Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #321 on: November 09, 2018, 04:15:56 AM »
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?
« Last Edit: November 09, 2018, 04:27:01 AM by Larsson »

Mjwever

Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #322 on: November 16, 2018, 06:50:27 PM »
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?

Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #323 on: November 17, 2018, 11:25:58 AM »
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.

Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #324 on: November 19, 2018, 02:49:04 PM »
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

Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #325 on: November 27, 2018, 03:57:56 AM »
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

Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #326 on: November 27, 2018, 10:09:37 AM »
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

Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #327 on: November 27, 2018, 11:56:35 AM »
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

Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #328 on: November 28, 2018, 02:16:00 PM »
Thanks, I'll try some different caps and let you know.

Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #329 on: December 02, 2018, 09:32:23 AM »
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.


Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #330 on: January 06, 2019, 12:34:12 PM »
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

Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #331 on: January 16, 2019, 06:14:28 PM »
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?
Audio mastering for hire..

Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #332 on: January 17, 2019, 04:18:27 AM »
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

Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #333 on: January 17, 2019, 02:26:47 PM »
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?
« Last Edit: January 17, 2019, 02:30:11 PM by Ricardus »
Audio mastering for hire..

Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #334 on: January 18, 2019, 01:07:54 PM »
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

Re: D-EF47 Tribute To Oliver Archut U47 Build Thread.
« Reply #335 on: January 18, 2019, 01:11:18 PM »
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.
Audio mastering for hire..