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Hi,
I got a great price on a Bel Canto S300 power amp on Audiogon. It'll be my first foray into separates, so please be patient with a newbie. ;-)
When I bought the amp, I'd intended to use a tube preamp with it, but now I'm hearing that with the Bel Canto's RCA inputs being rated at "only" 10K ohms, most tube preamps will be an impedance "mismatch" for that power amp.
Is this so? I've combed through these forums and found some instances of people using tube pre's with this amp -- somebody was using a Conrad Johnson PV-something. But another poster write that he'd gotten an email from Bel Canto discouraging him from using a tube pre with this amp. And what's this whole "impedance matching" thing about, anyway?
Thanks for any enlightenment you can offer -- I'm way confused at this point.
I've been using a Manley Shrimp (output impedance = 50 Ohms) with the S300 -- I'd be tempted to say I'm happy as a clam, but mixing sea creatures is almost as bad as mixing metaphors.
Sibelian,
Tell me more! How's it sound?
Sibelian,
I bought a Manley Shrimp used on Audiogon today! It was either that or the Bel Canto Pre3 (also used). But I really want to hear what my system will sound like with a good, tube preamp, and the reviews (user and reviewer) on the Manley are pretty ecstatic. Given that the output impedance of the Shrimp is only a "shrimpy" 50 ohms, it should work fine with the S300.
Thanks for letting me know that you use this exact combo! It helped seal the deal for me. Will report back here on my impressions when everything's up and running.
I'm not particularly good at describing the attributes of components and haven't tried enough combinations to make comparisons, but I feel that the Shrimp and the S300 achieve a nice balance between warmth and resolution driving my B&W 705s. I listen to a lot of symphonic music on this system, and the only thing that seems to be missing is the scale and impact that you'd get with full-range speakers -- everything else seems right to me, especially the instrumental timbres and definition, and there seems to be plenty of power in reserve. I hope that's helpful.
Hmmmm....
What about the Quicksilver Line Stage with remote?
the gain did not work with a solid state power amp at all.
Spoke to Matt at Bel Canto today. He says that what's called for is a preamp with an impedance output of between 50 and 100 ohms. At least I have a ballpark figure to look at, now.
..so I guess I can comment.
1/ 10k is a silly low value for a poweramp input impedance and will limit your choice of preamps. I see no advantage of such a low value - none.
2/ A preamp should have an output impedance less than 1/10 the load of the following poweramp, which means it should be 1k or less, and most present day preaamps will be in that area. Our preamps have figures closer to 100 ohms, but the Audible Illusions range are around or even above 1k. CJ and ARC would all be comfortably below 1k.
3/ 99.9% of tube preamps have an output coupling cap, and in conjuction with a low input impedance poweramp this can lead to bass end roll off. Designer's chioces vary, but you'd need to listen to the expected match to be sure of compatibility.
This is the only real problem in matching a tube pre to a 10k input impedance poweramp, and the simple cure is to increase the size of the output coupling cap x5 or so.
Regards, Allen
Allen,I'm honored to hear from you, sir, and thank you for the input!
I noticed a Blue Circle BC-21 preamplifier at a good price on Audiogon. Out of curiosity, I called Blue Circle and spoke with the designer, whose name escapes me right now. Anyway, he said that the BC 21 has an output of something like 2.2K ohms and would mate just fine with the Bel Canto amp.
Thanks for mentioning also that Conrad Johnson preamps would also tend to have the right values. I've seen a fair number of those, used, on Audiogon as well.
Edits: 11/05/09
His name is Gilbert.I suspect you misheard what he said about the output impedance (that's the spec you would be interested in) as the Stereophile measurements were considerablyless:
The output impedance was quite low at 453 ohms at 1kHz and 20kHz, this increasing slightly to 727 ohms at 20Hz. So no problem with the Bel Canto amp.
Everything matters, don't forget to tweak your placebos!
Edits: 11/05/09 11/05/09
Nt
"Live free or die"
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