Go Back   Home > Forums > > >

Tubelab Discussion and support of Tubelab products, prototypes and experiments

Thread Tools
Old 27th August 2013, 07:42 PM   #1
kkcinc is offline kkcinc  United States
diyAudio Member
Join Date: Oct 2011
Default Making a simple se crank

I pulled out the simple se after a while. Been listening to a commercial pp kt88. I really missed the se amp. Sound quality is so much more magical. I want to really push it though. I tried 3k opt and the big edcor 5k. I also tried pentode. I like it in pentode but the bass is too boomy even with cathode feedback. I saw a thread on another simple way to get feedback but I lost it. Can someone explain that to me and tell me if it will help the boom. Also what about connecting to a different tap? Now I'm on the 8 ohm with 8 ohm speakers. 15'' threeway I might add.
  Reply With Quote
Old 2nd September 2013, 11:56 PM   #2
kkcinc is offline kkcinc  United States
diyAudio Member
Join Date: Oct 2011
I would love to see the other chat on other feedback option to tame the boom in pentode.
  Reply With Quote
Old 6th September 2013, 02:16 PM   #3
Tubelab_com is online now Tubelab_com  United States
diyAudio Member
Tubelab_com's Avatar
Join Date: Jul 2005
Location: West Virginia panhandle
There are two methods of applying feedback to the SSE. The traditional method is GNFB.

Lift the ground end of the cathode bypass cap on the 12AT7 and insert a resistor in series to ground. I used something small like 22 ohms to avoid gain loss. Then connect another resistor between the speaker lead and the junction of the cap and the 22 ohm resistor. The value of this resistor controls the amount of feedback. Use a pot to find the amount of feedback needed for your speakers. About 390 ohms worked best in one of my experiments. The phasing of the OPT secondary should be such that the amp's gain is reduced as the resistor value is reduced.

The other method is local output stage feedback, often called Schade. Wire a large resistor (300K and up) from the plate of the output tube to the plate of the 12AT7. Many experts will tell you that you can not do this with a triode driver, often this is accepted as a fact without understanding why it is true. The plate resistance of a triode varies with the applied signal, so the amount of feedback is constantly changing often increasing the distortion. This is especially true with a CCS loaded triode. However, I have seen cases where it works. Understand that the feedback resistor will see nearly twice the B+ voltage across it under full power so it needs to be rated for 600V or more. Use several 1 watt resistors in series.

NOTE: These are experiments that I have done on my boards. I don't particularly care if I blow something up, sometimes it's good fun. YMMV
Tubelab, I blow stuff up so that you don't have to.
  Reply to this post


Making a simple se crankHide this!Advertise here!
Thread Tools

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
Simple Simple SE questions nodiak Tubelab 58 5th February 2021 11:41 AM
Making a very simple volume control Wormwoodprophecy Analog Line Level 1 14th March 2012 07:54 AM
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

New To Site? Need Help?

All times are GMT. The time now is 10:45 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio