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PostPosted: 02 Oct 2011, 18:09 
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Hi.

I've almost finished my build of 2 of these also now. All being well tonight it will be enclosed in its little case. I liked the clear case so grabbed one from Jaycar as well :)

I've mounted the RCAs and speaker terminals to the back of the box, need to shorten the shaft on the pot and wire them all up.

Does anyone know if one PSU would be sufficient to power both of these cct boards (as its 24vdc 1a) or are two absolutely required?

I did power these up on my bench to confirm they worked AOK thru the Wharfedale Diamond 7's - very different sound thats for sure. Looking forward to a test through the Diamond 6's - can't believe how 'microphonic' the 6418's are!


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PostPosted: 02 Oct 2011, 18:48 
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I used two PSs. One is enough.

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Projects: "Lagoon" - tube preamp with cathode follower | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "retro-Hiraga" - Jean Hiraga Le Monster
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PostPosted: 02 Oct 2011, 22:19 
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thanks mark. will give one a shot and see how we go. the LM1875 is hardly being driven, 1.25v at the valve heater with 12v up at the top, i think 1A should more than suffice.

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PostPosted: 03 Oct 2011, 06:10 
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well i ran it up with 1 PSU only. is darn loud. works very well - VERY well. very different sound.
i do find when u do turn it up, the LEDs inside go dimm and flicker and the sound cuts out. this tells me that it needs the other power pack - so one doesn't appear to be enough. i will test and advise.
through my wharfedale diamond 7s - bass is good - strong - rich. plenty of mid / voice - the top end is there but a bit light on for me - i like very bright high ends though.
i do want a better listening session with a better variety of music and both PSU's running before a final verdict - however still - very impressed.
still can't get over how darn loud this thing is.

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PostPosted: 03 Oct 2011, 06:27 
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I should have specified that one PS is enough to run the amp at reasonable listening levels. BUT you may find even with two supplies the clipping etc. may not change at high volume levels. It will be more the chip is running out of puff or it cannot dissipate heat quickly enough. But prove me wrong.

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PostPosted: 03 Oct 2011, 15:08 
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i only get to about 1/4 on the dial mark - and its darn loud - more than enough to fill my study with sound. i am still utterly amazed (one that it works :D and two that it works so well.
(i've never ever done anything like this before - even my wife thinks i've gone nuts)

pic of the finished product attached :)


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PostPosted: 03 Oct 2011, 18:45 
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Graga: Dawn good work mate. The amp is a little beauty and I enjoyed mine before a friend bought it. Your install looks good. I have the kit for the 20W version. I must assemble it. I have no amp for my PC so there is an opening for it.

Keep us informed of your journey.

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Projects: "Lagoon" - tube preamp with cathode follower | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "retro-Hiraga" - Jean Hiraga Le Monster
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PostPosted: 03 Oct 2011, 19:15 
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thanks mark.
blimey 20w must be crazy! actually thats the one with the fan and the other bits and pieces - now that i think about it.
the wattage of the amp can be 'increased' by changing a couple of resistors which increases the amplification factor - however you will then have cooling issues for the LM whereby keeping it cool becomes a challenge - a larger heatsink might assist here in a setup similar to the multiple LM3886 setups where theres a ally / copper bar running across the LM binding it to an alloy case/heatsink.

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PostPosted: 04 Oct 2011, 04:49 
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mark. confirmed. both power supplies needed. with the additional power supply, the volume goes way up but then ; so does distortion. my 6 ohm diamond 7's might be giving it grief - i don't know - i suspect they are not very efficient - but still sound very nice
however - at a good listening level, to say i am blown away (not by the volume) but by the definition in my music, would be the understatement of my 38 years on this rock. i took my same listening cd out to the car (ok not the most acousticly perfect place to listen in) but just as a litmus test, and am still wondering where the rest of my music has 'gone'

strongly recommend to anyone who wants to experience audio in a way they never have before, to shell out and give pair of these a go.

a question if i may - what makes this sound so different? the valve pre-amp stage (gee the 6418s are sensitive) or the little LM3875? any thoughts?

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PostPosted: 04 Oct 2011, 07:51 
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Chip amps are very clinical and very detailed. These are both good things. I have made a number of chip amps over the years and they can sound extremely good. With the Oatley you just get a little bit of tube warmth as well.

Enjoy. If you like this then try an genuine Gain Clone to the original Gain Clone formular. Take a look at my Synergy (its not Gain Clone but a hell of a good chip amp). Talk to me if you wnat to go the Gain Clone way.

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Projects: "Lagoon" - tube preamp with cathode follower | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "retro-Hiraga" - Jean Hiraga Le Monster
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