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EHHA Rev A - Interest Thread - Page 111

post #1651 of 1659



your description does confuse me...

Is it 9V for the heater supplies or 12V? 12 V would be way too high for 6.3V heaters... I am using a 7V winding btw.

A regular 12V winding is 12-0, so you just hook it up to the heater supplies... :blink:

Or am I missing something?

post #1652 of 1659

Forget what I wrote - it was just nonsense.

I have a 9-0V winding and two 30-0V windings.


I got the instructions from Rondo Mueller how to connect everything.


Still will need some more time before I can work on...



To cheer up my mind I did something quicker and more easy:

post #1653 of 1659



or Double Helix or the likes?

post #1654 of 1659
DIY of course :-)

Got the single wires from a mogami 2534
post #1655 of 1659

I'm about to start doing preliminary case design. I know the dimensions of the complete boards are 150mm L x110mm W. What are the hole dimensions? My guess is 2.5mm in from the edges?

post #1656 of 1659



the board size is correct, but 2.5mm from the edges wouldn't leave much for the hole itself.

I measured on the print from the Cavalli website, and according to this the CENTER of the

holes is 5mm from the edges with the hole being a bit over 3mm for an M3 bolt.


Hope this helps!

Edited by stixx - 8/22/14 at 12:04am
post #1657 of 1659

Cool that's good to know. 5mm from the edges will help with my layout in Visio.

post #1658 of 1659

Question for the guys who added in the E12 protection circuits...


Looking at the directions on the E12 website, it looks like the EHHA would fit in the 2 channel passive ground camp, but with the special situation of having a split power supply requiring 2 E12s. Am I correct in this assumption? The only hang up I have is that I'm not 100% sure about the EHHA having active or passive ground. So if it's passive then I'd only wire up L+ on one and R+ on the other, right? ...and If it's an active then L+ L- and R+ R-. Would I just tap from the star ground for L- and R-? Hopefully, its clear what I'm asking.


Also, my bias seems to move around rather than stay static. Once warmed up and set I seem to get about ±5mV fluctuations. Is this normal?

post #1659 of 1659



Just a heads up. I don't want to make this a pity party. I recently killed a pair of DT880s while using this amp. I did all the checks - no dc offset, biased both boards, and temp wired everything up. I used KSC75s to test with. Since, I had lovely music (with a tad of really low level buzz in the left channel) I decided to try out my DT880s. I figured I could fix it with a ground loop breaker and/or better tighter wiring. The DT880s had the buzz, but way way less. Anyways, after a long listening session, I had turned off the amp with the pot all the way down. Then I fired it up the next day with phones plugged in and volume turned down. Once I raised the volume I could hear the right driver had way less audio than the left. I tested the phones with different amps, same result. I know another builder had similar issues and killed a few earbuds. He mentioned that he even had the volume down and could measure voltage spikes on power up and power down. I'm glad I'm going to be implementing E12s in this build to protect my other phones. I do realize that others haven't used E12s so it must be something else that caused it -- I'm using a crappy 1/8 jack for my signal output.  D'oh!

Edited by Mullet - 10/15/14 at 7:07pm
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