Tube buffer using 12AU7 - 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 17th October 2003, 04:20 PM   #1
diyAudio Member
 
Join Date: Nov 2002
Location: somewhere
Default tube buffer USING 12au7

dear all,
the circuit is a tube buffer using 6dj8 and low power supply.
can i use 12au7 to replace it?
if yes, need to change any resistor?

any any reference circuit that using a 12au7 to construct a tube buffer?

THANKS
Attached Images
File Type: jpg buffer_sch.jpg (47.8 KB, 1976 views)
  Reply With Quote
Old 17th October 2003, 05:17 PM   #2
diyAudio Member
 
ashok's Avatar
 
Join Date: Jun 2002
Location: 3RS
Default 12au7/ECC82

Hi Takashi,
I have used a ECC82 in place of a 6DJ8 in a headphone amp. The amp worked off a 36 volt single supply. The tube had about 18 volts across Plate and cathode.
It worked . It also sounded OK. The measured distortion is higher than the 6DJ8. The 6DJ8 tube sounded better - more open and clearer. Quite noticeable but not an enormous difference. You could live with the 12au7 till you get a 6DJ8.
Cheers,
Ashok.
__________________
AM
  Reply With Quote
Old 17th October 2003, 06:04 PM   #3
diyAudio Member
 
ashok's Avatar
 
Join Date: Jun 2002
Location: 3RS
Default 12au7 seems OK.

I checked the circuit. The 12au7 will work as is but it will have far more distortion. Running it at a higher plate current will be better say around 1 mA at least.

Make R3 = 820 ohms and R4 = 4.7K if you plan to use the 12au7. It should sound good. You will have to try out the 6DJ8 or any other tube to see how good (or bad) the 12au7 is. IMHO the sound depends on more than just the tube and so you can't trash the 12au7 because it sounds bad elsewhere. Maybe that was the wrong application ! Here I think it should be OK .
Remember that gain is less than one ( about 0.85 or so ). Distortion at 0.707volts (rms) input is just over 0.1%. Looks like you can feed about 5 volts peak at the input without clipping into 1M load.
Cheers.
ashok.
__________________
AM
  Reply With Quote
Old 18th October 2003, 05:13 PM   #4
diyAudio Member
 
Join Date: Nov 2002
Location: somewhere
thanks a lot.
  Reply With Quote
Old 18th October 2003, 07:04 PM   #5
diyAudio Member
 
Join Date: Nov 2002
Location: North Herts, UK
Default ...alternatives...

Stefano Perugini has written an intereesting article on using the 6C45pi at 24V instead of the ubiquitous 6DJ8. Battery 6C45pi is the link and pick Battery 6C45pi from the menu. It's worth reading even if you don't intend using the 6C45pi.

ciao

James
  Reply With Quote
Old 17th January 2004, 09:31 PM   #6
diyAudio Moderator
 
JojoD818's Avatar
 
Join Date: Mar 2003
Location: searching...
Default 6N1P

Hello,

I am so very new to tubes and would like to start my journey with a tube buffer such as the one shown above (takashi's post). I would like to build it because it uses low supply voltages so I can start asap. However, I can only find the 6N1P tube locally, can I use it in place of the 6DJ8? If not, which resistors must I change?

Thanks in advance,
JojoD
  Reply With Quote
Old 21st December 2005, 03:30 AM   #7
diyAudio Member
 
Join Date: Sep 2003
Location: Singapore
is there any better design using Constant Current Source?
  Reply With Quote
Old 21st December 2005, 05:40 AM   #8
diyAudio Member
 
ashok's Avatar
 
Join Date: Jun 2002
Location: 3RS
You can use a constant current source at the cathode and you will get a huge reduction in distortion . That is not because the ccs does any magical thing but just because the ac load on the tube is now much higher ( in ohms !) than if you used a resistor in place of the ccs.
You could try setting the current at 5mA for the ccs. The 6N1P also might work well here , without any changes. I don't have its data sheets .

Leave out the input capacitor . A capacitor at the output is essential though it needn't be very high voltage types. However if you pick a 'botique type ' cap it might just be a HV type.
Have fun.
Cheers.
__________________
AM
  Reply With Quote
Old 21st December 2005, 05:55 AM   #9
diyAudio Member
 
ashok's Avatar
 
Join Date: Jun 2002
Location: 3RS
Maybe something like this.
V1 could be 6DJ8/6922 or possibly 6N1P.
Q1 can be an IRF830 or even a bipolar if you want ( BC639 ?)
Q2 is a BC546b .
Attached Images
File Type: gif ccs ckt.gif (2.9 KB, 1177 views)
__________________
AM
  Reply With Quote
Old 21st December 2005, 09:13 AM   #10
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
Quote:
Originally posted by huangyong
Is there any better design using Constant Current Source?
Do a search for the "Heretical" line stage on this forum...
__________________
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
12AU7 tube preamplifier schema vnarchitect Tubes / Valves 6 12th May 2010 01:07 AM
Tube buffer before pre-amp/amp? Destroyer OS. Instruments and Amps 2 9th January 2009 08:09 PM
12AU7 SRPP buffer suggestions Salas Tubes / Valves 25 19th April 2007 09:34 PM
Haltron 12AU7 Tube SINGLEENDED Vendor's Bazaar 0 13th March 2007 04:23 PM
Tube Buffer IGC - need help .... Will Chip Amps 22 21st November 2003 08:54 AM


New To Site? Need Help?

All times are GMT. The time now is 04:46 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