[PRR]

> cap ratings?  ....im guessing at least 50v.

Nobody here can figure-out a 220K-27K voltage divider?

[zebra50]

also see zebra50's experiments with no input caps: http://www.groupdiy.com/index.php?topic=5743.msg502892#msg502892

Yes, I have three of these kicking around in little boxes, and none of them have input caps! It is probably not good practice, but with well matched components then I could measure no difference in potential across the two inputs. I've used THAT300, 2n4401 with good results.

To be honest, they don't often get used on sessions. If the ribbon mic is working well then a good clean preamp is all that is needed. If not, then the little booster box boosts the noise as well as the signal!

Cheers!

Stewart

[sodderboy]

The Cloudlifter claims no caps, transformers, or resistors in the audio path, so it's only silicon?

And their optimal load impedance is 3K.  That's quite high for most pre's which don't go much above 1K5.

I do not like long mic lines out of personal preference, but have no problems integrating runs over 400 feet when given no choice, either with splitters at the front end or not.  Of importance is not mic level but cable choice and mic pre quality.

If something like this makes a Soundcraft or Mackie sound better, great!
Mike

[abbey road d enfer]

The Cloudlifter claims no caps, transformers, or resistors in the audio path, so it's only silicon?

If you look at PRR's current-feedback schemo, some would trace a direct line from input to input via silicon and say there's no resistors in the signal path and other would say that "everything is in the signal path". Or if you use a THAT 1512, there's only silicon but there are silicon resistors.

And their optimal load impedance is 3K.  That's quite high for most pre's which don't go much above 1K5. 

That's a limitation due to phantom powering, but with the purely resistive nature of the source impedance it impacts only the max output level. I believe (I don't have the schemo) that the other performance factors are not altered when the load impedance is lower than 3k. Same situation with transformerless phantom-powered mics.

I do not like long mic lines out of personal preference, but have no problems integrating runs over 400 feet when given no choice, either with splitters at the front end or not. 

Long cable runs are just a fact of life; I don't think anybody would use long cables for any other reason than necessity.

Of importance is not mic level but cable choice and mic pre quality.

It is debatable; in terms of noise, the actual level is THE most important factor. Betweeen a super-LN pre (Grace, Green River...) and a sub-par one (Brick, TL Audio...) there's only about 5dB difference in EIN, so in the end level is the determining parameter that defines the noise performance. And the greatest cable won't make a bad pre sound good; and the greatest preamp won't compensate for poor cable... Audio degradation is a cumulative problem, all the elements must contribute to the overall performance.
I've never seen (heard) a cable inducing sound quality degradation other than noise; except predictible reduction of BW with long cable runs and high-capacitance cable -hear Starquad. Never had cable inducing distortion (connectors yes).

If something like this makes a Soundcraft or Mackie sound better, great!

A Cloudlifter won't make a Soundcraft or Mackie, or Neve or whatever sound better. It may make a mic+cable+preamp combination perform better; the reason would be that there is a mismatch in the combo originally. Typically the microphone would see inadequate loading and the mic pre would see inappropriate source impedance, then the addition of an active buffer would sort out the problem.

[ChuckD]

The cloud lifter was just lifted from PRR's FET version created here years ago...
I cracked one open and felt a little stupid for paying 150 bucks for a differential pair.

Here's PRR's :




The cloud lifter is pretty much this with JFETs instead: LSK170s ...  Just do a google search on the design I am sure you will find one.


I'd post the schematic with values but don't want to get any heat from folks.


Chuck

[okgb]

Let's say if you had a favorite transistor number inspired by that image ,
 what would it be ?

[ricardo]

If you want to know when a Cloudlifter would be good, have a look at Matt's
http://recordinghacks.com/2012/06/18/sm7b-audio-interface-shootout/

If you want to roll your own, read ALL of
http://www.groupdiy.com/index.php?topic=5743.240
Loadsa stuff from true gurus and pseudo gurus like me too.  And sources for Unobtainium bits etc.

One suggestion I make is that if you have a low output ribbon with a nominal 200-300R output, you'd be better off making a dedicated preamp using THAT1510 or another of the excellent single chip solutions from TI or AD without P48V.

But making up a complete preamp so it approaches the 1nV/rtHz performance of  THAT1510 is a major undertaking.  In particular, the PCB, wiring and construction has major implications in Low Noise design.

A simpler solution, much more likely to result in success is to take a good existing preamp, remove P48V & other evil bits and optimise it for 300R ribbons.

An obvious candidate is the Seventh Circle box with their T15 modules.

http://www.seventhcircleaudio.com/T15/t15_about.htm

This is a deluxe kit using only the very best components. It costs $99 for a single channel module … and you need a box, power supply etc on top of that.  But if I was rich, had the space and wanted to build a state of the art preamp, I would probably start with one of these.

But you can get a discontinued M-Audio DMP3 for less than US$100 on eBay.  It has a good reputation in some circles but is rather noisy.

If there are sufficient people interested, I'll start a thread on how to convert a DMP3 into a dedicated ribbon preamp with much lower noise along the lines of special order Millenia Media preamps and the AEA TRP

As a pseudo guru, I won't be doing any of the dirty work myself but counting on yus serfs to butcher their DMP3s.

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