D-EF47 Tribute To Oliver Archut U47 Build Thread.

[wstratton]

Make a wire jumper on the PSU pcb between "COM" and "CRD" then you are in fixed cardioid mode, leave out the lorlin switch.

Thank you, TLRT, that makes sense. I haven’t been able to find a straight answer online about the differences in frequency response between a KK47 and the one-sided TLM-49, aside from reading that the TLM-49 capsule has a narrower sweet spot, tending more toward hypercardioid. I think I’ll probably go in another direction, but it’s on eBay for 300 if someone braver (or more foolhardy?) than I decides to buy it and see how it stacks up. 

 

[TLRT]

Thank you, TLRT, that makes sense. I haven’t been able to find a straight answer online about the differences in frequency response between a KK47 and the one-sided TLM-49, aside from reading that the TLM-49 capsule has a narrower sweet spot, tending more toward hypercardioid. I think I’ll probably go in another direction, but it’s on eBay for 300 if someone braver (or more foolhardy?) than I decides to buy it and see how it stacks up.

For what style would you use the mic? I would rather use a good M7 capsule for EF800/802 tube.

 

[wstratton]

For what style would you use the mic? I would rather use a good M7 capsule for EF800/802 tube.

Mostly close-mic'd tenor male vocals. I'll probably do some room mic'ing too. I used to have a Soundelux E-47C, which used a Thiersch K-47 style capsule, and I found that to be a little too aggressive in the midrange. I decided to go with a Thiersch Blue Line m7 style capsule for this build.

 

[malcomyoung]

Hi all,

First time posting here.  Just finished assembling the PSU and microphone.  PSU voltages test fine with dummy loads.  When I connect the microphone, the B+ voltage drops way down.  With the trim pot set to maximum, I can only get the B+ to come up to 80 VDC.  I replaced the front capsule with a 67 pF capacitor with no change.  B+ is still low.  Any advice as to where I should look next is much appreciated.

Thanks in advance!

 

[Delta Sigma]

Hi all,

First time posting here.  Just finished assembling the PSU and microphone.  PSU voltages test fine with dummy loads.  When I connect the microphone, the B+ voltage drops way down.  With the trim pot set to maximum, I can only get the B+ to come up to 80 VDC.  I replaced the front capsule with a 67 pF capacitor with no change.  B+ is still low.  Any advice as to where I should look next is much appreciated.

Thanks in advance!

Is your heater adjusted properly? Don't adjust your B+ unless your heater voltage is where you want it. You could have a short or an incorrect component value somewhere. Don't just check your mic amp, it could be in your cable (short in the connector).

 

[malcomyoung]

Is your heater adjusted properly? Don't adjust your B+ unless your heater voltage is where you want it. You could have a short or an incorrect component value somewhere. Don't just check your mic amp, it could be in your cable (short in the connector).

Thanks so much for your response, Delta Sigma.  Yup.  I had the B+ and the Pattern wires crossed on the mic connector :-\  I feel pretty stupid not catching that myself.  In my own defense, it was late at night.

Thanks again.  Now to plug it in and see how it sounds!

 

[Purplenoise]

Hey guys, I am thinking of starting a EF47. I am not very good at reading schematics so I wanted to ask. Apart from tube and relay/pattern selection how close is this circuit to the original? I see that the grid resistor (r2 I believe) is 1G. Is there a specific reason for this instead of using 60 or 100M as in the original? Could I use 100M if I wanted to stay closer to the original? Or maybe 1G compensates for less bass using ef800 compared to vf14???? Thanks

 

[wstratton]

I finally finished my slightly modified D-EF47 build today! Plugged it in for the first time, and it sounds absolutely fantastic. No harsh sibilance to speak of, even when singing right on the grille. Currently using an NOS Amperex EF-80 tube, but I think I'll stock up on a couple NOS Telefunken EF-800's over the next year or so. Even with the EF-80, this mic has extremely low self-noise. Thank you very much to Dan/Dany and Oliver (RIP) for making these builds possible, to Spencer for the beautifully machined body, and to Dennis at AMI for advice on the cable wiring and a circuit modification to accomodate a pre-built PSU.

