Amp/Preamp Asylum

Looking for a new Amp or Preamp? If you're after tubes, post over here.

Return to Amp/Preamp Asylum

Tube preamp with Bel Canto S300??

24.155.243.155
Posted on November 5, 2009 at 08:00:41
rebbi
Audiophile

Posts: 23
Location: Austin, TX
Joined: September 4, 2008
 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.

RE: Tube preamp with Bel Canto S300??, posted on November 6, 2009 at 05:55:45
Sibelian
Audiophile

Posts: 30
Location: New York
Joined: August 18, 2005
 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.

RE: Tube preamp with Bel Canto S300??, posted on November 6, 2009 at 06:47:00
rebbi
Audiophile

Posts: 23
Location: Austin, TX
Joined: September 4, 2008
 Sibelian,

Tell me more! How's it sound?

RE: Tube preamp with Bel Canto S300??, posted on November 9, 2009 at 06:54:25
rebbi
Audiophile

Posts: 23
Location: Austin, TX
Joined: September 4, 2008
 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.

RE: Tube preamp with Bel Canto S300??, posted on November 6, 2009 at 17:56:40
Sibelian
Audiophile

Posts: 30
Location: New York
Joined: August 18, 2005
 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.

RE: Tube preamp with Bel Canto S300??, posted on November 5, 2009 at 13:49:16
rebbi
Audiophile

Posts: 23
Location: Austin, TX
Joined: September 4, 2008
 Hmmmm....

What about the Quicksilver Line Stage with remote?

the one i had..., posted on November 5, 2009 at 15:13:01
kuma
Audiophile

Posts: 5085
Joined: July 8, 2001
 the gain did not work with a solid state power amp at all.

RE: the one i had..., posted on November 5, 2009 at 18:46:52
rebbi
Audiophile

Posts: 23
Location: Austin, TX
Joined: September 4, 2008
 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.

We build tube preamps..., posted on November 5, 2009 at 09:07:08
Allen Wright
Manufacturer

Posts: 4729
Location: Schaffhausen
Joined: January 31, 2002
 ..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

RE: We build tube preamps..., posted on November 5, 2009 at 10:11:57
rebbi
Audiophile

Posts: 23
Location: Austin, TX
Joined: September 4, 2008
 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.

RE: We build tube preamps..., posted on November 5, 2009 at 10:32:02
bjh
Audiophile

Posts: 11876
Location: Toronto, Canada
Joined: November 22, 2003
 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!
I know AN M-5 and above are direct coupled to OPTs. Do you know others? Nt, posted on November 5, 2009 at 09:32:24
Frihed89
Audiophile

Posts: 8435
Location: Copenhagen
Joined: March 21, 2005
 Nt
"What did the Romans ever do for us?"

Page processed in 0.030 seconds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2009, Audio Asylum, all rights reserved ] [ Go Green ] [ Take5 ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]