Matching preamp to amp

Max,

Congrats on getting the BC21.1. Gilbert and Blue Circle are the kind of people that make this hobby fun. I'm thinking of ordering a pair of his high heel pump monoblocks! Did you get your BC21.1 with the Shallco stepped attenuator?

A passive pre that I like very much is the Luminous Audio AXIOM which in its basic form is only $125. With the AXIOM in the path it's obvious what the BC21 adds to the sound because no one region of the sonic spectrum is accentuated. What I noticed as the main differences are its balanced sound and excellent, detailed bass. However, with the AXIOM the midrange magic is missing and the depth of soundstage and liquid flow is gone as well. Ahh, those 6SN7 tubes!

http://cgi.audiogon.com/cgi-bin/cl.pl?preatran&1068325570

I still think the AXIOM is an excellent unit and Tim with Luminous Audio will make sure you get a unit that matches the output voltage and impedance of your source and input impedance of your amp. He'll also take in to consideration the sensitivity of your speakers and configure a unit that has the right amount of degrees of attenuation for your application.

It only has one input and one output, so it's basically just an attenuator, and it's about the size of a portable Smartdisk Firewire drive. Even if I rarely use it I won't sell it because I like it and who knows, I may be in your situation one day.

Good luck!

Gunbei, I'm not a Rowland owner and I'm basing this on a recollection of an old review, so please take this accordingly. I believe that Rowland believes(d) in matching output to input impedance as a form of power transfer. Maybe some Krell fans can report if this is the same thing that Krell does with their CAST system.

Gunbei,

Thanks very much for the advice/info re: Luminous Audio AXIOM. I will check it out and maybe give Tim a call.

I did indeed decide to go for the Shallco on the BC21.1. Everything I've read/been told recommends it. Gilbert and BC have been excellent to deal with and his pumps and purse are a hoot. I think they'd be great for a second system in the bedroom, with great WAF I would think. ;-)

Max

I posted this some time ago, but, I can't find it in the archives. It was originaly pubished in "the absolute sound" and written by David A. Wilson. I am of the understanding that "TAS" suffered a fire some time ago and this article is no longer available. With that in mind I don't think "TAS" will object to me posting it:" Guidelines For the Consumer...
IMPEDANCE.....PREAMP OUTPUT...........POWER AMP INPUT........
"HIGH"1.......OVER 600 OHMS...........OVER 100 K OHMS.......
"MEDIUM"1.....200-600OHMS.............20 K OHMS TO 100 K OHMS
"LOW"1........LESS THAN 200 OHMS......LESS THAN 20 K OHMS....
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1In DAW's opinion, no official standards exist."

I happen to come across some literature on the Audible Illusions L-1/3A preamps with output impedance of 1.2 kohms. Art Ferris designed them with tubes in parallel (thus halving their impedance),utilizing low-capacitance potentiometers,and increasing the preamplifiers current drive. Which prevents/minimizes high frequency rolloffs even with long cable runs.