Bi Amping the AR9 - How do you do it?

[frankmarsi]

On 3/11/2022 at 8:17 AM, Pete B said:

@frankmarsi

You can find the 700B and 700 Series 2 service manuals, and many others here in the AudioKarma data base:

http://akdatabase.com/AKview/thumbnails.php?album=94

Many of the service bulletins are included in those docs.

I'm not sure if you have to sign into AudioKarma to have access to the documentation.

Frank, do all of your amps have the White Oak upgrades?

https://www.whiteoakaudio.com/estore.aspx

Pete B.

To be honest as I always am, no. Though I have often thought I'd replace the driver-board on all of my Phase Linear amplifiers and not the front-planes that mount all of the power transistors first, as always, laziness took over. If and when I start to replace those components, I'd also want to add the "Watts-Abundant"  DC cut-off relay while I'm in there. Costs add up when talking about nine actual amps so, that further set me back. The Phase Linear PL-400 is a very sweet sounding amp and with 400WPC at 4 ohms are pretty much all one would need. When I bought into the main two PL-700's for the AR-LST's I did so to reach the ultimate levels those speakers were able to handle. When I bought the two AR-9's in 2014 and attempted 'bi-amping' with double PL-400's I wasn't all that pleased as I stated earlier. Upon switching the 400's out and placing a single PL-700 inline I enjoyed the 9's much more. How much, I'm not certain as the room they're in is not properly set-up just yet.

 Numbers would be 700WPC with the PL-700.  With 400WPC split for mids & highs using two PL-400's and 400WPC X's two for the low frequencies. . So on paper the PL-400's actually were performing with a higher total of 800WPC total for highs and mids and bass combined. Whether or not there was a loading problem with the PL-400's, I don't know.

On another note, I'm considering purchasing those absurdly priced fuses, and although the cost is crazy for the amount of fuses I'd require one must consider the actual element normal fuses are made with. That in of itself would convince more people to use better quality fuses. However, in actuality, I don't think those costlier fuses would sound better than a straight copper lead from the amplifier, how could they, it's just about better or neutral sounding protection.  Fifty years ago, I was never concerned about fuse construction., who would've thunk? Nonetheless, I've operated with fuses inline with all of my AR speakers since I first bought a pair of 3a's in 1971. It wasn't only out of practicing better judgement to use fuses. Rather in reality it was because I was blowing-out so many AR tweeters. In retrospect knowing that presently the tweeters can be rebuilt and, when I think about the number of AR tweeters I threw out, I become angry.

FM

[Pete B]

It is a lot of money for the White Oak rebuild so that is easy to understand.

Where you able to access the docs at AudioKarma, if not PM me your email address

and I'll send them.  There were a lot of warnings and several updates to the PL700 design.

I think the thing about a single large amp is that when a huge bass peak comes along

you have ALL of the amp power to drive it.

[Pete B]

@frankmarsi  I went to a CT Audio Society meeting today and met Ed Blackwood today.  We 

had a very long talk about power amp design and Phase Linear.  Ed is very well known for mods

and repairs of Phase Linear amps.  He is very knowledgeable and has a passion for power 

amp design.  He moved from the West coast to CT so he's closer now.

This is his webpage on the Wayback machine, he is still in business but not keeping up the web page:

https://web.archive.org/web/20080924133620/hometown.aol.com/phasetek

[frankmarsi]

Pete,  I've been in contact with Ed Blackwood since 2009. That was how we met when I purchased two Phase Linear Series II 700's he rebuilt.

We've had a number of long phone discussions about Phase Linear and that whole related world.

We recently messaged about another PL-700 I was interested in and consequently he advised against my purchase of it because he's such a perfectionist. He is a totally excellent rebuilder and everything is done by the book, to the 'T'.

His work ethic is impeccable in terms of neatness, completeness and precision. The second Series II PL-700 I bought from him was almost custom in that he waited for a cosmetically almost perfect face-plate as I required that any purchase I'd be making of an amp would have to be 'perfect'. He delivered on the first one in spades and as soon as I had for a couple of weeks I ordered the second PL-700 Series II. We've spoken different times since and he has consulted and advised me on other possible purchases of amps. His level of related knowledge is vast!

FM

 

16.3

[frankmarsi]

Surprisingly enough, he called me today, though I was out.

He left a message and mentioned he met with you and for some ungodly reason my name popped up. Good 'vibes' nonetheless.

And, thanks again for those manuals. That was very kind of you.

Below is the third PL-700 I bought specifically for my AR-9's. You can easily see the remarkably excellent condition it is in, and it arrived to my house in the same condition. It's also provides excellent service powering the AR-9's it lives with in system #2. Photo below is as it appeared in the ad when I first spotted it. And I agree in many ways when it comes to system-building  'to each his own'  but, when all is said and done there is nothing like using AR speakers with the absolute control and finesse afforded by the copious iron-fisted power this amplifier renders. There's no wondering if that bass note you just enjoyed was lacking in volume, size or degree of realism. There's no second guessing if you're getting all you feel you should be hearing out of a quality recording or not. When this much power is on tap, a sense of total soundcomtrol is always there when summoned by your program-source. And certainly just like any seasoned listener would provide for his thoroughbreds, all of my amps are fully adjustably fan cooled to add to that pleasurable degree of listening confidence.

