Upgrading to kit stereo tube amp from 5.1 digital receiver

April 11, 2013 12:11 PM

In past questions (1, 2), I've described my stereo setup and my desire to build a stereo tube amp. I have no worries about actually building the kit amp, but I'm not sure what I'd do with all my speakers. In thinking about this, I realized I don't know much about my stereo in the first place. Can you help me understand what it actually means to have a stereo amp?

Current set up is a legacy of my home theater days--B&W 601S2s for front channel, B&W DM302s for rear channel, and a B&W ASW1000 as a powered subwoofer. I also have a B&W CC2 center channel speaker that's not currently hooked up.

I really don't go for home theater anymore, and all I use the stereo for is music (mp3s, not vinyl).

I like the idea of the Bottleheads Stereomour amp, recommended by Caddis in my earlier question. (Totally cool--thanks, Caddis!)

However, I also like having front and rear speakers, and being surrounded by sound. The rears in my current system just play the same thing as the fronts--there's no DSP soundstaging. I also like the subwoofer.

Is there a way I could wire all of my speakers up to the Bottleheads amp--i.e., just run speaker wire from the stereo posts to each speaker, split somewhere along the cable run? I don't play music very loud, and the sub is self powered.

Is this possible, or would I need multiple amps? If I really am limited to running one pair of speakers off of a Stereomour, would the 601S2s be appropriate? And, since I'm kinda starting from square 1 in my knowledge, is there a good place to learn about hifi systems that's above home-theater-in-a-box level, but below (and not even aspiring to) the $1,000-a-foot-silver-interconnects level? Like, I'd like to know about speaker impedance, what load I'd be running off the amp if I'm wiring speakers in parallel, etc.

posted by Admiral Haddock to Media & Arts (2 answers total)

Best answer: with 3.5 watts a channel in the most powerful configuration, that amp is going to be struggling to even make much of anything meaningful come out of two of those speakers. It seems to honestly be designed to drive boutique super high sensitivity speakers that are made to be powered by under 10 watt tube amps, which is kind of a whole category of amps in and of itself.

Home theater speakers like yours are often designed to be run by both those high wattage 1000-3000 watts split up between the channels home theater monster amps(especially decent ones like your speakers) and handle big stabs of sound that usually exist in movies. This means their sensitivity is usually not great. This is defined by decibels per watt at 1 meter. I looked up your front channels and they're 90db/w. If you're really set on using that amp, you'll want something well over 100.

The thing is, it isn't just as simple as the watts/db rating, also look at the max power handling of the speaker. Some old klipsch or sansui speakers might only be 91db/w, but say "20w max" and sound great. I had a tiny tube amp like this driving sansui SP-30s and it sounded amazing. It was also 9w a channel though, not just 3.5.

If you want to keep those speakers, i'd get an external crossover and run in to the sub before the amp(i actually have this exact setup at my office currently), and then do a completely different amp kit, probably a push-pull class A+B one with 30 watts or more. Most of those will have multiple speaker terminals anyways, but if they don't, you'll probably be fine wiring both speakers to the same terminal if you don't listen to at ridiculous volumes, especially with most of the deep bass being shunted off on the sub.

So basically, the 601s2's would not be suitable for that amp at all. You can either build a different amp, or buy some vintage high sensitivity speakers. the new ones cost an arm and a leg, go look at NORH speakers for example made for this type of small amp.

Your wiring idea is fine, although you'd probably be better off wiring them in parallel, as in just an individual set of wires connected to the same terminal as the first set of speakers, not strung between the individual speakers or anything(which would be in series, see the diagrams here which although for car audio, explain it quite nicely)
posted by emptythought at 1:13 PM on April 11, 2013 [1 favorite]

Response by poster: Thanks so much, emptythought! I had no idea that speaker efficiency was a thing--you saved me a bunch of money! Instead, I might make one of Bottleheads' headphone amps.

Appreciate the help!
posted by Admiral Haddock at 5:18 AM on April 14, 2013