Highest quality design

[Progg70]

You don’t need any preamp with the Kit;s from www.aoaudio.se they have a passive volume control.
I think preamp make things much more complex then it should be and they belongs to the dinosaur time ;.)

[Pocoyo]

For Class A thing

1. Match Pair
2. Precision
3. Excellent work rate

If you use 4 transistor maybe you must buy it more
to have them match pair, improve your amplifier a lot

If you search for 100R resistor you must use 100R and
measure them first with better MULTIMETER get a best
precision and it will help you a lot

Try to hear and listen about component you will use
in the market from friends and read the data sheet
some component will bring some character

See you DOS, success

[si_jopie0382]

This is link for F4
http://www.diyaudio.com/forums/showt...92#post1401992

[D_o_S]

Hi,

I have looked at several pre-amp designs...

What is interesting though is the way that they are designed...

If I understand it correctly, all these preamps have 1 input, to which you direct your signal via some sort of switch...

However, the input signal may be in mV (say 100mV), and if simply by switching the signal, you loose 1mV, that is quite a big loss.

In my opinion, it would be better to amplify everything at once (so if you have 8 inputs, amplify all 8) and THEN switch the signal to the output, because the output will be like 1V, so 1mv on 1V is not such a big loss.

Or am I missing something?

[Zen Mod]

Originally posted by D_o_S
...........
Or am I missing something?

yes ........

for your proposal - you either need something as mixer, or dedicated preamp for each stereo input .

switching input on line level is critical , but not as having several preamps in one case ;

even if I know some made exactly that way ; do I like their sound - don't even ask .......

[Gordy]

Originally posted by D_o_S


Or am I missing something?

It is technically feasible to design as you imply. For eight inputs there would be eight amplifiers per channel.

One advantage is that each amplifier can have the gain pre-set for the input signal level (for example, one input may be 100mV and require a gain of 10, while the next input may be 500mV and require a gain of 2).

However the cost would be very high with eight of everything, and changing / modifying it would take a long time.

In standard designs the input switching loss is likely to be less than you assume, and gain is actually very cheap. Most CD players have an output so large that attenuation is more likely than gain.