KT90 Simple SE - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Tubelab
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubelab Discussion and support of Tubelab products, prototypes and experiments

Thread Tools Search this Thread
Old 6th February 2011, 05:49 PM   #1
diyAudio Member
Join Date: May 2003
Default KT90 Simple SE

I am thinking about a Simple SE build using KT90 output tubes. I am not terribly knowledgeable about tubes, so I want to make sure I am not missing something... My proposed parts list and construction plan is below.

*** Tubes:
- EH KT90
- some brand of 12AT7.... Any suggestions? Tubes by JJ, JAN-Philips, EH, and Mullard all look affordable.

*** Power
- Antek AS-4T360 transformer (can be wired 360-0-360 at 550mA, which is way overkill, but I do want headroom)
- Hammond 193M choke (10H, 300mA)
- Welborne Labs PS10 high-voltage regulated power supply (target is about 450V), solid state rectified
- DC (possibly regulated) heater supply

*** Output
- Hammond 1628SEA

I think I feel comfortable sourcing the other parts on my own. My thought is to bias the KT90's at about 100mA each. The regulator and DC heaters are intended to keep hum and noise to a minimum. My hope is that this amp will not only be a good introduction to tubes, but that it will also outperform my high-end Class A solid state power amp (hence the overkill power supply and high bias).

Does this look like a reasonable list? I guess I am looking at about 15W ultralinear and maybe 8W triode, right?

Thank you for any suggestions.
  Reply With Quote
Old 6th February 2011, 06:13 PM   #2
6L6 is offline 6L6  United States
diyAudio Moderator
6L6's Avatar
Join Date: Oct 2010
Location: Denver, Colorado
Why do you want a regulator on the B+ when you will have a big choke?

Tube or SS rectification?

If you want a killer sound, you should get a killer output transformer - My favorites are Electra-print. They are huge!! I've been using them for 10 years or so, never a problem and great service. You get what you pay for.
  Reply With Quote
Old 6th February 2011, 10:07 PM   #3
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
I can/do run my Simple SE with EH KT90s at 100mA. I have no problems with hum on my 98dB speakers. I have a 220uF C2 plus a 80uF motor run cap in parallel with it. I'm using the cheap Allied 6H choke. Spend your money on output transformers instead of regulators. There you will hear a difference. Go for the big, honkin Edcors at least. One Electron or Electraprint, if you want to splurge.

EH 12AT7 is fine. I've had all of my JJs getting weak after a few 100 hours. I won't be buying any more. NOS JAN is good too and will probably outlive anything else. Those military Mullards are excellent too...grab them now if you can afford it.
  Reply With Quote
Old 6th February 2011, 10:35 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
Sporting EH KT90s in triode. They do sound nice with my speakers and can rock in UL if needed.
Attached Images
File Type: jpg tubelab-simplese-kt90s.jpg (223.5 KB, 396 views)
  Reply With Quote
Old 6th February 2011, 11:18 PM   #5
diyAudio Member
Tubelab_com's Avatar
Join Date: Jul 2005
Location: West Virginia panhandle
*** Output - Hammond 1628SEA
I have a pair of 1628SEA's. They were in a Simple SE, and they have been in a few other amps. These transformers do bass better than any other SE transformers, unfortunately that is their only trick. If you want a good all round OPT look elsewhere. I like the big Edcor CXSE25-8-5K, but I limit myself to a near $100 budget. If you have the $$$ look to Electra Print.

DC (possibly regulated) heater supply
Not needed. The SSE has a very low hum level. A poorly implemented rectifier may create switching noise that could be coupled through the power transformer into the amp. A toroidal transformer is more likely to couple noise than a conventional transformer

- Welborne Labs PS10 high-voltage regulated power supply (target is about 450V), solid state rectified
Maybe a good thing, but I never tried it. As stated before, if you are going to regulate, you don't need a mega choke, a cheaper one, or possibly none at all, depending on the regulator, will do.

I use laboratory quality bench supplies to design and develop my amplifiers. The sound is excellent. The Simple SE with a choke and the suplemental motor run cap is 95% of the way to a fully regulated supply.
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
  Reply With Quote
Old 6th February 2011, 11:31 PM   #6
diyAudio Member
Ty_Bower's Avatar
Join Date: Mar 2007
Location: Newark, DE
I like KT90... though I don't have enough current capacity to run them to their full potential. I think you do need to run them at a fairly high current to get them to sound their best.

Click the image to open in full size.
  Reply With Quote


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
Tubelab SE vs Simple SE Pez Tubelab 25 29th October 2011 02:16 AM
Simple SE Simple Power Drive? Skorpio Tubelab 1 5th May 2011 09:45 AM
Tubelabs SE vs. Simple SE ?? albireo13 Tubelab 16 21st February 2010 09:00 PM
Simple Simple SE questions nodiak Tubelab 57 2nd February 2010 11:02 PM
Simple SE - Ei KT90? Ty_Bower Tubelab 22 7th July 2009 03:01 PM

New To Site? Need Help?

All times are GMT. The time now is 12:01 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2