DiY AMI U47

Help Support GroupDIY:

Melodeath00

Well-known member
Joined
Jun 7, 2012
Messages
416
Ok I have a Beesneez K7 on the way, and I need a mic to put the capsule in! This is my first mic build. Originally when I bought the K7, I was planning to build a 47FET, but cheap bodies are currently out of stock. So, I am 90% sure I am going to build an alternate tube U47, using AMI's schematic, which was my very first DiY plan anyway. I wont need to build the PSU or cable, and will have the mic body and transformer, and capsule. I am going to purchase a Telefunken EF800.

What I need help with is selecting the most "authentic" parts for the circuit. This is the schematic for those not familiar: http://www.tab-funkenwerk.com/id85.html

Can anyone provide any advice on what types of parts I should get? For example, styroflex or polypropylene. I am a noob when it comes to building, and I am no expert on the history of the U47, so I don't know what parts material-wise were originally in the circuit. I know clearly my diy U47 will not be exactly like a vintage U47, since I'm not using a Neumann capsule, Neumann transformer, or VF-14, but I'd like to get as close as possible. Even if the circuit parts don't affect the sound as much as these other components, I'd like to be as "authentic" as possible, even if it's just for fun. That's why I'm asking. Thanks!
 

Moby

BV.8, Bv.11, Bv.12, T14/1, etc... contact by email
Joined
Jun 3, 2004
Messages
1,877
Location
Serbia
Melodeath00 said:
I know clearly my diy U47 will not be exactly like a vintage U47, since I'm not using a Neumann capsule, Neumann transformer, or VF-14, but I'd like to get as close as possible. Even if the circuit parts don't affect the sound as much as these other components, I'd like to be as "authentic" as possible, even if it's just for fun. That's why I'm asking. Thanks!
You already made the answer in your question. Without exact head-grill, body, transformer and tube you will be far away from authentic sound of U47. Passive components affect this sound a bit but it will not lead you at vintage direction without "hart elements" . You can probably live without VF14M but the rest of parts are crucial for vintage sound. Best way for you is to experiment and find the color of sound what suits your needs ;)
BTW, the most of U47's passive components are obsolete too, so there is a slight chance to source them.
 

Melodeath00

Well-known member
Joined
Jun 7, 2012
Messages
416
Moby said:
Melodeath00 said:
I know clearly my diy U47 will not be exactly like a vintage U47, since I'm not using a Neumann capsule, Neumann transformer, or VF-14, but I'd like to get as close as possible. Even if the circuit parts don't affect the sound as much as these other components, I'd like to be as "authentic" as possible, even if it's just for fun. That's why I'm asking. Thanks!
You already made the answer in your question. Without exact head-grill, body, transformer and tube you will be far away from authentic sound of U47. Passive components affect this sound a bit but it will not lead you at vintage direction without "hart elements" . You can probably live without VF14M but the rest of parts are crucial for vintage sound. Best way for you is to experiment and find the color of sound what suits your needs ;)
BTW, the most of U47's passive components are obsolete too, so there is a slight chance to source them.
Well, I know it will not be exactly like a vintage U47, but I think it will be in the right ballpark. From what I understand, the AMI headbasket and transformer are at least pretty close, if not very close, and the K7 capsule gets extremely favorable reviews in comparison to a real K47.

So all of the component materials in the U47 are not made any more? Again, I am completely ignorant in this regard. I know some of you talk about carbon resistors and ceramic, poly-, etc...
 

Moby

BV.8, Bv.11, Bv.12, T14/1, etc... contact by email
Joined
Jun 3, 2004
Messages
1,877
Location
Serbia
You can try with carbon film resistors for a start
 

o3misha

Well-known member
Joined
Nov 19, 2012
Messages
228
Forget about old resistors. Modern resistors are much better and relible than old carbon composition resistors. Epecially high value resistors (like grid and polarization resistors). The material of resitors is important only in high current amplification circuits. Like guitar combo. Only type of capacitors in U47 is important  for sound. IMO
 

Melodeath00

Well-known member
Joined
Jun 7, 2012
Messages
416
Thanks for the replies guys. I'm still a bit lost, but I've done a tiny bit of googling today...

After this little bit of research, I've gathered the original U47 used metal paper (with tar) capacitors. I'm going to guess one cannot purchase this type anymore. Is that correct? Maybe the next best option is paper in oil or styroflex? I think styroflex is relatively easy to get, but where does one find paper in oil? Is that really a good option? Other choices are polypropylene, but that is not a "vintage" choice, right? I imagine these are pretty basic questions...

So resistor type doesn't have much effect on sound? How do R1 and R5 effect the circuit? I have read conflicting info as to whether these effect the tube biasing, or are filters for the capsule, and I see they are rated as 1G, compared to 100M and 60M in the original U47 schematic.

If anyone has any other thoughts regarding the original question, please chime in.
 

Moby

BV.8, Bv.11, Bv.12, T14/1, etc... contact by email
Joined
Jun 3, 2004
Messages
1,877
Location
Serbia
Thanks for the replies guys. I'm still a bit lost, but I've done a tiny bit of googling today...

