My new gainclone page

[fedde]

I made a page about my gainclone. If you are interested, please have a look at:
http://home.student.utwente.nl/f.s.b.../thor-amp.html

Fedde

[Peter Daniel]

Good info. After reading your page I have no choice, but to build one myself.

From a review by Herb Reichert (Listener): " The 25-watt Gaincard amplifier will outplay the Krells and Levinsons, it will reveal more of the poetry and structure of musical art than any silicon-based amplifier I have experienced, and it has plenty of cool factor. It seems able to drive a wide range of loudspeakers, and at $2750 complete (with one Power Humpty) this must be considered an excellent value. "

If this is true, maybe I should put more effort towards that little LM chip and not the Alephs?

[pinkmouse]

Nice site Fedde

Have you tried the Evox Rifa 5% MMKs yet? They work really well for the .1uf cap, almost as good as no cap at all!

My inverted gainclones are still in iteration, I am playing with components, and have found I can actually get shorter connections in some places by using a pcb, but this all may change...

Peter, I am not sure where the expensive prices charged for the Lab47 product comes from, but even in testing, the LM3875 is very special indeed, and for a very small outlay it's got to be worth a try. I belive the Gaincard itself uses a non inverting circuit, and even before optimising, the inverted configuration from Thorsten is just so much better.

If I can build these, then everyone else should have no problems at all, so give it a go!

[Ken L]

You guys are making me wish my renovations were over

Going kinda nuts - can't do, get to, or find anything.

that 47 clone is tempting I must admit.

Later

Ken

[Peter Daniel]

Reading through previous threads I remember that Dave (planet10) mentioned that LM chip works better with lower rails (18-0-18 transformer). Why would it be?

[fedde]

I do not know how the Thor-amp compares to the 47 labs gaincard. I will try that later this year...
Also, I do not know how it compares to the more expensive ss designs on this planet. At least, I think you could say that when you build such an amp yourself you have a very good quality/price ratio.

Pinkmouse: thanks for the capacitor tip. Probably, it will be hard to get them here in the Netherlands. I will try to find them.

I do not really have problems with the 47 labs pricing strategy. I think that if they are as good as some reviews say, they are worth the money. I mean, you also pay $150 for Windows, and that's even a somewhat crappy product IMHO (but it's getting better). And you get a cd, that's not very expensive is it ?. Most of the costs come from the development. Please don't start a thread about Windows, it was just an example
:-)

A more interesting topic would be to discuss what the exact advantages are of a low capacitance supply. Still beats me, more or less...

Fedde

[fedde]

Was that with the LM3875? When you have speakers with an impedance under 8 ohm, lower supplies probably work better. It's a pity that transformers are a little too expensive to experiment with. I would also like to try 225 VA toroids or more. I think that the gaincard also has a lower supply. Maybe I will try once...

Fedde

[Peter Daniel]

You could use Variac to lower the voltage and experiment.

[wchick]

Fedde,

Very interesting. Thanks for sharing. I once built an OP amp using LM675, and found it sound quite good but I didn't take extreme measure to shorten the signal path like you did. I will try to build one of these Gainclone when i have time.


Wallace

[planet10]

fedde,

Good work...

Originally posted by Peter Daniel
Reading through previous threads I remember that Dave (planet10) mentioned that LM chip works better with lower rails (18-0-18 transformer). Why would it be?

If you look at the power vrs rail voltage vrs load impedance you will notice that above 25V rails the 4 ohm output goes flat. The statement is based on my belief that all speaker loads are ugly when compared to a resistor and that the ability to deliver current into those loads is important. Now i actually haven't built mine yet so that is theoretical (and based on feedback from some others).

As to the cost of these things, if you are a good scavenger they can be built for well into Frugal-phile(tm) territory. I got free 1875 & 3875 samples from Nat Semi. Toroids are kind of hard to find salvage (ApexJr has surplus 120 VA 18-0-18 toroids fairly cheap) so that will be your biggest cost. Once when i was flush i ordered 10 surplus 225 VA 18-0-18 Plitrons. They shipped 18 so the end cost was very low. Heat sinks can be salvaged from dead computer monitors (you'll have to live with aluminum) and cases too can be salvaged or made cheaply. A trip to value village may even find you a matched pr of aluminum cooking pots or pans that could be used as case & heatsink! Then a handful of passive parts & some bridges. I suspect that $40-$80 USD is very doable.

And if 25 W isn't enuff, just bi-amp Or build more efficient speakers.

dave