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Power Amp for Passive Monitors

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Power Amp for Passive Monitors

Postby thefruitfarmer » Wed Apr 18, 2018 6:23 pm

I have a pair of K-Rok standards from years back and I am looking for a power amp to drive them.

Looking at an ART SLA-1, 100w into 8 ohms is good for the speakers.

However, some of the reviews have complaints about the noise of the fan. I would rather not put the amp in a separate room.

Can anyone recommend a alternative suitable power amp?

Can anyone tell me how noisy it is in practice? Is there a way to reduce the fan noise?
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Re: Power Amp for Passive Monitors

Postby James Perrett » Wed Apr 18, 2018 8:00 pm

Take a look at Phil Ward's article in this month's SOS magazine. He suggest a whole host of alternatives (although I'd disagree with his Teac recommendation).

Just noticed that the website doesn't have the latest issue up yet but hopefully it will be there in the next day or two.
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Re: Power Amp for Passive Monitors

Postby thefruitfarmer » Wed Apr 18, 2018 8:36 pm

Thanks James

Maybe I will call by the newsagents, that is a lucky coincidence,
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Re: Power Amp for Passive Monitors

Postby Forum Admin » Fri Apr 20, 2018 1:44 pm

The May 2018 issue is online from yesterday at www.soundonsound.com/magazine/2018-05
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Re: Power Amp for Passive Monitors

Postby Forum Admin » Fri Apr 20, 2018 1:46 pm

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Re: Power Amp for Passive Monitors

Postby thefruitfarmer » Fri Apr 20, 2018 2:07 pm

I called by WH Smiths and had the paper copy :) , like the review of the new Boss pedal too.
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Re: Power Amp for Passive Monitors

Postby Forum Admin » Fri Apr 20, 2018 2:51 pm

thefruitfarmer wrote:I called by WH Smiths and had the paper copy :) , like the review of the new Boss pedal too.

Nice one! :thumbup: :thumbup: :thumbup: :thumbup: :thumbup: :thumbup:
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Re: Power Amp for Passive Monitors

Postby thefruitfarmer » Sat Apr 21, 2018 5:34 am

Forum Admin wrote:
thefruitfarmer wrote:I called by WH Smiths and had the paper copy :) , like the review of the new Boss Angry Driver pedal too.

Nice one! :thumbup: :thumbup: :thumbup: :thumbup: :thumbup: :thumbup:

Old School, me.....otherwise I would be going for the powered monitors. My ears are used to the K-Roks so I am going to stick with them for now.
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Re: Power Amp for Passive Monitors

Postby ef37a » Sat Apr 21, 2018 5:56 am

Looking at the .pdf for that Art amp it says the fan is "speed controlled".
I would therefore bet it would not even start up very often for monitoring duties?

The speakers have a sensitivity of 92dB/W/mtr and so you will only need 1 or2 watts to produce the 'magic 85dB SPL' at a nearfield distances. If you 'give it the beans' and produce 100dB you are not going to hear ANY fan unless it is faulty!

In any case, the Book says the fan is "very quiet". If it ain't, ship it back at 'em.

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Re: Power Amp for Passive Monitors

Postby thefruitfarmer » Sat Apr 21, 2018 6:33 pm

ef37a wrote:
In any case, the Book says the fan is "very quiet". If it ain't, ship it back at 'em.

Dave.

I think I am going to take a punt on the ART SLA-1. The grumbles about the noisy fan are all from 2011 at the most recent so they may have fixed it by now. Can always swap the fan over anyway or return it to Thommans....
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Re: Power Amp for Passive Monitors

Postby James Perrett » Sat Apr 21, 2018 6:58 pm

For the price of an SLA1 you could also buy yourself a couple of Hypex UCD180 modules, the matching power supply and the wiring looms to build yourself an extremely high quality amp. You would still need to find a case - when I built mine I used a case from a faulty Quad 405 amplifier.
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Re: Power Amp for Passive Monitors

Postby R_A » Sat Apr 21, 2018 9:06 pm

James Perrett wrote:when I built mine I used a case from a faulty Quad 405 amplifier.

Speaking of the Quad 405. I use a Baldwin HiFi 405c to power my NS10MX.
https://www.reelaudio.co.uk/default.shtml
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Re: Power Amp for Passive Monitors

Postby thefruitfarmer » Mon Apr 23, 2018 8:43 am

James Perrett wrote:For the price of an SLA1 you could also buy yourself a couple of Hypex UCD180 modules, the matching power supply and the wiring looms to build yourself an extremely high quality amp. You would still need to find a case - when I built mine I used a case from a faulty Quad 405 amplifier.

I still have a broken Beyerdynamic Blueprint amp, which was great for years so I could possibly use that for a case...

I am a semi-pro musician rather than an electronics engineer so that option, although cost effective, is probably more trouble than it is worth for me. I am tempted though and I am at day release college studying civil engineering so I could maybe ask one of the electronic engineering students to put an amp together for me?

I have emailed ART, to ask about the fan noise, so will see what comes back.
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Re: Power Amp for Passive Monitors

Postby ef37a » Mon Apr 23, 2018 8:51 am

What SHOULD come back from Art is an SPL number. Don't know why it is so hard for many of these firms to give such information? How many active monitor specs' give self noise at 1mtr?

"Quiet" is hugely subjective, everything is 'quiet' to me!

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Re: Power Amp for Passive Monitors

Postby James Perrett » Mon Apr 23, 2018 9:40 pm

thefruitfarmer wrote:... so I could maybe ask one of the electronic engineering students to put an amp together for me?

It was more a mechanical engineering job for me - drilling holes and putting in mounting pillars. There are a couple of crimp connections to be made and solder joints to the input and output connectors but all the PCB connections come ready made.
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Re: Power Amp for Passive Monitors

Postby jimjazzdad » Tue Apr 24, 2018 12:57 pm

I have used ART SLA 1 amps for many years. I currently have 3 of them. It is a good amp at a good price. I use them for several things, including a small PA (running two amps, each in bridged mono for a stereo output.) Unless I am really driving them, the fans are on minimum and are very quiet, but not silent. One SLA 1 that I purchased second hand had the fan removed. It was used for studio monitors and I was told that the fan is redundant to the ample cooling fins unless the amp is driven hard. All this to say that it will likely work for you.
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Re: Power Amp for Passive Monitors

Postby thefruitfarmer » Wed Apr 25, 2018 9:26 pm

jimjazzdad wrote:I have used ART SLA 1 amps for many years. I currently have 3 of them. It is a good amp at a good price. I use them for several things, including a small PA (running two amps, each in bridged mono for a stereo output.) Unless I am really driving them, the fans are on minimum and are very quiet, but not silent. One SLA 1 that I purchased second hand had the fan removed. It was used for studio monitors and I was told that the fan is redundant to the ample cooling fins unless the amp is driven hard. All this to say that it will likely work for you.

Great, thanks for the reply. That's the response I was hoping for when I posted this thread.

:)
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Re: Power Amp for Passive Monitors

Postby thefruitfarmer » Sun Jun 10, 2018 2:37 pm

Just to bring this to a conclusion...

The ART SLA-1 is not making a disturbing noise from the fan.

I have been leaving it for over 72 hours and it has been fine.

It has enough power to drive the 100 watt speakers and the sound quality is good, especially considering the price.

I would have said that those reporting a noisy fan across the net might have just been unlucky enough to get a model where the fan was faulty and they are few and far between too. If the fan does kick in when the amp is at a high volume it's unlikely to be a problem given the volume of the music.

For the money I can recommend this power amp to drive your monitors, for those of you like me who do not have powered speakers.
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