D-EF47 Tribute To Oliver Archut U47 Build Thread.

[volker]

https://www.mouser.de/ProductDetail/KOA-Speer/MF1-2CC1402F?qs=sGAEpiMZZMsPqMdJzcrNwutZF3%252bdQ0PQbLPVjdugnMM%3d

https://www.mouser.de/ProductDetail/Vishay-BC-Components/SFR16S0001402FR500?qs=sGAEpiMZZMsPqMdJzcrNwl5vxkMOsrq%2fhxTZZR6JM9g%3d

https://www.mouser.de/ProductDetail/Vishay-Dale/CCF6014K0FKR36?qs=sGAEpiMZZMsPqMdJzcrNwh7Mtt2oBqGj1%2fCa3nmfllk%3d

https://www.mouser.de/ProductDetail/Vishay-Dale/CMF5514K000DHR6?qs=sGAEpiMZZMsPqMdJzcrNwrWeLsWOg9zoPBS%2fiCgP6O4%3d

https://www.mouser.de/ProductDetail/Vishay-Dale/CMF5514K000BHR6?qs=sGAEpiMZZMsPqMdJzcrNwh7Mtt2oBqGjK0DP9f35gRk%3d

Learn to use the parametric search.

 

[Larsson]

I pulled the trigger yesterday and made an order of almost everything to complete this build. This will be soo much fun!!  At first it seemed a daunting task but after reading up and studying the schematics it actually seem pretty easy to build. It’s just a matter of not killing myself in the process  ;D Thanks Dan for providing the kits! 

Can anyone recommend a high quality microphone cable to use for this build?

 

[Mjwever]

Can anyone clarify the power wiring  for an Australian PSU? Do I need the 230v Toroidal at all or can I just connect direct to the PCB, bearing in mind our voltage is actually 240v?

 

[Larsson]

Can anyone clarify the power wiring  for an Australian PSU? Do I need the 230v Toroidal at all or can I just connect direct to the PCB, bearing in mind our voltage is actually 240v?

Well you could but for safety reasons a transformer between the circuit and mains power is a good idea. I´m actually wiring up the 230V toroidal as i´m writing this and i´m in a 230V country myself. I believe it should be connected in series on both input and output.

 

[rmburrow]

A transformer isolated AC power supply is a REQUIREMENT, not an option, especially for a microphone or other low signal device.  In the old days, "AC-DC" equipment (especially radios) were built with the chassis "grounded" to one side of AC.  Many people were electrocuted on contact.  You probably read about musicians being electrocuted from guitar amplifiers, etc. that were at AC rather than ground potential. Later, the polarized line cords helped but wasn't the real solution.

Contact with 230 volts off your wall will be an uncomfortable or potentially fatal situation.  Assuming the average human has a body resistance of 150 ohms,  contact with 230 volts off your wall could allow as much as 1.5 amps to flow.  Since 100 mA can be fatal, 15 times that can be bad news.  Don't be cheap with powering your equipment.  You also need to fuse the primary of that transformer to protect against fire or injury in case a component fails.

AC line power in some ways is like a sewer.  Transients, RF, "hash" from fluorescent and other lights, digitial devices, etc.  get the "free ride" on the AC power system.  A power transformer is the first "line of defense" for keeping noise out and for safety reasons.

 

[Hank Dussen]

What would be the consequence of lowering C2 from 1uF to 0,47uF as in the original  U47 schematic?
Does this resolve in a higher bass roll off?
I'm asking this since I have some 0,47uF PIO caps.

And what about C3? Can this be lower as well?

 

[dmp]

What would be the consequence of lowering C2 from 1uF to 0,47uF as in the original  U47 schematic?
Does this resolve in a higher bass roll off?
I'm asking this since I have some 0,47uF PIO caps.

And what about C3? Can this be lower as well?

I would try different caps and see what you like. I have done this in mic builds to pick a value. I've found it is much easier to hear the differences with the mic picking up music versus your voice.  A smaller cap might give a a better voicing for what you want out of the mic. 0.47uf is within the common range you'd want to use.
C2 interacts with the output transformer so it isn't a simple HPF but generally the larger the cap the lower the rolloff freq.
If you lower C3 too much you might have a little more noise, since C3 filters B+ in the mic

 

[ln76d]

What would be the consequence of lowering C2 from 1uF to 0,47uF as in the original  U47 schematic?
Does this resolve in a higher bass roll off?
I'm asking this since I have some 0,47uF PIO caps.

And what about C3? Can this be lower as well?

C3 - rather i would suggest to try go higher - for example 2.2uF
C2 - try - you can use the switch and two 470nF caps in parallel. Connect to switch out one from the circuit and you can hear A/B what's the difference. 

