#26 pre amp - Page 64 - 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 September 2010, 05:06 PM   #631
CFT is offline CFT  United States
diyAudio Member
 
Join Date: Jul 2006
Location: Hong Kong
Thanks eboz and Kevin.

I would certainly like to try it out sometime later....!!

The fact is, this preamp was built by a friend, and he, and other master, are, oh well, perhaps a bit old fashioned, and when I mentioned - how about using grid bias....and both shook their head, and said cathode bias would sound better....both masters have over 20 years of tube amp building experience and so didn't feel like challenging them then, so perhaps will play around with it later on I told myself ...

So, I will use Kevin's circuit as a reference..... but how would you connect the other end of the input transformer, in my case? Thanks for the advice : )

Last edited by CFT; 23rd September 2010 at 05:09 PM.
  Reply With Quote
Old 28th September 2010, 11:59 AM   #632
Kriskom is offline Kriskom  Indonesia
diyAudio Member
 
Join Date: Nov 2003
Location: Jakarta, Indonesia
Default A new poison for you Tsang !!

Hi CF..

Congratulations on yr new kid on the block !
Once yr on this baby , there wuld be no return back !! Other line-amps wuld sound terrible !!
1)
I fully agree with Kevin's suggestion , use the battery bias !

2)
This is another poison level for you :
If you are on the 381 halfwave rectifier , - (which is a solid plate anode?) , try get yourself on the german Telefunken/Valvo/Loewe/Tekade RGN354 half wave with "meshplates".
You need to reduce a bit the rectifier heater supply (from 5V ? ) to 4V ( yu need to use two serialled 0.33 Ohm at each leg) of the german tube.

The "german rectifier meshplates" are way superior to the 81 type tube. Yu wuld be amazed !

Enjoy yr music !
Paul
  Reply With Quote
Old 28th September 2010, 02:13 PM   #633
eboz is offline eboz  United States
diyAudio Member
 
Join Date: Mar 2006
Location: Boise, ID
Send a message via Yahoo to eboz
Quote:
Originally Posted by CFT View Post
Thanks eboz and Kevin.

I would certainly like to try it out sometime later....!!

The fact is, this preamp was built by a friend, and he, and other master, are, oh well, perhaps a bit old fashioned, and when I mentioned - how about using grid bias....and both shook their head, and said cathode bias would sound better....both masters have over 20 years of tube amp building experience and so didn't feel like challenging them then, so perhaps will play around with it later on I told myself ...

So, I will use Kevin's circuit as a reference..... but how would you connect the other end of the input transformer, in my case? Thanks for the advice : )
CFT: I think that not many people use an input transformer for the sole purpose of blocking DC. Many use one to go from balanced input to unbalanced, but it could also simply be used as a 1:1 input. You would use the grid leak resistor to set the input impedance and connect the bottom leg of the resistor with the battery there. This could very well sound a lot better than using a cap for blocking DC.

BTW I thought you made a mistake by saying you are using a half wave rectifier. I guess that is in fact what you're using, but it's rare that I've seen it used for B+.

Last edited by eboz; 28th September 2010 at 02:16 PM.
  Reply With Quote
Old 28th September 2010, 02:20 PM   #634
Kriskom is offline Kriskom  Indonesia
diyAudio Member
 
Join Date: Nov 2003
Location: Jakarta, Indonesia
Hi CF....

If you then are on a fullwave rectifier, yu can try out the german/european ( Phillips, Valvo, Telefunken, Loewe, Tekade) AZ1 meshplates.
In the same genre family you will have the RGN 1054 or 1064 meshplates, the AZ11 meshplates.

I tried various rectifiers and settled on a AZ1 Valvo meshplate. You shuld at least try out the meshplate versions ! They mad4e a real difference

Chiao
Paul
  Reply With Quote
Old 28th September 2010, 04:25 PM   #635
CFT is offline CFT  United States
diyAudio Member
 
Join Date: Jul 2006
Location: Hong Kong
Hi Paul, nice to hear from you here. Your DHT26 webpage is another inspiration

Yeah? definitely will check RGN354 out!!

Though I recall that the master said those German rectifiers might not be a best fit sonically with the American 26, 01A, etc..... for Ba (with a tip) that will be very nice he said.....and he has built quite a few of them...including a preamp with Ba driving a 45...... ( and hey, it might not be completely true....along with cathode bias... ) anyway will try that out if not too expensive.....

And hi eboz, the input transformer also provides some gain....thanks for the info here, definitely will look into grid battery bias

BTW, the 381 is indeed a half wave rectifier which I was told sounds better than using a full wave one, like the 380 employed in my older 26 preamp shown.

Last edited by CFT; 28th September 2010 at 04:45 PM.
  Reply With Quote
Old 29th September 2010, 04:23 AM   #636
Kriskom is offline Kriskom  Indonesia
diyAudio Member
 
Join Date: Nov 2003
Location: Jakarta, Indonesia
Hi CF...
Best of enjoyment w yr new #26....
I am interested with Rods heater supply regulator ! Where to ctc this gentleman ?


Regards
PJ
  Reply With Quote
Old 29th September 2010, 08:40 AM   #637
diyAudio Member
 
Join Date: Sep 2003
Location: London
Those mesh plate rectifiers are indeed nice - have a special softer feel that is quite intoxicating. Strangely I'm getting very good results with a 5Y3GT - I'm using that right now even though I also have AZ1 mesh. It REALLY helps to have bigger chokes (at least 2) and choke input and also only polypropylene caps in the PSU - I use motor runs. So LCLC. The difference is very audible.

andy
  Reply With Quote
Old 29th September 2010, 09:05 AM   #638
CFT is offline CFT  United States
diyAudio Member
 
Join Date: Jul 2006
Location: Hong Kong
Hi Andy,

Speaking of chokes, I noticed that my first choke in the LCLC vibrates a bit....do you know what the reason is? My friend said using them in a full wave setting it's quiet, but for half wave it will always shake....
  Reply With Quote
Old 30th September 2010, 12:34 PM   #639
diyAudio Member
 
Join Date: Nov 2006
Quote:
Originally Posted by andyjevans View Post
It REALLY helps to have bigger chokes (at least 2) and choke input and also only polypropylene caps in the PSU - I use motor runs. So LCLC. The difference is very audible.
I may be getting mixed up Andy but I seem to remember you trying a VR tube shunt power supply? I may well be wrong, but if so I'm interested in what you thought. I currently have a 26 as first pre stage with a voltage-dropping resistor and decoupling cap from the main 425V LCLC supply but was thinking I'd try an 0A2 or similar. Is this something you've tried?
  Reply With Quote
Old 15th October 2010, 12:21 PM   #640
diyAudio Member
 
coolzero's Avatar
 
Join Date: Sep 2009
Location: UAE
Hi All,

Here's the results of my recent mods I have done for my pre.

1. Changed the 5Y3 rectifier tube in my HV supply to Type 80 - Considerable improvement over both the ends; top and bottom improved dramatically.

2. Replaced my filament supply with Rod's filament PSU -Thanks to Rod, this change made a huge difference. Overall sound became more natural and focused. I can say for sure, Rod's filament supply is without the doubt the best filament PSU I used so far with my 26 pre. Except for the fully choke loaded filament supply (which was mentioned in this thread before) I tried almost all the filament supplies available with my pre-amp prior to Rod's filament supply. Nothing came close..

Big thanks to Rod for his kind assistance.

Last edited by coolzero; 15th October 2010 at 12:26 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 03:47 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