tube mic preamp kit?? - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 25th August 2006, 08:09 AM   #1
diyAudio Member
 
Join Date: Aug 2006
Default tube mic preamp kit??

Hi. I am pretty new at this stuff. I've got the idea in my head that it would be fun to build one of these preamp kits. They've been talked about in previous threads.

http://eshop.diyclub.biz/index.php?cPath=149_106

The schematics are available at kitsparts.com.

Any recommendation on which would be the most suitable for a good two-channel microphone preamp for a home recording setup? I would need 48v phantom power for condenser microphones. I'm sure this is kind of a dumb question, but I would like to learn a lot building and I'm scared that without some advice I'm going to buy and build something that turns out not to be useful.

Thanks.
  Reply With Quote
Old 25th August 2006, 09:28 AM   #2
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
None of them are microphone amplifiers. Be warned: A microphone amplifier or a phono stage is the hardest thing to make successfully. Not an ideal first project.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 25th August 2006, 10:47 AM   #3
diyAudio Member
 
chrispenycate's Avatar
 
Join Date: Aug 2006
Location: Geneva, Switzerland
I don't see where a valve/tube microphone preamp is that difficult a project. After all it's a transformer, a low noise stage, a variable gain stage and an output driver, all linear, flat frequency response. The most complicated is the output stage; if you want a low impedance balanced line driver it's basically a tiny power amp, with an output transformer which is not easy to find; but that would be true with any tube gear you want to interface with professional studio material. Basically, if the circuit is reasonable, the sound of the preamp is the sound of the input transformer, and can be very good indeed.
Certainly, any components (particularly switches) in the low level signal path have to be highest available quality and reliability (but this is a general condition, the only really special case being if you want an attenuator switch before the input transformer).
Even if one adds a highpass filter, a variable input impedance and a hi z DI input, the project should be well within a neophyte's range; far easier than a good equaliser or a varimu compressor. And if someone else has done the metalwork… (Qmaxing out B9a holes reasonably in line was always a problem of mine, as was labelling controls with lettraset)
All right, few more slight problems; it doesn't appear they do metalwork, and stabilising the phantom power from your tube ht is an interesting extra project, plus I don't think they plan for DC heaters (not essential, but so easy to do nowadays) but still…
  Reply With Quote
Old 25th August 2006, 11:10 AM   #4
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
For a condenser microphone amplifying conversational speech, you normally need to set the gain of the microphone channel to about 55dB, for a ribbon, 75dB. That's to bring the level up so that peaks reach +8dB above 0dBu (0.775VRMS). We'd like a S/N ratio of at least 60dB referred to peak level, and hum needs to be at least 15dB better than that, so hum needs to be below -67dBu at the output, or -122dBu at the input, which is 0.6uV. Achieving that level of hum is possible, but it requires careful attention to earthing, layout, screening, and DC heaters. Not really a good first project. If you look at the number of threads on this forum about hum in power amplifiers, you'll see what I mean.

And then there's the provision for variable gain to allow for microphones being rammed down saxophones, the quiet phantom power you mentioned, etc, etc.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 25th August 2006, 05:45 PM   #5
diyAudio Member
 
Join Date: Aug 2006
Default first project idea

Well, the more I look into things, the more I realize I don't know. I've got a pretty good background in basic physics, simple dc circuits, and some experience with the soldering iron, but practically no experience with analyzing and modifying these rather intimidating a/c designs.

I think my best bet is probably to learn some more basics and start out building and testing a really simple amplifier design or two before I try to make anything useful.

I'm reading through some of the resources posted on the "learning for newbies" thread. I would really appreciate any advice on a good first project and resources to help me get a good grasp of what is going on inside of the circuit.
  Reply With Quote
Old 26th August 2006, 02:14 PM   #6
mryan is offline mryan  United States
diyAudio Member
 
Join Date: Jan 2006
Location: usa
Default tube mic preamp kit

If a person is looking for a good tube mic preamp kit, the Hamptone is very well designed and professional mic pre available in kit form.
http://www.hamptone.com/
  Reply With Quote
Old 26th August 2006, 02:31 PM   #7
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
Well, well, well, a valve microphone amplifier kit. It looks quite plausible, and with transformer balancing in and out. A challenging first project, but by no means impossible.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
need diy tube preamp (line-stage) recommendation and general tube advice Musiclover4 Tubes / Valves 16 18th May 2013 03:19 PM
FA: Eico HF-85 Tube Preamp & HFT-90 Tube Tuner joe-electro Swap Meet 0 31st May 2009 04:14 PM
Tube Preamp Popping on Source Input Change (?) / 6DJ8 Preamp On Chip Amps MartyM Tubes / Valves 3 16th October 2008 04:52 AM
tube preamp using submini tube unclejed613 Tubes / Valves 11 19th August 2007 07:14 PM
Is it possible to get "tube sound" with just a tube preamp and chipamp output? Spasticteapot Instruments and Amps 43 15th May 2006 05:28 PM


New To Site? Need Help?

All times are GMT. The time now is 10:09 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2