What resistors to use on KT88s tubes? - Page 3 - 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 4th October 2012, 06:34 AM   #21
MGH is offline MGH  United States
diyAudio Member
 
Join Date: Jul 2004
Location: Texas
LOL...didn't pay close attention to the pic.

Mundorf (M-Resist Supreme resistors) makes wire wound resistors that many feel are better than Mills. However, the values are limited and they are expensive.
  Reply With Quote
Old 5th October 2012, 06:55 PM   #22
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 6
Quote:
Originally Posted by mr2racer View Post
Carbon composition stray with age and absorb moisture. If you like that sound then use them for control grids only. For the cathodes use metal film. Personally I prefer metal film throughout.
However, C-comps have much less internal inductance, and are pretty much ideal resistances up to ~100MHz or so. Since grid/screen stoppers are RF components, you want the C-comps here (and for RF projects, if you do them as well). Otherwise, metal film for sensitive signal paths (less noise).
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  Reply With Quote
Old 5th October 2012, 10:05 PM   #23
MGH is offline MGH  United States
diyAudio Member
 
Join Date: Jul 2004
Location: Texas
So which c-comp resistor do you recommend? Thanks
  Reply With Quote
Old 5th October 2012, 10:33 PM   #24
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Hi Miles;

please answer my question honestly.

For example you have an amp that has metal film resistors inside.

You have in a drawer some C-comp resistors.

How big is the chance that you open your amp and replace grid stoppers?

Anatoliy
__________________
The Devil is not so terrible as his math model is!
  Reply With Quote
Old 5th October 2012, 10:34 PM   #25
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
Are you saying that say a 5% different impedance at 1Mhz of a grid/screen stopper will impact the operation of the output stage for an audio amp?
  Reply With Quote
Old 6th October 2012, 12:59 AM   #26
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Quote:
Originally Posted by trobbins View Post
Are you saying that say a 5% different impedance at 1Mhz of a grid/screen stopper will impact the operation of the output stage for an audio amp?
No, he's saying that the lower inductance construction of a carbon comp makes it more suitable as a grid stopper. I stopped using CC resistors altogether at least 20yrs ago and have found MF resistors to be generally effective, but there may be some instances where they are useful, and in VT RF applications they are the logical choice..
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 6th October 2012, 10:46 AM   #27
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
Oh, I thought the inference was that because they were great for RF then they were ipso facto a requirement for stoppers in KT88 audio amps.
  Reply With Quote
Old 6th October 2012, 09:01 PM   #28
diyAudio Member
 
Join Date: Aug 2010
Location: Near Eindhoven, the sanctum of the pentode. and among that other things.
Send a message via Skype™ to v4lve lover
try ferrite Beads

v4lve
  Reply With Quote
Old 8th October 2012, 01:58 AM   #29
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 6
Quote:
Originally Posted by Wavebourn View Post
Hi Miles;

please answer my question honestly.
OK

Quote:
For example you have an amp that has metal film resistors inside.
Yes

Quote:
You have in a drawer some C-comp resistors.
I have a stock of C-comps since I also do RF projects.

Quote:
How big is the chance that you open your amp and replace grid stoppers?
No chance. I retired the last commercial amp I had years ago. All my designs use C-comps for grid stoppers, metal film for passive plate loads, feedback resistors, and everywhere else in the signal chain.
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  Reply With Quote
Old 8th October 2012, 08:01 AM   #30
ChrisA is offline ChrisA  United States
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by MGH View Post
My KT88 power amp requires 2 and 5 watt resistors on the grid, screen (?), and cathodes. I was thinking Kiwami's here, just because someone told me he had good experience with these in this application because of their slightly warm balance. I was told the Mills noninductive resistors are also good, but how do these compare to the Kiwami? Any other recommendations? Thanks.
The brand does not matter. The type does, slightly

To all those saying that carbon comp resisters change value with age and so on. Why worry they are only 20% tolerance devices. So even when they are new the value is kind of random, by 20% And this is good enough

The big thing about CCs is the resistance varies based on the voltage across them. In other words they depart from Ohm's Law. But only by a small amount. The effect is a slight compression of the dynamic range.

CCs also create some noise "hiss". The metal type are cleaner sounding and better for a HiFi amp. But hiss and compression as good in a musical instrument amp.
  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
Aikido preams pcbs and various parts(tubes,capacitors,resistors,etc) nicusim Swap Meet 3 7th June 2012 01:07 AM
JJ KT88s and other octals kruesi Tubes / Valves 35 10th April 2011 06:52 AM
JJ KT88s for sale. sts9fan Swap Meet 0 4th August 2009 07:38 PM
Genalex repro KT88s bobgroger Tubes / Valves 3 30th September 2008 12:42 PM
KT88s and grid current SpreadSpectrum Tubes / Valves 3 21st March 2008 07:33 PM


New To Site? Need Help?

All times are GMT. The time now is 09:19 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