2. amps-preamps
  3. 1119841768

I need help selecting a tube amp

OK Tube-heads. You win.

Can anyone recommend a suitable tube amp to drive some old JBL horns? (for 4435 Studio monitors, compression driver model 2425H). Nominal efficiency of 25% (500Hz to 2.5kHz)

With the advice from a friend I recently hooked up an old tube amp to my JBL studio monitor horns and was totally blown away. Those old large format studio monitors finally reached out and touched me. I felt like I was wrapped by a warm blanket after years of being in the cold. Norah Jones, Allison Krauss, Fleetwood Mac, Dire Straits and other vocal-and string oriented SACDS were amazing. I couldn't stop listening.

So into by the sound I've decided to begin educating myself about tubes with the hopes that in the end I'll be able to narrow my search, and ultimately purchase five amplifiers for my surround system (highs).

My system consists in part of five two-way JBL 4430-series studio monitors (vintage the 80's). I've been driving them with Crown's wonderful solid state Reference amps. I've always loved the lows, but the highs always seemed edgy and sterile - that is, until the other night when I tried tubes on them for the first time. What a wonderful surprise! I use active crossovers set at 1k for the bi-amping.

My head end is all Emm Labs: CDSD transport, DAC6e and 6-ch. pre.

My friend (who recommended I try the tube amp) says my horns are a good candidate for tube amplification due to the their efficiency. So I looked up the driver model 2425H online under JBLs vintage page and found that they are "25% nominal efficiency (500Hz to 2.5kHz)"

Help. What does this mean to someone who is looking for a suitable tube amp to drive them?

There are also sensitivity specs like: 117dB SPL, 1W @1m. The specs also say the recommended wattage is 100W. How do I make sense of these specs when choosing a tube amp, correct wattage or trying to get a good match? I need a starting point!

I look forward to being enlightened by all of you tube-masters interested based on your knowledge and experience, and who really know your stuff.

Signed truly tube-happy,

Dean
quantumavman
albertporter's avatar
Ag insider logo xs@2x
albertporter
4,949 posts
 
Maybe something like push pull KT88 with some power behind them? The JBL you mention is very efficient but the large, stiff woofer is what needs the 100 watts the factory suggests.

Your Crown amps with their high damping factor would be great for controlling the JBL woofer, but as you said, pretty dismal for the horn drivers.

Depending on how loud you listen and how much control you need (personal taste) you could do with as little as Dynaco Mk 3 mono blocks with KT88 (60 watts), all the way up to Atma-Sphere MA 1.5 or VTL 450 mono blocks.

Of course there are much sweeter transistor amps than the Crown. I would not be surprised if the new Rowland might not sound really good with these old JBL's.
jax2
3,031 posts
 
At 117db sensitivity the world of tubes is WIDE OPEN to you. Everything from flea-powered SET to the more muscular Push/Pull and Pentode designs may work well with your speakers. From the wide variety of your programming, and given that you may be used to the low-end muscle of your SS amp, you may want to look at selections in PP Tube amps which are quite versatile. You should probably state your price range, and whether you want an integrated or separates before folks start blurting out all kinds of recommendations (it is about as open as asking someone "what kind of car should I get"). Virtually anything from 3 watts to 100 watts in tubes will be enough to play those speakers plenty loud. Just a generic good place to start might be a 30W PP design. There are many manufacturers with such offerings in a wide price range so, beyond that, you'd have to be more $pecific.

Marco
karmakarma
22 posts
 
Hello, I can't speak to the specific speakers, but I presently biamp with a SS Van Alstine 220 wpc amp for the woofers on my Meadowlark Hot Rod Herons. I found that a Jolida 302a (50 wpc) with the volume at 2 o' clock gives me lucious mids and highs and serious thump on cone drivers.

I tried a Yaqin 40 wpc tube amp, too, and that still had enough power to push the mids and highs. If you keep the Crown on the lows, an integrated tube amp with moderate power might suit you.

Solid state kills on bass. I wouldn't give that up unless I had to. Another solution might be a Van Alstine FetValve amp which gets great reviews for combining the best of tube and SS sound.

Good luck.

Karmakarma
More to discover