Tube as i/v converter - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, etc.

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 11th June 2004, 02:12 PM   #1
ingram is offline ingram  Malaysia
diyAudio Member
 
Join Date: Dec 2003
Location: east of the sun
Default Tube as i/v converter

Hi all,
I've made a simulation using tube as i/v converter
http://www.geocities.com/aykm/temp.htm
Any suggestion?has any1 tried this kind of ciruit b4?
Anyway,im going to build this circuit but it would take a while.
  Reply With Quote
Old 11th June 2004, 11:06 PM   #2
andrei is offline andrei  Canada
diyAudio Member
 
Join Date: Dec 2002
Location: Canada
I don't see the point of this circuit. Your tube is not amplifying anything, it is connected as a vacuum diode. If you are going to use transistors for current steering anyway, you might as well replace the tube by a resistor...

Grounded grid stage looks more interesting to me, although of course the input impedance is going to be higher than transistor's.
  Reply With Quote
Old 11th June 2004, 11:26 PM   #3
Banned
 
Join Date: Apr 2002
Location: Germany, Clausthal
what about something like Click the image to open in full size.
  Reply With Quote
Old 12th June 2004, 12:55 AM   #4
diyAudio Member
 
Join Date: Oct 2001
Location: .
Used forum search engine. It led here.
http://www.ultranalog.com/cdenhancer/cdenhancer1.html
  Reply With Quote
Old 12th June 2004, 07:06 PM   #5
diyAudio Member
 
Join Date: Dec 2001
Location: Eindhoven
Hi

Cathodes are the only low impedances so look for high gm tubes, with gm as flat as possible as function of Ia.

Furthermore this converter type suffers from the same drawbacks as a cathode followers (so remeber about current sources and cascodes !)

cheers
__________________
Guido Tent
www.Tentlabs.com
  Reply With Quote
Old 12th June 2004, 10:00 PM   #6
ingram is offline ingram  Malaysia
diyAudio Member
 
Join Date: Dec 2003
Location: east of the sun
hi andrei,
my thought is ,the sound will be dominate by the charateristic of the tube if use as iv converter.In simulator the wave form has the kind of distortion as described in a passlabs article:the positive half is slightly higher than negative half.Im curious how it would sound in reality.

till,
I was planning to build a similiar circuit but the operation point of tube tend to drift with age,using dc servo as shown in this website seems like a better method
http://peufeu.free.fr/audio/extremis...plement_4.html
But on second thought the IV conversion is still done by resistor in grounded grid configuration,so i assume i wouldnt differ much from a common base transitor.
  Reply With Quote
Old 12th June 2004, 10:05 PM   #7
Banned
 
Join Date: Apr 2002
Location: Germany, Clausthal
My idea was to use the resistor from GND to V- and the tube to V+ with a high value for R and really high voltages for V-/V+. This way the DAC could make all the voltage needed in the whole amplifier chain, one or two source followers behind should give the necessary current for driving the speaker. This way we would have a DAC driving speakers without preamp and power amp needed.
  Reply With Quote
Old 12th June 2004, 10:20 PM   #8
ingram is offline ingram  Malaysia
diyAudio Member
 
Join Date: Dec 2003
Location: east of the sun
rfbrw,
I've seen that website b4 but dont quite understand how it work,how come the ground is floated??

Guido,
5687 seems like the best choice here,it can operate at low voltage,with decent gm, cheap,readily available,and also sound good when used in preamp.
6H30 have better specification but cost more,my second choice
5842 have highest gm but need higher operating voltage.And it's songle triode.
Vacuum diode doesnt have my desired voltage swing and im not sure of its sonic when use in signal path.
The safe bet would still be 5687.
Can you elaborate more on the "same drawback" of cathode follower?
May i also ask do a digital expert like you use tube amp?

  Reply With Quote
Old 13th June 2004, 02:44 AM   #9
diyAudio Member
 
Join Date: Oct 2001
Location: .
Quote:
Originally posted by ingram
rfbrw,
I've seen that website b4 but dont quite understand how it work,how come the ground is floated??

It is the same as the Pass D1 circuit without the follower on the output or the ability trim the input to 0v.
The circuits you linked to do not look to be servoed to me in that there is nothing keep the input impedance seen by the dac as close to zero as possible. A sevoed variant of the tube iv would look something like the circuit below.
Attached Images
File Type: gif tubeiv.gif (4.1 KB, 266 views)
  Reply With Quote
Old 22nd June 2004, 09:10 PM   #10
diyAudio Member
 
Join Date: Dec 2001
Location: Eindhoven
Quote:
Originally posted by ingram
rfbrw,
I've seen that website b4 but dont quite understand how it work,how come the ground is floated??

Guido,
5687 seems like the best choice here,it can operate at low voltage,with decent gm, cheap,readily available,and also sound good when used in preamp.
6H30 have better specification but cost more,my second choice
5842 have highest gm but need higher operating voltage.And it's songle triode.
Vacuum diode doesnt have my desired voltage swing and im not sure of its sonic when use in signal path.
The safe bet would still be 5687.
Can you elaborate more on the "same drawback" of cathode follower?
May i also ask do a digital expert like you use tube amp?

Hi

CFs distortion habbits from

1 - current modulation (mostly the low cathode resistor value)
2 - voltage modulation (anode - cathode)

both can be understood when studying thecharateristics

1 is worse than 2 (mu times) and 1 is also affected by external load like input impedance of next stage (but often high with tubes

Applying a current source as a load for the CF, decreases distortion, also when drive at the cathode.

2 can be reduced by applying cascoding on top of the anode, but again, yields less results

consider penthodes like E83F or E55LL as well

Try it, you'll like it......

cheers
__________________
Guido Tent
www.Tentlabs.com
  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
DC - DC converter anechoic Parts 0 7th July 2007 04:39 AM
AD1865 tube i/v converter drobert Digital Source 17 24th November 2005 08:39 AM
DC/DC converter to power tube amp? needtubes Tubes / Valves 2 24th June 2005 02:35 AM
tube i/u converter tda1545 alchemy Digital Line Level 0 5th June 2005 07:13 PM


New To Site? Need Help?

All times are GMT. The time now is 11:21 PM.


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