Neumann U67 Clone : D-U67 Tube Microphone Build Thread.

[poctop]

Just added a note on using the aMI adaptor board to avoid any confusion look a the picture on the first page ,
Dany,

 

[Winetree]

Waiting for capsules (beesneez), transformers ( Bv-12),
bodies (chugger), parts (mouser), Got the PS cases ( grand master )

what tubes are you using?
I've been looking at old NOS telsa and telefunkun ef806(s)
matcheded pairs at 25 days delivery.

Wanna see my empty P.S.B.'s

 

[poctop]

Waiting for capsules (beesneez), transformers ( Bv-12),
bodies (chugger), parts (mouser), Got the PS cases ( grand master )

what tubes are you using?
I've been looking at old NOS telsa and telefunkun ef806(s)
matcheded pairs at 25 days delivery.

Wanna see my empty P.S.B.'s

I have been happpy with those
http://www.ebay.com/itm/Vintage-Amperex-Electron-Vacuum-Tube-EF86-6267-No-Reserve-/300801068578?pt=Vintage_Electronics_R2&hash=item4609240e22
and those,
http://www.economik.com/tung-sol/ef806s-gold-ef86-6267/

Thanks For the Offer  ,
Best,
Dan,

 

[imo]

hello,
Just jumping into first steps of power supply build.
Curious as to why the heater voltage is run on a negative rail. I understand that the tubes don't care regardless, as long as they get the right amount, but just hadn't seen that before
Thanks
Ian

 

[tskguy]

I asked the same question, and the answer is. Because Neumann did it that way!! The microphone and power supply are 100% true to the original circuit.

 

[poctop]

hello,
Just jumping into first steps of power supply build.
Curious as to why the heater voltage is run on a negative rail. I understand that the tubes don't care regardless, as long as they get the right amount, but just hadn't seen that before
Thanks
Ian

It is just a matter of reference,  the only answer i could figure out to this question was to permit the electron to say hello to each other travelling down the line  8), or .......
Best,
Dan,

 

[ioaudio]

Actually the biasing of the tube is derived from the negative voltage, so yes, it's important.

-max

 

[poctop]

Actually the biasing of the tube is derived from the negative voltage, so yes, it's important.

-max

Indeed , 

thanks Max
Dan,

 

[imo]

Its funny. In looking at the schematic, i didn't even notice the negative heater rails until i was about to start building. My eyes saw what they wanted to see.
My power supply seems to be in good working order. I put some test points on the back panel.
I am around 250V B+, and -9V H unloaded. Does anyone know what the load of the mic circuit is, and for grins, how to figure that? would we just be looking at the plate load of the EF86 through the BV12?
Ian

 

[poctop]

Its funny. In looking at the schematic, i didn't even notice the negative heater rails until i was about to start building. My eyes saw what they wanted to see.
My power supply seems to be in good working order. I put some test points on the back panel.
I am around 250V B+, and -9V H unloaded. Does anyone know what the load of the mic circuit is, and for grins, how to figure that? would we just be looking at the plate load of the EF86 through the BV12?
Ian

Might be something wrong with you H-  there is a Zener over there in that section and if i remember well when there is no load the we should see the Zener regulated voltage trough it at about -16V ,  did you use  check back the schemo just to make sure,
Thanks
Dan,

Edit: Just Measured my power Supply to give you an idea , so 250VDC unloaded for the plate is what i have when my conditions are met with the mic eventually plugged in,

Regarding the Heater Voltage it should read -16V ish when no mic is connected,
I attached a picture of my psu just so you can have a visual cue if somthing is not right,

 

[imo]

I did the 56k series. Using the Triad. Actually getting closer to 240v unloaded with the pot opened up. I can trim it down from there. The heater voltage is around -16. Sorry. I wrote that on memory, which was a bit off. I am not able to trim the heater voltage without a load. Is that ok?
Do you know the load of the circuit?
Thanks
Ian

 

[poctop]

I did the 56k series. Using the Triad. Actually getting closer to 240v unloaded with the pot opened up. I can trim it down from there. The heater voltage is around -16. Sorry. I wrote that on memory, which was a bit off. I am not able to trim the heater voltage without a load. Is that ok?
Do you know the load of the circuit?
Thanks
Ian

Ouff ! , Memory can play tricks isnt

I am not able to trim the heater voltage without a load. Is that ok?

Correct you need the mic ( Load)  plugged in for that , it draw about 200ma for heater current ,

 

[poctop]

Here is a great post from Gus, ( thanks Gus).
basically you follow ohms law and power law 

http://www.groupdiy.com/index.php?topic=21696.msg256063#msg256063

http://www.groupdiy.com/index.php?topic=37428.0

Just make sure you get the right Wattage with the resistor you are using if any, but it looks like your allset to go

People

This is a very short example.  Building a load for a power supply should be a meta or sticky better written than this.

