DiY AMI U47

[Moby]

Can you please tell me where you are hearing noise? Neither mic sounds noisy to me. Do you mean the room sound possibly? Is it at the end of the fingerpick example? If so, you're probably hearing the fans of my laptop at full speed, as opposed to mic noise.

The mics were aligned vertically and I played with the soundhole as close to between the mics as possible. But again, I did this shootout very quickly. The differences in the voice seem to match the differences in the guitar, IMHO.


BTW: I'm still planning to try out some more EF800 tubes and see how they affect the response of the mic, as well as doing some definitive frequency response sweeps to discover the objective differences. The ADK definitely has more 5kHz than the DiY, which seems to have more lows, and more "air."

Yes, fan noise, you can ignore my comment about that, I just hate the fan noise. Mic sounds good

 

[AusTex64]

CS-4 schematic is here: http://lucasmicrophone.lefora.com/attach/view/ma/e071bc3a026d682c1badeae847c662466fe3c885.jpg

 

[Aaronrash]

So I've been studying more on the EF12 and the heating voltage is the same as the EF800 (6.3V) The only difference is that the EF12 bias is -2V and I'm guessing the bias for the EF800 is 0V? Does anybody know what the bias voltage for the EF800 is? I also hear filament voltage so I'm guessing that's the same thing.

The good news is upon studying Chungers C12  build his power supply looks like a good candidate. It have 6.3V heater, -1V bias and the nominal 120V for the polarization voltage. All witch have trimmers and are completely adjustable. Also it would be so much cheaper than Oliver's supply witch is $475.

Aside from that if we get all the power right, I still have no idea how I would wire the EF12. It has less pins than the EF800 but the schematic is here. http://www.hifitubes.nl/weblog/wp-content/telefunken-ef12.pdf

Maybe Robert could comment, you seem to have allot of experience with tubes!

 

[Aaronrash]

Alright, I've done enough studying to the point where I've got everything figured out for using the EF12 with the AMI alternate kit. I'll post when I start the build.

 

[originalmusician]

Alright, I've done enough studying to the point where I've got everything figured out for using the EF12 with the AMI alternate kit. I'll post when I start the build.

I'm not sure if this is beneficial to you or not, but thought I'd post a few EF12-related links.

http://hps.infolink.com.br/rafafredd/EF12%20K.pdf

http://groupdiy.com/index.php?topic=42566.0

http://www.offsetguitars.com/forums/viewtopic.php?f=27&t=42991&start=15

 

[tubestation]

Hello!
I was just studying the vf14 to ef12 conversation.Everything looks sensfull, but why do they push the Capsule Voltage from 60 to 80 V?Isn t that a little high?I wrote several posts about using a M7/k47 in a G7 witch has a Capsulevoltage of 80 V and that this is too high for a Capsule like this and the Diagramm gets sucked into the Backplate.I also wrote that these Capsules sound best at 60 V.Do they try to push the Output from the Capsule to compensate the Gainloss with the ef12?
Thank you very much.
Lothar

 

[o3misha]

You may set it at 60V. Just use 2M resistors in the devider. 80V - it's just recomendation for new Thiersh M7 or new Neumann K47 capsules. Dangerous area is starting only from 90V. With 80V you will have a bit more sensitivity and better signal/noise ratio. With old M7 or old K47 use 60V polarization. Old diaphragmes has lost itheirs pliability and 80 V is too much for them.

 

[tubestation]

Hello!
Thank you for the nice Explaination.So a new Capsule will work fine at 80V,but for how long?I wouldn t like to get Problems after 15 Jears,when the aging process maybee starts to happen.The Dale style M7 don t like 80V (at least in my G 7 Mic,where a recalibration of the Voltagedivider in the Mic and the Powersupply for the Polarisationvoltage was nesessery) Don t you think that a change of the Capsulevoltage will change the sonic Charakter of the Microphone ? I think one of the Reasonns why the 47 is such a great Vocalmic is because the diagamm of the M7 Pvc is quiet thick at 10 um and therefor not supersentive and superfast.
Thanks again for making this interesting Schematic public.
Greetings from Berlin. 
Lothar

 

[Aaronrash]

Yeah I searched everywhere, talked to allot of people, read forums. It seemed like some big mystery for using the EF12 with the U47. I've talked with Adreas Grosser about it and it's clear as day now. Getting ready to start the build soon. I just need to find a voltage regulator for -6V the tube heats on negative voltage.

