100W Ultimate Fidelity Amplifier

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#9,302
linearpre

hello, Im try to do the Apex preamplifier.

Do you think is enought a zener to reduce the tensión to 15v or its better to use transistors?

Thanks in advance.

The two first pictures are my pcb, with zener and transistors. (not finished)

The others are the preamplifier and a example what i mean when i say reduce the tension with zener (the supply of bridge).
 

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#9,306
foro666 said:
hello, Im try to do the Apex preamplifier.

Do you think is enought a zener to reduce the tensión to 15v or its better to use transistors?

Thanks in advance.

The two first pictures are my pcb, with zener and transistors. (not finished)

The others are the preamplifier and a example what i mean when i say reduce the tension with zener (the supply of bridge).
Click to expand...

Yes you can use zeners for this preamp, nice pcb.
Regards
 
#9,314
Hello Mr.Mile and every one here ....
following some pages of this massive thread i learned that Phono preamp is different than Line preamp ... and Mr.Terry in his P30 building used both preamps MM-3(Line) and P30(Phono) so what is the difference?
2- if my audio source is consumer audio line level (0.4V) or (0.7V) and amplifier input sensitivity is Pro Audio Line level (1.2v) some times it's 800mV.... so in this situation i need a variable gain Preamp ( i think 12dB and below correct me if i'm wrong )with high quality , am i right?

Regards ... Mr.Mile,Mr.Terry , Alex MM , Andrew T , Thimios , ... and all you great kind guys.
thx in advance
 
#9,315
most power amplifiers have a sensitivity of 700mVac to 1.5Vac to produce maximum power (clipping of audio signal).

For this you can use a Buffer after your vol pot to send adequate signal to the power amplifier from most line level sources.

Some source will give a lower maximum output and for this situation it is convenient to have a switchable gain stage that itself is switchable between +6dB and +12dB.

That gives you three options. eg you have a 100W power amplifier with a gain of 28times resulting in a sensitivity of ~1Vac for full power.
no gain stage requires 1Vac for full power.
+6dB gain stage requires 500mVac for full power
+12dB gain stage requires 250mVac for full power.

In all of the above you can attenuate your signal normally by adjusting the vol pot.

If you have a vinyl replay record deck, you need an RIAA pre-amplifier to convert the signal coming from the cartridge to line level. This RIAA pre-amplifier can have a nominal gain of between +30dB and +60dB. It is better to locate this high gain amplifier near the record deck and use short high quality (no to low interference) short cables to make the connection. Long cables after the conversion to line level can be driven by any competently designed RIAA pre-amplifier.
 
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#9,316
thanx Andrew T...
i think the best option i have is Elliot Project 88 Preamp MKII ..
i calculated my required gain for differnet amplifier sensitivities (20.log(Vout/Vin))..my source is PC which out's Level is 0.447v so i need from 6 to 8 db gain.
if i couldn't adjust the gain precisely is there something to do to avoid signal clipping?

Regards
 
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