EHHA Rev A - Interest Thread
Jun 12, 2016 at 11:41 AM Post #1,726 of 1,752

bluemonkeyflyer

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By "engage" I mean it switches off the outputs.
 
 
I don't quite understand your question?
 
Amp out is not connected to star ground.
 
Amp ground (next to Amp out) is directly connected to the jack from both boards.
 
 
Star ground is connected to the ground tap of the power inlet (called "IEC" in my last post).
 
 
 
yes, see the picture for the wiring, it works now.
 
 
 
 
Hope I could clarify things a bit.

Sorry, I didn't mean the Amp Out terminal. I meant the ground terminal from the Amp Out Terminal Block.  Yes, I see the picture. What is the purpose of this extra ground connection?
 
I have the Amp Out ground terminals from both amps to Star Ground.
 
Jun 12, 2016 at 12:03 PM Post #1,727 of 1,752

Sathimas

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What is the purpose of this extra ground connection?
 
 I have the Amp Out ground terminals from both amps to Star Ground.

 
There is no extra ground connection, since the jack is not tied to Star ground,
but to the amp out ground terminals directly.
 
Tried this while solving my hum problems.
 
I could try the old sheme now ...
 
Jun 12, 2016 at 12:11 PM Post #1,728 of 1,752

bluemonkeyflyer

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OK. It may not matter, but weird ground eddies may be at play. Cavalli's Alternate Wiring Diagram shows the amp Out ground terminals are not connected. Instead, the amp In star ground terminals are connected to the star ground. It's worth a shot in the dark.
 
BTW, I edited my earlier post to clarify a few comments.
 
Good luck!
 
Jun 12, 2016 at 12:14 PM Post #1,729 of 1,752

bluemonkeyflyer

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There is no extra ground connection, since the jack is not tied to Star ground,
but to the amp out ground terminals directly.
 
Tried this while solving my hum problems.
 
I could try the old sheme now ...

OK. By "extra ground connection," I meant extra as one not shown on Cavalli's wiring diagram. No offense intended.
 
Maybe I should try your scheme to see if it helps my hum issue.
 
Jun 28, 2016 at 6:24 PM Post #1,731 of 1,752

Sathimas

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Well, this amp is driving me absolutely mad.
 
I changed the resistor-values according to ambs website to decrease the sensivity of the e12.
 
While doing that, I changed nothing about the internal wiring of the amp.
(It was hum-free before)
 
Now after getting the e12 (half) to work (still a bit jumpy) the hum is back.
 
Changed the ground wiring to cavallis alternative wiring then with no
effect - changed to normal ground scheme and the hum was gone.
 
For some reason, the e12 cut off the outputs then and when sound came back,
the hum was there too again - without changing anything in the wiring.
 
 
I just don't get it, this is ridiculous...
 
Jun 28, 2016 at 6:38 PM Post #1,732 of 1,752

Sathimas

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Adding my newest observation:
 
Had the phones connected directly at turning on the amp,
had no hum when the e12 let the signal pass.
 
Got hum, starting quiet and becoming louder after a few seconds,
the hum started to "oscillate" getting loud and quiet at maybe 1 
volumen-change per second - then the e12 started to switch on and off.
 
 
Any idea where the problem might be?
 
Jul 22, 2016 at 10:41 AM Post #1,733 of 1,752

Klechty

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As I see many people complaining about the hum, I will give you one tip.
Thus him is usually done by a bad tube implementation, so is the ehha.
Cut the capacitor ground, pin 9 of the tube. And directly connect it to the general ground.
 
Dec 13, 2017 at 4:05 PM Post #1,735 of 1,752

bluemonkeyflyer

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Hi there - I need the EHHA Rev A schematic for the troubleshooting of my and and can not find it anywhere - can someone give me a link (via p.m. if nessesary)

PM your email and I'll send you the schematics.
 
Jan 12, 2018 at 3:31 AM Post #1,736 of 1,752

Sathimas

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Hi there,

I'm back trying to bring my EHHA to life - hope there's still some people active here.

I'm still at the point I was about 18months ago (just had him sitting under the table...):

I'm not able to set up the AMB e12 properly.
When I try to get the voltage between the amps grund and VG to zero
this just won't work - the voltage drifts from about 200mV to -200mV.

I discussed that the AMB himself in over at the AMB-website and he says the
e12 is working properly (https://www.amb.org/forum/adjustment-problems-strange-behavior-t3250.html)

Does anybody have a hint for me where to start looking for the mistake?
 
Mar 22, 2018 at 11:21 PM Post #1,737 of 1,752

Mullet

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@Sathimas I've had strangeness with my E12s constantly drifting before. I deduced it to the connections on my phoenix type connectors. They were a little janky and needed to be readjusted. Not sure how you have yours setup. Did you ever solve your hum issues?

With regard to hum... oh boy! I've had very similar issues. Hum would be low in volume at some points, then at others be quite loud. The loudness also changed with the type of headphones. Thus far I've removed my E12s to see if that would do the trick. I also changed up how I'm doing the star ground. I basically tied the ground from the power supply to the amp board. Then don't run the ground from the heater supply board, but double up on ground from the gnd heater position at the amp board to star. This eliminates a few wires, but hum didn't subside. My next move is to use shielded cabling everywhere, but I'm skeptical that that'd work. Other than that the last ditch effort would be to change out the transformers. I'm using the Avel Lindberg trafos. I'm thinking they might be the cause. I'd be curious to see whether people using the SUMR transformer have experienced the same issue...

Any ideas would be helpful... I can take some pics to illustrate my setup if need be.
 
Mar 23, 2018 at 5:58 AM Post #1,738 of 1,752

muskyhuntr

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I used a SUMR transformer in my build. Spec'd shielded, potted and encapsulated. My build was quite.
I did not follow recommended grounding configurations. Check some of my prior posts to see what I did.
Sold the amp a few years back to fund other projects, so I cant pop the lid.

Me
 
Mar 23, 2018 at 7:41 AM Post #1,739 of 1,752

Sathimas

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The hum issue was not solved yet - I just can't find the time (and motiviation...)
to take the EHHA back to the workbench and tear things apart again.

I use custom wound transformes with shield, yet the shield is not used atm.

I'm grateful for any hint or whatever help you can give.


Maybe it's time to attack again :)
 
Mar 23, 2018 at 2:25 PM Post #1,740 of 1,752

stixx

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I remember very well your continuous fight to tackle the hum issues..

Same as muskyhuntr I sold my EHHA a few years back while it was still on the breadboard...
it was absolutely quiet then with a "standard" star ground.
--> everything goes to one point connected to chassis, but there can be sub-stars that
then connect to the last one that goes to the chassis. It is best to have your star ground
near the big capacitors of the psu. The ground of the E12s ties into the star theme as well.

I have had minor hum or buzz issues with my solid state amps but was able to get rid of them.
The reason was either an unshielded toroid (changed to a shieded one [Dynahi]) or improper
wire routing. With the amp on just moving wires around can give an indication... I used a small
sheet of copper on one of my other amps where signal was too close to mains wiring.

Still it sounds that you might have different issues... Since the E12s is causing you trouble I
would ditch it... better unconnect your 'phones each time before you switch on or off. Don't
remember whether the EHHA has start up spikes in voltage, but better be safe than sorry.

Then I would roll tubes (I still have some if you need them :) ) and do the wiggeling or
better moving. Just pressing wires down to the aluminum bottom made a difference in my
(successful) attempts. Hope it is not the proximity of things in your (beautiful) case.
 
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