[arteom]

Yeah I saw that, one of the sexiest builds I've seen. But I don't know if it would be too proper to copy it, wouldn't mind at all doing so if it was, and of-course if he didn't mind .

 

[ujamerstand]

You don't have to copy him. There are many places to buy custom enclosures. Par-metal and hifi2000 cases come to mind. You can buy large heatsinks from conrad heatsinks, or an ebay seller like this one. http://shop.ebay.ca/barrredboss/m.html?_nkw=&_armrs=1&_from=&_ipg=&_trksid=p3686

 

[arteom]

Yeah I was thinking of just ordering all the electronics and worrying about enclosure later, have some spare space to work. I think once I get all the parts it will be much easier to evaluate what case would work. 

 

[jdkJake]

I think building the amp proper, getting it fully functional and then considering casing options is a perfectly valid approach. At least you have a better idea of what you are really working with before you commit too many resources.

As for copying John's design, well, I doubt anyone could truly capture the look and feel John has obtained in his most magnificent implementation. Better to pay homage to his ground breaking work with the EHHA as a speaker amp and put you own unique spin on the final implementation, at least in casing it up.

Now if you order something from the horn shoppe as well, that is another matter altogether.

Then again, while they say imitation is the strongest form of flattery, ultimately, John's opinion on the matter is all that truly counts.

 

[johnwmclean]

Totally flattered, thanks guys!
 
arteom if want to copy by all means please feel free! If you need files for cutting I have them too as well as any help you should need. Goes for anyone interested!
 
Happy to give something back into the community.

 

[arteom]

Thanks John. Like said, it would definitely be a copy of one of the best looking amps out there, be it diy or commercial. I probably should go ahead and get the boards populated and running before I think enclosures. I will definitely keep in contact, I am grateful for the help you and the community here are offering John. God knows I wouldn't even think of going forward with this build without the great community here . 

 

[holland]

after 1.5 years, i'm going to start my build.   i dusted off my kit from GJA, checked my kit contents, and some bits are missing or incorrect (resistors are missing and/or wrong values, and heatsink is 1/4 the size of what's spec'd).  For whatever reason, the board is also not drilled correctly for the heatsinks.  The pins are spaced a bit wider than the pin holes.  Oh well, it must be an early board or something.  The heatsink has a 1 inch spacing on the pins, but the board is a tad smaller. 
 
Sachu, did you have that problem when you built your first ones?  Unfortunately, I measured the pin spacing with my caliper after placing the order for the missing pieces.  Bummer.  I might have to resort to off-board heatsinks, which means I probably can't fit my build in one case.  Another bummer.

 

[ujamerstand]

Which BOM are you comparing to? The EHHA rev.A or the original EHHA? It seem that you have the original version, and you should follow the original BOM as well. The heatsink pads are made for a different heatsink in the original boards, that's why the heatsink would not fit. But yeah, the supplied heatsink is a little small. If you want to build the rev.A version you can get boards from jeff, and if you want, I've got a BOM at mouser that takes the difference between the two versions. 

 

[Lifthanger]

the same thing happened to me this summer. My kit was also the same age as hollands. I didn't check the heatsinks yet, but there's some wrong and missing resistors.

 

[BebopMcJiggy]

The heatsink holes have always been a bit weird with the original ehha board I think, I think it had something to do with the pcb manufacturer or something and you are supposed to remove the pins and just not use them or something (from the heatsink).  Mine definitely have no pins at all on them.  But really, your heatsinks are 5/8" tall?  Maybe it would be different being used for speaker duty or something but my heat sinks really never even get very warm.

 

[holland]

Quote:

Which BOM are you comparing to? The EHHA rev.A or the original EHHA? It seem that you have the original version, and you should follow the original BOM as well. The heatsink pads are made for a different heatsink in the original boards, that's why the heatsink would not fit. But yeah, the supplied heatsink is a little small. If you want to build the rev.A version you can get boards from jeff, and if you want, I've got a BOM at mouser that takes the difference between the two versions. 

I have the original EHHA.  I bought the kit around the same time as Smeggy started this thread.   I'm using the parts list from Cavalli Audio's website.  The heatsink is 1.36" wide x 0.49" thick x 1.5" high.  I don't really want to go to the rev A as I'd prefer the S22 regulation and I already built a homegrown heater supply based around the LT1085 about 1.5 years ago too.
 

 
Quote:

the same thing happened to me this summer. My kit was also the same age as hollands. I didn't check the heatsinks yet, but there's some wrong and missing resistors.

check your heatsinks too.  they might undersized.  I was missing 10K resistors, the 47.5 ohm resistors were 47.5K.  No matter, I needed different resistors for gain anyway, and I needed compensation caps for the gain I intend to use.  I wish there were values for stuff other than 1 and 4.3 though, but I'm building a 3 channel, so 4.3 on the L and R and 1 on the G.  I try to avoid gain on G to avoid floating the G too much.
 
 
Quote:

The heatsink holes have always been a bit weird with the original ehha board I think, I think it had something to do with the pcb manufacturer or something and you are supposed to remove the pins and just not use them or something (from the heatsink).  Mine definitely have no pins at all on them.  But really, your heatsinks are 5/8" tall?  Maybe it would be different being used for speaker duty or something but my heat sinks really never even get very warm.

1.36" wide x 0.49" thick x 1.5" high.  I do have some of the right heatsinks on hand from other projects (only have 2), but they are quite petite in comparison to what is spec'd.  I think I use heatsinks this size for some small regulators.  No worries totally, as I'll just use them for something else.  Really, remove the pins?  I guess, I've never been good at that.
 
I intend to bias at 160mA instead of 100mA.  From what I understand even at 100mA your heatsinks should get quite toasty, somewhere between 50C and 70C.

 

[BebopMcJiggy]

Quote:

Yes, it would be possible to replace those fixed resistors with pots.

R22, R23 will be very tricky as mismatched pot settings will imbalance the complementary halves of the O/P stage.

Correct on the comp caps. You don't even really need them below 7.8. They were just needed to prevent the sq wave from ringing. You can see how much the slew rate drops with the big comp caps and I think you might notice this on very fast transients even though your ears can't possibly follow the audio at these speeds.

BTW, I know that the heatsink holes are a bit off. This is not Jeff's fault but mine because I suggested a particular supplier. This was for necessary reasons at the time to prevent the EHHA from going the way of the SOHA. No more to be said on this.

However, since none of you are likely to solder the heatsinks into the board, the easiest thing to do is to pull the mounting pins out of the heatsinks rather than trying to drill out the holes.

Was searching for this to make sure I was not giving you bad advice.  I don't think my heatsinks are any higher than 2" at the most and they barely get warm.

 

[holland]

Thanks Bebop.  My heatsinks are also 1/2 as thick at 1/2" instead of 1".  No worries though, I have the correct ones on the way from Digikey and Mouser.  I may still go offboard, not sure though, as I'll be going 160mA for bias, more if the heat is in check.  I need to do some calculations first.  Thanks again, very helpful post dig....this thread is a bit large to read through entirely.

 

[Lifthanger]

ok I checked it and the sinks are too small too. I'll solve this when I find some time next year. good luck with your build .

 

[gurubhai]

I am having some trouble with one channel of my BJT EHHA.
 
The output resistors gave smoke so I replaced them. I checked the voltage against new output resistors at startup &  it was 7 volts.I also replaced the BJTs but still the same issue.
Can anyone help ?