total noob want to build SIMPLEST mic preamp sound quality not issue

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There is something inherently exciting about harvesting bits and pieces out of idle gear you may have lying about and finding the right piece you need for your project.  I understand your enthusiasm and I don't mean for this to quash it in any way but my definition of easy on this one would be:

http://export.farnell.com/jsp/search/browse.jsp?N=500006+1004177&Ntk=gensearch_001&Ntt=2N3904&Ntx=mode+matchallpartial

They're cheap and you get an exact datasheet for it - Important to remember that a 3904 made by one manufacturer in 1987 could very well have a different pinout than a 3904 from a different manufacturer from a different year even though they are electrically equivalent.  If the pinout is unknown then you'll have to use a DMM to determine that - which is no big deal but the backtracking and guesswork can start to pile up.  Also time spent desoldering etc. 

I think your enthusiasm is more important here and I encourage you 100% to go for it.

Most would prefer film caps to electrolytics for coupling applications.

Best of luck on your build!


 
 
Hi thank you for the advice, there isn't a link for England?

wondering if anyone can advice me on the schematic. Is "output to next stage" a line level out put that can go to a line in on a mixer?  ???

Where the mic is on the schematic I'm replacing with XLR for dynamic mics.. Would the wire coming from C1 to the mic be positive? Will this go on the red wire of the XLR? And the bottom wire originally coming from the mic would be the negative XLR pin? (white wire)..
Hope that makes sense..
simplepreamp1.jpg

Nearly Done:  ;D
14022010412.jpg
 
I'm on a phone now and can't see the datasheets but If your voltage ratings are ok. Like the 3904 has a max voltage of 60 or something and your substitute is 30 but you only have a 9 volt supply than both would work
the other factors to look at on the datasheets are hfe ( which is kind of like gain but not exactly) and input impedence (which should be expressed in ohms)
these should be similar but there's a lot of wiggle room in a design like this.
Not so much wiggle in some of the more complicated low noise designs.
So if you are in the ballpark I say go for it and see how it sounds
 
See if this one works.

http://uk.farnell.com/jsp/search/browse.jsp?N=500006+1004177&Ntk=gensearch_001&Ntt=2N3904&Ntx=mode+matchallpartial

If not just go directly to Farnell.
 
I'm using a transistor I got out of a hi fi system mentioned in earlier post...

Any help with schematic would be great.. So it doesn't matter which wire goes on + or - xlr pins..
But what about having a pot for gain control and I need to attach an audio out put and 9v input, how would I go about doing this?
 
ok one last question before I go to sleep. (been working on this all day)
Why is there only on wire in for the power isn't that + and - ? I'll test with a 9v battery before mains..
Good night and thanks again.. Its nearly done (maybe lol)
 
The ground point (at the bottom in the schematic) is the negative side for both your power and your audio signal.

So the negative side for your audio in, your audio out, and your power negative all converge at the same point.

Can't wait to hear how it turns out!
 
Actually you want to hook the end of the capacitor that goes to the microphone to pin 3 of the XLR, and hook pin 2 to ground.

This is connecting the base of the transistor to the - side of the microphone rather than the + side, which is appropriate because the transistor will invert the polarity of the signal. So the output signal will be right.

Peace,
Paul
 
hi just wanted to say thank you for all your help I have left the preamp as I found an old electronics kit I was bought when i was young which has amps and other interesting things to make, I will learn a lot from it.. As I said I'm building up to do the Royer mod.. Just bought two of the 5840 tubes, wondering what would I have to change to make the schematics work for a UK 240v main?
Thank you all so ,much for the support!
Dom...
 
Disease8 said:
. Just bought two of the 5840 tubes, wondering what would I have to change to make the schematics work for a UK 240v main?

If you're following the article in tape op, you need change nothing other than picking the right mains transformer - something with a 240V primary and a secondary with 1 amp @ 24V (or 2x12V).

 
zebra50 said:
Disease8 said:
. Just bought two of the 5840 tubes, wondering what would I have to change to make the schematics work for a UK 240v main?

If you're following the article in tape op, you need change nothing other than picking the right mains transformer - something with a 240V primary and a secondary with 1 amp @ 24V (or 2x12V).

wicked thank you very much!
 
