DIY Tube Preamp - 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 11th November 2002, 01:48 AM   #1
diyAudio Member
 
Join Date: Sep 2001
Location: Sydney, australia
Default DIY Tube Preamp

Hi guys,

I want o have a go at making a preamp as my first foray into tube DIY.

I found the SJS line preamp (http://www.users.globalnet.co.uk/~valveamp/ under read it, line preamp , and second design + powersupply ) and the design looks nice and simple and fairly easy.

i jsut wanted a bit of help with the power supply section.
a) would a toroidal transformer be a good choice ?
b) what specs should i be looking for in the transformer. i guess it would be 220V primaries and 2 6.5v secondarys. but what about VA etc ??
c) where cana i get tubes locally ? ie australia

I was gonna chat to http://ourworld.compuserve.com/homepages/harbuch/ and see what thier price would be on the xformer.


any other things i should be aaware of with this design ??
  Reply With Quote
Old 11th November 2002, 07:27 AM   #2
diyAudio Member
 
Join Date: Aug 2001
Location: Melbourne/Australia
This link has a list of valve suppliers in Australia - http://home.mira.net/~gnb/elec/valveaus.html
Even Jaycar is selling a limited range of valves.
I find it just as easy and cheaper to order them across the net from places like http://www.thetubestore.com
You can also try guitar/music shops.

For the transformer, I think toroidals are fine, but many people have different opinions/preferences. They are one of the easiest to mount.
I would be interested to see the costs of the harbuch transformers in small/custom runs...

Looking at the design, if your are going for easy, I would use a solid state power supply instead of the valve rectifier shown.

Regards,
Tim
  Reply With Quote
Old 11th November 2002, 07:52 AM   #3
halojoy is offline halojoy  Sweden
On Hiatus
 
Join Date: Nov 2002
Default I don't know much about tube-design

But I found this page with a good tutorial.
(searched Google, keywords: tube line amplifier beginner)

My First Tube Amplifier

Here is another "TUBE DIY Page"
http://tubesall.hihome.com/

This is a real good one. Well described projects:
http://www.glass-ware.com/tubecircui...t_Archive.html

let's tube it
  Reply With Quote
Old 11th November 2002, 10:25 AM   #4
diyAudio Member
 
Brett's Avatar
 
Join Date: Jan 2002
Howdy,

I'll make this really brief as I'm madly trying to finish a project for tomorrow. I live in northern NSW and build tube gear (and have for years). I'll try to add more later or feel free to email.

a) Transformer: Torroids are too wide bandwidth and let in far too much junk that's a hassle to filter out later. An EI is a much, <b>much</b> better solution. An electrostatic shield between the primary and secondary is a good investment too, esp if you're having them custom made. Try www.tortech.com.au in Sydney (strathfield?) All custom transformers are expensive, esp as you will need a few different winding for B+ and heaters.

b) I took a look at the schematic and I like it.
Transformer specs;
Primary: 230V
Secondary 1: 330V - 0 - 330V at 100 mA for the B+
Secondary 2: 6.3V at 2A for the GZ80
Secondary 3: 8V at 1.5 A for the signal tubes

The first two secondaries are over-specified by a large margin. Most of the cost of a custom trans is on labour, so it's better to over spec it, because it sounds better, and because most people who play with tubes will build something else later and it's good to have the extra rating in case you want something with a lot more grunt, always handy in a line stage. Besides, over-speccing means parts run cooler and are more reliable.
Actual continuous current draw on the secondaries will be a max of about 15 - 30mA, 600mA and 600mA.

I also wouldn't bother with DC on the heaters as they're indirectly heated, and so would get a 3.15V - 0 - 3.15V heater for the signal tubes, and use a resistive divider from the B+ to bias them via the centre tap to 40V or so.

c) Best place in Oz for tubes is David Crittle at www.retrovox.com.au.
However, he may not have what you want.
I'll give you a pair of new 6N1Ps if you send me your address details. Nice tubes.
I hardly buy any tubes locally. Most of mine come from the US, HK, Italy, Lithuania or the UK and it is a zero hassle fast reliable deal. I can recommend reliable sellers I've dealt. Airmail is fast, reasonably cheap, and unless you buy expensive tubes, you'll seldom cop import duties or Govt Suck Tax (keep under $A499 landed incl postage). I will provide more details of parts and tube sources later (I don't have all the URLs from where I'm posting. Trust me, importing is a yawn.

The PSU chokes are a minor hassle, but they're small so postage should be cheap. These will probably have to be impoerted. I always use Lundahls, but they cost around $A160ea and take about 4 weeks to order through the Australian importer.

More manyana

Cheers
Brett
  Reply With Quote
Old 11th November 2002, 11:13 AM   #5
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default PREAMP

Hi,

Keep in mind Mr.Shiltons' warnings against either topology 2&3.

To my mind #2 is the better of the two,but you can't drive long interconnect cables with that due to high output impedance.

The PSU as proposed is pretty much universal so no quibbles there.

Depending on the tube of your choice you may have to burn off some excess voltage.

If that's the case,I would regulate it ,if you want to do that with tubes you will then have to provide the extra heater current unless you want to just put in some glowdischarge tubes or a string of zeners that are decoupled locally.
To my ears it well worth the extra outlay.

Happy building,
__________________
Frank
  Reply With Quote
Old 11th November 2002, 11:24 AM   #6
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default SIMPLE PREAMP

Hi,

Here's a nice little circuit that is up to the task.
It will be a lot better at driving cable capacitance and should mate well with the PSU.

Click the image to open in full size.

Cheers,
__________________
Frank
  Reply With Quote
Old 11th November 2002, 04:58 PM   #7
G is offline G  United States
diyAudio Member
 
G's Avatar
 
Join Date: Apr 2002
Location: Belleville, IL.
Hi Fred,

What is the approximate output impedance of the circuit you posted? Would it drive a Zen V4 with an input impedance of 47K or so?

G
__________________
Gavin
  Reply With Quote
Old 11th November 2002, 05:05 PM   #8
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default PHRED??QUI?MOI?

Hi Gavin,

Since I don't see anyone named Fred here I assume you mean the circuit with the 6SN7s' a bit higher up.

Zout should be around 2K and it should be able to drive a 47K Zin.

Cheers,
__________________
Frank
  Reply With Quote
Old 11th November 2002, 05:07 PM   #9
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
Thanks for the clarification Fred.
  Reply With Quote
Old 11th November 2002, 05:34 PM   #10
G is offline G  United States
diyAudio Member
 
G's Avatar
 
Join Date: Apr 2002
Location: Belleville, IL.
Sorry Frank. I haven't had my gallon of coffee yet this morning.

G
__________________
Gavin
  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 04:19 PM
FA: Eico HF-85 Tube Preamp &amp; HFT-90 Tube Tuner joe-electro Swap Meet 0 31st May 2009 05:14 PM
Tube Preamp Popping on Source Input Change (?) / 6DJ8 Preamp On Chip Amps MartyM Tubes / Valves 3 16th October 2008 05:52 AM
tube preamp using submini tube unclejed613 Tubes / Valves 11 19th August 2007 08:14 PM
Is it possible to get "tube sound" with just a tube preamp and chipamp output? Spasticteapot Instruments and Amps 43 15th May 2006 06:28 PM


New To Site? Need Help?

All times are GMT. The time now is 04:09 PM.


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