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Old 21st October 2004, 10:06 PM   #1
kimarin is offline kimarin  Norway
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Smile Tube mic preamp

Many cheap tube mic pre's today operates on voltage under 100v (abaout 50V) and the old vintage stuff did have usualy over 200V ht.
I'm considering building this paia tune pre amp www.paia.com/fantusch.gif in 8 ch in a rack unit. What if I rise the voltage on the tube to 250V , would that make it more vintage sounding? I wanna build a cheap tube mic preamp without input transformers to keep the cost down, and I wonder if this pre is a good alternativ... Anyone knows if this is a good sounding pre ??
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Old 22nd October 2004, 12:12 AM   #2
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I built the Paia Tube preamp a number of years ago, and while it does make an interesting fuzz-box distortion amp thing, it is certainly not a high end microphone preamplifier by any standard. You can't just increase the voltage to 250V and expect better performance. The circuit is intentionally designed to "starve" the plates, thus resulting in massive amounts of distortion.

Any "tube" preamp with a million solid-state components and one tube running at low voltage could never compete with what a real tube preamp can do, IMHO.

There are other ways to achieve transformerless input, but in general making 8 channels of tube preamplification is not cheap by any stretch.

-E.

P.S. The Paia preamp is unbalanced input, unbalanced output, and really doesn't have enough gain to be considered a microphone preamp.
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Old 22nd October 2004, 11:36 AM   #3
mcs is offline mcs  Denmark
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Could a good mic preamp with cheap transformers be an option?

Then have a look at the Gyraf G9 with OEP transformers...

If has transformers in both in and outputs, but if you don't need balanced outputs I guess you could just leave out the output transformers.

Have a look here: http://gyraf.dk/gy_pd/g9/g9pd.htm

I have an almost complete board, but I haven't tested it yet.

Best regards,

Mikkel C. Simonsen
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Old 22nd October 2004, 01:19 PM   #4
kimarin is offline kimarin  Norway
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Lightbulb Cool

Sounds interresting. Actualy I want an all tube mic preamp , the cost was an issue here. Where is it possible to get these transformers and are they cheaper then for example sowter??
Are there supplyers here in Scandinavia??
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Old 22nd October 2004, 01:52 PM   #5
mcs is offline mcs  Denmark
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You can get the transformers from RS or Farnell. They cost about DKK 100-150 each.

Best regards,

Mikkel C. Simonsen
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Old 23rd October 2004, 09:30 AM   #6
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This circuit of mine is a nice sounding dynamic pre. Excellent transient response and smooth vocals. Easy to build

http://www3.telus.net/small_business/Geek/DynMic.png

And if you wanna go all-out:
http://www3.telus.net/small_business...reampFINAL.png
http://www3.telus.net/small_business...pressFINAL.png
http://www3.telus.net/small_business...PowerFINAL.png
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