Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

6V6 line preamp
6V6 line preamp
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 14th September 2018, 02:37 PM   #3381
Anchan is offline Anchan  United States
diyAudio Member
 
Join Date: Jul 2009
Ok, is 200V ok on those FT-3 input caps, or do I need to go 600V. Size is a bit of a concern.
Prices not bad on them on eBay.

Quote:
Originally Posted by skrstic View Post
FT-3 is Russian teflon capacitor. 180R/5W , 470/2W and 5K/10W (2x10k/5W).


I borrowed from a friend a 4.7uF Mundorg capacitor. Is it OK to try?

PS. Hum is gone. Bad ground wiring.
  Reply With Quote
Old 14th September 2018, 03:36 PM   #3382
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
6V6 line preamp
Theoretically 200V is alright for that input position in the buffer version (cathode follower) but prefer a higher rating if you can because the thicker film material inside achieves better spec and reliability.
  Reply With Quote
Old 14th September 2018, 03:45 PM   #3383
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
6V6 line preamp
Quote:
Originally Posted by skrstic View Post

I borrowed from a friend a 4.7uF Mundorg capacitor. Is it OK to try?

PS. Hum is gone. Bad ground wiring.
Good news about solving your hum. If you mean 4u7 in the output position, that's also legit. When you want same bass and upper bass "feel" between systems calculate the RC time (translates to frequency) of your output cap and next stage's input load (each system's poweramp) to be roughly comparable in phase shift.

RC High-pass Filter Design Tool
  Reply With Quote
Old 14th September 2018, 03:49 PM   #3384
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
6V6 line preamp
Quote:
Originally Posted by nikosokey View Post
Two words and from me. Ever since I finished this construction never came down from my audio system....
Nikos, nice video presentation, once again congratulations on your first but thorough tube preamp build.
  Reply With Quote
Old 17th September 2018, 12:37 PM   #3385
skrstic is offline skrstic  Serbia
diyAudio Member
 
Join Date: Oct 2007
Location: Belgrade
A friend suggested me the following changes ...
Is it OK to try it?
Attached Images
File Type: jpg 6V6bufferCCT (proposal).jpg (87.4 KB, 119 views)
  Reply With Quote
Old 17th September 2018, 01:14 PM   #3386
IDM is offline IDM  United Kingdom
diyAudio Member
 
Join Date: Apr 2005
Location: Newcastle upon Tyne
I think that design change would put the grid at at more than -200v relative to the cathode. With rather tragic consequences.

Built as is, the cathode follower version is quite stunning. I was unsure of the extra signal path capacitor, but can honestly say it is not an issue.

Just build as Salas Shows, you wont be disappointed
Cheers
Ian
  Reply With Quote
Old 17th September 2018, 03:25 PM   #3387
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
6V6 line preamp
@skrstic

You could use a 50k log volume pot or less, if your signal sources are at ease with such values, so to achieve wider bandwidth if you like. But I wouldn't recommend any other area for changes as Ian wrote. There are Tocos 50k log pots offered online in good prices. They are subjectively well blending parts in this. Most Tocos on offer are linear pots so watch for that crucial detail in the various sellers descriptions.
  Reply With Quote
Old 17th September 2018, 04:43 PM   #3388
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
6V6 line preamp
Quote:
Originally Posted by IDM View Post
I think that design change would put the grid at at more than -200v relative to the cathode. With rather tragic consequences.
It would lower the valve's now bias current roughly by four times rather. Whatever practical changes to the cathode resistor(s) values would not compensate a much raised THD result vs the original topology. Including the raised presence of higher harmonics than the second one. Some loss of level would take place too when for same I-bias.
  Reply With Quote
Old 18th September 2018, 10:39 AM   #3389
skrstic is offline skrstic  Serbia
diyAudio Member
 
Join Date: Oct 2007
Location: Belgrade
Quote:
Originally Posted by IDM View Post
the cathode follower version is quite stunning...
Just build as Salas Shows, you wont be disappointed
It is relay good preamp.
  Reply With Quote

Reply


6V6 line preampHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Help me design my DAC/Line Preamp. kuroguy Tubes / Valves 7 2nd April 2009 08:31 PM
preamp line ctt richwalters Tubes / Valves 1 7th March 2008 04:34 PM
Preamp for Line In and Mic blur Instruments and Amps 1 4th January 2007 04:02 PM
Line stage preamp, based on SY's "Heretical Unity gain line stage" Danko Tubes / Valves 23 18th July 2005 04:07 AM
Line preamp for 2A3 amp Petman Tubes / Valves 0 24th May 2002 03:11 PM


New To Site? Need Help?

All times are GMT. The time now is 04:43 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki