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Recommended Preamp for pairing an Adcom 555II Amp and Theil CS 3.5 speakers

My Bryston 0.5B preamp was inadvertently put down over the holidays by an incident now known as 'The Sippy Cup Mystery'.  Regardless of the cause, I need a new preamp for my system.  I am driving a pair of Thiel CS 3.5  (with the electronic bass equalizer) speakers with an Adcom GFA-555II amp.  The majority of the eclectic music (classical, 80s, folk, funk) being played on the system is streamed from iTunes through my Audioengine B1 DAC.  I have read a number of posts with various recommendations for the GFA-555II or the Thiel CS 3.5s but not for their paring.  Short of winning the lottery this week, cost is a factor. Any suggestions or directions would be very much appreciated.
iowanna33
jmcgrogan2's avatar
jmcgrogan2
6,346 posts
 
You might want to be mindful of the Adcom’s low input sensitivity and input impedance numbers.

The Adcom GFA-555 II Spec sheet states an input impedance of 100Kohms, which should be fine with almost any preamp.

http://www.kenrockwell.com/audio/adcom/gfa-555-ii.htm#spex


The CJ PV-10A output impedance is measured by Stereophile at 690 ohms.
https://www.stereophile.com/content/conrad-johnson-pv10-preamplifier-measurements
No problem at all.

Good reco Jerry (pops)!

Cheers,
John
layniesdad83
28 posts
 
Brown Audio in North Texas is reported to make a fine tube-pre for about a grand.
pops
2,273 posts
 
Thanks John, and I am sure the OP appreciates your research.  I always said you almost know as much as me...  :-0
unsound
7,329 posts
 

I used Stereophile's specs:

https://www.stereophile.com/content/adcom-gfa-555-power-amplifier-specifications

but, I suspect John's might be more correct.

If the 3.5's eq is used between pre and amp, it would probably also offer some "buffering" in this regard as well.

georgehifi's avatar
georgehifi
10,312 posts
 
iowanna33
  Recommended Preamp for pairing an Adcom 555II Amp and Theil CS 3.5 speakers


Your lucky you don't have the 3.6 as they are a pig to drive to get the best out of, these 3.5's are a different beast and quite easy for your Adcom 555 mkII

https://www.stereophile.com/images/archivesart/189CS35FIG1.jpg

Stereophile's John Atkinson:.
" Jim Thiel has used some form of conjugate load system in his crossover designs to give such flat curves with frequency. (This is where elements are added to the crossover to compensate for phase and impedance changes to result in a simple resistive load.) I would suggest, therefore, the Thiel CS3.5 should be easy to drive, even given its 4-ohm rating."


Cheers George
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