Neumann U47FET Clone: D-U47 FET Microphone Project PCB Build thread

[EvLoutonian]

Thanks Dan - that's what I wanted to see!
Looking good.

 

[MatthisD]

I have tested my build with the PCBs mounted in a smaller diameter(47mm) body. I tried spreading out the rails to fit the PCB which would have been handy but it was a couple of millimeters too wide for the body so one PCB had to be mounted to a blank piece of board, which took a while to figure out, and then trim both sides down to fit the body.

It worked first time with no problems. All voltages read as the schematic, varying slightly where I have 510K instead of 470k resistors which I don't have any of. The FET section has pads for individual components if not floating that section, as in my case as I'll be changing components there later on. I have a jumper in place of the trimmer, R6: 6.8K and running without PAD or low cut components.
Thanks to Dany for the PCB.

 

[MatthisD]

Response tested with 68pF substituted for capsule and mic preamp for gain and phantom supply.

 

[poctop]

Response tested with 68pF substituted for capsule and mic preamp for gain and phantom supply.

Thanks Matt,  your new mic is already customized a i can see,
Keep us posted 
Best,
Dan,

 

[poctop]

Merged info tht was on wM ,
Thanks,

 

[EvLoutonian]

Hi.
We're a little more limited for choice of affordable quality electronic components here in Australia, so I'm trying to get more informed on component choice, for different parts of the circuit (especially capacitors, but also resistors & other parts).

Can someone indicate why would a certain type of cap be chosen for each part of this circuit, especially identifying if there are a few that you'd select the most critically?

I'm not really clear why the majority of cap's on the pre-filled Mouser order form are tantalums. I know I need to replace about 50 of these in my old ARP Omni synth, but presumably new ones installed in a mic in 2012 will be good for another 40+ years!

Thanks!
Evan

 

[poctop]

Hi.
We're a little more limited for choice of affordable quality electronic components here in Australia, so I'm trying to get more informed on component choice, for different parts of the circuit (especially capacitors, but also resistors & other parts).

Can someone indicate why would a certain type of cap be chosen for each part of this circuit, especially identifying if there are a few that you'd select the most critically?

I'm not really clear why the majority of cap's on the pre-filled Mouser order form are tantalums. I know I need to replace about 50 of these in my old ARP Omni synth, but presumably new ones installed in a mic in 2012 will be good for another 40+ years!

Thanks!
Evan

the original were tantalum and 18pf and 33pf styro , some people like elctrolytic better and others dont,
Even tough i used electrolytics in my demonstration i'd rather stick to the Tants because i love em and i think there suffered from a bad reputation of failure used in the wrong spot , they have better high frequency behavior then the elc but this is all personal taste ,

Check this out here

http://www.electro-tech-online.com/general-electronics-chat/26407-electrolytic-caps-vs-tantalum-caps.html

From that paper:


Among the advantages [of tantalum] are:
! Small size
! No liquid electrolyte
! Superior temperature stability
! Wider operating temperature range (up to +125°C)
! Long storage (shelf) life
! Larger reverse voltage tolerance
! Low dissipation factor
! Self healing
Aluminum electrolytic capacitors do have several advantages over
tantalum capacitors.
Most prominently:
! Lower cost
! Higher availability
! Shorter production lead times
! Low leakage current
! Higher voltage range (up to 400 VDC)

Some of the most prominent electrical performance differences between
tantalums and aluminum electrolytics
that should be resolved before substituting an aluminum electrolytic for
a tantalum capacitor are:

! Aluminum electrolytic’s higher dissipation factors/ESR, which in turn
reduces their ripple current
capabilities.
! Aluminum electrolytic’s larger capacitance change over temperature.
Electrolytics can change up to six
times more than tantalums.
! Aluminum electrolytic’s capacitance change over frequency.
! Aluminum electrolytic’s changes over time -- up 20% after 2,000 hours
for aluminum electrolytics.

