Preamp schema: Input to buffer to potentiometer to gainstage or what?

[Groundloops]

Please forgive me my ignorance and YES I´ve searched and YES Google is my friend as well but I found nothing conclusive at all ...

What is the right schema for a preamplifier: Input to Buffer, then into potentiometer and then into gainstage?

If not: What is right and why?

THX!

[analog_sa]

Originally posted by SmellOfPoo
Please forgive me my ignorance and YES I´ve searched and YES Google is my friend as well but I found nothing conclusive at all ...

What is the right schema for a preamplifier: Input to Buffer, then into potentiometer and then into gainstage?

If not: What is right and why?

THX!

There is no "right schema".

At least 95% of all preamps have an unbuffered pot at input, followed by a gain stage. Some have a pot sandwiched between gain stages, while others have the pot at output.

[Gordy]

It is as analog_sa said.


Also, if you do not need gain, then you can try:
input > attenuator (or pot) > unity gain buffer > output

[AndrewT]

Hi,
all the options will work.
If no gain is needed then :-
input > pot > buffer > output

with gain:-
input > pot > gain > output

The advantage of a pot at the input is avoiding input overload. Active stages before the attenuator receive full signal and the attenuator cannot reduce the signal level in the preceding active stages.

If you need high gain for any particular input then usually splitting the gain among two or three stages is better.
Better still is to pre-amplify the lowest level signals at source and send a higher signal level to the pre-amp. But ensure this pre-pre cannot overload on worst case signal and/or transient spike.

[Groundloops]

Ehm ... What you think about this: http://sound.westhost.com/project88.htm

Simple enough, worth to give it a try?

[Gordy]

Yes, it is a reasonable starting point.
Give it a go, and use this power supply...
http://sound.westhost.com/project05.htm

[Groundloops]

Are there any drawbacks in the PSU compared to one with true symmectrical layout?

[felixx]

Also my option if you do not need gain:
input > attenuator > unity gain buffer > output
But keep that in mind....any design you accept,a really good power supply is a MUST.

[Gordy]

Originally posted by SmellOfPoo
Are there any drawbacks in the PSU compared to one with true symmectrical layout?

There may be. However I recommend that you start with the simple system. Please also note that some of the biggest differences are likely to come from the way you wire the ground of the system. So in case you have not seen these, have a read...

http://www.gbaudio.co.uk/data/ground.htm
Ground loops

http://www.tcaas.btinternet.co.uk/jlhearthing.htm
Grounding

http://sound.westhost.com/earthing.htm
Grounding

http://www.dself.dsl.pipex.com/ampi.../balanced.htm#7
Balancing and grounding

http://rane.com/note151.html
Grounding and shielding from Rane

http://rane.com/note110.html
Interconnection from Rane

[Groundloops]

@ Gordy: Thank you, man!