From KT90 to KT88 - 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 6th February 2011, 03:51 PM   #1
ManUtd is offline ManUtd  Norway
diyAudio Member
 
ManUtd's Avatar
 
Join Date: Sep 2003
Location: Hof,Norway with Nice Mountains!
Default From KT90 to KT88

Can i just swap them?
My amp uses 4 peaces KT90 and i want to change to KT88.
Do i have to put in one by one adjusting bias seperately?
What`s the difference in bias on these tubes?

Regards,
ManUtd
  Reply With Quote
Old 6th February 2011, 04:09 PM   #2
rknize is offline rknize  United States
diyAudio Member
 
rknize's Avatar
 
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
They should swap fine. What amp is this? The KT88 does have slighly lower plate dissipation, so you may want to turn the bias down a bit before putting them in. Do them in pairs or all at once, not one at a time.
  Reply With Quote
Old 6th February 2011, 05:22 PM   #3
ManUtd is offline ManUtd  Norway
diyAudio Member
 
ManUtd's Avatar
 
Join Date: Sep 2003
Location: Hof,Norway with Nice Mountains!
Quote:
Originally Posted by rknize View Post
They should swap fine. What amp is this? The KT88 does have slighly lower plate dissipation, so you may want to turn the bias down a bit before putting them in. Do them in pairs or all at once, not one at a time.
Thanks for Your reply.
It is a chinese amp. Push Pull design.
Ming Da MC368-B90
  Reply With Quote
Old 6th February 2011, 05:39 PM   #4
rknize is offline rknize  United States
diyAudio Member
 
rknize's Avatar
 
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
Sounds like that amp will bias for EL34s as well.
  Reply With Quote
Old 6th February 2011, 07:01 PM   #5
ManUtd is offline ManUtd  Norway
diyAudio Member
 
ManUtd's Avatar
 
Join Date: Sep 2003
Location: Hof,Norway with Nice Mountains!
Default Scematic

Quote:
Originally Posted by rknize View Post
Sounds like that amp will bias for EL34s as well.
Here is scematic with KT90.
Is it 33k at V1 and V2 ? for Bias adjustment?

What will readings be with KT88 ?
Attached Images
File Type: jpg schematicsmc368b90.jpg (451.9 KB, 367 views)
  Reply With Quote
Old 6th February 2011, 09:54 PM   #6
rknize is offline rknize  United States
diyAudio Member
 
rknize's Avatar
 
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
Correct.
  Reply With Quote
Old 7th February 2011, 08:26 AM   #7
ManUtd is offline ManUtd  Norway
diyAudio Member
 
ManUtd's Avatar
 
Join Date: Sep 2003
Location: Hof,Norway with Nice Mountains!
Quote:
Originally Posted by rknize View Post
Correct.
Thanks,

And those measurement should be similar, no difference in measurement?
  Reply With Quote
Old 7th February 2011, 01:58 PM   #8
diyAudio Member
 
richwalters's Avatar
 
Join Date: Sep 2003
Location: Alps:Tube amp designs over 150W, SMPS guru.
220K grid leaks must be a record value with fixed bias around 500V B+. Pray it doesn't get flogged.
  Reply With Quote
Old 7th February 2011, 02:22 PM   #9
ManUtd is offline ManUtd  Norway
diyAudio Member
 
ManUtd's Avatar
 
Join Date: Sep 2003
Location: Hof,Norway with Nice Mountains!
Quote:
Originally Posted by richwalters View Post
220K grid leaks must be a record value with fixed bias around 500V B+. Pray it doesn't get flogged.
I`ll check with my amp inside.
Found this schematic on net.
  Reply With Quote
Old 7th February 2011, 03:44 PM   #10
rknize is offline rknize  United States
diyAudio Member
 
rknize's Avatar
 
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
The amp may have been designed with EL34s in mind. If the coupling caps are 0.47uF per the schematic, you should be able to use 100k gird leaks without losing LF response.
  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
MA XDSE KT88 vs YAQIN MC-100B KT88 esangenisd Tubes / Valves 3 23rd May 2010 11:38 AM
FS: Ei/Yugo KT90 quad, 6H30, svet KT88 quad - melbourne avian Swap Meet 9 15th April 2010 06:46 PM
KT90 why this ? richwalters Tubes / Valves 8 19th February 2008 01:42 PM
Replacing KT88 with KT90 - Beginner's questions horace Tubes / Valves 25 3rd November 2007 07:48 AM
KT88 vs. KT90 bench test richwalters Tubes / Valves 4 23rd December 2004 11:19 AM


New To Site? Need Help?

All times are GMT. The time now is 12:50 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