topic discussion: Passive mic pre designs

[pucho812]

for artists you hate recording :razz:

 

[Curtis]

Passive mic preamp? Isn't that just the cable? :razz:

 

[JohnRoberts]

Megaphone horn, as in old wax cylinder recorders?

JR

 

[bcarso]

That reminds me of the picture of that woman singing into the counterweight of the boom mike stand.

 

[emrr]

1:10 input transformer feeding a Hi-Z line input would count, and be all you need with most rock instruments.

 

[BradAvenson]

http://www.realios.com/ra9033br1.html

All transformer gain with a unity gain buffer.

 

[emrr]

[quote author="BradAvenson"]http://www.realios.com/ra9033br1.html

All transformer gain with a unity gain buffer.[/quote]

Cool. A useful box, I think. You wouldn't use it every day, but it'd be handy. I see this as the front end to a chain also having high gain limiters, so you're not throwing so much away at that stage.

 

[rafafredd]

I always though about that. But i imagine a big 150:50k input transformer, then a WCF tube stage, then aother big 1k:50k, another WCF, and the third stage another big 1k:50k and another WCF and a 1k:600 on the output. NET gain would be close to 56dB with no active voltage gain and three dual triodes... But don't follow my plans! It's just nuts! :green:

 

[clintrubber]

"Passive voltage gain"... sounds like an exercise in... in what actually ? What's the point ? Someone in need of a new buzz-word ?

The intermediate buffers can still overload... and might even have lots of that nasty-nasty voltage gain on board themselves, but just tamed down to unity with NFB.

But if it it gives somebody a warm feeling - despite the zero dissipation -, as in "class-A environment friendly passive voltage gain".... then why not ? :thumb:

Now for "passive phantom power", how about that ? :razz:

 

[emrr]

I agree with the companies basic premise, which is that many mics and sources require very little gain at all. Many vintage fixed 40 dB preamps require a 20 dB pad when working with rock sources, and 20 is enough. There are very few transformer coupled pres with high input step-up ratios that also have sufficient headroom to handle modern sources in the following stages, since the need for high gain was assumed. I've thought about single stage cathode follower after a 150:50K input; just the two components and nothing else. Unbal medium-Z out. I'd use it pretty frequently.

 

[skipwave]

I kinda think Pucho was just bullshitting, but..... this idea has come up before.

http://www.groupdiy.com/index.php?topic=6231

Hah! I just noticed my drafting mistake in the second pic, the Sziklai mod. Do you see it? :green: I also noticed the 48V supply in the first pic, which was someone else's error. Don't do that.

 

[pucho812]

[quote author="skipwave"]I kinda think Pucho was just bullshitting, but..... this idea has come up before.
[/quote]

Bull shitting or making a joke :wink: