#26 pre amp - Page 98 - 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 23rd May 2011, 07:46 PM   #971
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
Originally Posted by massimo View Post
Merlin, if you have two diodes only, as in that rectifier, for a full bridge you need a sec with CT or two indipendent secs.
With just one sec, you can implement a hybrid bridge: 1 tube + two ss diodes. See latest andyjevans schematic.

Edit: see post #913
Thank you Massimo, wil you see the football Champions League Final?
  Reply With Quote
Old 23rd May 2011, 08:03 PM   #972
massimo is offline massimo  Italy
diyAudio Member
 
Join Date: Dec 2002
Location: Milan, Italy
Maybe yes, if only I can find a Man United scarf

Joking aside, I saw you already asked what kind of ss diodes: 1N4007 or better rated at 1.000 V
SF4007 ultrafast/soft recovery are quite nice if you can find them. If not send me a PM with your address and I'll send you a pair.

If you want to use your AZ1 only with a proper Xfrm, pls consider that if you have a 240 V/100 mA sec (let's say), you will need a 480 V/200 mA CT or two secs 0-240V + 0-240V/100 mA each to be 100% equivalent. (That's another reasons why tubes are $$$: you need big Xfrms!)
  Reply With Quote
Old 23rd May 2011, 08:18 PM   #973
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
I have on hand:

1N4007
UF4007
Fairchild 4A 600V Hyperfast II

Wich one will be the best suitable, the Fairchild right?

You are right, tubes needs a lot of iron & it's expensive, lately I bought for a friend a Tx 150VAC 100W CF125 & choke 10H 100mA MR8L from Giuseppe Bartolucci how knows to do impressive iron.

About football don't worry I only wait a very good match.
Attached Images
File Type: jpg DSC00042.jpg (393.1 KB, 441 views)
File Type: jpg DSC00041.jpg (521.9 KB, 425 views)
  Reply With Quote
Old 23rd May 2011, 08:25 PM   #974
работник
diyAudio Member
 
Rod Coleman's Avatar
 
Join Date: Jul 2004
Location: Warwickshire UK
Hi Felipe,

1N4007 has large recovery-time, and makes big current-pulse noise (difficult to measure, easy to hear)

UF4007 Fairchild works really well, just add series-RC snubber across the secondary winding:

100-ohm 0,5W carbon composition and 22nF to 47nF 1500V FKP (LCR PC/HV/S best, or PAnasonic MKP 1000V).

No need for > 1A type!
  Reply With Quote
Old 23rd May 2011, 08:28 PM   #975
massimo is offline massimo  Italy
diyAudio Member
 
Join Date: Dec 2002
Location: Milan, Italy
Rule of thumb: chose a diode with 3 times VAC. Thus the Fairchild rated at 600V aren't enough for a 240VAC sec (the one you mentioned earlier), but good for 150VAC
  Reply With Quote
Old 23rd May 2011, 08:31 PM   #976
massimo is offline massimo  Italy
diyAudio Member
 
Join Date: Dec 2002
Location: Milan, Italy
Rod, take a look at the Vishay SF4007 and tell us your opinion. Use to be a TFK design (and at that time was specified as Soft Recovery as well)
  Reply With Quote
Old 23rd May 2011, 08:44 PM   #977
работник
diyAudio Member
 
Rod Coleman's Avatar
 
Join Date: Jul 2004
Location: Warwickshire UK
Hi Massimo, I tried some of the SF4007 - I could not find any difference in sound against UF4007, using a 300B power amp for testing

With UF4007, the recovery time is very brief, and with B+ supplies, the current pulse is quite small. Together, these properties make the recovery pulse easy to suppress with the RC-snubber.

BUT - if you have SF4007, It is always best to compare by listening, and maybe the low cost of the UF4007 made too much influence on me!

Also, the wiring around the rectifiers, snubber, secondary wiring and C1 should be short....
  Reply With Quote
Old 23rd May 2011, 08:51 PM   #978
massimo is offline massimo  Italy
diyAudio Member
 
Join Date: Dec 2002
Location: Milan, Italy
Thank you Rod.
BTW the SF aren't that expensive (or at least weren't when I bought them).
  Reply With Quote
Old 23rd May 2011, 10:11 PM   #979
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
Originally Posted by Rod Coleman View Post
Hi Felipe,

1N4007 has large recovery-time, and makes big current-pulse noise (difficult to measure, easy to hear)

UF4007 Fairchild works really well, just add series-RC snubber across the secondary winding:

100-ohm 0,5W carbon composition and 22nF to 47nF 1500V FKP (LCR PC/HV/S best, or PAnasonic MKP 1000V).

No need for > 1A type!
Thanks Rod, I forgot the volts & power to use your heaters for 26, could you remember me the values?
  Reply With Quote
Old 23rd May 2011, 10:20 PM   #980
massimo is offline massimo  Italy
diyAudio Member
 
Join Date: Dec 2002
Location: Milan, Italy
I'm not Rod, but.....
Xfrm: 6VAC/5A (30VA)
Diodes 4x 1N5822 or MBR1045
Caps: 2x 10-15mF (I bought 12mF pana TS-UP)
Resistors: 2x 0.1-0.47 Ohm 5-7W (one for + side and one for gnd) to adjust raw dc at about 6.2-6.5 V

Sorry, I forgot to add: Xfrm must be EI with split bobbins (pri & sec), not a toroidal one.

Last edited by massimo; 23rd May 2011 at 10:34 PM.
  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



New To Site? Need Help?

All times are GMT. The time now is 02:07 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