Pre/power amp for LST

[djcheung]

Hi there,

It's been a long time since I last visited.

I have a question and need some recommendation on a preamp for my setup on the LST. I have a Crown XLS2502 which sounds good for the LST when connected with the AR-C06 preamp, but it has a constant buzzing noise on both speakers.  Tried with the Xiang Sheng 728a preamp, the buzzing noise has improved but now they sound very thin on the bass. 

Looking for a reasonable preamp on a budget that could work well with the Crown and LST !

Any information is much appreciated.

Best regards,

David.

[nefertem]

Hi Dave are you sure it is not something in the amp circuit not causing the problem did you try a other amp or intergrated amp?

[frankmarsi]

Using AR-LST's on a budget? Is it possible? I say no.

I myself, do not endorse 'chip-amps' that are made for powering 'bass-bins' and house PA systems.  I'm not familiar with that pre-amp as it was made during AR's 'sell-out' defunct era.

However, I'm sure the many scholars out there will give you their suggestions even if they typically have systems that might be less than truly listenable.

Simply put, what sort of system did you ultimately what to have?  How close to 'real' do you want your music to sound? You'll need a good plan for sure.

Many slap AR speakers together with any old amplifier/receiver and are content with something that's not the best they could do. Some think and even insist their speakers sound good on the floor, others insist on using long expired phono cartridges that resemble a dull shaving razor, poor quality interconnects and cheap speaker wire that one would tie up fire wood together with, or a low-end CD player that isn't any better than a 1980 walkman,  are  the way to go?  NOT!  Some are emboldened by the mere fact that they have AR's, and pay no mind to rest of the system and do not pursue the best levels their system could be.

AR-LST's are super-power hungry so that 'chip-amp' will hold you until you upgrade to a more suitable pre-amplifier/amp combination while keeping in mind that you'll ultimately need more quality. Also, LST's require specific room-placement or can be slighted if not addressed.

What will your sources be. How is the room situated, what are its dimensions? 

Your best option is to do your own research and for the most part it's not advisable to find credence in the words of certain folks who are not familiar with AR-LST's or have minimal experience with a system's proper set-up or room placement.

My suggestion is to spend time on the web and search the forums which describe  better and higher-end systems while absorbing what you can from there.

Understand the web opened the flood-gates to everybody and their cousins who are mostly 'johnny come lately' types and only parrot what they've read elsewhere in the last couple of years while speaking as if they're experts. These less than intelligent individuals lurk around here and on other sites, primarily A.K.

AR-LST's were AR's 'capital-ship', their crowning glory of the whole AR line at that time, these speakers deserve the best one can possibly do to allow them to sound their ultimate best. System planning is pivotal and of course, the best plans will render the best results.

Ultimately you have to ask yourself the question: Am I worthy of AR-LST's and do I deserve them? Will I set them up as they were meant to be?

FM

[Carnivore]

47 minutes ago, nefertem said:

Hi Dave are you sure it is not something in the amp circuit not causing the problem did you try a other amp or intergrated amp?

Agreed, it sounds like something in the signal path. I can't see how the speakers would cause the amp to buzz unless there's some weird short going on in the crossover or something.  Can you hear the buzz if you swap out the LSTs for different speakers?

[djcheung]

I know LST and budget cannot be spoken in the same sentence ! 

I have tried swapping out the LST with a pair of 3a and the buzz is still there. However, if I use an integrated amp then they are dead silent. The integrated amp that I have tried - Pioneer SA-508 and Yamaha DSP-Z11. The Pioneer is obviously very under powered , the Yamaha is much more powerful but it does get a bit warm. I am using the Yamaha to drive a pair of 9s.

A Mcintosh will definitely fits the bill but way over my budget. As some other guru here use the Adcom but they are rather difficult to get hold of here in the UK.

I am trying to see if I can make the best use with the equipment I have before spending .

Best regards,

David.

[ar_pro]

You simply need to isolate the problem with your electronics: power amplifier, preamplifier, source.

Connect the Crown amplifier to your speakers by itself, without the preamplifier. Can you hear any buzzing? Move the Crown level controls through their full range to be certain.

If no buzzing is heard, connect your preamplifier to the Crown, and repeat the test of listening for noise at different volume settings of both the Crown and your preamplifier.

If no buzzing is heard, connect a line level source like a CD player to your preamplifier, and repeat the test.

