Tim Campbell
Well-known member
It could be a short between the backplates or you've wired the capsule incorrectly.
Telefunken ELA M 251 Clone Tube Microphone Build Thread (D-Ela M 251E)
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Hi Tim,
I am using one of the two capsules I recently purchased from you. Perhaps you can tell me if you see any problems here with the wiring? I used the red wiring for what I believe is the front of capsule and blue for back plate. There is certainly a chance I misunderstood the diagram that came with the capsules as the solder points appeared different to me than the actual capsule. I'm new to this so please be gentle
I am using one of the two capsules I recently purchased from you. Perhaps you can tell me if you see any problems here with the wiring? I used the red wiring for what I believe is the front of capsule and blue for back plate. There is certainly a chance I misunderstood the diagram that came with the capsules as the solder points appeared different to me than the actual capsule. I'm new to this so please be gentle
Tim Campbell
Well-known member
Just giving this a quick look I'd say that you removed the wrong tabs on the metal rails holding the pcb. It appears that the remaining tabs might be shorting solder points on the pcb.
Anybody have a similar setup? Using a tab t14, electro harmonix tube and tim campbell capsule. I feel the 8-12k is overly present. Is this just my experience or anyone have the same result? This thing is also ridiculous sensitive as well. I was picking up the wind blowing outside! (not really)
Tim Campbell
Well-known member
The tube can have a lot to do with how bright the mic is. My experience with EH tubes has not been good. You don't mention which EH tube model but I assume their 6072. The best tube is of course the GE 5 star 6072 but they are expensive and hard to get. RCA 12ay7's are duller but a little lackluster. Many have had good luck substituting brand name 12at7's. You might also tame it a bit with some alternate value capacitors.
The quickest mechanical fix is a nice thick, foam wind hat
Where are you located?
The quickest mechanical fix is a nice thick, foam wind hat
Where are you located?
Banzai said:
That's correct the AMI T14 Hi roll off is not at the same freq. as the Haufe T14/1. it's extended a wee bit.
Nusoundz description "8-12k is overly present" does not sound like the result of a component with a slight freq. extension.
It is possible AMI T14 is contributing 1-1.5 db, however not the fundamental cause.
micaddict
Well-known member
Bonnie1 said:
Not to hijack, (well, not for long anyway), but what about the T67 versus Neumann's BV12 in this regard?
Tim Campbell
Well-known member
Bonnie1, since we haven't establish what the frequency response of the mic in question truly is, just that it's "overly present", it's hard to be sure that any additional boost at 8-10k wouldn't be contributing to this. Imagine if the mic has a particularily bright tube, a smaller value, poorer quality capacitor in the tone circuit and an AMI transformer. I'm sure it would be much brighter than if the reverse were true.
Here is Telefunken's freq. response for that mic.
Here's AKG's original freq. response for that mic.
We haven't really asked how this evaluation was done. Headphones? Recording and playback? Bright compared to what other mic?
Of course if none of these changes bring about the desired reduction in 8-10k NuSoundz is always welcome to send the capsule to me and I'd be glad to damp down the top end.
Here is Telefunken's freq. response for that mic.
Here's AKG's original freq. response for that mic.
We haven't really asked how this evaluation was done. Headphones? Recording and playback? Bright compared to what other mic?
Of course if none of these changes bring about the desired reduction in 8-10k NuSoundz is always welcome to send the capsule to me and I'd be glad to damp down the top end.
micaddict said:
Hi Micaddict, are you asking about freq. response T67 vs. Neumann BV12? AMI/TAb's new website will launch soon and we will provide such comparisons as well as test setup etc...
So we don't hijack this thread any longer, please PM me or start a new thread for further discussion.
micaddict
Well-known member
Roger.
I have indeed ordered a GE 5 Star tube to see if I get the desired result or a more favorable one. I'm sure it could be a couple different things going on. I'm not blaming any particular component at this time as it's to early to point out the exact cause. I appreciate the feedback and will update once I have received the tube and perhaps post some clips with each tube.
NuSoundz said:
The main point is that if you don't have all original spec parts, then these original microphone circuits should only be used as a starting point. To make everything fit together and sound right, you can still make adjustments to the capacitor and resistor values.
If it was my mic and the response was too bright, I'd start with the 30M grid resistor.
Absolutely. I'm not expecting an exact replica of the real thing but a loose relative is fine. However, if the mic is unusuable in many applications (requiring too much eqing etc.) then I have a problem with that.
Regarding the resistor, what would you suggest as a "not so bright alternative". I'm new to this so please excuse the ignorance on my part.
Regarding the resistor, what would you suggest as a "not so bright alternative". I'm new to this so please excuse the ignorance on my part.
Other options
If you are running microphone from 120VDC, then you could try lower polarisation voltage to ca. 55V like in original ELA M250/251. If you are using 500k for divider, then you could replace R5 for 420k/422k/427k.
If you will not hear difference in response, then worth back to the 500k/500k divider.
My standard suggestion is to use MP capacitor as the output C1, range from 0.5uF-1uF.
Other thing is headbasket, some can bump frequency response, especially in hi-mid and hi range.
If you are using standard apex/alctron donor for C12, what kind of headbasket it use?
Original or Chunger optional headbaskets with single mesh layer or two layers?
Or some different donor body?
Last option is to try Haufe T14/1, guys here want to make groupbuy, so you have opportunity, to buy it cheaper.
If you are running microphone from 120VDC, then you could try lower polarisation voltage to ca. 55V like in original ELA M250/251. If you are using 500k for divider, then you could replace R5 for 420k/422k/427k.
If you will not hear difference in response, then worth back to the 500k/500k divider.
My standard suggestion is to use MP capacitor as the output C1, range from 0.5uF-1uF.
Other thing is headbasket, some can bump frequency response, especially in hi-mid and hi range.
If you are using standard apex/alctron donor for C12, what kind of headbasket it use?
Original or Chunger optional headbaskets with single mesh layer or two layers?
Or some different donor body?
Last option is to try Haufe T14/1, guys here want to make groupbuy, so you have opportunity, to buy it cheaper.
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