[jdkJake]

Well, if you smoked it, you will certainly need to replace Q1. Good place to start.

I would also check the output of the 78L15/ 79L15 regulators and make sure they are still putting out +15/-15 respectively.

Are the MOSFETs biasing?

 

[BloodInside]

Thanks for your response.
 
The 79L15 regulator is putting out -2.9 volts and the 78L15 regulator is putting out 20.67 volts. I measured those voltages on the opamp pins 4 (for the 79L15) and 7 (for the 78L15) to the ground.
 
So they are probably toasted as well? Judging from the maximum rating of +/- 18V on the opamp, that one is probably smoked as well.
 
The testpoints on the BJT's measure -0.005 volts (TP2) and 0.000 volts (TP1). Turning the BIAS pot doesn't make any difference, so I assume the bias mechanism is broken as well. 
 
I'm also measuring around 5.332 volts DC output now. Quite a difference from yesterday when I just blew them.
 
So far I should at least replace Q1, V+, V- and the TL081. Any more suggestions before I place my order?

 

[runeight]

Order all the sand in the output section, both O/P devices, the two Vbe devices, and the follower drivers, some opamps, and more than one of each regulator.
 
Given that power was reversed everywhere many of the other transistors might be toasted too. Since they are so cheap I would order replacements for all of them just in case. And maybe even another CRD.

 

[BloodInside]

Thank you for your support. I've just placed the order, probably will get all the components within two weeks. 
 
At least now I know what price you pay when you hurry things... A good lesson for next time.

 

[BK_856er]

Quote:

Quote:

Should I connect the Belden drain wire somewhere to optimize shielding?
 
Similarly, should the mesh shielding of the navships coaxial output wiring be connected anywhere?

 
 
It's safe/fine to connect all the shields to star ground.  I connect the input shield to the input ground (which is tied to star ground later).  Do not connect the other end of the shield to input ground.  Connect it only at one end at the jack (or a wire to star ground).  After it goes to the pot, the wire from the pot goes to the amp board...the shield on that wire, tie it to the shield on the input wire, as if you broke the shield at the pot.
 
Output wiring, connect the shield to star ground, but only at the point of exit from the amp.  As with input, leave the end floating.
 

Thanks for the details!  I followed the concept of connecting only one end of the input/output shielding to star ground, while leaving the opposite end floating.  I hope it won't be an issue, but I made the RCA jack and the board the floating ends for the input and output wiring, respectively.  Below you can see the bare drain wire going to star ground and also the connected shielding at the pot.
 
Wish me luck....first powerup with final case and wiring tomorrow when my brain is fresh!
 
BK
 
 

 

[BK_856er]

Mission accomplished.  Sounds wonderful!  Very detailed, engaging, nice bass impact.  Critical listening to come later.
 
Just a few minor things to sort out:
 
- mixed up the RCA jack colors
- bulgin dual-color switch driven by an e24 glows red and not blue
- need to figure out a method to mount the e24 overtemp sensor
- slight buzz (none at min volume positions, but is constant throught rest of travel, decreases when touching the casework)
- will verify bias after things run in for a few hours - case is staying nice and cool
 
The new v2.0 e12s seem to work great.  Mutes the output for 30sec on startup.
 
With sensitive test headphones only ~10% pot travel is used.
 
I really underestimated what it would take to go from powered mockup in a cardboard box to the final product.  Lots of late nights doing up all the wiring and casework.  Very satisfying in the end.
 
BK
 

 

 

[sachu]

nice work
 
when you get some hadtime on it..curious to some comparisons against the V200

 

[BK_856er]

 
Quote:

 
Quote:

 
Those look nice BK. The new versions look to be far simpler and certainly less expensive to build. I am really glad to see Ti fixed the mounting hole locations. They should be far easier to work with as well.Do you still need to heatsink the transistors? Or is that now optional?

