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

[dmp]

Thanks for posting the clips.
Curious if you could do the calibration sweep of them and compare the amplifier response. See my post back on page 11 showing the response with the bv12
Wondering if the feedback winding on the T67 vs BV12 differ.

 

[Studio Mollan]

Thanks for posting the clips.
Curious if you could do the calibration sweep of them and compare the amplifier response. See my post back on page 11 showing the response with the bv12
Wondering if the feedback winding on the T67 vs BV12 differ.

You're right. I'll try to do that. Couldn't you modify the feedback to work best with a certain transformer. The cap in the schematics is specified 80-160 so maybe trying different values there can "tune" the circuit to the transformer?
Anybody?

Also I would like to confirm that the output is wired for 200ohm or not. I few posts back someone said the clone didn't have the same output as an original u67. Different output impedance could be the answer to that question.
/
Emil

 

[tskguy]

Have you ruled out the capsule??? I would be more inclined to think it was the capsule more than the TX...
  Wave and I built 67's at the same time his has a AMI tx and my tx is an IoAudio  and they could be a matched pair, If it were me I would swap capsules and see if it fallows the capsule.

Eric

 

[Studio Mollan]

Have you ruled out the capsule??? I would be more inclined to think it was the capsule more than the TX...
  Wave and I built 67's at the same time his has a AMI tx and my tx is an IoAudio  and they could be a matched pair, If it were me I would swap capsules and see if it fallows the capsule.

Eric

Well I guess it might, but given my two pairs sound identical and try only parts that differ is the transformer I just figured that's the issue. All capsules bought at the same time from beesneez. I'll try to perform more tests on them and try to figure out what's wrong.

 

[dmp]

With comparing two identical pairs, it seems unlikely that is capsule variations.
I wonder if the feedback loop of the t67 is wrong. If they aren't correctly rolling off the high end, it would definitely sound brighter.
Sweeping the amplifier response will answer this.

 

[Studio Mollan]

With comparing two identical pairs, it seems unlikely that is capsule variations.
I wonder if the feedback loop of the t67 is wrong. If they aren't correctly rolling off the high end, it would definitely sound brighter.
Sweeping the amplifier response will answer this.

So you think that the IOaudio is the most authentic sounding? I havent worked with a real one so im kind of guessing which one is closest. My immediate impression is that the IOaudio is dull but it might just as well be the other way around. I sure find the brighter AMI ones more usefull int the studio.

 

[dmp]

I don't know, but I don't think subtle differences in the transformer winding wouldn't cause such a big difference. I think there is something out of spec in one of the mics.

 

[Studio Mollan]

I don't know, but I don't think subtle differences in the transformer winding wouldn't cause such a big difference. I think there is something out of spec in one of the mics.

You're probably right I'll try to crosscheck them and see if i might done something wrong on them. Still anybody who's heard both versions, and maybe the an original, please share your experience. Would be very gratefull!

/
Emil

 

[Studio Mollan]

Thanks for posting the clips.
Curious if you could do the calibration sweep of them and compare the amplifier response. See my post back on page 11 showing the response with the bv12
Wondering if the feedback winding on the T67 vs BV12 differ.

So you just ran a 1k signal through the test input and recorded the output from the microphone? Capsule mounted or a cap instead?

 

[dmp]

Either way, manual excerpt below.  The 1500 cps is a misprint I believe and should be 15000 cps.
Basically set it to omni, feed the calibrating input and measure the mic output level for the 1kHz signal. Then change to 15kHz and the level should be 10 dB lower.

"For purposes of checking the frequency response of the amplifier, a test signal may be fed to the instrument jack marked "calibrating input" at one end of the power supply. Proceed as follows: From the 600 ohm output of a signal generator, feed a 1000 cps tone at a level of -18 dbm to the calibrating input. You may use the model z-58 dummy head or can proceed with the regular head assembly plugged in. The three switches are set for "omni", full sensitivity, and linear frequency response. The following output levels are to be observed at the output of the 150/250 ohm impedance, using a vacuum tube voltmeter:

1000 cps:    -38dB    1dB
40 cps:        -43dB    1dB
1500 cps:  -48dB      1dB

 

[poctop]

Thanks for posting the clips.
Curious if you could do the calibration sweep of them and compare the amplifier response. See my post back on page 11 showing the response with the bv12
Wondering if the feedback winding on the T67 vs BV12 differ.

You're right. I'll try to do that. Couldn't you modify the feedback to work best with a certain transformer. The cap in the schematics is specified 80-160 so maybe trying different values there can "tune" the circuit to the transformer?
Anybody?

Also I would like to confirm that the output is wired for 200ohm or not. I few posts back someone said the clone didn't have the same output as an original u67. Different output impedance could be the answer to that question.
/
Emil

I can confirm that the output from the 2 audio coil are connected in series and connected trough the adapter board for the AMI and the main pcb for Max transformer  , meaning 200ohm output impedance  not to be confused with DCR of the coil it self.
Best,
dAn,

 

[poctop]

Posted this a While Ago , with the 2 Iron ,  this is what you should expect as comparaison ,

See here,

http://www.groupdiy.com/index.php?topic=49675.msg629064#msg629064

http://db.tt/OrBatA9S First clip is the BV.12

https://cdn.groupbuilder.com/groupdiy/u/39511/58d028199409f First clip is the AMI

 

[Studio Mollan]

Thanks for posting the clips.
Curious if you could do the calibration sweep of them and compare the amplifier response. See my post back on page 11 showing the response with the bv12
Wondering if the feedback winding on the T67 vs BV12 differ.