 

[Hank Dussen]

Thanks, I'll try some different caps and let you know.

 

[Larsson]

Completed the PSU today. Everything seems fine  I hooked up a ~17 ohm load from H+ to GND and adjusted to 5.05V. With the switch in Cardioid I used a 150K load on B+ -> GND and adjusted to 105.5V. When set to omni I hooked up a 220 ohm resistor between PTRN and GND to simulate the reed switch. Voltage on B+ dropped to somewhere around 75V.

A question about the cable shield (Pin 3) on the mic side: Do you guys connect this to GND pad as well or tie it separately to the body? The GND pad on the mic PCB grounds the body as well.

 

[Larsson]

I finished the mic a couple of days ago and man this thing sounds great  8) Incredibly silent and with a huge but smooth bottom and detailed top end. I used a beesneez K7 and beesneez b-bv08. The transformer had to be mounted to the backside of the PCB with plastic spacers to fit inside the body. The body was unfortunately bought from micandmod. Expensive for it’s bad Chinese build quality. Get your stuff from this forum is my conclusion. The head grille is nice though.

 

[Ricardus]

This is the mic I want to build next. I've read this entire thread but didn't see a complete and concise explanation of calibrating the PSU using resistors as temporary loads. Or did I miss it?

 

[Larsson]

Or did I miss it?

Here is an answer From Delta Sigma, page 15:

"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."

 

[Ricardus]

I did see that, but it sounded like it might have been from earlier in the development of this project, with the PSU circuit possible changing, but if that's it, that's it. The thread for this mic isn't as complete as the one for the D87, which I built two of a few weeks ago. My first venture into building my own mics. More to come!

How many watts should the 150k-210k resistor be?

 

[Larsson]

I did see that, but it sounded like it might have been from earlier in the development of this project, with the PSU circuit possible changing, but if that's it, that's it. The thread for this mic isn't as complete as the one for the D87, which I built two of a few weeks ago. My first venture into building my own mics. More to come!

How many watts should the 150k-210k resistor be?

Worked fine for me =). P = I*U which gives you approximately 0.0007*105 = 0.0735W.  A standard 0.25w resistor works fine.

 

[Ricardus]

Worked fine for me =). P = I*U which gives you approximately 0.0007*105 = 0.0735W.  A standard 0.25w resistor works fine.

Thanks!

This is my next build. After a coupla Hairball 1176s, and some CAPI 312s.

 

[mosvelit]

Hello there,

I'm new to this group and this is my first ever build 

Hope some of you could lend me a hand on some doubts I have:

1st: I bought a Haufe BV08 transformer for this mic but it has 6 wires instead of 4. I understand the two brown wires are some kind of shielding for the core.

I’d need to know where exactly each colour should be connected to. I looked at the schematic provided by Haufe but can’t make too much sense about which is the primary and secondary winding. Here it is:

https://www.don-audio.com/bilder/HAUFE-BV-08_T-7853.jpg

2nd: where each pin from the 7 pin xlr connector should be connected to the board.

Thank you for your help in advance!

Cheers,

 

[Larsson]

Hello there,

I'm new to this group and this is my first ever build 

Hope some of you could lend me a hand on some doubts I have:

1st: I bought a Haufe BV08 transformer for this mic but it has 6 wires instead of 4. I understand the two brown wires are some kind of shielding for the core.

I’d need to know where exactly each colour should be connected to. I looked at the schematic provided by Haufe but can’t make too much sense about which is the primary and secondary winding. Here it is:

https://www.don-audio.com/bilder/HAUFE-BV-08_T-7853.jpg

2nd: where each pin from the 7 pin xlr connector should be connected to the board.

Thank you for your help in advance!

Cheers,

Good luck with the build. Google "U47 schematic" to see how to set up the transformer. As the BV8 has dual windings on both primary and secondary you need to tie these together. So.. GN and GN should be tied together. The same for BL and WS. RT goes to P+, SW to P- which goes to ground.  BL goes to A+, WS to A-. Read through the thread to find info on how to connect the XLR.

 

[mosvelit]

Good luck with the build. Google "U47 schematic" to see how to set up the transformer. As the BV8 has dual windings on both primary and secondary you need to tie these together. So.. GN and GN should be tied together. The same for BL and WS. RT goes to P+, SW to P- which goes to ground.  BL goes to A+, WS to A-. Read through the thread to find info on how to connect the XLR.

Thank you so much for your answer! Yes I already looked at the scheme but the wire colours on the secondary were flipped in the one I looked at and I was a bit confused.

I'll manage with the rest of the wires but the ones that I still don't understand where they should go are the brown ones on the Haufe (see the attached pic). I assume maybe they should both go to ground? Or maybe not even connect them.

 

[TillM]

both brown wires are ground.