6GX8 as Audio Level Indicator? - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs 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

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
Thread Tools Search this Thread
Old 21st October 2011, 03:49 AM   #1
diyAudio Member
steve516's Avatar
Join Date: Feb 2011
Location: Chicago, IL
Default 6GX8 as Audio Level Indicator?

Hi all.

I'm building this amplifier:


my question is this: I have all the parts, tubes, iron (well maybe, see ahead) and I'm ready to go on this except for one thing. I have no experience with level indicators and eye tubes, so the 6GX8 is making me worry. I have 8-ohm speakers and right now i have an OPT that is 5k Primary PP with an 8ohm secondary. So- does this mean I can't use the level indicator? Or can I put the indicator on the 8ohm secondary?

I'm confused as hell on how that even works. It would seem that the 16ohm tap could be only used exclusively for the indicator, or am I wrong and you can also attach your speaker?

Or do I just put the indicator circuit at the 8ohm tap and run my speaker in parallel?

No clue here, any help appreciated.

  Reply With Quote
Old 21st October 2011, 05:31 PM   #2
TheGimp is offline TheGimp  United States
diyAudio Member
TheGimp's Avatar
Join Date: Aug 2009
Location: Johnson City, TN
The 16 ohm tap would put out more voltage (1.4141 times as much) but the tuning indicator only represents a 10K load.

Put it on the 8 ohm tap along with your speaker. It will be less sensitive on the 8 ohm tap but based on the telefunken spec below I don't think it will be an issue.

That said, I don't see how it works.

It is configured as a 'gridleak bias' stage, but the input resistor is too small (470K) for gridleak operation.

Telefunken :


Be sure the 0.18/200 is a low leakage cap. Any leakage will kill the gridleak bias operation.

Shows -4V bias to shut off the eye (close) but shows a 3M grid resistor in series driven by the signal source. I'd change the 470K to a 3Meg resistor.

The data sheet is not completely clear. It might be that the tube is meant to be biased off (hence the 470K) and negative going peaks cause the movement towards closure.

Last edited by TheGimp; 21st October 2011 at 05:50 PM.
  Reply With Quote
Old 21st October 2011, 06:46 PM   #3
Yvesm is offline Yvesm  France
diyAudio Member
Yvesm's Avatar
Join Date: Jul 2004
Location: Ardeche
Originally Posted by TheGimp View Post
. . .
It is configured as a 'gridleak bias' stage, but the input resistor is too small (470K) for gridleak operation . . .
Think to the grid / cathode diode, it's just a peak rectifier.
The link cap charges itself thru that diode on positive alternances making the grid more negative and reducing plate current.
It discharges thru the grid leak resistor.
  Reply With Quote
Old 22nd October 2011, 02:24 AM   #4
diyAudio Member
steve516's Avatar
Join Date: Feb 2011
Location: Chicago, IL
Thanks for the help guys. I'll try it and see what happens!
  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
Funny 6E2 cateye audio level indicator (video) siliconray Siliconray Online Electronics Store 1 18th October 2011 03:51 PM
LED peak level indicator forsakenrider Analog Line Level 5 16th March 2011 01:12 PM
please critique this level indicator gain Parts 10 4th October 2008 05:32 AM
Peal level indicator...needs help! jazzpeter65 Solid State 0 19th December 2003 07:40 AM

New To Site? Need Help?

All times are GMT. The time now is 11:19 AM.

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