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Old 9th June 2012, 07:31 PM   #1
krassyg is offline krassyg  United States
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Default Tweeter Class A Amp

I am looking to get or build a class a solid state amp for the tweeters and maybe mids of my Focal Utopia clones. I am currently using one of these for the quad amplification:
Onkyo PA-MC5500 - THX Ultra2 9-Channel Power Amplifier | Model Information | Onkyo USA Home Theater Products

What would be the best option that I have? I see a lot of 30W to 50W DIY Class A kits on ebay; are they any good? Would it be an improvement over my current amp?
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Old 9th June 2012, 11:37 PM   #2
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At Nelson Pass site you should find an old ('80s?) 40w class-A amp project that many people used them for powering their tweeters until the late '90s.

That shouldn't have changed that much, as class A amps are still considered better sounding than all other classes. They are just not efficient, but at low power levels that shouldn't be such a big deal.
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Old 10th June 2012, 04:28 AM   #3
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build, buy a kit, or DIY?

There are a few very nice DIY options, if you search here.

A bit depends on the sensitivity of your tweeter vs. the mid driver, and also the nature of your xover, plus the actual power handling of the tweeter... that will help determine what power range amp you need or want.

Also, consider a tube unit too... fwiw. Can sound wonderful done right.

The Pass forum and the First Watt site have some class A amps too...

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Old 10th June 2012, 06:27 AM   #4
krassyg is offline krassyg  United States
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I am looking to buy a kit; I am not at a level that would allow me to build my own. I am good with a soldering iron and I do have the basic knowledge when it comes to electronic cirquits.

The tweeters and mids are the same used in the Focal Utopia EM. The crossover is a digital crossover built into the Onkyo TX-NR818; will upgrade to the pre/pro version when it is released in the fall.
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Old 12th June 2012, 01:20 AM   #5
krassyg is offline krassyg  United States
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What would be the absolute best DIY kit that I can buy?
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Old 12th June 2012, 12:48 PM   #6
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Not that many "non-clones" class-A amp kits to pick from.

Get in contact with Audioxpress to see if they still have some Pass class-A kits left.

In the Pass forum might have info on that too.

There's also the JLH class-A amp around, but I'm not aware of any kits, maybe on eBay. Google that.
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Old 12th June 2012, 12:50 PM   #7
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Not that many "non-clones" class-A amp kits to pick from.

Get in contact with Audioxpress to see if they still have some Pass class-A kits left.

In the Pass forum might have info on that too.

There's also the JLH class-A amp around, but I'm not aware of any kits, maybe on eBay. Google that.
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Old 12th June 2012, 12:59 PM   #8
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You don't really need a massively powerful amp for the tweeters, and you won't notice any difference between class A or B. (JLH or Hiraga will be fine)
Build a class A for the midrange as that's where your hearing is most sensitive.
As a guide you want 150 Watts class B for the bass, 30 W class A for mids and 20W class B for the tweeters.
It can get more com[plicated than that as you can compare average versus peak power levels for the frequency bands where for the treble the ratio is very high, but for the time being try to keep it simple.
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Old 12th June 2012, 01:01 PM   #9
wahab is offline wahab  Algeria
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Neither JLH class A amp or Pass F5 style amps are suited to drive tweeters
since they have high distorsion ratios at high frequencies , quite higher
than usual AB class amps.

A good solution would be to use a proved AB amp kit and then bias it
in class A for the five first watts.
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Old 12th June 2012, 04:06 PM   #10
AndrewT is offline AndrewT  Scotland
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You don't need a lot of voltage drive for a 100dB/W tweeter in domestic listening.
You will need ~ double the voltage drive for a 94dB/W tweeter.
And double the voltage drive again, if you use an 88dB/W speaker.

From there I see two bits of information that must be researched:
What peak SPL will you expect from your tweeter?
What sensitivity will the tweeter have that you eventually want to drive?

Without that crucial data you and everyone else, can only guess.
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Last edited by AndrewT; 12th June 2012 at 04:14 PM.
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