Because I was wary of working closely with high voltages, I ended up ordering an AMI power supply after getting most of the way through building my own PSU, and Dennis very kindly gave me some advice on swapping out a couple resistors in Dany's PCB in order to accomodate this change. I ended up using a Thiersch Blueline capsule and AMI's T47 transformer. So far, I think the sound compares very favorably to the previous tube microphones I have owned. I used to have a Soundelux E-47C, which was a beautiful mic, but I found that the Thiersch K47 capsule gave it a pretty harsh midrange on my voice. Before that I owned a Pearlman TM-2, and I had the same problem with that microphone (again, on my voice--it was a beautiful microphone on many other sources).

Aside from being intimidated by the wiring on the PSU, which I ultimately gave up on, I found that the only really pesky part of this build was wiring the microphone's 7 pin cable, in particular getting the grounding right the Amphenol connector--the Binder connector that I ordered to connect to the PSU was much easier due to its more robust construction. My only advice on this is to take it slow if you're using unmatched 7 pin connectors and to think through various methods for grounding.

I tried to upload a picture of the microphone, but the board's server is rejecting it despite it being within the size guidelines, so here's a link to a Dropbox file if you want to see it: https://www.dropbox.com/s/b84tl2kh185be8p/IMG-0153.jpg?dl=0 I used an enamel snake pin for the mic's badge, in tribute to it being a sibilance tamer (the hissing of the snake--dorky, I know).

FYI, if anyone is having trouble with wiring their PSU build, I have a small collection of photographs of finished PSU builds for reference that other builders have kindly sent me--if you PM me I can dig them up and send them to you.

I'm extremely happy with how this turned out, and despite spending money on some components that I didn't use, would gladly do it again in order to learn about the internals of tube microphones. Maybe it's time to do an E LAM 251 build...

 

[Delta Sigma]

Hey guys, I am thinking of starting a EF47. I am not very good at reading schematics so I wanted to ask. Apart from tube and relay/pattern selection how close is this circuit to the original? I see that the grid resistor (r2 I believe) is 1G. Is there a specific reason for this instead of using 60 or 100M as in the original? Could I use 100M if I wanted to stay closer to the original? Or maybe 1G compensates for less bass using ef800 compared to vf14???? Thanks

I haven't tried any other amp but since no one responded, I figured I'd chime in. If you want to stay close to the original circuit, build from the original schematic and try a solid state drop in replacement like the Phaedrus. Next closest would be the parallel 408As. The benefit to this amp is that the tubes are readily available and you avoid having to heat sink your big dropping resistor.

Try anything between 60M and 1G and see what you like. Not sure you'll hear any bass improvement when geting beyond a few 100 meg. I read somewhere (PRR on a guitar amp forum?) that the bigger your grid R the more hiss you get.

From what I've read, nothing will get you to a VF14. It also doesn't seem that hard to get a great mic based off the U47 design, whether it sounds like the original or not probably doesn't make any practical difference in the long run.

I also suspect that you could find a greater change in sound by swapping capsules and transformers before tubes, even when it comes to the legendary VF14.

 

[Purplenoise]

I haven't tried any other amp but since no one responded, I figured I'd chime in. If you want to stay close to the original circuit, build from the original schematic and try a solid state drop in replacement like the Phaedrus. Next closest would be the parallel 408As. The benefit to this amp is that the tubes are readily available and you avoid having to heat sink your big dropping resistor.

Try anything between 60M and 1G and see what you like. Not sure you'll hear any bass improvement when geting beyond a few 100 meg. I read somewhere (PRR on a guitar amp forum?) that the bigger your grid R the more hiss you get.

From what I've read, nothing will get you to a VF14. It also doesn't seem that hard to get a great mic based off the U47 design, whether it sounds like the original or not probably doesn't make any practical difference in the long run.

I also suspect that you could find a greater change in sound by swapping capsules and transformers before tubes, even when it comes to the legendary VF14.

Thank you Delta Sigma. There is also a substitute from Saturn sound if I am not mistaken. I guess my question was more if the changes in the circuit were made to improve upon the design or to compensate for the tube differences...or both. Since none of the essential components ( trafo, capsule, tube) are the same maybe Oliver fine tuned the circuitry around them. I just wanted to know, if possible, if those changes are utilitarian or for more faithful reproduction. What I do know for sure is that the design sounds awesome and definitely very close to the originals since here at the studio we have two of the original point to point Oliver’s kits. Thanks again for chiming in

 

[Delta Sigma]

I guess my question was more if the changes in the circuit were made to improve upon the design or to compensate for the tube differences...or both. Since none of the essential components ( trafo, capsule, tube) are the same maybe Oliver fine tuned the circuitry around them. I just wanted to know, if possible, if those changes are utilitarian or for more faithful reproduction.