You're right. I'll try to do that. Couldn't you modify the feedback to work best with a certain transformer. The cap in the schematics is specified 80-160 so maybe trying different values there can "tune" the circuit to the transformer?
Anybody?

Also I would like to confirm that the output is wired for 200ohm or not. I few posts back someone said the clone didn't have the same output as an original u67. Different output impedance could be the answer to that question.
/
Emil

I can confirm that the output from the 2 audio coil are connected in series and connected trough the adapter board for the AMI and the main pcb for Max transformer  , meaning 200ohm output impedance  not to be confused with DCR of the coil it self.
Best,
dAn,

Alright. Thanks for clearing that up for me Dan!!
Can you chime in on the hi end difference between my Max/Ami transformers? I know you did a voice test early on which confirmed the max version having less hi end/more saturated. What's your first impression listening to the clips a few posts back? Transformer alone or something I've done wrong putting them together? How would changing value of C17 alter the sound?

 

[poctop]

Thanks for posting the clips.
Curious if you could do the calibration sweep of them and compare the amplifier response. See my post back on page 11 showing the response with the bv12
Wondering if the feedback winding on the T67 vs BV12 differ.

You're right. I'll try to do that. Couldn't you modify the feedback to work best with a certain transformer. The cap in the schematics is specified 80-160 so maybe trying different values there can "tune" the circuit to the transformer?
Anybody?

Also I would like to confirm that the output is wired for 200ohm or not. I few posts back someone said the clone didn't have the same output as an original u67. Different output impedance could be the answer to that question.
/
Emil

I can confirm that the output from the 2 audio coil are connected in series and connected trough the adapter board for the AMI and the main pcb for Max transformer  , meaning 200ohm output impedance  not to be confused with DCR of the coil it self.
Best,
dAn,

Alright. Thanks for clearing that up for me Dan!!
Can you chime in on the hi end difference between my Max/Ami transformers? I know you did a voice test early on which confirmed the max version having less hi end/more saturated. What's your first impression listening to the clips a few posts back? Transformer alone or something I've done wrong putting them together? How would changing value of C17 alter the sound?

I did not heard your sample yet , but  I will shorlty ,  and report back ,
I do like the "gritty" harmonics from IOaudio Transformer it really reminds me of the neumanish sounds,
as far a C17 goes it dictates the linearity of the High end the slope in other terms  , so it might have to be adjusted for your transfomer,
i would suggest you put up the lowest values and then the highest value to suit and listen out,
Best,
DAN,

 

[Studio Mollan]

Thanks for posting the clips.
Curious if you could do the calibration sweep of them and compare the amplifier response. See my post back on page 11 showing the response with the bv12
Wondering if the feedback winding on the T67 vs BV12 differ.

You're right. I'll try to do that. Couldn't you modify the feedback to work best with a certain transformer. The cap in the schematics is specified 80-160 so maybe trying different values there can "tune" the circuit to the transformer?
Anybody?

Also I would like to confirm that the output is wired for 200ohm or not. I few posts back someone said the clone didn't have the same output as an original u67. Different output impedance could be the answer to that question.
/
Emil

I can confirm that the output from the 2 audio coil are connected in series and connected trough the adapter board for the AMI and the main pcb for Max transformer  , meaning 200ohm output impedance  not to be confused with DCR of the coil it self.
Best,
dAn,

Alright. Thanks for clearing that up for me Dan!!
Can you chime in on the hi end difference between my Max/Ami transformers? I know you did a voice test early on which confirmed the max version having less hi end/more saturated. What's your first impression listening to the clips a few posts back? Transformer alone or something I've done wrong putting them together? How would changing value of C17 alter the sound?

I did not heard your sample yet , but  I will shorlty ,  and report back ,
I do like the "gritty" harmonics from IOaudio Transformer it really reminds me of the neumanish sounds,
as far a C17 goes it dictates the linearity of the High end the slope in other terms  , so it might have to be adjusted for your transfomer,
i would suggest you put up the lowest values and then the highest value to suit and listen out,
Best,
DAN,

Thanks Dan!
I could tell instantly that max's trafos were darker from your first speech tests and I liked it. That's why I got two ami and two max kits. To have two flavors at hand. But in use the difference is quite brutal.. I will try to mod C17 to get what I want. I like them dark sounding, I'm not looking for a hifi thing here, only to get some more hi frequencies.
I will also test the amplifiers and try to measure the transformers for faults. Do you know what the correct measurements of the BV12 would be? Can I tear this with a ohm-meter?

 

[poctop]

I recommend you contact Max for the DCR measurement of each windings,

best,
dAn,

 

[Studio Mollan]

A question about C17. The ones I got from the guy on the first page on this thread are labels 100j. Isn't that 10pf? 101 is 100. 102 is 1000. 100 is from what I've gathered 10.
That could sure explain strange hi end behavior.
/
Emil

 

[jpertusi]

...anyone...  Bueller?

"Do the numbered locations on the PCB (1, 2, 3 on the XLR out and 1 thru 7 on the MIC out) correspond to the pin numbers I should be connecting them to on the connectors?"

Is there a pinout for this section of the PCB?  I just want to be extra careful here...

Also... just got my bv12's!!!  Thanks Max!!!

Thanks as always gang.

 

[Bassniac]

Hey there.
What switch and lamp is everybody using for their PSU? (230Vs)

Cheers

 

[tskguy]

It really truly dumbfounds me how you guys are spinning all this comparison with different capsules!!
Please at least use the same capsule while doing these comparisons!! Or none at all! Remember 90 percent of the sound of a mic is the capsule. GEESH!!!