 

[o3misha]

Hello!
Thank you for the nice Explaination.So a new Capsule will work fine at 80V,but for how long?I wouldn t like to get Problems after 15 Jears,when the aging process maybee starts to happen.The Dale style M7 don t like 80V (at least in my G 7 Mic,where a recalibration of the Voltagedivider in the Mic and the Powersupply for the Polarisationvoltage was nesessery) Don t you think that a change of the Capsulevoltage will change the sonic Charakter of the Microphone ? I think one of the Reasonns why the 47 is such a great Vocalmic is because the diagamm of the M7 Pvc is quiet thick at 10 um and therefor not supersentive and superfast.
Thanks again for making this interesting Schematic public.
Greetings from Berlin. 
Lothar

There are only two right new M7s today, which are equal to Neumann Berlin M7s. There are Thiersh Red and Blue m7s. They can work at 80 V without problems. Thiersh M7 dangerous voltage  is 100V.

 

[AusTex64]

Hey Aaron,

This is an interesting article with comments from Mike Castoro, the founder of Wunder Audio. He's made a couple of U47 inspired mics:

http://recordinghacks.com/reviews/tapeop/wunder-audio-cm7/

I totally agree with this statement: <Castoro says there are three primary elements used to create the U 47–plus sound: the capsule, the transformer, and the tube… in that order.>

Note that Wunder/Castoro uses EF14, but also make a glass tube version too. Oliver's alt schematic calls for EF14. Flea uses EF12. I have no idea what the difference in tone is between EF14 and EF12 and EF800/802/804. Klaus Heyne says that no U47 will truly sound like a U47 without VF14M, period. Who's right? Hell if I know! I know my two new Eric Johnson Stratocasters sound and feel VERY, VERY much like my '57 Strat. Close enough that EJ is playing new Strats and leaves the old ones at home now. And he wouldn't do that if he felt there was ANY compromise. EJ is a no-compromise kind of guy when it comes to tone. With all due respect to Klaus, I don't subscribe to the idea that a great Strat (or mic) can't be made without the original components from the 50's.

I'm using a NOS Telefunken EF802 tube in my U47-ish build, with Thiersch PVC capsule and TAB transformer. This may sound lame, but if Tele EF802 is good enough for Oliver and Terry in the Lucas CS-4, it's good enough for me. I agree with the comments in this thread about how different tubes can sound different though. I thought that was cork-sniffing, until I actually tried different tubes, recorded the results and listened. Tube noise, microphonics and frequency response can vary pretty dramatically when in tube mics, more noticeably than in guitar amps, for example. One thing I've learned is don't build a mic without two or three tubes to try. Sorry for that expensive bad news! Just ran into this on a TAB C12 build. First Telefunken tube had low gain and was noisy, next tube of exactly the same type was money. This is really something to consider for the DIY tube mic builder, and something that sets the pros apart from guys like me. The pros have 100's or 1000's of tubes to try out before they find "the ones". Read what Klaus Heyne says about tube replacements on the REP forum.

FWIW, I'm in Austin. Maybe once your mic is done we could do a little comparison, especially if you use the same capsule and transformer.

Looks forward to your posts on the EF12 build. Hell, you may end up changing my mind about EF802's....

Robert

 

[Melodeath00]

Robert, I thought you were using the EF800, not the 802? I'm very curious to try the EF802, but I noticed the cathode resistor and the one of the resistors going to the tube plate in the CS-4 schematic are different values than those in the AMI kit. Did you follow the AMI kit values, but use EF802, or did you adjust to the values in the CS-4 schematic? Also, where did you get your EF802? I have emailed Oliver asking if I could buy one, and what his advice was regarding circuit-adjustment, but no response yet.

Aaron, did Grosser have anything interesting to say about the EF12? It sounds like talking to him really cleared everything up.

Since I have my U47-esque mic and a Manley Reference Cardioid, I am able to compare their responses to the responses of similar comparisons online. What I have found is that my U47-esque mic seems to be a little bit brighter than a real U47 (4kHzor 5kHz and up). Of course, I don't know the age/condition of the U47 from the online shootouts, nor even what capsule they are using. Maybe it's an M7 (I'm using a K7, which sounds closer to a K47). In fact, maybe their Manley is just brighter than mine. It's all relative to how both mics sound compared to one another. Regardless, it's interesting, and I wonder if maybe the EF800 is more open sounding than a VF14. Or maybe I could tame the highs with paper in oil caps? By no means am I displeased with my U47 build. It sounds amazing. I just find it interesting that it has more air in comparison so my Manley, than a genuine U47 does compared to their Manley.

Thanks!

 

[AusTex64]

<Did you follow the AMI kit values, but use EF802, or did you adjust to the values in the CS-4 schematic?>

It appears the U47 kit Oliver sells utilizes the CS-4 components without the relay. Note on the CS-4 schematic that the pinout on the PSU Binder is the same as what's shipping in the PSU we had to rewire to match the incorrect schematic on the TAB website.

I know Oliver's been totally busting ass leading up to AES this past weekend. Next time we talk, I'm gonna suggest he edits the CS-4 drawing to replace the U47 Alternate Tube with Remote Pattern Selection schematic he has on the TAB website. That should bring everything in line.

