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Old 29th June 2010, 06:48 AM   #1451
Nate805 is offline Nate805  United States
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Default my first lm3886 gainclone circa 2008

My first gainclone attempt. Great sounding amp implemented by an amateur audio / electronics enthusiast. 250VA toroid, two lm3886s, and one overly ridiculous star ground haha. I'm in the process of building a new amp, it's been nearly two years since this photo was taken when I built this amp.

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Old 29th June 2010, 04:11 PM   #1452
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I have just finished.
LM3886 Gainclone with PGA2311 stepped attenuator.
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Old 7th July 2010, 03:30 PM   #1453
koogar is offline koogar  United Kingdom
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Hey guys

Heres my 90% finished my Gainclone

its Based on the Audiosector Classic LM3875 kit built as an integated amp 300va 2x25v

The chassis was a scratch build from aluminium with a temp Corian front panel till i get a 10mm aluminium plate CNC machined.

The 48mm Volume knob was souced on Ebay from seller 8audio based in china but delivery was quick .

I wrote a quick and dirty guide below for bending aluminium if anyones interested in making their own chassis

http://bit.ly/d7ayVE

Rupert








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Old 7th July 2010, 03:34 PM   #1454
troystg is offline troystg  United States
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Very nice. Great job of DIY!! And I actually LOVE the Corian faceplate.
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Old 7th July 2010, 04:02 PM   #1455
Previously: Kuei Yang Wang
 
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Folks,

I think this one also qualifies as Gainclone, if only in the loosest possible sense...

Upfront, this will be a commercially available Kit/Finished item from diyhifisupply, however I think it may still give some ideas to some here, so I think it is worth posting up as well...

The whole project is as follows:

Small diyhifisupply project enclosure package fitted with:

192KHz/24 Bit Asyncronous USB DAC
Input Selection/Volume Control
Tube Amplification Stage
Nat Semi Chip based powerstages
Powersupply based around a custom 260VA Torroid Transformer with suitable windings to power the rest

Measured output power is around 45/65W into 8/4Ohm at clipping.

It looks like this (the picture includes the PC that stores the music and the TV that acts as monitor for this PC):

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Not the most inspring casework (for one it's black), but solid and professional looking.

The insides at some point in time during the build, prior to wiring everything up (it now looks a little messier, but not hugely):

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Here another set of piccies showing how it fits together:

diyAudio

All the signal circuitry is build into the Project case extruded Alu shell, the power supply is bolted to the case bottom plate, which closes up the case.

This whole thing was wired with 1mm solid silver in PTFE tubing for speaker connection, 0.5mm solid silver for the grounds and 0.25mm solid silver for the signals, power supplies are wired with coloured stranded copper.

The modules used in turn...

The DAC is basically a heavily modified Musiland Monitor 01 US. It is powered from a the Powersupply module that accompanies the clock module fitted (it has enough spare capacity). Outputs were taken from the positive voltage outputs straight into a pair of 0.22uF Teflon coupling caps.

Next is a Input selector/volume controlmodule based around DS-1666 100KOhm "stepped attenuator on a chip".

The output from that feeds the Universal Tube Stage (here with full 30dB Gain).

This in turn drives a modified "Fusion" Module. The original Fusion Module is intended as "afterburner" for SET Amplifiers (it is essentially a current multiplier). It is based around one of the "usual suspects" Nat Semi chips.

Here the Fusion module is modified to give some gain (around 3 - yes, I know, Nat Semi LM38XX Chips are not stable at gains of less then 10, well they are unless you are me, there are some circuit tricks that overcome this limitation) and the actual "Fusion" circuit is disabled, as the small signal tube stage lacks the necessary power to make this work.

The result is actually a lot better than I expected and a lot better than it should.

Dropped into the office system instead of a standalone Tubes USB DAC implementation of the same Musiland Monitor PCB, the Tram II DHT Linestage and a pair of our Lux 91 Monoblocks without any playtime the results were surprising musical and this little single box solution was by no means outclassed, even though the DHT Line Stage, 300B Amps and so on retained a bit of a lead. But TBH, I could live with this box, if I had to...

I'm going to build another one for my own office as soon as I get the time.

The rest of the story (for background, the PC side of things and other stuff) you can find here:

Fi For Flora

Ciao T

Last edited by ThorstenL; 7th July 2010 at 04:04 PM.
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Old 8th July 2010, 03:51 AM   #1456
Nate805 is offline Nate805  United States
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Default gainclone 2

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My second gainclone, based on some paralell 150w lm3886 boards i found on ebay, this thing rocks! Unlike my last amp, there is absolutely zero noise at the speaker terminals at any volume setting, and the chips stay very cool with the massive heatsink... Overall a great sucess
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Old 8th July 2010, 08:01 AM   #1457
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AWSEOME

Funny enough i am busy with VERY much the same amp:

I designed my own enclosure for the heatsinks i bought. received the enclosure yesterday so busy assembling everything now.

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In the end it is going to be stereo or switeable to bridge mode. Very much the same as the bpa300.
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Old 8th July 2010, 12:11 PM   #1458
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ThorstenL, could you explain how did you managed to make an LM3886 stable with a gain lower than 10?
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Old 8th July 2010, 01:59 PM   #1459
Previously: Kuei Yang Wang
 
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Hi,

Quote:
Originally Posted by regiregi22 View Post
ThorstenL, could you explain how did you managed to make an LM3886 stable with a gain lower than 10?
It is called lag/lead compensation and has been covered before.

Sorry, I will not publish any schematics or values for this, no need to make it too easy for copy-cats. The answers are in Horowitz & Hill.

Ciao T
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Old 8th July 2010, 02:50 PM   #1460
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Quote:
Originally Posted by regiregi22 View Post
ThorstenL, could you explain how did you managed to make an LM3886 stable with a gain lower than 10?
You can get almost any circuit stable with gains below 10, if you know where and how to compensate. Doesn't say that it does sound better/good

With kind regards,
Bas
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