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EHHA Rev A - Interest Thread - Page 2

post #16 of 1657

I'm in for a board.

post #17 of 1657

hmm after more thought; I think perhaps the original boards are more suitable for me; I already have an abundance of high quality regulated supplies (including a spare sigma22) and I like the option for using it for bookshelves at some point. i'll keep an eye on this thread for more details and thanks for offering this, but i'm not sure it would be wise and would actually in my case cost me more in money and time, as the supply already exists (just need to change the output voltage)

post #18 of 1657

I prefer to keep the on board power supply section. This should save me precious space in the chassis. However, if there is an option for us to bypass the onboard PS, it would allow us to make comparisons between the on board supply and other power supplies. (I've also got a sigma22 lying around)

post #19 of 1657

Perhaps the board could have could have the Amp and Power supply sections separated, and joined with jumpers if the local PS was used, and it would be a convenient connection point for an external power supply.  It would also be useful for anyone interested in experimenting with something like the JLH ripple eaters. 

That way a single board could be provided, going forward. 


Will the new rev board use the 6GM8 exclusively (no more 6922/6DJ8) ?  


Is there a reduction in sound quality in any way on the current EHHA with the 6922/6DJ8?



post #20 of 1657

I'd be interested in a board.

post #21 of 1657
Thread Starter 

Gents, here's one possibility. It's a single board that includes the on-board PS. However, it has a cut line that can be scored by the fab. You'll be able to snap off the PS section and connect your external rails to the interior terminal block which will now be close to the edge of the board.


There are two sets of mounting holes in the back so that when you cut off the back section you'll still have mounting holes.


You can see the cut line right above the green via in the center back of the board.


Do this suit everyone's needs?


EHHA Rev A Split Board.pdf

Edited by runeight - 8/13/10 at 6:15pm
post #22 of 1657

Works for me. 


Personally, I like having the option of the onboard power supply. Even a simple trace cut would have sufficed. This is just icing on that cake.


What is the size of the proposed board? Looks to be nice and manageable for lot's of casing options.

post #23 of 1657


Could we substitute the bipolar power supply with a lt1084 or lm338 based dual supply for higher current output? Or would a dual supply be unsuitable for the EHHA? 




What is the size of the proposed board? Looks to be nice and manageable for lot's of casing options.


I measured it, its about 11cm x 13cm, small enough to fit 4 in a 12 x 12 case without the transformer.

Edited by ujamerstand - 8/13/10 at 7:48pm
post #24 of 1657
Thread Starter 

Yes. The standard headphone amp would use LM317/337, but you could sub the 5A LM138/338 directly without any other changes.


It might be possible for me to give you mulitple filter cap sizes so you can increase the filter caps for high current use. The standard headphone amp size is 2200u. For speaker duty, bigger caps would be helpful but not absolutely necessary.


The board is 110mm x 130mm with PS and 110mm x 85mm with the PS section snapped off.


post #25 of 1657
Thread Starter 

No. Not a direct sub because the pinouts are different on the negative regulators. As best I can tell.

post #26 of 1657
Thread Starter 

Even more no. Responding without thinking.


Is there a 5A negative adjustable regulator?

Edited by runeight - 8/13/10 at 8:35pm
post #27 of 1657

None that I know of, but I could be wrong. I was hoping a dual supply supply would work?

post #28 of 1657

Looks like another great project.


I'll commit for 4 boards if this gets a board run made. I can't commit to getting it built in a hurry though, if that's an issue. Probably build next spring for me, as I already have an operating EHHA and several unbuilt projects I'm looking forward to.


Nothing has changed on the output buffers from the original? FET or BJT output options still work, yes? I have FETs on my EHHA and would like to hear what the BJT would sound like if I built another variant. 


A comment about the board layout. On any amp project that dissipates much heat/power, I have a personal preference for a board layout that puts the output devices on one end of the board to facilitate offboard heatsink options. It allows for a shallower case height, better heat management and looks "cooler" to have external case fins. I really like how the original EHHA board was set up this way. I know tradeoffs have to be made for other reasons though.

Edited by bada bing - 8/13/10 at 10:54pm
post #29 of 1657

nah a dual wont work without some sort of modification.


well this just became more interesting again, put me down as interested and yes several size patterns for caps is a great idea, if possible with some small amount of space for critical ones, so film caps can be used (non-essential, but would be cool) if possible, can you add intermittent (not plated through) holes for the in between pins so 2.5mm molex or similar can be used with 5mm grid? twisted pear does this and it works well. of course the middle pins can just be removed, but makes it easier having the holes there.

post #30 of 1657


I did some checks and found that a four board configuration would have a larger footprint than a balanced original EHHA + s22 setup. So molex pins on the boards would be nice; we could snap off the ps on two boards and power them with the other two boards. 



Originally Posted by qusp View Post

nah a dual wont work without some sort of modification.

That's true.... Edit: Actually I'm not so sure about this, dbel mentioned a dual supply as a possible PS for the EHHA at the old headwize thread... From my understanding it should work, but I'm wrong a lot of the time... Anyways, I would like to take 4 boards as well. :)

Edited by ujamerstand - 8/14/10 at 1:44am
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