<Also, where did you get your EF802?> I have befriended an older gentleman that collects tubes, ham radios and audio gear. He's my tube connection. He's kinda cranky and doesn't like dealing with the public much, it was a mutual friend referral. Sorry I can't help you on that one.

Robert

 

[scott_humphrey]

Check German eBay for EF802s.

 

[Melodeath00]

<Did you follow the AMI kit values, but use EF802, or did you adjust to the values in the CS-4 schematic?>

It appears the U47 kit Oliver sells utilizes the CS-4 components without the relay. Note on the CS-4 schematic that the pinout on the PSU Binder is the same as what's shipping in the PSU we had to rewire to match the incorrect schematic on the TAB website.

I know Oliver's been totally busting ass leading up to AES this past weekend. Next time we talk, I'm gonna suggest he edits the CS-4 drawing to replace the U47 Alternate Tube with Remote Pattern Selection schematic he has on the TAB website. That should bring everything in line.

<Also, where did you get your EF802?> I have befriended an older gentleman that collects tubes, ham radios and audio gear. He's my tube connection. He's kinda cranky and doesn't like dealing with the public much, it was a mutual friend referral. Sorry I can't help you on that one.

Robert

Hi Robert, yes, it looks like Lucas parts and the same basic schematic sans relay. However, the values for R2 and R8 in the Lucas schematic are different from the values I received and the ones you listed out receiving in Reply #64. I wondered if this was for EF802 optimization over the EF800/EF14. We're talking 100 ohm versus 110, and 51kohm versus 47kohm, respectively.

Check German eBay for EF802s.

Thanks. I've seen some EF802 tubes online and on ebay, but didn't know if they were "mic grade." More importantly, I'm not sure if I need to adjust my circuit before I swap tubes.

 

[scott_humphrey]

The NOS Telefunken EF802s that I've purchased have all been good--no noise problems, no microphonic duds. They seem consistent from tube to tube, and they are inexpensive  …for now. Good luck!

 

[AusTex64]

<Hi Robert, yes, it looks like Lucas parts and the same basic schematic sans relay. However, the values for R2 and R8 in the Lucas schematic are different from the values I received and the ones you listed out receiving in Reply #64. I wondered if this was for EF802 optimization over the EF800/EF14. We're talking 100 ohm versus 110, and 51kohm versus 47kohm, respectively.>

Good eye, I had not noticed those differences. I did not change those values when I installed EF802 in my build, and it sounds great. I'm gonna ask Oliver about that though....

 

[Melodeath00]

<Hi Robert, yes, it looks like Lucas parts and the same basic schematic sans relay. However, the values for R2 and R8 in the Lucas schematic are different from the values I received and the ones you listed out receiving in Reply #64. I wondered if this was for EF802 optimization over the EF800/EF14. We're talking 100 ohm versus 110, and 51kohm versus 47kohm, respectively.>

Good eye, I had not noticed those differences. I did not change those values when I installed EF802 in my build, and it sounds great. I'm gonna ask Oliver about that though....

Please let me know what he says if he replies. I sent him an email about it a little before AES, but haven't heard back.

 

[sr1200]

Im about to start a U47N clone.  I've sourced almost all the parts.  Going with a body from Equinox that I'll have to mod to put the polarity switch on the mic rather than at the PS case.  I have one question regarding the original 47N schematic, in the component designated as S1 (just behind the ST1 and 2 and infront of the transformer)  It is marked as 50ohm and 200 ohm.  Is this a relay of some sort or switch.  And if anyone has a source for this part or a data sheet or something would be much appreciated.

Also am i crazy for wanting to build the mic with a nuvistor over something more readily available?

 

[Phrazemaster]

Im about to start a U47N clone.  I've sourced almost all the parts.  Going with a body from Equinox that I'll have to mod to put the polarity switch on the mic rather than at the PS case.  I have one question regarding the original 47N schematic, in the component designated as S1 (just behind the ST1 and 2 and infront of the transformer)  It is marked as 50ohm and 200 ohm.  Is this a relay of some sort or switch.  And if anyone has a source for this part or a data sheet or something would be much appreciated.

Also am i crazy for wanting to build the mic with a nuvistor over something more readily available?

I am by no means the expert, or even that good with electronics, but I can tell you that if the schematic is like most U47 schematics I've seen, the S1 represents how the transformer can be wired; I think a switch could be installed to wire it one way or the other. I believe the 200R configuration is standard, but someone correct me if I'm wrong. But this is the transformer impedance (corrections welcome!).

Also, forgive if you are already aware of this, but since many old U47s were retrofitted with the Nuvistor tubes, it's widely held they don't sound nearly as good with this tube over the stock VF14. As the VF14 is as rare as the striped blue dodo-pottamus, using the EF12k or another tube is preferred.

Hope that helps a little; other opinions and corrections to my post welcomed.

Mike