D-EF47 Tribute To Oliver Archut U47 Build Thread.

[uffetuff]

Hi!

I've read through the thread but I didn't find exactly the problem I have. I actually took over this projekt from a friend, so it was finished when I got it but it didn't sound right. So I checked through the psu to make sure that the B+ and H+ values were correct.

Now to the stupid question. Should the mic be connected when doing the measuring? Without the mic connected the H+ run at 26v and nothing is happening when turning the pot.

I've also changed the tube in the mic, to see if that was the problem, but now I'm afraid to plug it in if the voltages are not correct. Don't want to damage it.

 

[Delta Sigma]

The power supply needs a load to be adjusted and measured. Best option is to make a dummy load to get close then plug in your mic and adjust closer.

 

[uffetuff]

The power supply needs a load to be adjusted and measured. Best option is to make a dummy load to get close then plug in your mic and adjust closer.

Ok, so i searched through the thread again and i f I got it right that means adding a resistor between B+ and 0v, and H+ and 0v?
I also found someone recommending 150ohm for the B+ and someone calculates 12ohm 2w for the H+. Can I use those values or do I need to calculate my own?

 

[Delta Sigma]

150 is way to big of a load (lower resistance=bigger load), they probably meant 150k (150,000).

105V with a load of 150k gives you a draw of 0.7mA. Dany's schematic shows a current draw somewhere around 0.5mA which would give you a load of 210k (210,000). Use anything between 150k and 210k. You don't have to be precise, you'll be readjusting once your mic is connected. This helps to make sure your power supply doesn't have any major issues without damaging your mic. You may even have trouble hitting 105V on the button if you select the wrong value resistor but then get it when you connect your mic. If your voltage is way out (something like 50V or 150V) don't connect your mic.

For the heater supply, your draw will be around 275mA plus 30mA for your relay. At 6.3V your load would be 20.5ohms. At 5.2V your load would be around 17ohms. i burn in my tubes at their rated value (6.3) then adjust afterward to a more mic friendly voltage.

While the value of your heater dummy load isn't critical the power rating is. The power is around 2W so use a 2W resistor and don't keep it powered long. Use a 5W if you want to keep in on there a while.

 

[Olegarich]

Hi Diy family, I did cehck schematics but i can't find what power transformes exactly needed for this project??

What priamries and secondories should be and how much VA??

Thanks

 

[TillM]

the BOM tells this one.
https://www.mouser.de/ProductDetail/553-VPT230-110

25VA

 

[Olegarich]

Still i can't understand a bit with those transformers. I'm in europe so my primary should be 220V

Bom says there is 3 power transformers, why 3?


Power Transformers DualPrimary 115/230V 12VA, 20V CT @0.6A

Power Transformers Single Primary 115V 12VA, 20V CT @0.6A

Power Transformers Toroidal Mount/25VA 115/230Vo Secondary

Can someone explain which  goes where?

 

[wlinart]

Still i can't understand a bit with those transformers. I'm in europe so my primary should be 220V

Bom says there is 3 power transformers, why 3?


Power Transformers DualPrimary 115/230V 12VA, 20V CT @0.6A

Power Transformers Single Primary 115V 12VA, 20V CT @0.6A

Power Transformers Toroidal Mount/25VA 115/230Vo Secondary

Can someone explain which  goes where?

Looks like the first transformer (Power Transformers DualPrimary 115/230V 12VA, 20V CT @0.6A) is for 220V countries
the second one for (Power Transformers Single Primary 115V 12VA, 20V CT @0.6A) 110V countries.
Those are the ones for the heater voltage.
Just choose the one you need based on the voltage in your country. (So you, Olegarich, would need the first one)

The third one is the one used for the B+ voltage. (thanks to the 115V/230V secondaries). You need one of those as well.

 

[TillM]

as Wlinart already said, you need two.
You said that you are in a 220v Country.
So you need this two.

https://www.mouser.de/ProductDetail/553-VPT230-110

and

https://www.mouser.de/ProductDetail/546-186C20

 

[Olegarich]

Allrighty, so now it's clear, thank you guys!

 

[Olegarich]

Hi guys! I'm waiting for the last parts to start building mic. Can't wait
I've read this thread couple times and I found that some people having buzz issue, when microphone is in cardioid mode.

