What's the difference between =

[Audio Al]

A

S U T

And a pre ?

Does a pre amp not boost the voltage to the main amp :scratch:

And A step up transformer does the same ?

Or have I got it all wrong :)

Please enlighten me

Al

[Greg2010]

Hi Al,
Have a look at Barry's post post "Passive SUT vs. active MC preamp", it may shed some light on the subject.

http://theartofsound.net/forum/showthread.php?t=23085&page=2

Regards,
Greg

[Reffc]

A

S U T

And a pre ?

Does a pre amp not boost the voltage to the main amp :scratch:

And A step up transformer does the same ?

Or have I got it all wrong :)

Please enlighten me

Al

Hi Al

they do different things. For vinyl replay there are two basic types of cartridge:

High output moving magnet (and high output moving coil);

Low output Moving coil.

Lets deal with the MM (high output...between 1 and 2mV usually) stages first. What the phono preamp does is to apply an equalisation curve (RIAA) to the information which lifts the bass and lowers the treble. This is because of the limitations of vinyl when wanting to cut a full bandwidth signal (ie...you can't cut a full bandwidth signal at a flat FR, so the bass is lowered and treble lifted on the LP surface during cutting, and needs modifying to return it to a flat bandwidth response during playback). A modest amount of gain is added to produce line level voltage of between 1.5 an 2Vrms;

The MC (low output) may only be around 0.2mV to 0.5mV and requires much greater amplification prior to RIAA, so a Step Up Transformer is used for this purpose since it's the best (cleanest) way of achieving the gain required. This can be a step up of between 40 and 60dB gain.

This then turns the signal into a level close to that from MM cartridge, so RIAA and final gain can be applied by the Phono preamp. The preamp on is own does not have sufficient gain for a MC cartridge unless it uses some sort of switchable (between MM and MC) gain cell or internal SUT.

The loading (capacitance and impedance) is often different between MM and MC carts too, so a preamp that allows variations for this loading allows greater flexibility when cart matching.

[Audio Al]

OK

Thanks

I think I may have to read this a few times :D