just redisgning the boards not the circuit
I been using Expresspcb.
It has limitations and is a little quirky.
Being of meager funds, being free helps.
Most of what I have, I put back together after someone has all but trashed it.
I bought the first SCS as a basket case.
Found out the hard way about how obscure the Hitachi's are.
After putting it back together(which included new boards)I can't help myself.
I like Hitachi lateral based amps.
Personally I think the SCS original board layout sucks.
Unequal, thin, all over the board traces. The boards fiberglass seems to have very little epoxy, which adds to the lifting problem.
I had the first boards made, but I'm making changes often and I can't afford to do that again.
When I redesigned the early boards I was using a circle ground. It doesn't seem to bother the sound quality. But much easier to work with.
I did not make any changes to the circuit design other than adding better protection(picos) and an offset pot. There is no protection circuitry.
I have tried the toner transfer, ink jet embossing powder hybrid and transfer paper.
The method I'm using know is going to sound nuts.
I'm limited down to .75mm width, .5mm spacing traces but for driver boards that works for me.
My mother (she is 73) had a Cricut paper/vinyl cutter. I used it for about a week to cut out some paper foil patterns.Then I bought a used one cheaply knowing I could damage it doing what I'm doing.
I design a foil pattern in Expresspcb, capture the printout in a print to file program. Further edit it in an old version of Corel photopaint 7. To increase the resolution. Use a raster to vector tracer. Then paste into a cutting program. I found the best results by taking a piece of vinyl contact paper, sticking it directly to a blank board, cut out the pattern, peel of the excess, then etch.
With the other methods I had problems with pits and undercutting on anything thicker than 1oz. I would most likely use those in more detailed patterns with lighter foil.
With the cut vinyl method I'm almost comfortable to try 4oz.
I also have a 2600a that I bought working but the offset is too high for me.
That one has been repaired a number of times and the boards show it.
Both amps were used hard in commercial environments.
I intend on keeping both of them. Then maybe will them to my daughter.
So I feel making better boards that if components fails won't take out the Hitachi's is in order.
When I'm finished I'll have boards that can be used in both. And have extras on hand for quick swaps.
Oh yeah, they could also be drop ins for the Hafler's with balanced inputs.
Please take a look at the schematic and specs.
I think the sound quality and power is under rated.