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Old 11th April 2002, 09:55 PM   #1
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Join Date: Jan 2001
Default Rod 3A project


I would like to build a solid state amplifier wich have really
good sound. After i was looking on the web for amplifiers i think
the Rod 3A project is good for me.
I would like to know wich resistors and capacitator in the circuit must be
the premium quality (Holco, Black Gate, Caddock, Solen..)
I want to build realy good power supply to. Any recomendation?
Do any know other good tweaks to get this amplifier even better.


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Old 12th April 2002, 09:49 AM   #2
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Join Date: Jul 2001
Location: The Netherlands
The amplifier is a good, stable, design but not the 'Highest-Fi' .. but the PCB's offcourse should be very nice.... Rod also has a Class A version of it.. Single Ended that is but then again: if your willing to spend money... you could try one of the Hiraga designs on the 'Class A website' ... I would like to tell you that I finished my JLH 1969 10 Watter Class A amp (I'm so happy and it still amazes me how good it sounds..

good luck
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Old 12th April 2002, 11:29 AM   #3
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i was looking the shematic on class a website but if i build the
class a amplifier i would chouse Aleph or A JLH Class-A for the Quad ESL57 beacouse they have more power ( i have 4 ohm speakers)
Last year I build DoZ amp and i am very happy with sound but
there is hot enough power (15 W).
i would like to build somethink realy state of the art.
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Old 12th April 2002, 12:03 PM   #4
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Did you measure how much power you need?

I did.... my oscilascope never trigger beyond 3Vrms... that's right.. I needed about 2 to 3 watts.. even the snare-drum transients never reach beyond that..

You could try to calculate the power needed by measuring the gain of your preamp, pwer amp and CD output... I would like to hear it if you need more then 10 watt..

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Old 12th April 2002, 12:26 PM   #5
sonnya is offline sonnya  Denmark
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Tschrama it depends alot on your speakers dB/watt and from what i know the Quad ESL57 (electrostat?) need a lot more power to give the same level as normal speakers.

I would agree with you on normal speakers in my home i think i use a maximum of 10 watt at high levels without damaging my ears.

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Old 12th April 2002, 01:54 PM   #6
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i do not have my oscilascope at home right now.
how can i calculate power by gains of cd, preamp and amp.
would you calculate power for me?
preamp gain 18 dB
amp DoZ 12 dB
cd out 2V rms 200 ohm output impedance
speakers 91.5 dB 4 ohm (jm lab point source) same drivers like aria5.

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Old 12th April 2002, 02:19 PM   #7
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Location: The Netherlands
Well .. I admire your attitude.. Here in Leiden we have a saying from a well know scientist:

"Meten is weten! "

"You never know anything till you measure" it so here goes:

If you want to calculate the power you need, you first need to adjust the dials of your preamp and power amp the way you normally use them.

Assuming you use logaritmic pot's in you amp's your can assume the half-way is about 1/10th and more or less lineair wise up and downwards..

Now if you know your maximum preamp gain and the loss in the volume pot you can calculate actual preamp gain (this could well be negative).
Add to that your poweramp gain and apply that to your 2Vrms CD out:

somthing like:
-20dB(volume pot halfway)
+12dB poweramp gain
+10dB (gain = 3.16) total gain applied to 2Vrms =

6.32 Vrms at the very maximum because your CD can nver put out more than 2Vrms

6.32 Vrmm in to 4 Ohm gives: 9.98 Watt

at 91dB sensitivity this gives 101dB.. which is rather loud indeed.. given the fact that I asuume you use stereo this would eb 107dB (spl).. well then I allready feel soory for your neighbours

Did I do it correctly?

I think i did but i do make mistakes (sometimes

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