What Class A amplifier, 10-20 watts for fullrange speakers.

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vishalk

vishalk

Member
Joined 2017
Hi All

Need some advice, currently using a valve amplifier which is only 3w to power my alpair 7.3's.

Sometimes i switch it and use a class D amplifier which is around 20w which changes the sound

https://www.amazon.co.uk/KKmoon-TDA...=1491395486&sr=8-2&keywords=class+d+amplifier

cheap but surprisingly it performs well.

I would like to try a Class A amplifier, i am happy to build one if some of you can suggest a well known kit (i am looking for clarity and packs a punch).

I also found this

Finished classic Hood 1969 gold seal Class A amplifier 10W+10W | eBay

which looks pretty good? anyone had any experience with this amplifier? I was thinking i could purchase this and then tinker with it.

Thanks
 
A

AndrewT

R.I.P.
Joined 2004
A 10W to 20W ClassA as an upgrade from a 3W ClassA is probably a wise choice.
If you go for a solid state ClassA power amplifier then choose a transformer with a VA about 10times the total maximum ClassA power.
let's suppose you choose to build a 20W+20W classA amplifier fed from one dual secondary transformer. I'd suggest you need a 400VA transformer.
20W into 8ohms is roughly equivalent to 18Vpk of maximum output signal.
You will need supply rails of roughly +-23Vdc to obtain that 20W ClassA target.
A dual 16Vac, or dual 18Vac, transformer will get you close to the 23Vdc supply rail.

So you would need a 230:dual 16Vac 400VA transformer.
 
mpmarino

mpmarino

Member
Joined 2004
cjkpkg said:
One of the pass designs would fit the bill...the amp camp amp or maybe mini aleph.
Click to expand...

For sure.

Although I haven't personally built any, it sounds like some of the Pass First Watt amps would be perfect. I'm 'pretty sure' Nelson Pass is a big fan of full range drivers.

Although out of stock right now, the Diyaudio store offers a first watt F6 kit - likely well supported on the forums.
 
M

Mrcloc

Member
Joined 2016
If Class A = 100%,
Class AB = 90%
Class D = 60%

That's my opinion, and I'm willing for it to change, but so far it hasn't. I don't like Class D whatsoever. It has a good place, but not in the audiophile world, IMO.

If you do the class A thing, post what you do here - I look forward to seeing what you do. Class A is the ultimate, but it's expensive and somewhat difficult, relative to Class AB. My next project is a 20W class A, but as AndrewT has said, you need a large transformer for the recipe to work. :)
 
C

cjkpkg

Member
Joined 2008
i have built F4, F5, F6, and Mini Aleph. F5 is my favorite. I could never get the buzz out of the F6 and sold the parts. F4 was OK but my system didnt have enough gain and also ended up selling it. You can put a mini aleph in a 2U enclosure since you dont need that much heat sinking and have a nice compact setup.

You can get the boards from one of the vendors here Chipamp.com for both the aleph and a really nice aleph power supply.
 
vishalk

vishalk

Member
Joined 2017
Mrcloc said:
Looks nice. Why would you tinker?

A great design I've build a few of is here. Very nice sounding, very easy to build. But then you need to do power supply, wiring, everything, and then the enclosure.

Good luck! Nice place to be, is the starting point.
Click to expand...

Thanks Mrcloc, i just like to take tings apart and see how they work. And do general things like improve it somehow :D
 
vishalk

vishalk

Member
Joined 2017
AndrewT said:
A 10W to 20W ClassA as an upgrade from a 3W ClassA is probably a wise choice.
If you go for a solid state ClassA power amplifier then choose a transformer with a VA about 10times the total maximum ClassA power.
let's suppose you choose to build a 20W+20W classA amplifier fed from one dual secondary transformer. I'd suggest you need a 400VA transformer.
20W into 8ohms is roughly equivalent to 18Vpk of maximum output signal.
You will need supply rails of roughly +-23Vdc to obtain that 20W ClassA target.
A dual 16Vac, or dual 18Vac, transformer will get you close to the 23Vdc supply rail.

So you would need a 230:dual 16Vac 400VA transformer.
Click to expand...


Thanks for the advice :) do you have a link to the suggested power supply?
 
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