Driving the 9s

[Guest]

Due to having a relatively large and generous family which will gather at our home this year I will be able to get my AR9s up and running, I'm guessing, before January 15th. I can taste it.

Due to a friend's generosity I have two preamplifiers to choose from: an SAE 2900 and a Luxman CL-35 MKIII.

My plan, at this point, is to buy an Adcom 555 amplifier. Why? Mostly because they are semi-affordable, but also because they are bridgable. If I find myself wishing for more umph I'll just buy another one later, when I can afford it.

My question is this; What's the difference between a GFA-555 and a GFA-555 MkII? Should I stay away from either one? Can someone with Adcom experience guide me?

Bret

[ar_pro]

The 555II was a fine amplifier, and an excellent match for the characteristics and requirements of the AR-9. I used two (in vertical biamp mode - not bridged) of the amps for several years, with great success, and absolutely no problems. Adcom offers their older manuals (including the 555 and 555II) in pdf format at this site: http://www.adcom.com/ownersmanuals.htm .

[ToastedAlmond]

I had a 555 for awhile, and I thought the top end was rather harsh and grainy. Apparently, a lot of others did as well, as many found the 555II free of the hash and graininess manifested by the earlier model.

George

[Guest]

Thank you, George. I'm not sure my ears are still up to hearing all you can hear, but I'll avoid the original 555 just the same.

Bret

[Guest]

Thank you for your input. As I am telling someone else in this thread I'm not sure I can hear power amplifier "sonics" anymore. I was hoping if there were a major design flaw someone would chime in.

Oh, there is one recurring rumor about all Adcom amps; "they run hot."

Well, I have yet to see a big power amplifier that stayed cool if you were pushing it, but the rumor makes it sound like this is excessive in the Adcom.

I do have a question about your method of using your 555s.

>I used two (in vertical biamp mode - not bridged)<

Why did you find that the way to go? I assume you were using an active crossover, or am I not understanding? Did bridging them (if you ever tried) change the way they sounded? I realize that it will change the specs a little, but probably less than I can hear.

Lastly - did you graduate to something like a Krell/Audio Research or buy another Adcom?

Bret

[ar_pro]

I always thought that the 555II ran sort of cool, never showing any sign of a problem - in my opinion, it was a solid, well-designed and reliable amplifier, with no oddball characteristics.

I did try the Adcoms in bridged mode, driving the AR-9 full-range, and decided that the system sounded MUCH better with the binding post jumpers removed, and each amplifier independently powering the upper & lower sections of one speaker. No external crossover is necessary, and the result was a clean, detailed sound with LOTS of low-end capability.

I'm currently using a new McIntosh amplifier, driving the 9s from the autoformer's 4 ohm tap - it's a great match!

[Guest]

>(in vertical biamp mode - not bridged) <

After reading the 555 II manual I understand.

For the benefit of those reading along who don't know this - an AR9 can and does sometimes fall to 2ohms or less. The Adcom amplifier in bridged mode "sees" an 8ohm speaker as a 4ohm load. So connecting a bridged amplifier to a 4ohm speaker means the amplifier "sees" a nominal 2ohm load. If the speaker falls to less than 2ohms during operation a bridged amplifier "sees" a load of less than 1ohm.

That's close enough to a dead-short that apparently even an Adcom isn't built to take it.

Bret

[Guest]

I didn't do much discriminating and only a little research. I'm taking everyone at their word, of course. Thanks for pointing me to the manuals page at Adcom. I read it.

My 555MkII is on it's way.

I'll be sending for the "missing" 2 woofers (AB Tech, & I'm having the originals repaired - we will see what we will see) Monday.

I'm very anxious to hear them again. I just hope my memory isn't going to disappoint my ears.

If I don't like the replacement woofers you will see them show-up on ebay.

Bret

[Guest]

Just thought I'd revisit my own subject and tell anyone who cares what I've done about driving my newly repaired AR9s.

I have bought (ebay) an Adcom GFA555MkII and an Adcom GTP-740 (which I stole).

The only thing missing is a quality CD player.

OR - and I ask the experts here - can I use my cheap Sony 400 CD changer and use the optical output to a good D/A converter and get away with not having to have a second CD player? I'd prefer not to buy another piece of equipment and since an optical output ought to be an optical output ought to be an optical output, seems reasonable to me. Or are the optics in question?

Bret

[ToastedAlmond]

I don't know why, I just know what I read. It seems a good many folks are disappointed with the sound of optical cable as opposed to good co-axial. I can't speak from experience with the optical cable, but I do use decent co-ax between a Rat Shack CD-3400 portable, and an Audio Alchemy DDE V1.0 DAC, and it sounds just fine. Not as good as the one box Euphonic Technology ET-650 I grabbed, but nice.

I have a couple extra cd machines laying around, including a Denon DCD-810, but they get destroyed in shipping. No key/transport locks, and laser alignment takes a beating too!

Good luck with the new stuff Bret!

George

[Guest]

>It seems a good many folks are disappointed with the sound of optical cable as opposed to good co-axial.<

Never would have thunk it. Find it difficult to fathom. One more thing to turn over and over in my mind.

Thanks for the good luck. I'm kinda old to be getting "giddy" but this is the most "just plain fun" I've had in years and years.

Bret

[Guest Nigel]

>OR - and I ask the experts here - can I use my cheap Sony

>400 CD changer and use the optical output to a good D/A

>converter and get away with not having to have a second CD

>player?

Bret;

Does have a digital co-ax output? Most have both digital optical and digital co-ax. The optical signal coming off the disc is converted to an electrical signal immediately. For the optical connection, the signal is re-converted to optical, and then back to an electrical signal.

Nigel

[Guest]

>For the optical connection, the signal is re-converted to optical, and then back to an electrical signal.<

I see. All that converting stuff is usually not a good idea. It looks like I'll have to just get another CD player since I have no confidence in the ones I own to give me everything that is on the disc.

Thank you.

Bret

[Guest Sean]

After auditioning several different digital sources with my 9's, i've found that the Philips SACD 1000 has unleashed performance from these speakers that i never knew existed prior to putting it into the system. This unit can be used in multi-channel mode, is a good cd / dvd player and can also play SACD's. While its' list price was originally $2000, you can now find them new for around $500 - $700 as they are discontinued. If you look on Audiogon, you can find them used for just a bit less. As to how compatible this player is with the rest of your system and cabling, only an in-house audition could answer that. Sean

>

[Guest]

>Philips SACD 1000 <

Thank you for the heads-up on that. I'll look-see.

Bret