Leak Stereo 20 questions - Page 3 - 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 28th April 2006, 04:33 PM   #21
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Accurate vacuum tube volt meters, and for those who could afford them good scopes from outfits like HP, Tek, Fairchild, etc.. I'm sure the UK had at least one comparable instrument manufacturer and metrology labs with high accuracy standards to calibrate them. It wasn't totally the stone age ya know...
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 29th April 2006, 04:00 PM   #22
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
Default It's those doggone transformers...

The problem was not so much measuring to 0.1dB - there were test sets having scales to 0.1dB resolution, it's more that such instruments were designed for professional (balanced) audio and they inevitably used a transformer for the input balancing. Despite various myths, 600R was not universal, so these test sets also needed to be able to present a high impedance load (typically 50k) and that's where the problem arises. The input transformer required to be able to present a 50k balanced load was generally not flat to 20kHz +/-0.1dB. It was only when op-amps enabled "electronically balanced" inputs with decent CMRR that test sets magically became flat to 300kHz +/-0.05dB or better.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 29th April 2006, 09:21 PM   #23
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
My old Heathkit AC VTVM ran straight in, single-ended with a scope probe. It's been some decades now since I lost it, but I'm pretty sure it had 0.1dB resolution. It was designed for service people and amplifier clinics, not broadcast/studio use. I'd guess there were equivalent units from Eico, HP, and the rest of the usual suspects.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 30th April 2006, 11:57 PM   #24
diyAudio Member
 
Join Date: May 2005
Location: Pretoria, South Africa
EC8010,

From what I can remember we had General Radio stuff at varsity and early at the CSIR, all with 600 ohm output impedance, although I am not saying that was general. The Leak TL12-type circuit with pentode input would not have suffered much until the source output impedance went above 10 K.ohm. It is these triode-input stages that would need a source impedance spec. for tests and amplifier output specs.
  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
LEAK stereo 70 cutting out Minimuslover7 Solid State 10 24th August 2009 04:56 PM
Xindak attenuation for use with Leak Stereo 20, help please camperman Tubes / Valves 15 20th May 2008 07:12 PM
Leak Stereo 20 clone? possibly with 6V6? bikehorn Tubes / Valves 26 29th March 2007 01:52 AM
Leak stereo 70 fault harrygrey382 Solid State 16 25th February 2007 04:07 PM
Mods on leak stereo 20 bronto64 Tubes / Valves 22 26th April 2004 08:27 PM


New To Site? Need Help?

All times are GMT. The time now is 07:34 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