[bluemonkeyflyer]

Finished my build, fixed some grounding issue but still getting hum when the volume is above 50%. Any ideas on how to deal with it?

 
Looks real good, FA.
 
Here's what I did based on guidance from experienced builders:
 
For the hum, you could try shielded cables from RCAs to the pot and tie the shield to the RCA ground terminals, not at the pot.
 
Maybe moving the pot to the TRS jack position and moving the TRS jack to the pot position would help by shortening the distance from RCAs to the pot.
 
I had spaghetti wires all over the place so I cleaned up the mess with the shortest wiring configuration possible with tightly twisted all hookup wires, laid them out at 90 degrees where they crossed, moved the transformers and boards as far away from each other as possible, and made my star grounds like Stixx described.
 
I still have it mounted on 14" x 19" plywood and it's dead quiet until the volume pot is turned up to 80%. From what I've read, here, installing inside a metal enclosure may further improve the "blackness."
 
The bit in the middle is a ground loop breaker.
 
The sound quality is great! I'm looking forward to 3 more amp builds....
 
....Now, be gentle. This is my first build so don't laugh too much:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 

 

[stixx]

No reason for laughing... you did everything right!
Now just put it in  case big enough.

 

[FallenAngel]

Thanks for the help guys!
 
It seems simply connecting the 6.3V supply eliminates the noise completely.
 
I did manage to make the ground slightly cleaner, but really not by much.
 
It works great now but there's one major thing that I'm sure you could all comment on: What's with the nasty turn-on noise? It feels like the first 5 seconds are buzz and a nasty click before it goes dead quiet. What could I do about this? How have you dealt with this?
 
Thanks again.

 

[bluemonkeyflyer]

  Thanks for the help guys!
 
It seems simply connecting the 6.3V supply eliminates the noise completely.
 
I did manage to make the ground slightly cleaner, but really not by much.
 
It works great now but there's one major thing that I'm sure you could all comment on: What's with the nasty turn-on noise? It feels like the first 5 seconds are buzz and a nasty click before it goes dead quiet. What could I do about this? How have you dealt with this?
 
Thanks again.

 
Get amb.org epsilon 12.
 
Otherwise, don't turn on the amp with headphones plugged in and don't turn off with headphones plugged in or you risk zapping 30k mV into your headphones. I fried a set of Koss PortaPro when I forgot to unplug them before powering on.
 
The epsilon 12 will protect your headphones in the event of a surge or power failure.
 
I'm interested how you laid out your star ground.

 

[FallenAngel]

Having already burned two pairs of headphones in this amp, I think a muting circuit is a must.

 

[FallenAngel]

I actually have an old e12 v1.1 board, so I'll probably stick that in.

 

[Chs177]

I actually have an old e12 v1.1 board, so I'll probably stick that in.

There are kits on ebay and ali based on upc1237.
http://rockgrotto.proboards.com/thread/8187/headphone-protector

 

[FallenAngel]

There are kits on ebay and ali based on upc1237.
http://rockgrotto.proboards.com/thread/8187/headphone-protector

sold out

 

[Chs177]

sold out

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.Xupc1237+headphone.TRS0&_nkw=upc1237+headphone&_sacat=0
Or just search ebay with keywords: upc1237 headphone. You will find several kits.

 

[Klechty]

Here's another revisited EHHA .
6h28b mini tube to reduce the high.
Replace the japs trans by BC639/BC640.
Replace the current constant tube diode (j511) by a more accurent one (lm334z).
Added a dc protection based on the E12.
Change the output current.
And more ....
 

 

 

 

 

[FallenAngel]

  Here's another revisited EHHA .
6h28b mini tube to reduce the high.
Replace the japs trans by BC639/BC640.
Replace the current constant tube diode (j511) by a more accurent one (lm334z).
Added a dc protection based on the E12.
Change the output current.
And more ....
 

 

 

 

 
VERY cool!

 

[Klechty]

thanks.
i'm working on another one with some others improvements.

 

[Sathimas]

Back with new problems ...
 
My post some months ago was (maybe) too enthusiastic.
 
Since the Ehha is said to be producing voltage spikes capable of frying headphones
I installed an AMB e12 which is now troubling me.
 
I can turn on the amp, go through the adjustment of the e12 and listen to some
music then for several minutes, then the e12 engages and stays "shut".
 
Offset on the EHHA channels (G and OUT) is drifting a bit but never higher
than 4 to 5mV, mostly it stays at 0.
 
Starground to IEC is connected via the groundloopbreaker I installed last year.
I have no audible hum as long as the e12 lets the signal pass.
 
I can not re-adjust the e12 on the "warm" amp since the voltage between VG
and G of the amp is about 160mV then and drifts around a lot. Impossible
to get it back to zero.
 
Here's the wiring used at the moment:

 
 
Any idea? 

 

[bluemonkeyflyer]

  Back with new problems ...
 
My post some months ago was (maybe) too enthusiastic.
 
Since the Ehha is said to be producing voltage spikes capable of frying headphones
I installed an AMB e12 which is now troubling me.
 
I can turn on the amp, go through the adjustment of the e12 and listen to some
music then for several minutes, then the e12 engages and stays "shut".
 
Offset on the EHHA channels (G and OUT) is drifting a bit but never higher
than 4 to 5mV, mostly it stays at 0.
 
Starground to IEC is connected via the groundloopbreaker I installed last year.
I have no audible hum as long as the e12 lets the signal pass.
 
I can not re-adjust the e12 on the "warm" amp since the voltage between VG
and G of the amp is about 160mV then and drifts around a lot. Impossible
to get it back to zero.
 
Here's the wiring used at the moment:
 

 
 
Any idea? 

 
I have Epsilon 12 powered off the +30 and -30 rails. It doesn't engage until the amps heat up and stabilize.
I'm using the standard wiring diagram, not the alternate one....it made no difference in hum at higher volume pot settings. A ground loop breaker helped a bit.
 
What is the purpose of the star ground connection from the amp output terminal?
Do you have the star ground from the amp input terminals connected to the star ground?
 
BTW, I had a problem with two Epsilon 12's (each tried separately, not together) in my EHHA Rev A. There were two problems:
1. 2N7000 was not soldered on top of the board...the solder did not flow up from the other side so I added some solder on the top joints.
2. This did not solve the problem. I re-biased EHHA Rev A and both Epsilon 12's work.

 

[Sathimas]

Updated the picture of the wiring, didn't seem to work properly.
 
Quote:

 It doesn't engage until the amps heat up and stabilize.

 
By "engage" I mean it switches off the outputs.
 

 What is the purpose of the star ground connection from the amp output terminal?

 
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).
 
 

 Do you have the star ground from the amp input terminals connected to the star ground?

 
yes, see the picture for the wiring, it works now.
 
 
 
 
Hope I could clarify things a bit.