Continuity, as in a beep from a continuity tester? One side of your heater is tied to the 6.3V supply, the other to ground. The heater is probably 10 or 20 ohms. Likely enough to make a beep.
Telefunken ELA M 251 Clone Tube Microphone Build Thread (D-Ela M 251E)
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Homestudio
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Thanks Delta, okay tested R3, R5 both 58.5. R2 is 53.1. My thinking now is the trany’s the culprit since I’m getting no signal out of the mic. Is there a way to test this? Again much thanks.
mihi_fuchs
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You can measure the resistance/conductivity of each coil and that they are non-conductive to each other. Other than that you can feed it a sine wave and see what’s coming out on the other end.
BR
Michael
Homestudio
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Thanks Michael, I’ll try your suggestions. I’m assuming the trany needs to be removed from the circuit to do the tests.
Much appreciated
mihi_fuchs
Well-known member
for measuring the resistance/conductivity not necessarily. also if you feed the sine wave right into the coil, i do not see a point why it should be removed. just do not power up the mic, as it‘s not nessecary and complicates handling (safety regards).
good luck - hope you find the fix fast.
BR
Michael
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Checked the capsule and the backplates are shorted. Would this be a cause for no signal output?
mihi_fuchs
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Depends on pattern selection - but at least in cardioid there should be no influence on that (the second Half of the capsule is "offline" in that polar pattern). At least according to the original schematic. Which schematic did you use again?
BR
Tim Campbell
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What capsule did you use?
Homestudio
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This is Danny’s D-Ela M 251E pcb.
Capsule is a JLI-86U. After sorting things out I’ll be installing the Beesneez CK12.
Also using a EH 6072 for testing.
Capsule is a JLI-86U. After sorting things out I’ll be installing the Beesneez CK12.
Also using a EH 6072 for testing.
mihi_fuchs
Well-known member
Maybe post a pic of back and front of your pcb. In cardioid it should work with conn backplates. Make sure you connected to the right backplate connection. Other than that you can check if you have the right relays (normally closed/open is an option; i don‘t know if the polarization of the coil matters - i‘d need to recheck with the schematics).
Hope you get it running soon - it is a really nice mic
…
egroys
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Does anyone here have experience with the Phaedrus 6072M they could share?
Tim Campbell
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At about 200 dollars for the Phaedrus 6072M you could buy many great sounding EH6072 tubes or even get lucky with finding a GE that sounds good
Last edited:
egroys
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I have some for sale ín the black market. They have cleaner sound and lower noise than NOS 6072's
EH6072 tubes are the quietest tubes of all I have tested and compared in all AKGs circuits and they are very cheap. But also the "flattest" and most boring candidates for 251 (also C12 / SM204) tested with all my capsules from Beesneez, OPR... and MBHO as well as AKG Nylon. GE has a mojo that I miss in "almost" all other tubes tested, but which somehow every "real" C12 capsule demands to interact and deliver this optimum of sound quality...
My 50 €¢
My 50 €¢
Tim Campbell
Well-known member
HerbertR before I heard the ElectroHarmonix tube in my FLEA 251 I would have agreed with you. I own a vintage 251 with a GE 5 star 6072 and at least a dozen NOS GE 6072 5 stars. I tried switching the EH tube out and really it made no difference. I will say that FLEA claims to hand select their tubes.
Tim, I've ordered about a dozen EH6072s over the last year from various sources in France and Germany... and the quality is pretty good and consistent. And there hasn't been a tube more noisy or even bad as the noise level of a good GE6072A or Siemens Halske ECC801S that I've ever bought. But I've also never found an EH with that ultra elegant, cutting midrange presence, with those perfectly balanced sibilances, highs and lows that the GE delivers. Not a little bit or at least with a homeopathic dose of GE. Would be intersting how much FLEA test to find a fitting one and how do they really sound compared to GE...
Tim Campbell
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Well I have only heard the one tube. Maybe it was a fluke.
RuudNL
Well-known member
I have also very good expeiences with the EH tubes. Low noise and durable.
In fact I replaced the factory 'selected' EF86 in my Neumann U67 (re-release) with an EH with as result a lower self noise!
In the past I have also used JJ Electronic tubes. They work for a couple of weeks but after that they develop a high noise level and start 'crackling'.
What I also find suspect about the JJ's is that they start with a rather high noise level that gets lower after a couple of minutes. The EH's have a noise level that remains the same.
Does JJ electronics even test or 'burn in' the tubes they produce, of do they leave the testing to the end user?
In fact I replaced the factory 'selected' EF86 in my Neumann U67 (re-release) with an EH with as result a lower self noise!
In the past I have also used JJ Electronic tubes. They work for a couple of weeks but after that they develop a high noise level and start 'crackling'.
What I also find suspect about the JJ's is that they start with a rather high noise level that gets lower after a couple of minutes. The EH's have a noise level that remains the same.
Does JJ electronics even test or 'burn in' the tubes they produce, of do they leave the testing to the end user?
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