After this little bit of research, I've gathered the original U47 used metal paper (with tar) capacitors. I'm going to guess one cannot purchase this type anymore. Is that correct? Maybe the next best option is paper in oil or styroflex? I think styroflex is relatively easy to get, but where does one find paper in oil? Is that really a good option? Other choices are polypropylene, but that is not a "vintage" choice, right? I imagine these are pretty basic questions...
Yes, Bosch MP see the pic of the NOS one ;)
20130409_234849.jpg

Paper in oil is OK but with slight different sonic character. Most of people prefer Polyester but that's a matter of taste.
 

Melodeath00

Well-known member
Joined
Jun 7, 2012
Messages
416
Can Bosch MP be bought NOS?

Is polyester the same as polypropylene, or styroflex? Forgive my ignorance, and thanks!
 

Moby

BV.8, Bv.11, Bv.12, T14/1, etc... contact by email
Joined
Jun 3, 2004
Messages
1,877
Location
Serbia
Melodeath00 said:
Can Bosch MP be bought NOS?

Is polyester the same as polypropylene, or styroflex? Forgive my ignorance, and thanks!
Google is your friend  :)
 

Melodeath00

Well-known member
Joined
Jun 7, 2012
Messages
416
Those are rated 400V, as opposed to 250V like in the schematic. What effect does that have if I used them? I appreciate everyone's help
 

HellfireStudios

Well-known member
Joined
Oct 17, 2011
Messages
513
Location
The Sunshine State
Melodeath00 said:
Those are rated 400V, as opposed to 250V like in the schematic. What effect does that have if I used them? I appreciate everyone's help

Going up in voltage won't hurt anything, but make sure they will fit. The higher the voltage the larger the size. Datasheets are a great resource for dimensions.

-James-
 

o3misha

Well-known member
Joined
Nov 19, 2012
Messages
228
Melodeath00 said:
Those are rated 400V, as opposed to 250V like in the schematic. What effect does that have if I used them? I appreciate everyone's help
1uF/400 caps are too bulky for U47. You may use only 1uF/160VDC or 0.5uF/250VDC. Also, you may use square PIO Bosch or RFT PIO or Russian PIO caps with very good results. I also like  modern capacitors like Jupiter  caps 1uF/600V paper in wax . The price is also around 50USD. Jupiters are also bulky, but you may use C3 1uF Jupiter and C2 Polyester cap. But you have to realize that caps don't affect on sound very much in comparisson with capsule and transformer. Caps affects on coloration of sound, in Hi freq-s. Old Pio or MP caps will give you softer High end. Polyester or Polypropilene caps are more neutral. Resistors :  Neumann  used R1 and R2 both 100M and both C2 and C3 1uF/160VDC caps for first 100 or so U47s. But  in later U47s Neumann used 60M R2 and 0.5uF C3. This suggests that there was a struggle with excessive bottom end to get better midrange.  I would not recommend using a high-resistance resistors  with value higher than 500 Mohm for tube microphones, its not necessary at all. I would start with 100M. With bigger value you may loose a bit midrange, IMO.
 

Melodeath00

Well-known member
Joined
Jun 7, 2012
Messages
416
Thank you! So these 400V Bosch are too bulky most likely.

I figured capsule and tube and transformer will have a bigger effect than capacitors, so that's a good point.

So those resistors don't affect the bias of the tube at all, and only effect frequency response? I wonder why Oliver recommends 1G instead of the original spec.
 

Pip

Well-known member
Joined
Nov 17, 2004
Messages
629
Location
New York City
Capacitors will change the voicing of a microphone depending on where they are in the circuit. The voltage is not as important as the value, keeping in mind you have to have a good amount of safety over the circuits maximum potential so as you dont blow things up. For example in a C12 Microphone the power supply B+ tops out at around 200VDC so I would choose an output cap of no less than 250VDC, anything above that that fits go for it. Same with a U47. The original output cap had a value of .5mfd @ 250VDC. It was also a fairly large metal can paper in oil.

I prefer Polypropylene or paper in oil in the output. It is what sounds best to my ear. But experiment thats what its all about. Capacitors are relatively cheap and EBAY is your friend.

AMI transformers are awesome. Tab Funkenwerk website one of the best. Also checkout MK47 Build thread on this forum.

The tube is all about its functionality more than what kind. I like the EF80 or EF800 for a modern day U47 but buy a few as not all tubes are up to snuff for a microphone circuit. Again EBAY can be your friend.

Capsules rule and here I give some web sites:

http://www.thiersch-mic.de/en/eindex.html
http://microphone-parts.com/
http://www.vintagemicrophonepcbkit.com/index.html
 

EvLoutonian

Well-known member
Joined
Jul 7, 2010
Messages
184
I'm loving that you started this thread, as this should be my next mic DIY project after I complete the MK47.

(I'll also be using EF800, but with the Equinox body kit, & probably Equinox capsule, as I already have one here .. but not sure yet).

