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
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.
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.

KiD
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.