Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Bijou All Tube Futterman Headphone Amplifier
New Posts  All Forums:Forum Nav:

Bijou All Tube Futterman Headphone Amplifier - Page 102

post #1516 of 3981
10/6/08 at 12:44pm
Quote:
Originally Posted by luvdunhill View Post
my favorite way to find this out is when you have a couple wires coming from say an unregulated PSU with a large cap and you measure out the two wires to be the same length and then cut them with some cutters... nice big flash and pop just a few inches away from your hands
Reply
post #1517 of 3981
10/6/08 at 1:07pm
Quote:
Originally Posted by runeight View Post
Yes, done that too. The current was so high the cutters wound up with two notches in the blades where the wires were cut and very tiny blobs of melted metal flew out and stuck into the plastic of my glasses.
yeah, or the irresistible urge to find out if a device is running hot and shorting the screw to the tab with your finger, despite the use of an isolator. I did this with ended up with both an entry and exit holes a few millimeters apart on my index finger ...
Reply
post #1518 of 3981
10/6/08 at 1:16pm
Quote:
Originally Posted by runeight View Post
Yes, done that too. The current was so high the cutters wound up with two notches in the blades where the wires were cut and very tiny blobs of melted metal flew out and stuck into the plastic of my glasses.
LOL, I accidentally arced a short piece of solder across the mains voltage before I got all the heat shrink on my amp. It splattered everywhere.
Reply
post #1519 of 3981
10/6/08 at 3:54pm
Quote:
Originally Posted by holland View Post
Nice work, Ferrari. I can't quite make it out, but is the casework complete? I can't tell if the headphone jack is just a hole or not. :P Either way, the blue diffuse backlight coming out of the headphone jack is quite nice.
Obviously not! It was trying only a part of the faceplate out. Unfortunately I have to travel for work again and will not be back home before saturday, so I will try to finish it in the coming weekend. There will be NO backlight coming out of the headphone jack when completed!

Quote:
What transformer are you using? I probably missed it.
This one. PS output rock solid at 250V with EZ81 rectifier.
Reply
post #1520 of 3981
10/6/08 at 8:21pm
Quote:
Originally Posted by amphead View Post
Holland welcome to the "dark" side of amp building. ;-)
Thanks. I've had the boards since the initial group buy. Talk about procrastination...but not as bad as my Dynahi which, till this day, sits in half built state. I'll probably start building next month, give me some more time for research and parts sorting/selection and orders. The PCBs look like it'll just take a day to stuff, if that much at all.

Reading through this thread, I hope I hit none of the snags. I'm definitely not looking to see any self-inflicted flesh wounds.

Are tubes safe to be exposed? I intend to internal mount the transformer and all the wiring, caps, etc., leaving just the tubes out. I don't want anything on top of it (cage, etc.), but am concerned about electrocution (can the internals of tubes arc outside the tube?), particularly with kids in the vicinity. I have heard stories of arcing in really high voltage scenarios, but am not sure for something like this.
Reply
post #1521 of 3981
10/6/08 at 8:30pm
I have never heard of arcing outside the glass at the voltages where we are using the tubes. They have been safely used in lots of audio equipment where the tubes are sticking out the top. I guess this doesn't mean it's never happened, but in in the last 40 years, I've not ever seen a story about this. Now, when you get to really HV things are different. Very different.

However, as you know, with regards to kids, the glass will be very hot and can create serious burns if they actually grab and hold. So, just be sure that they are protected from that.
Reply
post #1522 of 3981
10/6/08 at 8:38pm
The short answer is yes, it is safe to have the tubes exposed. The tube envelope is made of glass/silicon. Silicon is an insulator unless doped with another substance, but there are reasons not to touch tubes, because you may be burned, depending on current draw. If you touched running tubes with wet fingers, I wouldn't give you any guarantees for how long you would be around afterwards. So amplifiers with exposed tubes are not children/pet friendly for obvious reasons there. Exposed tubes help the chassis to run cooler, however they are exposed to the possibility of being broken when struck accidently, however that might occur. Edit: LOL, I posted the same time you did Runeight and we both touched on the same ideas.;-)
Reply
post #1523 of 3981
10/6/08 at 9:26pm
Thanks. I will search for some more enclosed tube protectors instead of the more open ring type ones.
Reply
post #1524 of 3981
10/6/08 at 10:38pm
Thread Starter 
You can find these very cool ones at VT4C - pricey I know.




..dB

EDIT

VT4C also sells the r-core transformer which can be used for the bijou ( $32 )
Reply
post #1525 of 3981
10/6/08 at 11:01pm
Would there be anything special I should keep in mind if I were to do a 2-chassis bijou? Would the star-ground still be necessary?
Reply
post #1526 of 3981
10/6/08 at 11:40pm
Thread Starter 
The primary thing that comes to mind would be the umbilical, it would be better to keep the HV and heater separate thus 2 umbilicals and make sure there is some locking mechanism so that they don't pop out easily. Your Grounding can still be focused on a ground node in the psu chassis..dB
Reply
post #1527 of 3981
10/6/08 at 11:54pm
Quote:
Originally Posted by JamesL View Post
Would there be anything special I should keep in mind if I were to do a 2-chassis bijou? Would the star-ground still be necessary?
I would think twice before going this route. Assuming the single chassis implementation is well designed, there are a few benefits, such as less capacitance needed after regulators which can have a positive effect on the amplifier, as well as better immunity from EMI/RFI. I did some comparison using one of Tangent's LMNP devices and noticed that I actually got less noise from the power supply in the single box configuration. There may well be reasons for using a separate power supply, but I'd like to suggest that it is not always a better choice like many people think.
Reply
post #1528 of 3981
10/7/08 at 12:04am
Thanks for the suggestions.
luvdunhill, sonic benefits aren't the primary reason I'm thinking of using a dual chassis, though if there are any significant disadvantages to doing so, I will rethink it.
Reply
post #1529 of 3981
10/7/08 at 5:07pm
while measuring DC offset last night, i noticed that there is attenuated buzzing with the pot at 1/2, gets louder when turned up, then fades again at full travel. no noise when pot at sane listening levels, in fact, dead quiet. i have Amphead's ground mod on the PS.

so i did some troubleshooting...

-installed ground loop breaker = did nothing
-rechecked and tightened grounds/starground = nothing

i then disconnected interconnect from source to amp - buzzing got louder. so i shorted the Phoenix connector Input to Input ground with a short lead, with the pot connections intact. voila, dead silent throughout all positions on my cheap Radio Shack 100K pot.

currently, i have my L/R input phonos connected to pot with a single 4 wire Mogami mic cable. 1 individual wire connects to each of the L/R signals and grounds. i've tried disconnecting the shielding from the phono jack, but no love.

my pot is mounted on acrylic, with a tagged wire running directly to star ground from the body. maybe some solder could have leaked into the pot from the hole that i tacked the ground wire to. this ground tag spot also happens to correspond to the area of travel on the pot where i get the buzzing.

any suggestions as to what to do next? crap pot?

[IMG][/IMG]

[IMG][/IMG]
Reply
post #1530 of 3981
10/7/08 at 6:49pm
As always not 100% here but, it looks like a grounding loop at your RCA's. They appear to be grounded to both starG and thru the input board. And all the noise from the starquad shield could potentially be going thru your input ground, which can cause some bad noise from my experience. I think (?) its always best if shielding is separately grounded to starG.
Reply
New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Bijou All Tube Futterman Headphone Amplifier