I'm in a similar boat, as far as lack of experience and knowledge on specific component selection etc.
(and some other questions as demonstrated in my current MK47 build thread posts re. cable wiring).
Shall watch on here with interest! 
Evan
 

Melodeath00

Well-known member
Joined
Jun 7, 2012
Messages
416
Ok, my AMI kit is on the way and I have the K7 on hand. So now it's time to get to business with these parts. Since I have spent a good amount of money on the core parts (capsule and transformer/kit), and they are the major component of the sound, I don't want to go too crazy with the resistors and capacitors.

Am I correct in assuming that C1, C2, and C3 will have a bigger affect on the tone/sound than C4 and C5? I believe C4 and C5 are only there for the polar pattern switching. If so, maybe I should opt for PIO or polyprop for C1, C2, and C3, and something even cheaper for C4 and C5?

Oliver informed me that the 1G resistors are to get more bass out of the capsule. Maybe I should get a set of 1G and a set of original schematic 100M and try both?
 

marcus4audio

Well-known member
Joined
Apr 23, 2013
Messages
69
Melodeath00 said:
Ok, my AMI kit is on the way and I have the K7 on hand. So now it's time to get to business with these parts. Since I have spent a good amount of money on the core parts (capsule and transformer/kit), and they are the major component of the sound, I don't want to go too crazy with the resistors and capacitors.

Am I correct in assuming that C1, C2, and C3 will have a bigger affect on the tone/sound than C4 and C5? I believe C4 and C5 are only there for the polar pattern switching. If so, maybe I should opt for PIO or polyprop for C1, C2, and C3, and something even cheaper for C4 and C5?

Oliver informed me that the 1G resistors are to get more bass out of the capsule. Maybe I should get a set of 1G and a set of original schematic 100M and try both?
R2 dont go over 250 M Ohm
the tube is not stable with high pressure level
with 100 or 200 M Ohm all is fine
 

Pip

Well-known member
Joined
Nov 17, 2004
Messages
629
Location
New York City
Melodeath00 said:
Ok, my AMI kit is on the way and I have the K7 on hand. So now it's time to get to business with these parts. Since I have spent a good amount of money on the core parts (capsule and transformer/kit), and they are the major component of the sound, I don't want to go too crazy with the resistors and capacitors.

Am I correct in assuming that C1, C2, and C3 will have a bigger affect on the tone/sound than C4 and C5? I believe C4 and C5 are only there for the polar pattern switching. If so, maybe I should opt for PIO or polyprop for C1, C2, and C3, and something even cheaper for C4 and C5?

Oliver informed me that the 1G resistors are to get more bass out of the capsule. Maybe I should get a set of 1G and a set of original schematic 100M and try both?


I assume you are doing Mr. Archuts remote switching version. C3 is the one that is going to most effect the sound. In the original this and C1 were a dual PIO Can cap. Keep in mind that some of these more exotic options are big. There is only so much room inside the can ;D

As to the resistors I say yes try both. I myself am starting with the 1G NOS Tesla Glass.

I am interested in how the AMI body is to work in. I just finished a build using the Equinox Systems offering and had some issues. That being said they make a great product for the price and they seem very passionate about what they do. It's just as I was building the MK47 project working towards this project I found myself wanting when it came to internal mounting options.

Lastly PSU's what are people going with. As most of the newer designs call for a tube that leaves the single supply voltage concept behind, I was wondering what people had in mind.
 

Melodeath00

Well-known member
Joined
Jun 7, 2012
Messages
416
Pip said:
Melodeath00 said:
Ok, my AMI kit is on the way and I have the K7 on hand. So now it's time to get to business with these parts. Since I have spent a good amount of money on the core parts (capsule and transformer/kit), and they are the major component of the sound, I don't want to go too crazy with the resistors and capacitors.

Am I correct in assuming that C1, C2, and C3 will have a bigger affect on the tone/sound than C4 and C5? I believe C4 and C5 are only there for the polar pattern switching. If so, maybe I should opt for PIO or polyprop for C1, C2, and C3, and something even cheaper for C4 and C5?

Oliver informed me that the 1G resistors are to get more bass out of the capsule. Maybe I should get a set of 1G and a set of original schematic 100M and try both?


I assume you are doing Mr. Archuts remote switching version. C3 is the one that is going to most effect the sound. In the original this and C1 were a dual PIO Can cap. Keep in mind that some of these more exotic options are big. There is only so much room inside the can ;D

As to the resistors I say yes try both. I myself am starting with the 1G NOS Tesla Glass.

I am interested in how the AMI body is to work in. I just finished a build using the Equinox Systems offering and had some issues. That being said they make a great product for the price and they seem very passionate about what they do. It's just as I was building the MK47 project working towards this project I found myself wanting when it came to internal mounting options.

Lastly PSU's what are people going with. As most of the newer designs call for a tube that leaves the single supply voltage concept behind, I was wondering what people had in mind.
Yes, I'm building Oliver's circuit. Thanks for that info. So maybe I will try to do PIO for C1 and C3 at the very least. I'm extremely inexperienced, so I have no real clue as to relative sizes of the working space and the capacitors.

I also bought the AMI PSU. It's NG-style (non-regulated) and has remote pattern switching.
 

Latest posts

Top