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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
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
123henry97
17 posts
 
Yesterday I was listening to a pair of 1958 JBL speakers with 117dB sensitivity. The owner (in Red Wood city, He sold me the table for turntable) drives them with a pair of 12 WPC mono tube amp. The volumm was not even haft way (about 6 watt) It was loudy enough in a 15WX18DX10H room.
Your speaker is with 117dB sesitivity, IMO you just need a small wattage tube amp and spend money on trying to get a high quality one. You should check this out by yourself from your local dealer or friend before you pay for.
jalanc42069
131 posts
 
Hello QAVman, wow, that soumds cool. 117db!, what that means is your speakers will put out 117decibels, measured with a 1 watt signal, measured at a distance of 1 meter from the speaker. That's freakin' loud! I don't know how large your listening room is but basically, any tube amp will do it, so start auditioning to find something that sounds good to you. Personally, I would look at the single ended triode amps first, they have a sweetness and presence in the midrange that is hard to beat, my favorite is the 2A3 sound, but 300B, 45,845, etc also sound great. SETs are usually noted for being a little soft in the bass(unless you spend the bigbucks, although i recently heard the Almarro 205 SET amp - 5 watts/$800., and the bass was great), but i assume you have subs. I've also heard some great push pull and OTL amps, which usually are stronger at the bottom. Although i havn't heard it yet, Transendent Sound makes a hybrid single ended/OTL amp called the SE OTL that appeals to me(best of both), they can be used in stereo or mono. Five of those would be a cool set up! I've heard they work excellent with the Klipshhorns, so they might sound great with your JBLs.( i have no affiliation with TS, i'm just a fan, and hopefully future buyer. These are loose generalizations on the different topology styles and by no means are they universal, so see(hear) what your ears say. Good luck and have fun. Thanks for reading this (too) long post. Regard, Alan
darkmoebius
900 posts
 
Hi Dean,

How big is your room? I remember those speakers because they had them in a auditorium at my college back in the 80's. You've got five of the 4435's in one room? Good Lord! Aren't two enough?

Why don't you first tell us:
1. how big your room is.
2. what type of music you listen to(and/or movies),
3. how loud you like to listen to things
4. how much you'd like to spend
5. what the rest of your system is made up of

The stated overall sensitivity(woofers & tweeter) is 98dB/8ohm. So, unless you are intrested in bi-amping with one amp for tweeters and another on the woofers, that's the number you should work with.

The JBL spec sheet can be found here:
http://www.lansingheritage.org/html/jbl/specs/pro-speakers/1981-4430-35.htm

My speakers are rated at 97dB & 98dB. I've got 7 watt per channel single-ended-triode Welborne DRD 300B monoblock amps in a 16'x20'x8' room and I can go pretty damn loud. Not rock concert levels, but enough so that the people in the house next door know what I'm listening to.

The most important aspect with speakers that efficient is that your tube amps be ULTRA quiet. Any hiss or hum will be clearly audible and annoying.

But, give us some info on your system, personal tastes, and budget - and I am sure we can find quite a few perfect choices for your needs.
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