In the near future I will be purchasing a temperature programable fan controller to give me even more certainty that my system is always running at peak performance.  I already use adjustable fan speed controllers as I've said but,  having speeds change automatically will be a joy.

FM

Below: Elegance in beauty of simple design lines, monstrous in its brutal power reserves.

[Pete B]

I mentioned that you were having problems bi-amping AR-9 s, your name didn't 

come up until it hit me that you two might have talked.  I'm very curious to learn

about what went wrong bi-amping, probably needs a zobel.

[frankmarsi]

Pete B.,

Nothing actually went wrong in bi-amping the AR-9 other than an amp failure but, it was more a matter of sound quality or at least how I perceived it at the time once I installed operating amps. I felt the speakers sounded better when I installed the single larger amp. It was a while ago and I may have been biased concerning the newer larger amp being installed. I also think back to 2009 before I installed double 700's feeling the double 400's came across with a touch more tonal sweetness but, that was using the afore mentioned amps with the double AR-LST's per-side. Comparatively speaking the PL-700's simply out-power the smaller PL-400's and it can be discerned at higher volumes. Another consideration is the PL-700's have been 85%+ rebuilt, whereas the PL-400's where all original. I also felt the PL-700's displayed a more effortlessness overall, especially at higher levels.

Which is as little odd as essentially both amps are virtually identical except for the power rating and transistor complement, maybe slight circuit changes. It may be something as you mentioned earlier but, an amp is work horse and should and does amplify what is before it in the chain. Whether or not the upper amp was not happy by only running the highs and mids shouldn't be a problem anymore than an amp running only the lows.  In terms of a Zobel network, I wouldn't know what component values of resistance or capacitance to assign. Then again, my knowledge only goes so far. Some one like yourself or Ed Blackwood would know better.

P.S. I have a video running a single set of LST's powered by a single PL-400 and as a team I felt the sound was really impressive. I'll try to locate that video, but my allotted space is mostly used up already and it may be too big on this site. But it wouldn't explain the matter at hand. I'll go search for that video now. I do recall it being "ELO"'s song 'Mr. Blue Sky' on a wonderfully good condition vinyl disk I had bought used and cleaned on a VPI 16.5 machine. That's why I recall it as I was very pleased I had found a good condition copy of that albumin ai was just newly setting-up my present system in 2013. As a person made insane by vinyl, I sometimes have a few copies of a disk due to varying states of condition. If I've purchased a used copy and after cleaning it fails my audio requirements, I continue my search for a better condition copy until I find what I'm looking for. The stupid present day virus has curtailed my vinyl hunting safari's since it began 2 years ago but, I'm slowly starting to feel the desire coming back though.

FM

[Pete B]

Back in 2016, you wrote:

2-9-16

Back in 2014, when I first hooked up my newly re-foamed AR-9s, I had plenty (6) PL400s to try the ‘bi-amp’ configuration.

Having never heard AR-9s in my home before, I was very excited that I could actually ‘bi-amp’, something I  had read about often but never tried before.  I didn’t get the pleasure I was seeking because one of the aging amps failed in a few days, then another failed, then another.  Consequently, I have given up until I get those old amps rebuilt, which will probably happen later this year. But, I did a few days of listening.

Obvious to me, I did not receive the effect I was expecting while the amp was running just before it gave out. What I did notice first off was that the speakers were not properly set up in the room as the speakers were sitting one third in the room when they should have been against the front wall for best bass output and balance.

[frankmarsi]

Yes, and at one point I switched in another two PL-400*, sorry if I was confusing. I still wasn't completely happy with the sound I heard beyond the first couple of amp breaking down. Listened to that set-up again with working PL-400's yet, not fully happy. Shortly there after I removed the two PL-400's and placed a PL-700 in their place and things were sounding better. What I didn't receive with the double PL-400's was what I had expected from them. After all the AR-9's had a large amount of power with the double/bi-amp set-up but, the sound didn't impress me. Once the single PL-700 was in line, the over all sound was as good as expected. Again, the room placement of the speakers wasn't optimum so my testing was not entirely proper or accurately done.

*The PL-400 amps used had been sitting dormant un-used since 2006-7. This in of itself may have attributed to my dismal results. The newer PL-700 had newly been refreshed. So my results are not scientific in any way and should not be referred to as quantifying.

FM

[khanahai17]

Hello Pete B, long time no speak  but, to answer your question, no I don't have any copies of service bulletins or any other documents from the factory.  get-mobdro.com

[Shacky]

On 2/9/2016 at 9:33 AM, owlsplace said:

If I had the option I'd try SS for the LF amp and tube for the HF amp -- that said, I haven't done it

Roger

That’s what I’d like to do!

[DavidR]

From the AR9 Owners Manual