71A - Page 5 - 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 9th March 2013, 04:41 AM   #41
Ceglar is offline Ceglar  Australia
diyAudio Member
 
Join Date: Jan 2008
Blog Entries: 2
I can suggest either 01A or 112A. Both are 0.25A filament types like the 71A, which makes battery heating easy, which might be a consideration if you're building this for low level stage.

Shane.
  Reply With Quote
Old 9th March 2013, 05:42 AM   #42
diyAudio Member
 
Join Date: Apr 2010
Location: Malaysia
Hi Ceglar,
01a is my first choice if I would to add a driver stage in front. I'm planning to built a single stage 71a preamp for start.
It would be a 100K step volume pot > Lundahl LL1674 1:4 step up > 71A > Tamura A-4714 with 5k primary and 600ohm secondary.

2nd stage would be taking out the Lundahl step up and add a driver stage for 71A.

My objective doing this is to compare 71A tube with 45 as preamp by using Tamura A-4714 as line transformer.

My system consist of :

Turntable : Garrard 301
Tonearm : SME 3012 S2
Cartradge : Denon DL 103 Pro
Phono Stage : Audio Image - multi curve
Preamp : 45 with Tamura A-4714
Power amp : 300B
Speaker : Tannoy Westminster TW
  Reply With Quote
Old 10th March 2013, 12:29 AM   #43
diyAudio Member
 
nvduybom's Avatar
 
Join Date: Aug 2009
Location: Da Nang, Viet Nam
Hi Noodle88,

My friend used input transformer 600 : 75 K with good result.

his schematic :

Regards,

Van Duy
Attached Images
File Type: jpg shema pre71.JPG (14.1 KB, 328 views)
__________________
http://www.vnav.vn/forum
  Reply With Quote
Old 10th March 2013, 03:49 AM   #44
Ceglar is offline Ceglar  Australia
diyAudio Member
 
Join Date: Jan 2008
Blog Entries: 2
Quote:
Originally Posted by Noodle88 View Post
Hi Ceglar,
01a is my first choice if I would to add a driver stage in front. I'm planning to built a single stage 71a preamp for start.
It would be a 100K step volume pot > Lundahl LL1674 1:4 step up > 71A > Tamura A-4714 with 5k primary and 600ohm secondary.

2nd stage would be taking out the Lundahl step up and add a driver stage for 71A.

My objective doing this is to compare 71A tube with 45 as preamp by using Tamura A-4714 as line transformer.

My system consist of :

Turntable : Garrard 301
Tonearm : SME 3012 S2
Cartradge : Denon DL 103 Pro
Phono Stage : Audio Image - multi curve
Preamp : 45 with Tamura A-4714
Power amp : 300B
Speaker : Tannoy Westminster TW
I wonder how much gain you really need, whats the signal level at the output of your phono stage with average program material?

71A biased at -40V can swing more than enough to drive 300B, linearly, and still with headroom. Rp is decent enough and 20mA Ip is good to drive the Cin of 300B without any slew rate issues. Battery heated, its a nice quiet DHT driver.

I like LL7903 as 1:4 to 01A DC 71A IT 2A3/300B. Nice quiet and simple enough.

Regards,
Shane
  Reply With Quote
Old 11th March 2013, 03:08 AM   #45
H.Michi is offline H.Michi  Japan
diyAudio Member
 
Join Date: Jan 2009
I have no idea about your proposal, as I don`t know about LL1674.
Try to just replace existing 45 tube with a 71A?

The 71A single stage with fillament bias hold the signal pass to a minium.

Regards
Hiro
  Reply With Quote
Old 11th March 2013, 12:16 PM   #46
diyAudio Member
 
Join Date: Apr 2010
Location: Malaysia
Ceglar,
DL 103 output is 0.3mV,my phono stage is at 60db and it has a gain of 67db. I suppose there is 0.3v output from phono.

My current 45 preamp is done as:
S&B TX-102 TVC (configure with +6db) > lundahl LL1674 1:4 step up >
45 DHT > Tamura A-4714 with 600 ohm output.

As poweramp :
6n1 mu follower > 45 DHT > Tango NC20F > 300b > Tango 3.5k output trans.

I do think my current set up have enough gain and head room.
I'm not going to have enough gain or head room if I would to replace my 45 preamp with a single stage 71a preamp without the 1:4 step up.

I quest a 2 stage 71a preamp is the solution.

Cheah
  Reply With Quote
Old 12th March 2013, 12:04 PM   #47
diyAudio Member
 
nvduybom's Avatar
 
Join Date: Aug 2009
Location: Da Nang, Viet Nam
You can replace 45 driver stage with 71A, my friend tried and he chose 71A. he used Lundahl (unknow) - 71A - LL1677-300B - XE20s.

I did amplifiers and pre-amplifiers with 45.
- Power: 417a-45-James transformers.
- Pre: Lundahl 1544a (or 6j5) - 45 - LL1692A.
I like the sound power amplifiers 45 but low power (I test with Fostex 208 BLH speaker). With pre45 I failed, may be my preamp schematic is not good.

Cheer.
__________________
http://www.vnav.vn/forum

Last edited by nvduybom; 12th March 2013 at 12:06 PM.
  Reply With Quote
Old 19th September 2013, 04:19 PM   #48
diyAudio Member
 
nvduybom's Avatar
 
Join Date: Aug 2009
Location: Da Nang, Viet Nam
I just winding 4 x 4,2mH for 71A filament and 2 x 14H for B+ .
Attached Images
File Type: jpg IMG_0854.jpg (767.4 KB, 206 views)
__________________
http://www.vnav.vn/forum
  Reply With Quote
Old 20th September 2013, 02:57 AM   #49
diyAudio Member
 
Join Date: Apr 2010
Location: Malaysia
I had completed my 71a preamp few months back. It sounded fantastic !
Well worth the effort.

Cheers,
Cheah
  Reply With Quote
Old 20th September 2013, 02:58 AM   #50
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Please post details of where you ended up..
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  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
FS: 71A NOS tubes Jimmy D. Swap Meet 1 11th July 2012 02:13 AM
FS: 71A tubes Jimmy D. Swap Meet 2 9th February 2010 10:23 AM
Hytron big 71A Diy martin Tubes / Valves 13 13th April 2006 09:27 PM
a 71A monoblock Joel Tubes / Valves 30 30th December 2002 09:19 PM
My current 71a amp Joel Tubes / Valves 10 29th October 2002 09:25 AM


New To Site? Need Help?

All times are GMT. The time now is 02:35 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