PRR provided a one-transistor preamp that performs quite well when decent quality capacitors are used. Then you can mix and match all manner of nasty-to-pretty input transformers to play with a whole box of krayolas:

http://www.groupdiy.com/index.php?topic=5396.msg65934#msg65934

Oh, and I second whoever suggested you stay clear of mains voltages for the time being. Stack up four 9V batteries in series: first black wire to circuit ground, then red wire to the next black wire, repeat, repeat, and last red wire to the point marked "+36V". Done.
 
I wanted to say thanks for the replies to this I never got round to it but I am planning on getting back into modding some of my mics and possibly making a proffessional sounding mic pre or modding a not so expensive one into a good sounding pre.
Cheers for the support this forum rocks and so do you guys!

Any ideas on the cheapest and best way to get a really GOOD sounding pre amp cheap? Including building it yourself?

(should really open a new post as the title is the opposite of this lol)
 
Certainly the questions are basic enough you could do
some research  [ google  ] and have better questions
thus getting better answers
Solder the parts directly together and skip the wire
 
Any ideas on the cheapest and best way to get a really GOOD sounding pre amp cheap? Including building it yourself?


There are a number of good sounding mic pre plans around here - some in kit form.  Most all are very affordable relative to buying a commercial piece.

May want to inform us on your price figure for "cheap".  Others can hone in on this number but I'd say 250-350 USD should  get you a very good sounding preamp.  This figure may vary depending on a number of factors - component choice, faceplates, fascia, etc.  A lot of your budget cutting can be done in sourcing components.  7$  pot(perfectly adequate) or switch vs 35$ ones. 

"Cheap" to most people means things like Behringer, ART and others.  You couldn't build one of those pieces for less than they're sold for.  You could build an EZ1290 for much less than what a real Neve or any of the current clones sell for. 

Since you are now at the next level - I'd suggest picking a worthwhile project and going for it.  You may have to scrape some extra $ together but I think it will be worth it.  When you factor in the amount of personal time invested - "cheap" often isn't really ever cheap.  I say make it count.  Go for a "wow" and try to avoid winding up with a "meh".    ;)     
 
lassoharp said:
Any ideas on the cheapest and best way to get a really GOOD sounding pre amp cheap? Including building it yourself?


There are a number of good sounding mic pre plans around here - some in kit form.  Most all are very affordable relative to buying a commercial piece.

May want to inform us on your price figure for "cheap".  Others can hone in on this number but I'd say 250-350 USD should  get you a very good sounding preamp.  This figure may vary depending on a number of factors - component choice, faceplates, fascia, etc.  A lot of your budget cutting can be done in sourcing components.  7$  pot(perfectly adequate) or switch vs 35$ ones.   

"Cheap" to most people means things like Behringer, ART and others.  You couldn't build one of those pieces for less than they're sold for.  You could build an EZ1290 for much less than what a real Neve or any of the current clones sell for. 

Since you are now at the next level - I'd suggest picking a worthwhile project and going for it.  You may have to scrape some extra $ together but I think it will be worth it.  When you factor in the amount of personal time invested - "cheap" often isn't really ever cheap.  I say make it count.  Go for a "wow" and try to avoid winding up with a "meh".    ;)     

Yeah £200 ish is sorta the area I could aim for. Thing is I could get a Focusrite ISA for £400. I guess I am a little confused, I wanna learn about electronics and upgrade a mic pre or at least have one that is my "go to" pre amp. I guess its just about finding the most practical way of achieving this. I was trying to find a mod for the art mp I have perhaps to get that more usable, but I know this will never be up to scratch with a Focusrite ISA or any kind of "Neve" style mic pre I decide to build. And of course this would take time and focus, and I am not great with either of those..
 
Probably worthwhile to carefully gather some user feedback from whatever build candidates you choose.  Lots of stuff already posted around the forum and you could always start an opinion thread.
 
The SSL9k is a good easy preamp to build and the parts aren't too hard to get, its just opamps resistors and caps. Boards avaliable from Gustav in the White Market. All info in the Metas. And they sound rather good!
 
Get a data sheet for the THAT 1510/1512 preamp sheets and build one of the suggested circuits, like the one in Fig. 3. Then get the sheet for the 1600 seris of line drivers for the output and build one of those. You'll get a decent preamp, quiet and clean. You could start with 4 9-volt batteries for the power supply, then get/build a mains supply later.

You'll spend most of your money on the box, connectors, pots, etc. It won't be a huge amount, and you can save up the rest for a fancier preamp down the road.

Peace,
Paul
 
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