Mic and Mod U47 noise issue

My friend got tube u47 kit from micandmod and built it but it has really loud noise.What can cause this noise?

Here is sound sample

https://soundcloud.com/tuncak-1/u47

Shitty source of purchase  -  sorry i couldn't resist

ln76d said:

sh*tty source of purchase  -  sorry i couldn't resist

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But it happened

Even they sent wrong components and my friend sent it back to fix all of them.They said only cold solder and sent back.But he still got noise.Then he told this to micandmod and they said "it's tube mic.so this noise is normal."...

Now trying to get rid of that noise.

In my opinioin their kit is completely not worth the money - there almost everything is chinese.
They call it "replica"...
As i stated few times here - in my opinion 6028/408a tubes aren't any equivalent to the VF14 - even if two are used.
I'll be testing 6ak5 vs 6028 - so maybe it will be a better replacement?  It's a pin to pin replacement but with slightly different specs.
For the noise source first i would look for the heater dropping resistor - or all the noodle with the plate voltage.
Also i would check two different pcs of 6028.
It doesn't sound like the capsule area noise but it's worth to check soldering aand clean soldering points at high impedances places.

Also!

Polystyrene/styroflex capacitors are capricious!

Measure all the important voltages according to the U47 schematic.
With 6028 never they will be the same but it could help to identify source of problem.

Thanks for replies!

I'll tell this to my friend.

Now he measuring voltages and heat of components.

On the U47 there is no capacitor between the capsule and the grid.  Capacitor issues especially with styroflex are not rare, but here I don't see where it could happen.
Noisy tubes is also the first thing I would suspect.

berl said:

On the U47 there is no capacitor between the capsule and the grid. 

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No one said it is.

Capacitor issues especially with styroflex are not rare, but here I don't see where it could happen.

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In polarisation voltage filter - so is more likely than grid cap fault.

BTW.  IT'S NOT U47!

It's a chinese microphone for self build and even if someone called it U47 it doesn't mean it has something to do with original unit = in circuit, quality, components and sound!

OK! I am going to jump in on this even though I am one of the most vocal members regarding M$M and their kit.

It sounds to me like noisey tubes. The 408a is not known for it's low noise spec's. Truth is for a tube mic that doesn't sound that horrible. It's not good but it isn't the worst. What pre is he using and what is the input impedance? Read the threads regarding tube selection and types.

It's a tube with which is hard to work in microphone circuit.
In my opinion it isn't any equivalent (even two in parallel) to VF14 - and it's not about any magic of VF14 - only about completely different specs.
Am using single 6028 JAN ECG Philips in my S16 microphone and to be honest last thing which was problematic was the tube noise. 
Am not saying that it isn't problem in case tubes in m&s kit

I got one of these kits. Initially, I got loud grounding noise so I did a ground lift with AC plug adapter, fixed that. Next I realized the gain was very low and seems out of phase. After some experimentation, I realize if I disconnect pin 2 from the XLR connector the signal and phase is good. The mic is very sensitive now. The RM capsule was very sibilant, I replaced it with  RK 47 and now sounds very good. I posted another thread regarding the signal on pin 2, hopefully someone can help me find the issue.

Pip said:

OK! I am going to jump in on this even though I am one of the most vocal members regarding M$M and their kit.

It sounds to me like noisey tubes. The 408a is not known for it's low noise spec's. Truth is for a tube mic that doesn't sound that horrible. It's not good but it isn't the worst. What pre is he using and what is the input impedance? Read the threads regarding tube selection and types.

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Telefunken sure tried to 'sell' the 408...seems like M$M picked up on this aspect of
modern 'U47' builds...