### end quote

There are numerous advantages to using tantalum capacitors over other types of capacitors. First, tantalum capacitors have a higher volumetric efficiency (CV/cc) when compared to other types of capacitors. For instance, a 10-microfarad tantalum capacitor can replace a 100-microfarad aluminum capacitor. Tantalum capacitors are easily mounted onto circuit boards, and give engineering designers the ability to place these components in closely-confined printed circuit board space, as well as utilizing tantalum capacitors' excellent power dissipation characteristics. Second, tantalum capacitors have superior frequency characteristics than many other types of capacitors, including aluminum electrolytics. A comparable CV tantalum capacitor has an ESR ten times better than an aluminum electrolytic capacitor. Third, tantalum capacitors are highly reliable – electrical performance qualities do not degrade over time. Tantalum capacitors do not lose capacitance unlike electrolytic capacitors – in fact, the shelf life for tantalums is regarded as unlimited. Fourth, tantalum capacitors don't wear out – in fact, if there is an imperfection in the dielectric layer of a tantalum, the resistance of the manganese dioxide layer will typically convert to a form that is even more resistive. The new oxide form plugs up the faulty region and results in a reduction in current flow. Finally, tantalum capacitors have an excellent wide operating range, from –55 degrees Centigrade to +125 degrees Centigrade, with a minimal amount of degradation in electrical properties throughout this range.

 

[EvLoutonian]

Cool, thanks for the great detailed response, poctop!
MUCH APPRECIATED!

 

[poctop]

I was just messing arround with the idea of mouting the AMI T49 in the U47 FET build and it will work  i dont have one here but they are the same package as my T67 shown here just less pin to solder i have used in the demonstration the AMI adaptor board from the D-U67 Project in there is fits like a glove ,
there is actually no AMI adaptor board included for the U47 FET at the moment tough but really nice room for different tranformer , i might consider having one if needed.

Sorry had taken a quick bad picture,
but here it is ,

 

[tonycamp]

Hi Dan, when is the next batch of pcbs coming? I don't know how i missed this, i even posted i was in for 1? :

 

[poctop]

Hi Dan, when is the next batch of pcbs coming? I don't know how i missed this, i even posted i was in for 1? :

Sorry you have missed it , they are coming this week,
Stay tuned,
Best,
Dan,

 

[gevermil]

Hey Dan
Any consensus on the transformer ?
Are you happy with the AMI T49

 

[poctop]

Hey Dan
Any consensus on the transformer ?
Are you happy with the AMI T49

I am still waiting for My T49 but found that in term of space used in the mic it should just fit in there 
can't wait to try it and compare to my 2480 and the original ,
i have to say i was really impressed with the 2480 so far, 
i might be getting a sowter also question of having more fun ,  i should have the pcb available by tommorow
Best,
Dan,

 

[EvLoutonian]

I'm still up for helping to co-ordinate the group buy of transformers if I know what most people want to go with?
I was just waiting to hear back just how many want to go this way.
We were offered good group discounts.

 

[Jim50hertz]

Hey Dan
Any consensus on the transformer ?
Are you happy with the AMI T49

I am still waiting for My T49 but found that in term of space used in the mic it should just fit in there 
can't wait to try it and compare to my 2480 and the original ,
i have to say i was really impressed with the 2480 so far, 
i might be getting a sowter also question of having more fun ,  i should have the pcb available by tommorow
Best,
Dan,

Are you sampling Mark's transformer (the Samar audio)?

 

[EvLoutonian]

I'd love to hear about results from Mark's SAMAR transformer for this mic, too.  Is someone up for trying both?

 

[mdemesmin1]

  i should have the pcb available by tommorow
Best,
Dan,
[/quote]

Hi Dan,

Im new here, i would really like to tryout one on those PCB.
Who do i need to send the paypal payment to?

Regards;

 

[poctop]

  i should have the pcb available by tommorow
Best,
Dan,

Hi Dan,

Im new here, i would really like to tryout one on those PCB.
Who do i need to send the paypal payment to?

Regards;
[/quote]


Welcome to the Forum , 

here is the link to get the pcb ,
click on the order button ,

http://www.groupdiy.com/index.php?topic=49675.0

Best
Dan,

 

[poctop]

All Pcb available now,
Thanks ,
dan,

 

[poctop]

Are you sampling Mark's transformer (the Samar audio)?

It is on my wish list  ,  Actually I have asked Mark to supply some info in the thread ,
Keep ya posted,
Dan,