(Tri)-amplifier thoughts?

[taudo]

Howdy all!

Now that I've (provisionally) finalized the design of my VOTT's, I find myself thinking about the rest of the chain - most immediately amps. I thought it would be fun to solicit this group's opinions on that subject.

In the 20 years that I've looked away from this hobby, it seems to me that much of the engineering orientation that previously prevailed has been overshadowed by trendiness and/or pure snobbery (how else to explain "designer" speaker cables with an MSRP of $23,500/pr? And why is it that "audiophile" electronics must now look like they were designed by Nicoli Tesla - or a Klingon?)

Perhaps it is because I have the gene for contrarianism, but I see a great deal of wisdom in Julian Hirsch's admonition that "all competent amplifiers sound pretty much the same" - especially when driven well below clipping.

If this is so, it will be relatively easy to acquire the 6-10 channels of amplification my planned system requires. There are lots of competent professional (as opposed to "audiophile") amplifiers out there that have all their specs superior to human discriminative abilities by at least an order of magnitude - and cost an order of magnitude less than their "audiophile" adversaries, to boot.

So, what say you all? What amplifiers would you recommend for a tri-amped system as below?

Horn: 511B with factory "goo" in the vanes and outside dampening
Driver: 807 re-magged body with GPA 902 replacement diaphragm
MR: GPA remanufactured 416-8A
SW: JBL 2235H in the sealed-off bottom 7 cu ft of reinforced 828 cab

As always, thanks for the opinions!!


taudo

[Fitts]

My two cents worth for the ideal amplifier system given your drivers:

A fixed bias push pull tube amp of about 30 watts per channel driving the horns (no protecting cap would be needed or desired.) I think something like a Dynaco ST70 or McIntosh 30 watter would sure be nice here.

For the Altec 416 and JBL drivers I would look for amps with lots of iron, big power supply caps and good sized heat sinks. I have learned over the years that some amps are designed so that as the power goes up the class of operation goes down. These amps typically have physically small power supplies and very little heat sinks. With this in mind, I would probably look for an amp with a big damping factor for the JBL drivers using something like a Crown DC300A.

MOSFET output amps are tube like in their nature and would probably be a good choice for the 416 Altecs. I like the Hafler series when it comes to MOSFET amps.

I'd put it all together with a Rane crossover.

Keep us posted,

[joyspring]

Taudo,

You're absolutely on the mark about the `engineering orientation' -- apart from the real engineers working on DSP, storage, etc., there's very little in the audiophile realm.

Ditto for pro audio, where many of the `real' engineers have left (and the real musicians, songwriters/arrangers, etc. for that matter) and the clueless `gearheads' and arrogant hacks have taken over. How else could one explain this asinine `vintage audio' trend the past twenty years in the recording industry?

What's next? Wax cylinders have more `punch', `slam', `air'? Give me a break!

Audio in general is all marketing. We have 24-bit/192kHz US$150 DVD-A players and all folks want are vinyl LPs with &lt 80dB S/N and chronic RIAA errors because some `expert' recommends some US$2000+ turntable setup.

Getting back to amplifiers though... the Julian Hirsch quote is absolutely correct: all quality amps do sound nearly identical below clipping. This has been proven via double-blind tests. There is no need to look at specialised tube gear when economical and well-built solid-state amplifiers will do the same job with ONE big advantage - CONSISTENT performance (that is, no sonic degradation as tubes age).

For this reason, it's features that will drive your decision. The biggest feature I'd recommend is passive cooling (as opposed to forced-air cooling), especially if you're not housing the amplifiers in a `machine room' or closet. With the extremely low noise floor of current (and future) digital media, it is wise to remove all extraneous noise from your listening environment.

Hafler, Crown, Bryston and McIntosh are all reputable companies that produce quality kit.

And always purchase a larger amp than you think you'd need... why? Because the dynamic range of 24-bit/192kHz is so large, it's rather easy to clip on musical peaks. The large amp provides insurance for HF drivers.

The Rane AC23(B) is an excellent three-way 4th-order (24dB/octave) Linkwitz-Riley active crossover.

