Buffer stage

[thorpej]

Thanks,
I think maybe I wasn't clear from the question though from the answer I sort of got what i was asking if I understood correctly.
You don't have both buffered and unbuffered preamp out jacks.
Just the buffered ones ?

There is zero advantage to the unbuffered outputs, even when driving a tube amplifier.

 

[heyraz]

A buffered stage is another stage. If any stage has the potential to introduce noise,
isn't an additional stage by definition a disadvantage?
Why buffer an external processor loop or tape output?

 

[gadget73]

the tape loop won't really be in the path unless you actually connect something to it. The way the PAS works though, load on that connection can affect how it performs so having it buffered keeps the load on the preamp stable.

 

[peterh]

A buffered stage is another stage. If any stage has the potential to introduce noise,
isn't an additional stage by definition a disadvantage?
Why buffer an external processor loop or tape output?

Since connecting a low-impedance thing will place additional load on riaa stage.

 

[thorpej]

A buffered stage is another stage. If any stage has the potential to introduce noise,
isn't an additional stage by definition a disadvantage?
Why buffer an external processor loop or tape output?

The PAS is very sensitive to loading conditions for correct performance of the phono stage. In fact, if I connected one up to my main tube power amp (which has an input impedance of ~91K ohms), it probably wouldn't work correctly.

 

[BinaryMike]

You don't have both buffered and unbuffered preamp out jacks.
Just the buffered ones ?

Correct. The PAS output circuit always sees an optimal load regardless of what the actual load looks like. The PAS in the photo is one I built for a friend many years ago, using the mods from Audio Amateur magazine in addition to the open-loop diamond buffers and an outboard regulated PSU of my own design. It sounds very good indeed.