Cloudlifter CL-1Repair

[abbey road d enfer]

The original value is 33pF if I remember correctly. Anywhere from 10 - 56pF would be ok.

Those are “frequency limiting” caps. They shunt very high frequency noise to ground so that your FETs aren’t trying to amplify massive EM spikes or radio waves.

Even 56pF is useless; that's a fraction of the cable capacitance.

 

[abbey road d enfer]

This is what I was thinking, what is the benefit of using this method with resistor and capacitor in parallel instead of a classic RC low pass filter (the signal passes thru the resistor and the capacitor filter the desire frequencies to ground)?

The Low Pass filter is constituted of the source (microphone) impedance and the capacitors. If teh mic had zero impedance, there would be no low pass filtering.

 

[abbey road d enfer]

I would love to be able to power my cloudlifter with batteries so I can use it with a portable amp when I 'busk' in the subway.
Ideally, with two or three 9volt batteries.

Given the circuit that smilan provided, is that possible ?
If so, where would I apply the battery power ?

You have to understand that this circuit works only with power applied via resistors to the drains of the output FET's; basically you need to recreate a phantom supply. It could work with only two 9V batteries and 2.2k resistors.

 

[analogguru]

> 10pF

>> For a 160 Mhz LPF?
>> Typically I put 10nF there, which results in a 50kHz
>> cut-off even with a 600 ohm mic.

You have to ask this question the "designer", not me. 10pF is the original value which is used inside the Cloudlifter, and the thread started with the question to repair one.

 

[abbey road d enfer]

> 10pF

>> For a 160 Mhz LPF?
>> Typically I put 10nF there, which results in a 50kHz
>> cut-off even with a 600 ohm mic.

You have to ask this question the "designer", not me. 10pF is the original value which is used inside the Cloudlifter.

The "designer" of the Cloudlifter obviously has only a vague notion of what does what in the circuit, starting with the use of a cascode arrangement to solve an unrelated problem.

 

[analogguru]

The "designer" of the Cloudlifter obviously has only a vague notion of what does what in the circuit, starting with the use of a cascode arrangement to solve an unrelated problem.

I see you got it.... but obviously there are people around who think they need to inwaste their hard earned money in such a piece...

 

[abbey road d enfer]

I see you got it.... but obviously there are people around who think they need to inwaste their hard earned money in such a piece...

"Inwaste"... I like that.

 

[TromNek]

You have to understand that this circuit works only with power applied via resistors to the drains of the output FET's; basically you need to recreate a phantom supply. It could work with only two 9V batteries and 2.2k resistors.

(many thanks to both tubetec and abbey)

Works great with the two 9Vs, and just as well with only one 9V (and 1.2k resistors).

In their patent filing they have a circuit to pass phantom through to the microphone.
I may create that with a switch for when I want to use condensers that are far away from the source and they need a little gain.
I may need to use three or four 9Vs for that application.

thanks again for all your help

 

[Gus]

How did that get a patent?

 

[TromNek]

How did that get a patent?

Mine work pretty good. I bought a used CL-2 and CL-Z for $100 off craigslist many years ago.
They worked fine with my ribbon mics for recording classical guitar and other quite sources.

Perhaps my old ears don't hear the problems you see in the design.
Or the other equipment in my signal chain is not high enough quality to hear any problems.

Now that I can battery power them, they are a perfect gain stage for my little portable roland street cube for busking. The mic preamps on the street cube get real noisy if I push them too far.

From a practical viewpoint, my $100 was not an inwastement.
But, maybe I'm just fooling myself.

 

[Gus]

How did a differential amp get a patent?

TromNek my question was simple it had nothing to do with your reply

 

[abbey road d enfer]

How did that get a patent?

Get a lawyer to write enough bullshit in Klingon language about how electric field moves particles, and you can file a patent for a resistor.

 

[TromNek]

Get a lawier to write enough bullshit in Klingon language about how electric field moves particles, and you can file a patent for a resistor.

Yup, makes me wonder how far a company can push what they consider is a 'new' and patentable design. I guess the patent office isn't very discerning.
It's not the differential amp that they patented, it's the implementation of applications around it.

They listed a bunch of different implementations/variations, maybe hoping to get royalty monies from a couple of them.

 

[DaanP]

I have a CL-Z (board# 1914, pretty old) and yes many of those jumpers are for the CL-Z.
JP1- Not Present
JP2- HP Filter switch
JP3- Jumpered
JP4- Variable Impedance Rotary Control (very funky pot with 6 leads, only two are used)
JP5- Jumpered
JP6- Not Present
JP7- Gain switch, two wires

Variable Impedance
there is a blue device (inductor?) installed on the board where you see the "White Box with C3".

Hope I got that mapped out correct? Let me know if you want me to verify anything.

Hi I'm new here,
But the blue device mounted on position C3 is a film capacitor.
The capacitor creates the HPF filter and can be shorted by JP2 (disabling the HPF) if i'm not mistaken.

 

[Bonfire]

Wondering if anyone has actually measured the caps on a cloudlifter? I desoldered them on mine, but I managed to destroy one. The other one is measuring at like 620 pF. I was expecting it to be 10 pF based on this thread. I'm super annoyed that I damaged the second one because I wanted to observe the same value on both to make sure I'm getting a good reading.

 

[abbey road d enfer]

There's no way the input caps would be as small as 10pF. 620pF looks like a suitable value.
In doubt replace both with anything between 500pF and 5nF.

 

[Bonfire]

There's no way the input caps would be as small as 10pF. 620pF looks like a suitable value.
In doubt replace both with anything between 500pF and 5nF.

Thanks @abbey road d enfer

I think you are prob right. It's strange that others in this thread have claimed that it is 10pF. Just wondering where that came from. I saw a hand drawn schematic in another thread that also said 10pF. Curious where people are getting this info because I'm pretty sure its not 10pF based on the cap that i measured.

 

[Walrus]

The one I measured was around 1.5-1.8nF.

 

[abbey road d enfer]

It seems there's a significant Cloud around the value of these caps.
analogguru seems to be adamant on the 10pF value, but everyone and their sister seems to have different but substantiated opinions.
Maybe the manufacturer put any old value they had available there? It would not be such a big surprize since their "designer" does not seem to know precisely what he's doing.

 

[Bonfire]

@abbey road d enfer It could just be different revs versus totally random. The cloudlifter that I opened up was an older one (Rev 20A). This one has no ground pour on the top + doesn't have jumpers and headers that I've seen newer ones have.

@Walrus did you measure both caps by any chance? Just curious if you go the same value for both.

The caps are so easy to destroy. It's like they don't have a case around the outside or something.