C800 finished!!!!!

I finish my C800G :grin: .
That works!!!!!.
I make PSU with 6X4 tube and stabilized voltage for heaters. I use two zeners (110V+120V with 0,1uF poly in parallel), three caps (first 10uF and 100uF others) and two 10K resistors.
I saw 240V when microphone is connected????
Other voltages:
Plate and grids: 64V with 100K plate resistor
Cathode: 1,78V
Heaters: 5,7V
Capsule: 47,2V.
I used Russian 6AU6, Soundking 106 capsule and Lundahl LL1577, wired 7:1.
Single mesh.
Tube is out of aluminium body (like on original C800G). I made one aluminium cover to protect tube.
Also I haven big caps and I use one 3300uF near heaters.
On first listening I hear less low than my AKG414EB. Microphone is very sensitive.
Not big noise (higher than 414) and no hum.
Questions:
Is plate voltage low (on original 90V)?
Cathode voltage is (1,78V)higher than on original (1,4V)?
Soon pics!!!!!!!!

WOW! :shock: :thumb: :thumb: :thumb:
cant wait to see the pics

steff

try running the tube heater at 6.3Volts for a few hours then at 5.7V do this a few times. This seems to drop the noise of the russian 6AU6 tubes I have. The noise should be low in this microphone. Make sure the build is very clean around the high Z parts of the circuit.

Congratulations. Please post pictures when you can.

[quote author="thomasholley"]Congratulations. Please post pictures when you can.[/quote]

This is Duka's C800:

Good work, Duka!

:thumb:

Jakob E.

Are you going to use a cooler on the tube? Is that why the tube is horizontal?

Looks Nice

GREAT!
Very good work!

[quote author="Gus"]Are you going to use a cooler on the tube? Is that why the tube is horizontal?

Looks Nice[/quote]

Thanks to all who help me. :grin:
Jakob who influenced me and all guys who make mike and modification and learned me about building.
Vili (tebi takodje) you too for hosting.
Gus: I make tube outside because body is not big, tube dont heat inside of mike and if I find way (now, I havent it) to cooling tube. Now aluminium can have a holes above.
Did you read my questions about voltages?
Thanks
If somebody have questions about building I am so glad to tell everyone about it

Yes I read the about the voltages I forgot to post.

The 240V should not be a problem. Zeners are not exact. You could try a 110V for the 120V if you want about 230V. The tube used will change the other voltages a little. The russian 6au6 tubes I have seem to need to be run for 4hrs or so at 6.3V and then at the lower voltage when you first use them. They seem to be fine from then on. I don't think there is much you can do with the other voltages except to change the tube.

I have been adding a switch to my power supply builds to switch between 6.3 and what ever underheating voltage I like with different tubes. Steve Bench has a writeup on the web somewhere about cycling heater voltages.

My microphone is low noise, how is yours after a few hours of burn it? Are you using a grid to ground resistor? I ask because my build seems to have less noise without a 1gig grid to ground. I am looking for a 3gig to try. Your HV using a tube should give you the lowest power supply noise. I am now using UF4007s. try to find some super caps to try in the heater power supply, when I added super caps it seemed to even less noise.

Excellent Duka!

I really like the way you constructed this Duka. The layout ia excellent. Have you had much of a chance to listen yet?

Did you do the machine work yourself or was the body a professional job? Looks great. Wish I could do something more like that, rather than just a brass pipe.

Daniel

Very very nice!
This one is waaaay down on my list of DIY 'to do', but man! these pics make me want to dive in!

Peace!
Charlie

very nice work duka!
there are many hours of effor there, I can tell.

:thumb: :thumb:

To all: Thanks :grin:

Gus: My friend who gave me 6AU6 prepared tube for use. He have about 2000 tube. I used 1G grid to ground resistor. Any sugestion about cathode voltage???

Thomas: I used a lot time to make construction. I make a pcb (drawing).Unfortunately I cant find way to incorporate Omni-Cardiod switch. Also I havent small switch for it. I will try to make one short clip.

Daniel: I am DIY man. No profesional works! My friend who have a lathe help me to make a two pieces of body. Also he makes a hole for grill. On next two construction (in progress) I made it by hand. Pcb I drawed but my friend make eching. Everything other I made.
I used aluminium for body. I must find way to polish it or to paint in black. Also I make a shockmout for this microphone.

Duka,

Just curious. How does the head attach to the body? I don't see any threads on the main body, nor screws on the sides of the head. Is it simply just a snug fit over the main body?

Daniel

[quote author="AudioJunkie"]Duka,

Just curious. How does the head attach to the body? I don't see any threads on the main body, nor screws on the sides of the head. Is it simply just a snug fit over the main body?

Daniel[/quote]

Hi Danial
I made body from bottom plate where is mounted XLR, top when I mounted plate + ruber foam and capsule and two aluminium rods 7mm x 10mm with M3 for mounting bottom and top. Then I put body and finnaly grill head. My english is not good but you can see pic on first page.
I have some drawing and if you dont understand I can explaind with it.
Duka

Awesome! I like how the tube sticks out of the side of the mic. It's good for cooling and it looks cool, too.

Duka,

Nice work!
If you have a splitted backplate capsule, as on schemo, I would suggest to take advantage of it and make fig8 pattern, as well.