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,

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.

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.
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.
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.

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
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:

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.
Get a reasonable priced EL84 based push-pull amp (i.e. Dynaco, Heathkit, Pilot ) and see if you like it.
14 to 17 Watt per channel is definitely enough for this baby.
Decware makes a nice product at a great price point for low power tubes. This makes them a good starting point.
Welcome to the Darkside! You will never go back. Take your pick of amps as most anything should power your speakers. I would suggest giving Cary and VAC a serious look.

Cary V12 will do the trick (CAD280). 50 WPC in Triode. Lovely sound. You can drive KT88s if you really want to, but that may be too tight for your speakers. Good luck.
It's great to learn and get help from those in the know...

I sent most of you individual emails, but I've listed below the most detailed reply figuring you'd have more info to work with.

Here are some A's for your Q's. Please note I'm looking for tube amps for the HIGHS ONLY. I will bi-amp and keep the Crown Refs on the lows/15's. I'm also very picky about (self) noise – great suggestion as you mention.

Q: You've got five of the 4435's in one room?
A: Yes. Actually I have:

(2) 4435's for L/R (dual 15, 2-way)
(2) 4430's in the RL/RR (single 15, 2-way) and
(1) 4425 center (single 12, two-way
(2) 4645C 18" Subs
All JBL. I have a dedicated room painted all black and acoustically treated..w/a small 5k video projector in a hush box. Can you believe it? My wife's very cool about it! I consider myself very lucky. [laughs].

Q:Good Lord! Aren't two enough?
A: They were until I discovered hi-res surround music done right! HUGE soundstage. A ton of dynamics.

Q1: how big your room is.
A1: 20'W x 40'L x 9' Tall

Q2: what type of music you listen to(and/or movies)
A2: Everything. Mostly quality vocals, folky, older acoustic jazz, acoustic music. Movies: Not too into action. mostly drama, and good adventure/documentary stuff.

Q3: how loud you like to listen to things
A3: Not very loud, which is prob a surprise considering these monster speakers and amps. But not quiet either. middle range. Comfortable.

Q4: how much you'd like to spend
A4: under $1500 per monoblock, a grand per/(x5) would be perfect

Q5: what the rest of your system is made up of
A5: OK here I go:

EmmLabs CDSD SACD Transport (3 x fiber ST conn)
Modified Denon AV-3910 (w/custom 3xAES outputs for DVD-A)
EmmLabs DAC/6e 6-ch DAC
EmmLabs Switchman-3 6-ch preamp (4x1)
All balanced .5M interconnect (custom Monster M1000i)
Ashly XR1000 active crossovers
(3) CrownRef 1's (for L/R abd Sub)
(3) Crown Ref 2's (for LR/RR and center)

Side note. I have 5 active Genelec 10" two-way monitors on top of each JBL for a much more accurate sound. Combining and mixing both systems is magical actually. Sound weird, but works. Heaven is in the middle of this setup. I have set up the system to the SACD recommended standard for surround geometry. 30-deg in front, 20-deg off to the sides. Center is center and all other speakers are equidistant to the main listening position.

I hope this helps. Have you heard of / about Manley Labs Tube amps? Do you have any experience with them? Also, can you recommend a tube amp that's SUPER quiet? Also, I will place each amp at each speaker, so a monoblock config would be best.

Thanks in advance,