This should tell you where the problem lies.

 

 

[lARrybody]

I too use a Crown XLS 2502 to drive a pair of 9's. I have used several preamps, but currently use a vintage Yamaha C70.  I use a Art CleanBox pro to convert the unbalanced RCA outputs from the Yamaha to XLR balanced inputs to the Crown. There is no noise. I use decent but not expensive interconnect cables. I definitely prefer this combination over my previous Adcom GFA 5500 II and GFP 5500 II  setup which wasn't all that bad. Isolate where your noise is coming from and nip it in the bud. Again I ant say enough good things about the Art CleanBox pro.

[djcheung]

Hi all, after going through the steps suggested, I think I may have tracked down which bit is causing the buzzing noise.

1. Connect power amp to speakers only, no buzz

2. Connect preamp to power amp and speakers, no buzz

3. Connect a cd player to preamp, power amp and speakers, buzz..... even with the power off on the cd player. Remove the cd connection ,then no buzz.

So it looks like that it is the connections before the preamp ! I do have a simple 'ground loop isolator' and I swear that it didn't reduce the buzzing noise when I tried it before. I think I must have connected it to the wrong point. 

I have now connected it between the source and the preamp all all very quiet, no buzzing noise.

Thank you all very much again. Now I can go back and enjoy some quiet quality music.

Best regards,

David.

[Carnivore]

It might be worth getting an inexpensive mains socket tester and use it to check for proper wiring and ground. They plug into your socket and have 3 lights on the front that show whether the wiring is correct, polarity reversed, or has an open earth/ground.  I see them for £5-6 on amazon.co.uk.  It could be that one of your audio components is plugged into a socket with an open ground or reversed polarity.

[djcheung]

Hi all, after going through the steps suggested, I think I may have tracked down which bit is causing the buzzing noise.

1. Connect power amp to speakers only, no buzz

2. Connect preamp to power amp and speakers, no buzz

3. Connect a cd player to preamp, power amp and speakers, buzz..... even with the power off on the cd player. Remove the cd connection ,then no buzz.

So it looks like that it is the connections before the preamp ! I do have a simple 'ground loop isolator' and I swear that it didn't reduce the buzzing noise when I tried it before. I think I must have connected it to the wrong point. 

I have now connected it between the source and the preamp all all very quiet, no buzzing noise.

Thank you all very much again. Now I can go back and enjoy some quiet quality music.

Best regards,

David.

Hi all again,

After doing some not digging around and think I have found the real culprit of the source of the buzzing noise.

Following Carnivore's direction of investigation, I have identified that the power block - Tacima CS947 - is the source of the interference. I have now replace the power block and the ground loop isolator and all are quiet .

Thanks very much for all your help.

I can now stay 'budget' for a little longer.

Best regards,

David.

[Carnivore]

The capacitors and especially the MOV's in those power blocks (conditioners / surge suppressors ) have limited lifespans. It probably served its purpose by absorbing some power spikes over time.  Most people don't realize those devices are consumables that need to be replaced after a few years. Glad you sorted it out, anyway!

[jurgen59]

I have  bought 2 x DENON POA 6600A to power the LST and they are great for the purpose, and affordable

 

Regards

 

Jurgen Prinsen

[frankmarsi]

@jurgen59    if you asked me, I looked up some specs for that Denon amplifier and power wise it has the qualifications to handle LSTs, now the consideration is long term use and actual sound-quality. Will they hold up at high volumes and continuous use at 4 ohms? This I can't speak to as I have no experience with these models. In any case, do use the appropriate fuses.

 Speaking of Denon, it has been around for many years and have generally produce quality products. I'm particularly a fan of their MC cartridges and their entry level DL-301 Mk.II which is excellent and I would endorse it to anyone wanting to dip their toes into the moving-coil cartridge pool. If one has not enjoyed a quality MC cartridge, they don't know what they're missing!  I also own their DL-304 MC cartridge which to me although is more costly than the 301 II, oddly comparatively falls short in the excitement-factor department and is rather overly polite compared to most other cartridges though, if one listens exclusively to classical music, it does satisfy in most areas, just not entirely with rock music.

In terms of pre-owned moving coil step-up-transformers, I use the Denon models AU-340 and AU-320 for my main system and use two AU-320's in system #2. These two models are excellent transformers if looking to keep costs reasonable.  

FM

 

 

 

 

 

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