[nattonrice]

John this build is gonna be amazing!
Seriously out doing me here =P

 

[johnwmclean]

Quote:

Originally Posted by sachu /img/forum/go_quote.gif With a 10A DPDT (in you case you will need a 4PDT for balanced) on-on switch, the output of the amp boards go to the input of the switch and from there you will wire one possible output set of pins on the switch to the speaker (put the zobel in there on the binding posts) and then the other set of outputs from the switch go to the headphone out..

Sachu why 10A, I can only find goliath switches with that rating, would this really be needed for the signal path?

... also would an on-off switch be better suited, switching the outputs to the speakers on and off, and leaving the headphone outputs as intended, from the pcb straight to the jack.
With an on-on switch, I’ll have to run the signal output wiring back through the amp to the headphone jack.

 

[sachu]

Not really, even the miniature ones that are rated for 3A-5A would do.
Don't use the wiring scheme you just mentioned. I ended up blowing up my amp boards with something like that. Use an ON-ON switch for output switching not an ON-OFF switch. An ON-OFF switch is likely to blow your amp boards as well is what I have heard. I will get back to you on why this happens when I can get dBel to jog my memory about it. I am guessing because when you switch it on and off it creates a momentary short in the output (similar to those caused by the TRS jack) blowing your output MOSFETs and resistors.

 

[jjazzyj]

Well, I've been procrastinating a lot about finishing the EHHA. Mostly because I love/hate chassis work. So here's an in progress view of my 50% completion.

Front Panel:

4PDT switch for Pre Out
4PDT switch for headphone enable

Dual 1/4" Stereo/XLR Mono for Headphone(s)

Dual Stereo/Mono volume controls

RCA/XLR input with selector switches. Can convert unbalanced to balanced.

RCA/XLR for unbalanced/balanced pre-out

AMP CPC 9pin power connector to Sigma22/heater supply

One EHHA board left to go!!! Then cleanup, mounting, wiring and testing.

 

[sachu]

wow..nice to see so many EHHA builds and balanced too coming along at once. Sweet work there jjazzyj

 

[jjazzyj]

Quote:

Originally Posted by sachu /img/forum/go_quote.gif wow..nice to see so many EHHA builds and balanced too coming along at once. Sweet work there jjazzyj

I forgot to add, that just like the matching Sigma22/heater power supply chassis the bottom is clear polycarbonate. So all the EHHA boards have bottom mounted LED's for sexy blue under amp glow.

I'm sure that 1 month in that 'feature' will irritate the crap out of me when I watch movies.

Thanks for the feedback sachu! As long as I don't blow up too many MOSFETS when I hook it all up I'll be happy!!! Luckily I have enough extras to build another Balanced EHHA or Balanced B22...

 

[sachu]

^^^ lol i don't quite mind the blue and super bright orange LEDs(for amp boards) on mine..it kinda lights up the room at night. The coolness of it hasn't waned for me...yet

 

[aloksatoor]

hehe im going with bright white ones orange and blue wont match the brown wood of my chassis......

 

[jjazzyj]

First post on this thread with the new BBS!
 
Well, I did a bonehead manoever last night, soldering one of the trimpots in the wrong orientation. De-soldering plated through holes sucks. Took me 30 minutes to do. I usually use my fingers as a heatsink on the component or in the case of resistors a hemostat. Tested ok after removal so I probably didn't damage it, hopefully.

 

[adamus]

erm.... arent they symetrical?

 

[jjazzyj]

The part is, but a pot is a resistor divider, so just because it is symmetrical doesn't mean you can swap the orientation around.

 

[jjazzyj]

Now the wiring extravaganza begins. The wiring harness is not attached but here is the star ground wiring which the rest of the wiring looks like.
 

 

[jjazzyj]

Ok, so I got all my wiring hooked up. (One board at a time, though I have to insert two tubes and hook up the heaters for two boards because I'm using 12.6V heater supply). Turned on the heaters and they lit up just fine. Waited a minute then turned on the S22 (which tested @ 28.9V pos and neg) Within 10 sec R4 starts to smoke. I immediately killed the power. Checked for shorts a third time. None. Check resistor values, check transistor values. Tried again, R4 smokes again. Adjusted R6 from what I thought was halfway. Tried again, this time R14 smokes, but not R4 (luck probably). This time hooked up my grippy probes across R14, this was one probe on one side and one on the other side of R14. After waiting a minute with the heaters turned on again, turned on the S22 again. Measure the full 28.9 volts across it, as if something was shorted to GND it seems. S22 is ok through all this BTW. I tested the -30 and +30 inputs on the EHHA board to Star GND and did not get a short but around .500 ohms. Nothing seems shorted.
 
I did not test for shorts after I put the tube in. Is is possible that the tube has a short in it? I'm not sure what is going on at this point since all my values and orientations are correct. Unless IC2/3 are toast.
 
Any suggestions?

 

[sachu]

Sorry to hear about the problems Jazzyz..
 
It is really hard to say what could have gone wrong...
 
can you post a pic of the board..a macro shot with a link to it in high resolution would be useful.

 

[runeight]

It is possible but unlikely that the tube has a short. This is a very unusual problem in this amp.
 
Are you sure that Q1, Q2, and Q4 are PNP (2SA1145) devices and that Q3 is NPN (2SC2705)? The first thought is that Q2 and Q4 are either shorted or the wrong polarity and are passing too much current.