Questions about line boost for ribbon microphone

[liquidfuzz]

I'm new here, so this is my hello world post.

A while back a built a ribbon microphone. It's quite good for HIGH volumes, but I would like to add some signal boost so that it, possibly, also can handle lower volumes. I asked some random questions about it in an unrelated forum and was suggested to go to this forum.

I've been reading this old thread about a similar project. http://groupdiy.com/index.php?topic=5743.0 Now I'd like to make my own realization of it, but don't really know what stuff to use. Well, usually I build tube amplifiers and it really doesn't matter what caps, resistors, tubes, etc I use. -HiFi wise these amps sound like crap! For this line boost project I'd like to push it more towards HiFi. When it come to transistors I'm totally newbie, so advices would be highly appreciated.

In my build there's a Lundahl transformer with an out impedance of 75 and a 1:37 winding. Is there maybe an updated version or so of the pre.amp. described in the thread above, I believe it's known as the PRR ribbon pre amp. Is this circuit suitable for this kind of transformer/signal?

 

[emrr]

I maintain that additional gain from a secondary line amplifier after your preamp will always give the best noise ratio.  This assumes the preamp is reasonably quiet up to a given gain level, and you optimize that gain quantity.  Many preamps are very noisy at max gain, and much quieter just below max gain.  Many people use compression on the way in, and usually those compressors have make-up gain that is there to use, with less penalty than what you get trying to used a device between mic and preamp.  Plenty of people hoping to sell such a device will say I'm wrong, I will say they have yet to convince me otherwise. 

 

[liquidfuzz]

emrr - Interesting points, but I have no current diy project and the abstinence is getting worse.  :-[

 

[emrr]

: )

Diy blueball is the worst.

It's hard to beat the 'free' gain of a mic to grid transformer.  You haven't detailed your tube amp builds to define why they aren't hifi.  They certainly can be.  Or what you are using now that isn't cutting it.  Noise, you can use high ratio transformers with some op amps, and get low noise figures.  Then you run up against the laws of nature, and sometimes a ribbon won't cut it, period.  I have some very quiet modern preamps that are still not quiet enough with some modern high output $$$$ ribbons with certain sources.  We simply ask too much of these systems.  The aforementioned scenario does benefit from optimized gain in the preamp (lower than max) with additional line amp gain afterwards.  Far better than max preamp gain. 

So, next diy....?  Definitely build something.  Try the PRR booster approach and see if it works for you.  I like those ideas with very long lines which benefit from higher level in that long line, to cut down on induced noise.  That's usually not a factor for most of us. 

 

[liquidfuzz]

True, I forgot to mention a tiny detail. I build guitar amps... 8)

Turns out I can't even simulate a simple transistor circuit. Hmm... I attach the LTspice file I put together in hopes of seeing some nice transistor action. Feel free to point out where I messed up.

 

[liquidfuzz]

I'm going to start tinker with some circuits now. There are some instances of big capacitances in these, so I guess I have to go electrolytic. The thing is, I haven't used el.caps in the signal path before. Are there some kind of el.caps I should go for, that could be consider HiFi, or is it just all snakeoil..?

Edit, clarification