My understanding is that the transistor heatsinks are no longer required, but that conclusion is only based on the fact that Ti does not mention them on his v2 pages.  I should probably get confirmation on that detail.
 
In addition to the changes in the circuit, there is a hefty ground layer covering most of both sides.  Definitely took more heat to solder!
 
BK
 

Just to follow up this detail...I checked with Ti just now and he says at +/-30V the TO-92 slip-on heatsinks are a good idea for Q1 and Q2 on the latest v2.0 e12.  I had some on hand and installed them.
 
BK
 

 

[BK_856er]

I have now resolved all the small outstanding issues with my build, so I'm declaring victory on this one.
 
The buzz with certain sources connected turned out to be far more problematic than I first thought (after the initial euphoria of a working amp wore off).  Huge thanks to my mentor jdkJake for patiently walking me through all the trouble-shooting steps via numerous pm and ultimatley suggesting a ground loop breaker.  The ground loop breaker totally solved my buzz issue.  Should this be standard?
 
Now to get down to business and really get to know this most excellent amp. 

 
BK
 

 

[dBel84]

I routinely do not install one in my builds, but it is the very first thing I do if there is buzz because it is a much more accessible fix than most others when it comes to tackling hum. My EHHA ended up with one, my SOHA II did not etc ..dB

 

[holland]

I always install a ground loop breaker as part of my ground bus, using a diode bridge, a cap, and a resistor.  It's harder, sometimes, to fix it after the fact.  You'll see it when I post up my EHHA I pictures soon...almost done with the casework.

 

[BK_856er]

Quote:

I always install a ground loop breaker as part of my ground bus, using a diode bridge, a cap, and a resistor.  It's harder, sometimes, to fix it after the fact.  You'll see it when I post up my EHHA I pictures soon...almost done with the casework.

Sounds like there is more than one way to do it.  I'll be watching out for the pics.  A new thing I noticed is a little pop through the headphones on power-off.  I usually turn the volume pot all the way down before powering off, but this time I forgot.  I'm assuming it's related to the new grounding scheme.  If a different ground loop breaker setup helps with that I'll definitely give it a try.
 
BK

 

 

[dBel84]

This pop is most likely a small amount of offset as the amp powers up / down and the rails settle. ( ie before the servo has chance to control the offset and zero it ) My general recommendation is to always remove headphones before switching off / on an amp. Some headphones are more sensitive than others but prolonged exposure to 1-2V ( even for a few seconds ) cannot be a good thing. Some people use the offset sensing circuit that AMB released ( the epsilon 12 ) while others use a more simple relay to cut the output at power up / down (Millet max etc amps) . Personally, I unplug my headphones after every session..dB

 

[johnwmclean]

 
Quote:

Quote:

A new thing I noticed is a little pop through the headphones on power-off.  I usually turn the volume pot all the way down before powering off, but this time I forgot.  I'm assuming it's related to the new grounding scheme.  If a different ground loop breaker setup helps with that I'll definitely give it a try.
 
BK

Why? I see you have epsilon 12s installed so this shouldn’t be a problem.

 

[BK_856er]

Quote:

This pop is most likely a small amount of offset as the amp powers up / down and the rails settle. ( ie before the servo has chance to control the offset and zero it ) My general recommendation is to always remove headphones before switching off / on an amp. Some headphones are more sensitive than others but prolonged exposure to 1-2V ( even for a few seconds ) cannot be a good thing. Some people use the offset sensing circuit that AMB released ( the epsilon 12 ) while others use a more simple relay to cut the output at power up / down (Millet max etc amps) . Personally, I unplug my headphones after every session..dB

I already have dual v2 e12s installed.  The rails might be discharging faster with the loop breaker installed (?) and the relay therefore can't open fast enough, so I get a slight pop on power-off.  I'll verify the e12 offset setting to see if it's changed since I added the breaker.  Unplugging the headphones is probably a good practice.
 
BK