For power and crossover points:

807/902-511B - 416-8A (in 828 enclosure):
30 W/8 ohms, 800hz crossover

416-8A - JBL 2235 (in 828 enclosure):
This is a bit more difficult as the horn loading stops at 200hz; however, crossing over that high defeats somewhat the advantage of using a separate subwoofer...

I'd cross over at 125hz and use an inline parametric EQ to flatten any significant dips in the octave between 100 - 200hz.

150 W/8 ohms for the 416-8A

400 W/8 ohms for the 2235H (compensating for the slightly lower sensitivity)

This arrangement will give you very high peak SPL, more than enough to accomodate an average 85dB listening level with 20dB peaks at an average listening distance in an average room.

BobR

[taudo]

BobR, Dave,

Greatly appreciate your thoughts! I was up all night herding drunken cowboys at a local rodeo (for fun, I'm a reserve cop), so when my head clears I may have an additional question or two.

Interestingly, I've come to some of the same (tentative) conclusions. I've got a Rane ME-60 graphic equalizer on the way, and the next good AC 23B that shows up on eBay is _mine_. I've seen several favorable comments on Rane gear on this board and their manuals are so well written that they alone make the purchase worthwhile.

Again, thanks for the thoughts!

taudo

[HiFiPlayer]

taudo

Have you ever make a consideration to the old model of Dahlquist DQ-LP1 ?

To your new plan, I believe Bi amps would be enough. I preferred using 2 of same model amplifiers to fill with.

Power amps suggestion:

200W MOSFET Pure Class A Power amplifiers

Single End UV-211 or 845 Tube Power amplifiers

[taudo]

HiFiPlayer,

Thanks for the recommendations! I'll have to look into these. Right now, I'm partitioning off the lower 7 cu ft of my 828's to install the subwoofers.

I'm going to try a system using a Rane AC23B 3 way crossover feeding a trio of Crown amps. All are ordered and on the way. I hope to have everything hooked up within the next month and will post a report.

Thanks again!

taudo

[HiFiPlayer]

Taudo

I?m sitting right here to waiting for your report.
That just a suggestion, forget it. Other hand, I also want to have an AC23 too.

I have a similar speaker project will start soon.
My target: 4 ways ,
Frequency response: 32Hz to 21.5kHz ,
Sensitivity: 98-99db/ 1W

Alnico drivers
UHF JBL 2405
HF 808-16A + 511B
LF 414-16A
SUB 416-16A

[taudo]

HiFiPlayer,

I'm interested to know why you chose a 416-8A as both MR and sub. It's my understanding that 416's don't have the excursion for good sub use. Please expound on this - I'm always eager to learn. Thanks!

taudo

[HiFiPlayer]

Taudo

To the bass reproduction, 416-16A really as you described that I know. Then I believe that the 2245 is a very good choice as Sub use as GM?s suggestion. My reasons are: -

1. My speaker?s LF is enactment at from around 32Hz to 35 Hz. So I think that 416-16A maybe can earn one's wings. Cause it just response and make up for below 40 to 45Hz.
2. 414 and 416 are also 99db sensitivity.
3. As my experienced, a real flat curve 40Hz can makes you shocked. For example; TAD 2404 is 95db/1W, frequency response: 25 to 20kHz. But its LF speaker is rolling off from around 75Hz by measured. Actually, its 40Hz is about -12db! As I know that too many speakers are also have similar problem. So don?t be trust any speaker?s spec.

However, I really want to hear to the some fans opinions as GM, thevott, Mirrophonic Sound System, BobR and also you or anyone if possible.

Thanks for look!

HiFiPlayer

[Altec 1234]

Another amp to consider is what the esteemed Dr Linkwitz uses to drive his impressive Linkwitz Orion system.

He uses eight of the 12 available channels of an ATI AT-6012 amplifier, and the sound is as good as I've heard from a dynamic driver system.

You needn't spend more... (It's still $1600 street though.)

http://www.linkwitzlab.com/orion_us.htm

http://www.ati-amp.com/at6012.html