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How much power is enough when going to a tube amp?

J

Jbsound

New Member
Hi. I'm a solid state guy looking to add a tube amp but not sure how low I can go in output power (watts) for my speakers. I am using Borea Triangle 3 ways with double 6 in. woofers. They are rated at 92 percent.
I don't need to shake the walls but I also want to drive the speakers nicely.

How does 15 watts per channel sound for a tube amp. Can I even go lower?
Thanks.
Jim
 
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I guess it's 92dB sesitivity. How much is enough depends on a number of issues. Preferred listening level, size of room, listening distance, etc. I use tube amps of 4 to 50 watts with my 92dB rated towers but it is a moderately small room and listening distance is 8 or so feet. I am also not into rock concert levels but I turn them up occasionally.
John
 
Jbsound said:
Hi. I'm a solid state guy looking to add a tube amp but not sure how low I can go in output power (watts) for my speakers. I am using Borea Triangle 3 ways with double 6 in. woofers. They are rated at 92 percent.
I don't need to shake the walls but I also want to drive the speakers nicely.

How does 15 watts per channel sound for a tube amp. Can I even go lower?
Thanks.
Jim
Click to expand...

25-40 watts per channel would be plenty. You *might* get away with a single-ended amp but that's a bit specialized and probably not suitable for your needs. Many vintage tube amps would work well--Heathkit, Dynaco, Eico, Fisher, etc. Or a modern push-pull EL34 amp.
 
most tube amps aren't that cranky about impedance dips honestly. Some solid state amps will just blow up if they see that kind of load though. It usually causes a dip in output power and usually you'll get some extra distortion because of the mismatch but unless its at full power its likely nothing you'd ever notice. Not going to damage the transformers though. You can run a tube amp into a dead short without that happening. The tubes won't like it much but usually will survive the experience unless you just run it full out until something either leaks smoke or starts to glow bright red.
 
botrytis said:
Dynaco No - Heathkit - no - the transformers are not beefy enough. I have been through this and why I don't have any tube amps anymore - they did not sound good on speakers like this Borea. As I said, the bass area is a 3-ohm dip - that will be enough to frazzle most tube amps (maybe Macs would work).
Click to expand...

Can you tell us what would make a tube amp better suited for low impedance loads? What happens when a tube amp gets "frazzled"?
 
I have a 3 & 1/2 watt tube amp in another room attached to 87db sensitive speakers and it can get very loud if pushed. Just saying.
 
For 92db sensitive speakers I'd say you want to be looking at 25w push pull tube amplifiers. Any less power and you could be left wanting more grunt.
Consider the 7591 or 7868 offerings from fisher and HH Scott.
If they don't sing on A 25 watt scott then they may not be tube friendly speakers...
I'd also be looking at amps which have a 4 ohm tap. If your impcurve dips that low, you may decide to run on the 4 ohm tap and that gives you one additional option that isnt available on say a SCA35 which from the factory had 8, and 16 ohm taps.
I'd give tubes a try if I were you. Most of us here are here because we have added a lot of enjoyment to our lives by listening on and maintaining tube equipment. I've got to scratch my head a little when a stranger pops in to say "I don't use tube amplifiers"
That's fine, but what relevance does that have to anything going on here?
Do you drop in to the local motorcycle club just to tell them you drive a car?
The OP, should not let the naysayers spoil a good time. If you found us, you have the spark within you. We are here to try and ignite your passion, not extinguish it.
 
botrytis said:
Broad brush strokes but, do your speakers dip to 3 ohms? His do and that is why a beefier tube amp would be more appropriate.

Not all speakers work well with tubes.
Click to expand...

My speakers dip to about 3 ohms in a couple of places. I use the 4 ohm amp taps and don't seem to have any problems. The impedance phase angle at those freqencies is low or near zerp degrees.
 
The man stated he didn't need wall rattling power, but everyone seems to think 20+ watts. Under 20 should perform perfectly for his situation, I run 12wpc on 96db speakers and if it's half way up the neighbors can sing along with the music. Price point is a big consideration, going above 20wpc, with a tube amp can get expensive.
 
Jbsound

The answer to your question is simple math. What is the distance between your listening position and the speaker? What is the average DB SPL that you listen at and how much headroom do you need above it?

With 0.3 watts of input your speakers will produce 80 DB SPL at a listening position 3 meters from the speaker and have an additional 17 DB (97 DB SPL) of headroom with a 15 watt amp.

Steve
 
Hajidub said:
The man stated he didn't need wall rattling power, but everyone seems to think 20+ watts. Under 20 should perform perfectly for his situation, I run 12wpc on 96db speakers and if it's half way up the neighbors can sing along with the music. Price point is a big consideration, going above 20wpc, with a tube amp can get expensive.
Click to expand...

The reason I suggested 20+ is that not all 91dB speakers are the same. ;-) Push-pull EL34s are lovely, there are lots of modern amps available in a range of prices, the tubes are readily available, and he's sure to have enough power for all kinds of music.
 
Yes, I meant 92 db. For my speakers.
All your comments make a lot of sense and have been helpful!
My guess is to try and stay at 20 wpc or higher which is a challenge ($$$$) to play it safe. I was considering the famous Dynaco s70 but I'll look into the Fisher and Scott ideas too. Should be a fun experience to see how it turns out!
 
steve... said:
Jbsound

The answer to your question is simple math. What is the distance between your listening position and the speaker? What is the average DB SPL that you listen at and how much headroom do you need above it?

With 0.3 watts of input your speakers will produce 80 DB SPL at a listening position 3 meters from the speaker and have an additional 17 DB (97 DB SPL) of headroom with a 15 watt amp.

Steve
Click to expand...
Based on your math that makes sense! I listen at about 9 ft.
 
trainbuftony said:
For 92db sensitive speakers I'd say you want to be looking at 25w push pull tube amplifiers. Any less power and you could be left wanting more grunt.
Consider the 7591 or 7868 offerings from fisher and HH Scott.
If they don't sing on A 25 watt scott then they may not be tube friendly speakers...
I'd also be looking at amps which have a 4 ohm tap. If your impcurve dips that low, you may decide to run on the 4 ohm tap and that gives you one additional option that isnt available on say a SCA35 which from the factory had 8, and 16 ohm taps.
I'd give tubes a try if I were you. Most of us here are here because we have added a lot of enjoyment to our lives by listening on and maintaining tube equipment. I've got to scratch my head a little when a stranger pops in to say "I don't use tube amplifiers"
That's fine, but what relevance does that have to anything going on here?
Do you drop in to the local motorcycle club just to tell them you drive a car?
The OP, should not let the naysayers spoil a good time. If you found us, you have the spark within you. We are here to try and ignite your passion, not extinguish it.
Click to expand...
 
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