  I often power up a just built or worked on  power supply on a simple resistive load bank.  This can save the circuit that you just built  from overvoltage 

  You need to know how to use ohms law and DC power.

Lets say a G7 go to the spec sheets and find the fil current and voltage
Use Voltage 6.3 VDC and current .2 amps to start

a resistor to sub for the heater would be 6.3/.2 for 31.5 ohms use a 33ohm it is close enought.
Next you know the current and voltage so voltage  X current = DC power
6.3VDC X .2amps =1.26watts

33 ohms at 2 watts
or three 100 ohm in parallel at .5watts for 33.3 ohms at 1.5watts.

Now if you underheat the voltage and current will be a little different but this should be close  for a load test of the power supply

Simple stuff

Then do the B+.  One way, Look at the cathode voltage divide the cathode resistor voltage by the resistor value this should be very close to the plate current.  Or you could use the voltage drop across the plate R

Then calculate the capsule voltage divider and pattern resistors total value and then that value current at the rated B+

Add up the currents and calculate the needed resistor value and wattage.


Ripple you will need a scope for.

Hope this helps,
Dan,

 

[dandeurloo]

Hey Guys I have the first of 2 PSU's built up.  I am getting -16v on the heaters and a range about around 250v on the B+.  So I think I am as far as I can go on this until I get some bodies and capsules. 

Here is a picture of how I did mine with one of my cases.  The mounting brackets are just some stuff I picked up a while ago at home depot for something else.  Those even had holes in them already so I didn't have to do to much drilling.  Seems to work nicely.

 

[bkbirge]

^------- nice mounting solution for the trimmers, that would give me confidence in trimming while it's turned on.

Is everyone using the capsule mounts from Peluso? I've got everything to start a pair of builds but the mounts. Was there a group buy for mounts somewhere?

 

[tskguy]

These look nice as well but may be a bit pricey,

http://www.thiersch-mic.de/en/estm_produkte.html

 

[dandeurloo]

I used the Peluso for my 87's and I have original capsule in those.  It worked great.  I have a pair of BeesNeez coming and I am not sure what will work with those for mounting.  If they don't come with one I will be getting Peluso mounts.

 

[Volume11]

I used the Peluso for my 87's and I have original capsule in those.  It worked great.  I have a pair of BeesNeez coming and I am not sure what will work with those for mounting.  If they don't come with one I will be getting Peluso mounts.

All of our capsules come with capsule saddle and mounting post, which are usually valued at $79. The Capsules will ship in a hard plastic case to protect them during shipping.  As with all of the BeesNeez Microphones they are manufactured in the BeesNeez Microphones factory on our property in NSW Australia.

In order to view and purchase the above options. Please visit our secure page attached to our facebook page. I have set up a category just for you, showing your reduced rates. Please feel free to email or PM me if you have any questions.

http://www.facebook.com/BeesNeez?v=app_139114646178872&app_data={%22transaction%22:%22viewcategory%22,%22id%22:%2201e59bdb-2a8f-503d-ae30-7270a877f16f%22}

Kind Regards,
Veronica Sneesby
Beesneez Microphones
www.beesneezmicrophones.com.au

 

[Volume11]

What value did you guys use for r20? I didn't have a 60 ohm in my mouser order and I don't see one in the bom. I did have an extra 60m though. Maybe a mistake in the bom? Anyone have a part number? I did a quick search and it turned up a bunch of values around 60r, nothing spot on though.

how many 60M had you , there is 3 used in the mic , R2, R9, R16,
also In the PSU  there is one of 56R For R20 Best,
Cheers,
Dan,

Just noticed this question. I will check first thing tomorrow and post back.

I am surprised that no one has posted any build pics yet. I found a local powder coating company that quoted me $15-40 for two mikes, depending on the colors I choose. I'll post some pics as soon as I get them done. Hopefully by then the capsules will arrive. I'm thinking of maybe getting the head baskets and retainer rings chromed as well.

Ok, everything was correct in my order and builds, so far. I combined the psu, d67, and 87 into one mouser order, and it made things a little confusing. Thanks!

 

[wave]

Hello fellow builders,
I still have to build my PSU but I wanted to let everyone know that Eric (tskguy) came by with his PSU and my AMI DU67 is ALIVE!!!!!
It works perfectly (all patterns) and sounds great except for the fact that I'm still waiting for my HK-67 capsule so I have a Chinese K-67 in there for testing that has way too mush 4-7K response.
PSU components are on the way. I'll have it built up this weekend and then I'll be able to finish up my build manual.

Great project but not the easiest one to do. It's very satisfying to have the mic work right out of the block tho.

Dave

pics and sound samples coming...