If I remember correctly, Oliver liked 1G grid resistors and any redesign he did, used 1G:
http://www.tab-funkenwerk.org/articles-tech-documents-2/ami-microphone-schematic-archive/um57-schematics/
http://www.tab-funkenwerk.org/articles-tech-documents-2/ami-microphone-schematic-archive/cmv563-schematics/

Make sure you play with the grid resistor value. You may prefer a bigger value, 250M or so, over 60M.

The schematic looks drastically different because of the separate heater supply and deriving the bias from it.

 

[Purplenoise]

If I remember correctly, Oliver liked 1G grid resistors and any redesign he did, used 1G:
http://www.tab-funkenwerk.org/articles-tech-documents-2/ami-microphone-schematic-archive/um57-schematics/
http://www.tab-funkenwerk.org/articles-tech-documents-2/ami-microphone-schematic-archive/cmv563-schematics/

Make sure you play with the grid resistor value. You may prefer a bigger value, 250M or so, over 60M.

The schematic looks drastically different because of the separate heater supply and deriving the bias from it.

Thanks, I’ll start from 100M for r1 and r2 and fine tune from there. I was able to find a few really nice NOS hydra and Siemens ( big square ones) MP 1uf caps that test/measure really well and for c1 I’ll start with an NOS ceramic like the very first ones. For that position I also have nos wima tff’s and Mullard mustard. Resistors will be carbon film except r1 and r2. This is a fun build for schizophrenic tweakers like me lol.

 

[Purplenoise]

Has anyone used an ef802 instead of the ef800? Or maybe a comparison?
Do I need to modify anything to use the ef802 or is it a direct replacement? Thanks

 

[TLRT]

Has anyone used an ef802 instead of the ef800? Or maybe a comparison?
Do I need to modify anything to use the ef802 or is it a direct replacement? Thanks

Not need to modify anything(even east german WF brand EF860 tube is compatible) EF802 sounds a bit more opened top end I think. I have many tubes for sale if anybody needs some.

 

[Purplenoise]

Not need to modify anything(even east german WF brand EF860 tube is compatible) EF802 sounds a bit more opened top end I think. I have many tubes for sale if anybody needs some.

Thank you so much.

 

[duantro]

I just finished one of these up and it sounds great. One thing to watch out for is the headbasket screws from mk47 body from Chunger makes contact with capsule isolation pins if the pcb is too high in mount. Either get shorter M3 screws or make sure pcb isn’t too high.

 

[Purplenoise]

I just finished one of these up and it sounds great. One thing to watch out for is the headbasket screws from mk47 body from changer makes contact with capsule isolation pins if the pcb is too high in mount. Either get shorter M3 screws or make sure pcb isn’t too high.

Thanks for the heads up...I was thinking about that the other day.

 

[Purplenoise]

Hey guys, a couple of questions about the psu.
- Does the orientation of the pcb mount trim resistor matter? I am having it the other way around than what’s indicated on the psu ( trim screw away from capacitor)
- Can I use a three position pattern selector? ( same as 251 build). In that case I just connect two poles and com? Would I need to do anything else?
Thanks in advance.

 

[Purplenoise]

Almost done. Moby BV08, Siemens MP caps for c2, c3 and PIO K40 for c1. The tube is an ef802 and for now a new 3u audio M7 capsule ( which looks really good) until I get Danny’s M7. This time David from NLP audio (TLRT) build me a great psu with some extra protection.

 

[Purplenoise]

Up and running and sounding fantastic. The 3u audio M7 capsule was a big surprise...really balanced and smooth with no sibilance and a nice weight. Much smoother than the thiersch blue yet very articulate with a nice “vintage smoky-ness”.
Big thanks to Danny for all his work, Moby, TLRT and Delta Sigma for their valuable help and sharing of knowledge.
The psu was built by TLRT ( NLP audio) and it is really top notch.

  ——-UPDATE——-

So I installed a Neumann k47 and changed C1 to an NOS wima TFF. It sounds different of course but I think for now I prefer this sound. A little more detailed but still really smooth and “familiar”. The 3u m7 went in my 49 and I really like it there.