swing, the load will be in series with power resistor.

A theorectical ( not counting drop across transistor )
most effective class A single end
will be if 2/3 (66.66 % ) of voltage supply is across power resistor.
This is if LOAD=Resistor (for example 8 Ohm and 8 Ohm)


The circuit by Mad_K
is actually more effective than if using output at midpoint.
He uses output at 57.77% ( 13 Volt of 22.5 Volt )
I often use output at something like 60%.

Why often used 50%, is to give the transistor some better space to work in.
This will lower efficiency, but possibly reduce distortion.


Ahh yes I see. So why noty using a current source instead of the resistor? No, that would need another transistor! Ok, then why not an inductor? Low DC loss, but high AC impedance, so you get less dissipation, more power etc. Still one transistor source follower...

Jan Didden

PS I hate this waste for no particular reason . It's just bad practise....
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Old 8th February 2006, 01:31 PM   #15
Mad_K is offline Mad_K  Norway
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But it is FUN
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Old 8th February 2006, 01:42 PM   #16
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In our country we are saying : " It is not possible to make from fart some little ball... "
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Old 8th February 2006, 02:00 PM   #17
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by Upupa Epops
In our country we are saying : " It is not possible to make from fart some little ball... "

upupa -you are almost another mastertech

or is that insult to him?
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Old 8th February 2006, 02:11 PM   #18
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Insulting ? No....it's only funny, how some people can excavate miracle from simplicity....
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Old 8th February 2006, 02:48 PM   #19
thalis is offline thalis  Greece
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Obviously, they are Wise.
So, it’s not called funny, dear Upupa, its called wisdom. Wisdom gives (always did and always will) simple and powerful answers to ‘complicated’ questions.
Btw, in my mind you are the best sponsor of all these nice little adaptations of se topology (the more you surf through various threads to remind people that they will get no good sound from simple circuits, the more people you gravitate towards them), and I really admire your work and dedication to these matters;-))

Keep up the good work, Mad_K :-)
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Old 8th February 2006, 03:01 PM   #20
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Ridicule . . .
Destructive contribution . . .
Or what . . . ?

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