Ammeter connection for Tubelab SE - 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 30th August 2011, 08:09 AM   #1
diyAudio Member
 
Join Date: Nov 2009
Location: Vienna
Default Ammeter connection for Tubelab SE

Dear All,

I would like to connect two ammeters, one per channel to my Tubelab SE.

By default there is a 10 ohm resistor to measure the bias, on the high voltage leg, just before the OT. Now I should replace this with the ammeter.

Two issues:

1) I read around not to put instruments on the high voltage, for the risk associated with the potential failure.

2) The instrument would be in the signal path, as this is a SE amp. I don't know if this is good or not.

I tested on the bench and it works, not sure if I want it in the final build.

Any input ?

Thanks,

Davide
  Reply With Quote
Old 30th August 2011, 09:29 AM   #2
chrish is offline chrish  Australia
diyAudio Member
 
chrish's Avatar
 
Join Date: Oct 2003
Location: Sydney
My question is 'why'.

If there is a 10 ohm sense resistor there, why not use it? Have a voltmeter measure the voltage drop across the resistor. Place a switch in the circuit so that you can place it in the circuit to take the measurement, then switch it out when listening. If you are using an analog meter, you can even change the scale printing behind the needle (there is software to do this). You could have one switch do duty for both channels and only require one meter.

Cheers,

Chris
  Reply With Quote
Old 30th August 2011, 12:33 PM   #3
diyAudio Member
 
Join Date: Nov 2009
Location: Vienna
I have to confess the meter is almost only for esthetic reason.

The vintage style round meters look good to me, two was for a symmetry reason. But I don't want to compromise the sound and reliability for that. Maybe I should just leave connectors for the meter as I did in another built.

D.
  Reply With Quote
Old 31st August 2011, 06:26 AM   #4
chrish is offline chrish  Australia
diyAudio Member
 
chrish's Avatar
 
Join Date: Oct 2003
Location: Sydney
You can still do this, but using a voltmeter (not ammeter) that is switchable solves the in-circuit issue. Remember that an ammeter is really just a voltmeter measuring across a shunt resistor.
  Reply With Quote
Old 31st August 2011, 08:22 AM   #5
diyAudio Member
 
Join Date: Nov 2009
Location: Vienna
The ammeters I have a very small internal resistance, they work just fine just replacing the 10 ohm that is used to do the measure manually.

It can fail open or shorted. In case it fails open one channel will not work, in case will fail shorted the ammeter will not work. So in reality should not be a big deal. But still not sure what to do.

Thanks for the advices.

D.
  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
Tubelab SE vs Simple SE Pez Tubelab 25 29th October 2011 03:16 AM
Need Help with Tubelab SE lth1 Tubelab 9 1st October 2010 10:06 PM
tubelab se DimZ Tubelab 58 20th January 2009 01:47 PM
tubelab SimpleSe power transformer connection question dubdub Tubes / Valves 10 12th September 2008 02:30 AM
Tubelab SE finished but need help. Evenharmonics Tubes / Valves 50 8th July 2008 07:04 PM


New To Site? Need Help?

All times are GMT. The time now is 10:24 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