Glacier wrote a nice post how to solve that problem. Basic idea:

The goal here is to send ~48v to the mic on the "PAT" wire when the switch is in the Omni position, while sending a solid 0v when the switch is in the Cardioid position.


By saying "Solid 0v" does it means ground?  Do I understood it correctly, that when switch turned to cardioid mode you want that omni connection would be connected to the ground instead of floating free?

 

[Olegarich]

can anyone confirm if I'm on the right track?

 

[Delta Sigma]

Ignore the work "solid". 0V in this case is referenced to ground. It is the common return for the heater, B+ and bias supplies.

The relay, when energized, closes the contact that provides the Omni pattern. When de-energized, the contact opens creating a cardioid pattern.  To energize the relay, voltage is placed across the coil. If that voltage is removed the relay and floating leads can cause noise. Short the relay supply voltage to ground (as shown in Dany's schematic) when the relay is de-energized (cardioid).

Other sources of a "buzz" (100Hz in Europe, 120Hz in N.A.) are ground loops and under rated heater transformer.

See this for grounding:
https://groupdiy.com/index.php?topic=50021.msg796487#msg796487

 

[Olegarich]

Thanks man for the answer!

 

[r2d2]

HI  , any sound sample like acoustic guitar ,voice,etc..  recorded with a flat preamp (as well) ?
And also some sound comparison with the original mic (as well 2) ,
with links to sound samples in page 1.

 

[bakahed]

Hey,
I don't have the right resistor to adjust the H+ voltage so I cranked the pot all the way up and plugged in the mic.
The voltage was at 2 when it first powered up but kept rising up to 9v after 30 minutes of use. Turning the dial counterclockwise only increased the voltage so I didn't move it.
The pot gets so hot that I cannot keep my fingers on it after a while.
Is it safe to have the tube running at 9v? It didn't affect the sound or anything at all. The microphone has a very nice frequency response and there's barely any audible buzz.
What could be the reason for increased H+ voltage?
Thanks,

baka

 

[Murdock]

No, 9v is way to high. About 6.3v is normally used but olli (rip) underheated the tube in his design (about 5,2v). This should increase heater life and reduce noise. The original vf14 was also underheated.
What pot/resistor do you use?

 

[bakahed]

No, 9v is way to high. About 6.3v is normally used but olli (rip) underheated the tube in his design (about 5,2v). This should increase heater life and reduce noise. The original vf14 was also underheated.
What pot/resistor do you use?

Never mind, I figured it out. I had the multi meter on AC.

 

[[email protected]]

Hi All,

I'm somewhat stuck. I'm wondering if there is anyone (preferably in the states) who has successfully completed Dany's D-EF47 build with PSU, who would also be interested in finishing what I can not?

I got into this (these) builds with a more experienced tech who had planned to build a pair. He decided to go a different route and I am left at a stand still.

I actually delivered the pair of mics I have to a tech shop in Chicago  towards the end of 2016 and requested they try to finish them while I had been moving and had no access to my little work bench.

After all this time, I just picked them up unfinished and am not sure how to proceed. At this point, Id just like to have finished working mics and am Im willing to hire someone to finish these.

I can send any info and pics needed to get a sense of the status of these mics. Most of the Im local to the Chicagoland area. Referrals are welcome!

Most of what is left is:

-wiring the second mics Transformer to PCB and output conector
-wiring the Dany PSU (double check PCB)
-wiring the appropriate pin configuration for the Tab PSU
-wiring the mic cable for the Tab PSU
-mounting capsules
-testing

One mic is the following:
Theirsch M7 blue and capsule mount (not mounted)
Tab BV08 classic
EF800
Dany PCB (assembled)
Dany PSU build (assembled, but not wired)
Aputis Body
9 conductor Gotham cable

Other mic is:
Theirsch M7 Blue and capsule mount (not mounted)
Tab BV08 classic
Tab - EF800
Dany mic PCB (assembled)
Tab - PSU (built but not wired to mic input)
9 conductor Gotham cable

 

[dmp]

Is this how to the pattern switch?

Sorry if I missed it but I don't see this anywhere in the docs on the first post.