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Old 25th February 2003, 08:07 PM   #1
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Default newbie gainclone/power supply question

I've been reading everything I can find about the gainclone supplies. Last night I started building by Adire Audio Kit 281TLs, and they are coming along nicely. I haven't picked out a receiver/pre-amp yet but I am so incredibly tempted to build a gainclone. The question that I have is would it be possible to put the powersupply/amp in the same chasis? I assumed there would be noise/interference coming from somewhere because I haven't seen anyone do it yet..... but the original gainclone I am assuming had power on it.

Anyone?

Thanks,

rob
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Old 25th February 2003, 08:26 PM   #2
Philo is offline Philo  United States
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Sure, you can put it into the same chassis. There are a few commercial variations on the market as monoblocks with the xformer and BRs in with the chip PCB. How they sound compared to the original or Peter's version I couldn't say. I am building a dual mono integrated version that is almost finished (it better be or my wife will be changing my project priorities soon ). I am "encapsulating" the signal path and the respective components from the power supply with sheet copper. This should keep the RFI down. My prototype is wide open with the transformers about a foot away from the chips and the unit is very quiet, only a faint hum at full volume with no input connected.
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Old 25th February 2003, 08:53 PM   #3
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I'm also thinking about building integrated monoblocks with PS. Separate box, all those wires are a lot of hassle. Also wonder about the sound.
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Old 25th February 2003, 08:58 PM   #4
Philo is offline Philo  United States
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They do look pretty neat built into Hammond cast aluminum boxes. I think someone posted some pics of a pair of red ones that looked very nice. Well, it's decided, Rob. Build the monoblocks and get back to us.
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Old 25th February 2003, 09:02 PM   #5
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Rob,

Sounds like a good idea. Single chassis should be fine, especially if you're careful with wiring and shielding.

I have lived with Kit281s for awhile, and the Gainclone is probalby not the best amplifier for them (87db efficiency, difficult ~4 ohm load). I found a ~100 watt amp to not be enough to take full advantage of their capability, but that's just me. But a gainclone is a great idea... it doesn't have to be your main amp anyway, but with what people have been saying about them, it might. I did the same thing... built a Zen as first project before attempting something bigger. So, go for it.
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Old 26th February 2003, 05:46 AM   #6
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This is from the Kit281 page:

"Additionally, the system has an average sensitivity of 92 dB SPL @ 2.83 Vrms. It doesn't take a lot of power to get these babies up and running!"

Is that not accurate? With those specs i had envisioned the gainclone to be almost ideal, but nevertheless I am still not deterred and if worse comes to worse I can always end up with the gainclones powering my rear channel.

So my idea for the gainclone is a dual monoblock/powersupply in a single chasis. The questions are do I go ahead and use two power supplies or just 1? The other thing is, most of the gainclones I've seen have a volume (?) control on the front... would there be a way to either eliminate this and use the receivers volume still (For HT the remote would be nice) or to use one volume control for several channels?

Thanks Again,

rob
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Old 26th February 2003, 06:14 PM   #7
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Rob,

92db is an "in-room sensitivity" spec. I can't blame Adire for stating it that way because pretty much all manufacturers do so as well. The Audioxpress review of the 281s, which is at http://www.adireaudio.com/Files/AX-KIT281Review.pdf, measured the anechoic 2.83v sensitivity at 89.7db. But since they are 4 ohm speakers this output corresponds to about two watts, hence an efficiency of around 87db/1w/1m. This is more than a lot of typical hi-fi speakers, but getting big output from them will need more than a gainclone (30w?). In my 12x15 room listening at 8 feet, my old 100 watt amp clipped at around 103 db peaks (which is quite loud, but not enough for clean reference level or for loud/uncompressed music). Of course the gainclone will sound really good and far better than what's in a (more powerful) receiver... it just might not have the best dynamics. So, give it a shot.

1 power supply with a larger transfomer would be almost as good as two. It's probalby just a matter of money. And with separate power supplies you can also split up the chassis, put the (monoblock) chassis right behind your speakers and use shorter wires.

No volume control is needed, just replace the input potentiometer with a fixed resistor, maybe 50k. Maybe others will comment on what the best value there is.
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Old 26th February 2003, 06:25 PM   #8
JDeV is offline JDeV  South Africa
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I build 2 GC's already , in both cases they where all + PSU in 1 box. There where no sign of any interferences. I used only shielded wire from Input terminal to POT and from POT to IC. This amp , LM3875, sound very good and I am really impressed by it.
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