Advice on Peluso p67 mod?(Love the Du67 project! I should have done that!)

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achase4u

Well-known member
Joined
May 1, 2016
Messages
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So, I can take some pics to show what is in this P67, but I am not entirely sure beyond the 6Ak5 tube.  I replaced the stock one with an NOS Western Electric.

Are there some things I can take from the DIY build and move into this mic here?  I find it to be a little harsh at times and without the natural kind of de-essing and warmth/detailed mids of the originals I have heard(full disclosure, I never compared them side by side, or used a 67.  Just listened allot)

I really want to do the DU67 build... but I'll do that later.  This will be tons of fun...
 
Depending on the circuit you maybe able to tweak it to reduce the high end a bit. Talk to John Peluso. He's a nice bloke and will assist you.  Send him some samples and explain clearly what it is you're not happy with. I'm sure there will be a fix.

If the circuit is a replica of the original it is commonly known a change of value of C17 in the U67 original circuit will see the high end slope change.
 
Put the pictures of the circuit here so maybe we all find some solutions for better sound :)
 
Thank you for welcoming me!  This is exciting!

I suppose I could talk to John.  I wouldn't mind having some fun with this here though.  It might get my wheels greased for a full project mic!

I will post some pics of the mic internals today :) I'm curious what you guys will have to say... thank you!
 
If you are able to put pictures without tube installed (and make it without flash - traces need to be well visible from both sides), read capacitors values etc. I can draw schemaatic for it and then we can think about modding it ;)

It doesn't look like there's any deemphasis circuit, or deemphasis in U67 style.
I think that only similarity to U67 is the 67 in name :D
6AK5 is really good tube, so i think you should mod microphone, try to understand how the circuit work and then you can build du67 kit in other donor body.  Peluso is what it is - chinese microphone, "made in usa" but i think it's to pricey for donor microphone. Maybe we can make it decent sounding :)
What do you think?
 
Sounds like a plan to me!!!  Thank you!!!

I think the demphasis circuit with the transformer is what helps absorb the sibilance of sources...  lets do this!

Will post soon with non-flash pics and tube out.  Cap and resistor values as well.
 
It is possible, eralier i didn't noticed all transformer windings, it was looking like there are four only :)

Ok, so there are only four windings, so there's no U67 deemphasis circuit!
There's plate to ground capacitor 2.2nF to damp HF but this is not deemphasis circuit ;)
 
Don't have to pull anything (for now).
Check  value of R11 (third blue resistor).
Make good pics with visible traces.
 
You will have to also measure high voltage (plate + polarisation).
And make pictures of the capsule (wires) without headbasket .
 
ln76d said:
Don't have to pull anything (for now).
Check  value of R11 (third blue resistor).
Make good pics with visible traces.
Click to expand...

Ok sure thing.  I'll try to take more pics of the board.  Also R11.

:)
 
ln76d said:
It is possible, eralier i didn't noticed all transformer windings, it was looking like there are four only :)

Ok, so there are only four windings, so there's no U67 deemphasis circuit!
There's plate to ground capacitor 2.2nF to damp HF but this is not deemphasis circuit ;)
Click to expand...

Aha!!!  We MUST incorporate a proper transformer and deemphasis circuit!!!  The plotted curves from Peluso look fairly close to a 67, but there is much more to it than the curve!  That deemphasis circuit clearly has non-linear affect on treble that comes into the capsule.
 
ln76d said:
You will have to also measure high voltage (plate + polarisation).
And make pictures of the capsule (wires) without headbasket .
Click to expand...

I am comfortable reading high voltage as I have worked on guitar amps.  However my knowledge is limited on what to probe, so if you tell me what to probe, I will do so, safely.

Will take pics of the capsule without the headbasket.  Thank you!
 
Best would be if you will mesure all the points at the bottom of the PCB.
Try with DC 200V range and check all the points reffering to ground.
There should be high voltage in two points. If you will find polar pattern voltage you can check what's the value in the middle position and both sides of the pattern switch.
 
I should mention the thing about this mic is that it doesn't employ the same patterns and selector as a u67.  There is a 10db pad and hi pass filter on the mic, and the polar pattern is adjustable from omni to cardioid to figure of 8 via 9 selections.
 

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