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Old 18th May 2005, 07:02 PM   #1
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Default Best value/price GainClone ???

Hello everyody !


I've built my new TQWT speakers based on Fostex FX120 for one month now , Fostex FX-120 : the pure Full Range
and people on this forum ,
as well as a sound engineer who heard my system suggested me the amplifier could be replaced by a Gainclone for better results.

I searched for hours on the net and I found these solutions to be the best :

- non inverting circuit
- LM3875 chip
- not so high voltages for the supply rails (18v ~ and around 25V = )




Now, I have some little (novice maybe, sorry) questions :

- Are there several non-inverting circuits, because I'm not sure to have seen exactly the same schematics
- Why not use multiple capacitors in parallel (such as 10*1000mfd) to avoid inductance issues with high capacitance ? I were also very interested in the snubber trials by carlosfm but it seems not to always work
- people use BlackGate capacitors as input decouplers, but they seem to be polarized, contrary to film capacitors. What is the best, and are some film capacitors better than others ? Is it truly useful to put 6$ input caps ?
- is a 225VA transformer enough ?
- Does the circuit integrates a preamp ? Is it possible to enhance it or to replace it with another simple and cheap circuit ?
- Is the pot really important in the sound quality ?
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Old 19th May 2005, 07:46 AM   #2
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Default Re: Best value/price GainClone ???

Quote:
Originally posted by youyoung21147
- non inverting circuit
- LM3875 chip
- not so high voltages for the supply rails (18v ~ and around 25V = )
Everyone has there own preferences... but any of these give good bang for the buck.

Quote:
[Are there several non-inverting circuits, because I'm not sure to have seen exactly the same schematics
more variations on the theme... VBIGC my favorite.

Quote:
Why not use multiple capacitors in parallel (such as 10*1000mfd) to avoid inductance issues with high capacitance ? I were also very interested in the snubber trials by carlosfm but it seems not to always work
There are probably more variations in the power supplies than in the actual amp. Start with the basic amp and experiment from there.

Quote:
are some film capacitors better than others ?
Caps probably add more "colour" to a circuit than any other part... and which one sounds best can be very dependent on the rest of the build.

Quote:
is a 225VA transformer enough ?
yes


Quote:
Does the circuit integrates a preamp ?
With a volume pot the basic chip amp can be an integrated... sometimes a buffer helps (the buffer can be considered a pre-amp in some senses..

Quote:
is it possible to enhance it or to replace it with another simple and cheap circuit ?
sure

Quote:
- Is the pot really important in the sound quality ?
a fixed R instead should have sonic benefits over a pot (althou you are going to have a volume control somewhere in the chain.

dave
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Old 19th May 2005, 07:38 PM   #3
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Thanks for your answer Planet10

I heard about the "buffer" but don't really understand what it is. Does it replace the chip preamp ?

I have some ideas to build a multiple stage volume control, instead of a pot, but I'm afraid it may cost me more than a stereo Alps pot !!

How are calculated the values of the different resistors ? Does it depends on the chip or the input impedance resistor ?

I saw on decibel dungeon that carbon resistors sounded better for line in than metal resistors, though they come in larger tolerances (5%,which is anyway better than a pot). Is it true ?

Question for everybody : what are your favorite input capacitors ? Is it a problem if they are polarized ?

And last question, will I be able to get an very good Gainclone, though not the best, with 80 - 100 euros ?
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Old 19th May 2005, 07:51 PM   #4
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Quote:
Originally posted by youyoung21147
heard about the "buffer" but don't really understand what it is. Does it replace the chip preamp ?
In these days of CD as primary source the pre-amp has devolved into a buffer... really much the same thing.

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Old 19th May 2005, 08:05 PM   #5
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If I understand, it's somehow a power/voltage reservoir ?
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Old 19th May 2005, 08:09 PM   #6
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Quote:
Originally posted by youyoung21147
If I understand, it's somehow a power/voltage reservoir ?
More like an impedance converter... creates a high impedance in and a low impedance to drive the chip amp. Also isolates the chip-amp from the input.

dave
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Old 19th May 2005, 08:58 PM   #7
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Default Re: Re: Best value/price GainClone ???

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Originally posted by planet10


more variations on the theme... VBIGC my favorite.


dave

Explain something to me.. How can something be your favorite if you have never built one ?
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Old 19th May 2005, 09:14 PM   #8
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Default Re: Re: Re: Best value/price GainClone ???

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Explain something to me.. How can something be your favorite if you have never built one ?
Same way you can have a dozen favorite cars and you don't even have a driver's licence.

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Old 19th May 2005, 09:16 PM   #9
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Default Re: Re: Re: Best value/price GainClone ???

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Originally posted by jleaman
I bought My first Car today.. Honda To Drive Now!!!
Did you really buy a car... what happened to "the #1 priority is a new computer after i get my speakers paid for"

dave
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Old 19th May 2005, 09:49 PM   #10
jleaman is offline jleaman  Belgium
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Default Re: Re: Re: Re: Best value/price GainClone ???

Quote:
Originally posted by planet10


Did you really buy a car... what happened to "the #1 priority is a new computer after i get my speakers paid for"

dave

Car will be paid for soon. : O ) No more new computer ihave a dell laptop it is good enough : O ) Now ill get my licence and a car no more asking you to come get me... Speakers could possibly be paid off middle next moth...
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