----- Original Message ----
From: a k butler <akbutler@tiscali.co.uk>
To: Loopers-Delight@loopers-delight.com
Sent: Tuesday, January 2, 2007 12:18:51 PM
Subject: Re: Tubes in Pre-amps: your expertise and honest opinion.
>But, as read further i learned that the main benefit
>comes from DH-Set "SE" configurations and that the "PP
>(push-pull)" configurations do substantially less of
>this "warming effect"????
>
>so, i am wondering then, do all current technology
>tubes sound better/warmer then non-tube preamps? or
>are there only certain tubes that do this?
>
>how would i know technically (besides listening) if i
>have a SE tube or a PP tube from specs in my manual
>that read "Tube Type: 12AX7A hand selected"?
here's the techno babble:-
SE= single ended
PP= push pull
Those are 2 different configurations for valve power amps.
It's not a matter of tube type, but how they are connected.
The PP configuration is only used for driving loud speakers.
For pre-amping you'll be using a simple circuit which would (I guess)
correspond to SE, tho' I don't know if the term is actually
used for
non-power amp applications.
12AX7A is a very common general purpose valve, used in cheap gear and
very expensive gear.
Probably your cheap pre-amp has a chip to do the actual "pre-amp"
part of the process, then passes the signal through the valve to
colour the sound. ( and this is an often used method, even for high
end audio gear)
Sometimes in this sort of gear, the valve is run at low voltage,
which some claim doesn't give the same "valvey" sound, and this is
likely to be the case if you don't see the valve actually glowing.
(clever Behringer use LEDS to simulate the glow )
So:-
Best way to tell is to do what you already did...just listen :-)
andy butler
