[BK_856er]

 
Quote:

 
Interesting. I used a similar bit (dremel #194) and the depth guide to set the cut depth. What did the flexible extension shaft bring to the party?

My bit was conical and pointed at the tip, so I needed to present it horizontally in order to remove material.  The flexible extension allowed me to achieve a narrow angle of attack.  Your cylindrical, flat-bottomed bit is much better suited for a job like this, more like a router, but I was limited to what I could scrounge up late Sunday night.  Could not rest until I got that jack properly mounted jk style!  I really dig those bur bits - need to get a full set with different shapes...and a depth guide.
 
BK

 

[jdkJake]

Quote:

My bit was conical and pointed at the tip, so I needed to present it horizontally in order to remove material.  The flexible extension allowed me to achieve a narrow angle of attack.  Your cylindrical, flat-bottomed bit is much better suited for a job like this, more like a router, but I was limited to what I could scrounge up late Sunday night.  Could not rest until I got that jack properly mounted jk style!  I really dig those bur bits - need to get a full set with different shapes...and a depth guide.

I hear that! 

 
I love my dremel. I have no idea why I waited so long to get one. Over the past year or so, I have used it for all kinds of work. The cutting wheels work great for square cuts. I used them (finished with a file) for my power switch and IEC inlet. Good stuff!
 

 

[nullstring]

Has anyone listened to both the EHHA and the EHHA Rev A?
 
 
For some reason I have a hard time ordering until I know how the two revision compare.
 
I expect they are more or less the same, but I'd like someone to confirm that.

 

[gurubhai]

They both sound fantastic & yes, pretty similar.

 

[BK_856er]

My intention is to wire up the EHHA revA according to the alternate wiring scheme.
 
I have Belden 8451 (22ga, two-conductor, foil shielded, drain wire) to be used between the isolated Neutrik jacks and the TKD potentiometer, and between the potentiometer and the board.
 
Output signal to the dual AMB e12s and headphone jack will be with single conductor 24ga shielded coaxial cable from navships.
 
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?
 
Some pics below for reference.
 
BK
 

 

 
 
 

 

[stringgz301]

Need some advice.  I want to convert my EHHA Rev-A build to balanced.  Question is what to do about transformers.  As some of you may remember, I used Avel-Lindberg transformers in my build and have been pretty happy with them.  Trying to figure out the best path for a balanced conversion.
 
Option 1: swap out the AL 30VA 30+30 .5A secondary for an AL 63VA 30+30 1.05A secondary, and the AL 15VA 9+9 .83A secondary for an AL 30VA 9+9 1.67A secondary
 
Option 2: just duplicate the existing transformers so that there are 4 total in the case
 
Option 3: have SumR build a custom transformer with 9V secondaries
 
Option 4: double the spec'ed current on the sumR transformer others have used (with 7V secondaries) and swap out the diodes on the 2 existing boards to use the lower voltage
 
 
 
Thoughts?  Don't really like Option 2 because it will be a wiring mess.  Not sure if option 1 will work given that the new transformer is not a direct doubling of the original.
 

 

[holland]

Quote:

Need some advice.  I want to convert my EHHA Rev-A build to balanced.  Question is what to do about transformers.  As some of you may remember, I used Avel-Lindberg transformers in my build and have been pretty happy with them.  Trying to figure out the best path for a balanced conversion.
 
Option 1: swap out the AL 30VA 30+30 .5A secondary for an AL 63VA 30+30 1.05A secondary, and the AL 15VA 9+9 .83A secondary for an AL 30VA 9+9 1.67A secondary
 
Option 2: just duplicate the existing transformers so that there are 4 total in the case
 
Option 3: have SumR build a custom transformer with 9V secondaries
 
Option 4: double the spec'ed current on the sumR transformer others have used (with 7V secondaries) and swap out the diodes on the 2 existing boards to use the lower voltage
 
 
 
Thoughts?  Don't really like Option 2 because it will be a wiring mess.  Not sure if option 1 will work given that the new transformer is not a direct doubling of the original.
 

Option 1 or 3, as Option 4 is basically the same.  If you're ordering custom you might as well get what you want/need.  Option 1 should be fine.
 


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.
 

 

[sachu]

stringz, drop me a line and i'll give you some info on what to do for the transformer on the cheap...atleawst for the HV.

 

[jdkJake]

Option 1: swap out the AL 30VA 30+30 .5A secondary for an AL 63VA 30+30 1.05A secondary, and the AL 15VA 9+9 .83A secondary for an AL 30VA 9+9 1.67A secondary

So, based on my observations and measurements, if you go with option 1, I think you could actually go with the 50VA 830mA Y236207 part and be perfectly fine. Especially in light of your AC line voltage readings.

Of course a custom transformer is just that, whatever you want it to be. Just depends if you want to spend the extra cash.

BTW, personnel message from an old local, GO PACK GO!!!

 

[nullstring]

Hey guys,
 
What modifications to the Heater supply schematic need to be made if it is to run two tubes in parallel? (double the current)
 
I assume the only reason it is divided into two Heater supplies is the simplicity of adding it to the end of the PCB.
 
I am planning building an original EHHA + sigma 22.
I also plan on protoboarding the heater supply for the EHHA Rev A.

 

[sachu]

Just build both the heater boards for 6.3V and run one tube with each.

 

[nullstring]

Yeah, I just found some information on DC filament supplies.
In that information is suggested you use one supply per tube. (I swear, everytime I ask a question I figure out how to answer it myself. "DC filament supply" was the keyword I needed)
 
Anyway... It looks like I have alot of options as far as supplies go.
Sachu, I believe you have DC filament supplies on your original EHHA? What power supply did you go with?

 

[sachu]

Filament supplies as i made the mistake nearly two years ago now is for the filament in DHTs.
 
The one i used was the Pete millet design which just uses the LDO LD1085 same as the heater supply on the EHHA Rev A.

 

[dBel84]

A simple way to get high current heater supply is to use a high power opamp ( in a TO220 package or similar ) , I have started to default to this method and make an adjustable supply for any tube project - it is pretty simple to breadboard and offers more then the 1A limit of the LM317/337 LDO's. Of course there are 3A LDOs too but I have a box full of chips and no plans to build gainclones so it is a biased decision for me..dB

 

[BloodInside]

Finally had some time to work on my EHHA again today and screwed it up big time. The first board went up and running great, but I accidentally swapped the +30V and -30V wiring on the second board. The result: smoke coming from Q1. Immediately turned off the power and saw the wrong wiring. 
 
I fixed the wiring and applied the power again and it seems that the servo isn't functioning anymore. I'm measuring around 0,4V DC across the OUT and GROUND and it isn't stabilizing. 
 
Do you guys have any pointers on how to proceed?